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_cs.51934 | i think that it's true that AM is contained in $\Pi_2$ but I'm not sure how to prove it. How do I prove that $AM \subseteq \Pi_2$? | Proving that AM contained in Pi_2 | complexity theory;complexity classes | null |
_webapps.108868 | Consider the data below:1-Jan-2010 3 2-Feb-2009 95-Apr-2010 4 18-Apr-2010 510-Sep-2012 9 1-Oct-2011 8The first two columns are for individual A, the last two for individual B.Is it possible to create a graph such that both ranges are displayed under a common x axis? In other words, 6 data points 9noted with two different symbols with the corresponding date for each data point?This would be equivalent to a merge of two distinct graphs, to a common x-axis. | How to merge x-axis data from two ranges? | google spreadsheets;google spreadsheet charts | Is this roughly what you want?: |
_unix.213176 | I have a RHEL7.0 host which has this standard entry in /etc/hosts/:127.0.0.1 localhost.localdomain localhostSo resolving localhost.localdomain works:$ ping localhost.localdomainPING localhost.localdomain (127.0.0.1) 56(84) bytes of data.But trying to resolve the absolute version of the same fails:$ ping localhost.localdomain.ping: unknown host localhost.localdomain.And in general, trying to resolve absolute FQDNs against relative /etc/hosts entries fails. Now, if I change the entry in /etc/hosts to have a trailing period, I can then resolve the absolute FQDN. But then I can no longer resolve the relative FQDN. Seems if I want both absolute and relative forms to resolve, I have to explicitly include both forms of the FQDN in /etc/hosts.Is this odd behavior described in an RFC or standard somewhere so I can understand it better? Is it configurable somehow? | Absolute domain names in /etc/hosts? | rhel;resolution;hosts;etc | null |
_codereview.98825 | I have working code that uploads and resizes images. What im trying to figure out is how I can direct the browser to another page or view kind of the way facebook does, but still call the resize function in the background. Right now, the code waits to complete the resize before doing anything else. The Call to the upload and resize functions on the upload page :if ($result=$imageHandler->upload($files)) { //call image resize, call resize $success= new view($result); $imageHandler->imgResize($result);}And this is the FileHandler class that uploads and resize the image: <?php/* > Class fileHandler > Handle existing files and existing folders. */ class ImageHandler { protected $required; protected $imagePath; protected $allowedfiles; protected $default; //constructor public function __construct() { require_once 'UploadException.php'; $this->allowedfiles=array( 'image/gif', 'image/jpg', 'image/jpeg', 'image/png' ); $this->required=array('800', '1024','1200','1280','1400','1440','1600','1680','1920','2400','2500','2600','2880'); //use absolute path with defined constant here $this->default='images/'; }//UPLOAD FUNCTION CALLED FIRST, RETURNS UPLOADED IMAGE LOCATION . Includes Exception Handling public function upload($files) { //Check contents of Files array. Class should not interact directly with $_FILES or $_POST . //Check array is not empty and file type is allowed. if (!empty($files) && in_array($files['type'], $this->allowedfiles) ) { $temp=$files['tmp_name']; $destination=$this->default.$files['name']; //if all good, check file size less than 20MB or something? //proceed with upload. Include error handling in this if statement //if file upload unsuccessful, do error handling. else return new file location if (move_uploaded_file($temp, $destination)) { echo '<hr> file upload worked'; return $destination; //exit('all good'.print_r($files)); } else{ //call upload error handler. Get error Msgs. //throw new exception and pass it error code returned by upload! $error= new UploadException($files['error']); $error->getMessage(); } } else{ //handle failure with exception handler $error=new UploadException($files['error']); echo $error; exit('<br><br>execution stopped'); } } //takes image path returned by upload function public function imgResize($image) { $required=$this->required; $details=getimagesize($image); $count=count($required); $imgName=substr($image, strrpos($image,'/')+1 ); $imgType=$details['mime']; $width=$details[0]; $height=$details[1]; $imgRatio=$details[0]/$details[1]; $GDSrcImg=$this->createImage($image ); for ( $i = 0; $i < $count ; $i++ ) { //if the destination folder doesnot exist, create it. if(!file_exists('images/'.$required[$i])) { mkdir( 'images/'.$required[$i], 0764, true ); chmod( 'images/'.$required[$i], 0764 ); } else { $userDestImage = 'images/'. $required[$i] . '/' . $imgName; $newWidth = intVal( $required[$i] ); $newHeight = intVal( $newWidth / $imgRatio ); //maintain aspect ratio $dest = imagecreatetruecolor( $newWidth, $newHeight ); imagecopyresampled( $dest, $GDSrcImg, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height ); $finalImg= $this->finalImg($imgType, $dest, $userDestImage ); } } return $finalImg; } public function createImage( $img ) { $size = getimagesize( $img ); $typeImg = $size['mime']; switch ( $typeImg ) { case 'image/png': $newImage = imagecreatefrompng( $img ); return $newImage; break; case 'image/jpeg': $newImage = imagecreatefromjpeg( $img ); return $newImage; break; case 'image/gif' : $newImage = imagecreatefromgif( $img ); return $newImage; break; } } public function finalImg($imgType,$dest,$userDestImage) { switch ( $imgType ) { case 'image/png': $final = imagepng( $dest, $userDestImage ); //return $final; break; case 'image/jpeg': $final = imagejpeg( $dest, $userDestImage ); //return $final; break; case 'image/gif' : $final = imagegif( $dest, $userDestImage ); //return $final; break; } return $final; }} | Resize images in the background after upload | php;image | null |
_webmaster.59039 | I have set up a website which is visible from FF but not from Safari nor Chrome. I thought it is because of faulty WordPress install but obviously it is not because I have added a test.html in the root, FF views it but Chrome gives an error.Never happened before, tried Google but found generally app or html problems causing the issue. | Chrome fails to view a html file | html | seems you probably ran a cached instance of your site in FF while Chrome is actually telling you the you truly do not have a site being rendered. I checked your url in FF and I got the same as in Chrome (zip, nada, zilch, zero, nothing, absence of something, etc) :) check your site CNAME and DNS. You may not be directing the site to the domain properly.Right now you have these: NS1.NATROHOST.COM NS2.NATROHOST.COMAre these it?check your htaccess file. You may be blocking your entire site out |
_softwareengineering.11121 | Often some element of a path is variable, but the path as a whole needs to be documented in some manner for later programmers. Especially when using *nix systems, almost any character is a valid symbol for the path. Given that, I would like to delimit the variable portions of my path to prevent misunderstanding, but in a way that also survives best across different display environments (especially the browser).Methods I have seen include (example path in users home directory):/home/<username>/foo - needs special escape for web browser context/home/your_username/foo - unfortunately the variable element tends to be overlooked/home/{username}/foo/home/:username/fooWhich have you seen most often or had the most success with and why? If a double delimiter method (which seems to be the most common/successful), what lead your choice of delimiters? | Best way to delimit variable elements of a path in code documentation? | documentation;variables;file structure | By far I've seen (and used) /home/<username>/foo the most. Don't worry about special escapes for such comments because all of your code is going to need to have those characters escaped when displayed in a browser (you may very well have statements like echo <table>; in your code.If escaping isn't possible for some reason, you can surround the term with spaces or underscores to prevent HTML parsing: /home/<_username_>/fooOne added benefit of underscores is that some markups (like Markdown) will automatically make them italicized:/home/<username>/foomaking them understandable in a text editor and nicely formatted in a webpage. |
_unix.82746 | I use SENDMAIL, I noticed that none of my mail is sent. I have all my mail in the /var/spool/mqueuewhen I looked at the log and I have this error MDeferred: Connection refused by cluster8a.eu.messagelabs.com.What does this line mean.?i test to see if this remote host accepts incoming SMTP connections on SMTP port 25, by way of the following command: telnet cluster8a.eu.messagelabs.com 25telnet cluster8a.eu.messagelabs.com 25Trying 85.158.139.103...telnet: connect to address 85.158.139.103: Connection refusedTrying 216.82.251.230...telnet: connect to address 216.82.251.230: Connection refusedtelnet: Unable to connect to remote host: Connection refused | Can't send mail with sendmail | linux;sendmail;smtp | null |
_cstheory.11332 | In the usual presentations of the calculus of constructions (CC) with two kinds Prop and Type such that Prop:Type and impredicative on Prop, it is easy to show the following result:every closed term A such that $\Gamma \vdash A:\kappa$ (where $\kappa$ is a kind) reduces to a product, namely $A \rightsquigarrow^* \forall x^C.D$.The easy proof relies on the size of the longuest path from $A$ to its normal form, namely on strong normalization of CC (lexicographic induction on the length of the longuest path to normal form, and height of the derivation).In Benthem Jutting, Typing in Pure Type Systems, 1993, Information and computation there is the following result for all pure type systems:if $a \in T_S$ and $\Gamma \vdash a:A$ then $A \rightsquigarrow^* \forall x_1^{C_1}\ldots\forall x_n^{C_n}.s$ where $s$ is a sort and $T_S$ is almost the set of types.We can think prove first statement using the second: if $\Gamma \vdash A:\kappa$ then $\Gamma, x:A \vdash x:A$ and then $A$ reduces to a product. Unfortunately $T_S$ does not contain the variables.The question is: is there a proof of the first statement not relying on the strong normalization of CC ?My guess is that the answer is no: $A$ can $\beta$-reduces to an application, that can reduces to an application, ... The only way to know if it eventually reduces to a product is to effectively $\beta$-reduce it, and in the worst case to normalize $A$. | Forms of types in the calculus of constructions | lo.logic;type theory;type systems;calculus of constructions | null |
_webmaster.20368 | To whit: I run a men's lifestyle Q&A site. I have a total of 25 categories in which questions are submitted. Currently, however, these categories are in fact sub-categories, such that Bodybuilding, Cardio, Nutrition, Health and Sports for example, all belong to the Health & Body meta category, of which there are 5 in total. Is this the best structure for the site, or would it be better for SEO to upgrade the sub-categories (since there are - and probably always will be - only 25...) into full-blown categories? Thanks very much in advance for any light you're able to shed on this. | What is the optimal way to apply categories to a new site? | seo;sitemap | null |
_unix.216982 | I am connecting from a Mac (with OSX 10.6) to a Linux machine (with CentOS 6.6) by using the ssh command (ssh -X). On the Mac side, I am using the Terminal app. After logging into Linux, I can use Emacs (emacs -nw) or vim for my programming without problem, but all the other applications like Emacs (window mode), Firefox, visualization software, etc, do not recognize my keyboard input correctly. For example, if I enterabcon the Mac side, Linux applications show the characters asA07The same thing happens for GUI admin tools like system-config-users. These Linux applications use X11, and the Mac uses XQuartz 2.3.6, but I am not sure whether the problem is due to X. Setting an environment variable like LANG=C gedit did not work either. Do you have any ideas why this happens? | Remote X11 applications have wrong keyboard mappings (local: OSX, remote: Linux) | x11;osx;keyboard layout | null |
_unix.386235 | I have nginx version 1.10.2 running on a CentOS 7 box. When I try to start the service I am getting the following error: Aug 15 16:08:50 user.mylabserver.com nginx[2704]: Can't locate nginx.pm in @INC (@INC contains: /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendAug 15 16:08:50 user.mylabserver.com nginx[2704]: BEGIN failed--compilation aborted.Aug 15 16:08:50 user.mylabserver.com nginx[2704]: nginx: [alert] perl_parse() failed: 2Aug 15 16:08:50 user.mylabserver.com systemd[1]: nginx.service: main process exited, code=exited, status=1/FAILUREAug 15 16:08:50 user.mylabserver.com systemd[1]: Unit nginx.service entered failed state.Aug 15 16:08:50 user.mylabserver.com systemd[1]: nginx.service failed. | nginx fails with following error: nginx: [alert] perl_parse() failed: 2 | centos;systemd;perl;nginx | The relevant portion of the log is:Aug 15 16:08:50 user.mylabserver.com nginx[2704]: Can't locate nginx.pm in @INC (@INC contains: /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendThe first line indicates that the service startup is failing because it cannot locate the file nginx.pm.The remainder indicates with specificity the exact locations in which is it seeking that file.If that file does not exist in any of those directories, it appears that either a component of the service has been (re)movedIf it does exist, it is likely that you are not starting the service with a user who has permissions to see or read the required file. |
_unix.65510 | I have a directory full of text files. My goal is to append text to the beginning and end of all of them. The text that goes at the beginning and end is the same for each file.Based on code I got from the web, this is the code for appending to the beginning of the file:echo -e 'var language = {\n$(cat $BASEDIR/Translations/Javascript/*.txt)' > $BASEDIR/Translations/Javascript/*.txtThis is the code for appending to the end of the file. The goal is to add the text }; at the end of each file:echo }; >> $BASEDIR/Translations/Javascript/*.txtThe examples I drew from were for acting on individual files. I thought I'd try acting on multiple files using the wildcard, *.txt.I might be making other mistakes as well. In any case, how do I append text to the beginning and end of multiple files? | How do I append text to the beginning and end of multiple text files in Bash? | shell script;files;text processing | To prepend text to a file you can use (with the GNU implementation of sed):sed -i '1i some string' fileAppending text is as simple asecho 'Some other string' >> fileThe last thing to do is to put that into a loop which iterates over all thefiles you intend to edit:for file in *.txt; do sed -i '1i Some string' $file && echo 'Some other string' >> $filedone |
_webmaster.44775 | We just overhauled our entire site. The new site structure doesn't resemble the old one in the slightest. What do I need to do with Google, Bing and Yahoo to keep our ranking from sliding?We have created a number of redirect rules to send people following old links to the proper page on the new site. We have a site map and robots.txt. | Just overhauled our entire site. How do I keep Google, Bing and Yahoo from demoting us? | seo;google search console;search engines;yahoo;bing webmaster tools | Assuming you've done nothing to reduce the quality of your site, you should not see long-term ranking loss. You will however see movement, both up and down, for a few weeks.You say you've created a number of redirect rules. Unless it's a very large, complex site, this should be the case for all pages, and they should return 301 HTTP code. If you've migrated or retired content before, check for chained redirects: these should be avoided as they will increase page load time, cause unnecessary additional dissipation of PageRank (or equivalents), and may even not be followed at all in some cases.robots.txt (check specs here) should be present with a reference to a valid XML Sitemap.Install Google and Bing Webmaster Tools (Yahoo uses Bing's index, so BWT will cover for both) and monitor carefully. Submit your XML Sitemap, and use the various tools at your disposal (manage parameters, geotargeting, what have you) as appropriate to your site.Don't be immediately alarmed by drops in ranking. Typically things drop (or rise) for a while before settling down. |
_unix.211584 | I'm trying to figure out a very strange problem with yum on a fairly old CentOS 5.11 VPS using DirectAdmin.Executing the following command suggests the telnet package is installed:# yum install telnet...Installed: telnet.x86_64 1:0.17-41.el5 However, telnet is still missing:# which telnet/usr/bin/which: no telnet in (/root/local/node/bin:/usr/local/share/npm/bin:/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/share/adt-bundle/tools:/root/share/adt-bundle/platform-tools)My version of Yum is 3.2.22.Perhaps a hint of what is going wrong is that I appear to have different versions of rpm installed somehow. If I try to verify my RPM database, my database version appears invalid:# rpm --versionRPM version 4.3.3# rpm --verify telnetrpmdb: Program version 4.2 doesn't match environment versionerror: db4 error(22) from dbenv->open: Invalid argumenterror: cannot open Packages index using db3 - Invalid argument (22)error: cannot open Packages database in /var/lib/rpmpackage telnet is not installedIf I rebuild the RPM database using the following command:rm -rf /var/lib/rpm/__db* && rpm --rebuilddbYum gives a similar error, but complaining about a newer version:# yum updateLoaded plugins: fastestmirrorrpmdb: Program version 4.3 doesn't match environment versionerror: db4 error(-30974) from dbenv->open: DB_VERSION_MISMATCH: Database environment version mismatcherror: cannot open Packages index using db3 - (-30974)error: cannot open Packages database in /var/lib/rpmRemoving the /var/lib/rpm/__db* files gets Yum past this again, but installed packages still appear to be missing.I get the feeling that Yum is somehow misconfigured or that I have two different versions of RPM. What can I do to diagnose the problem to ultimately work to a resolution? | CentOS 5.11: yum installs, but packages remain missing | centos;yum;rpm | null |
_unix.218596 | What does it mean when threads are time-sliced? Does that mean they work as interrupts, don't exit while routine is not finished? Or it executes one instruction from one thread then one instruction from second thread and so on? | Threads vs interrupts | cpu;posix;interrupt;multithreading;thread | Time-sliced threads are threads executed by a single CPU core without truly executing them at the same time (by switching between threads over and over again).This is the opposite of simultaneous multithreading, when multiple CPU cores execute many threads.Interrupts interrupt thread execution no matter of technology, and when interrupt handling code exits, control is given back to thread code. |
_unix.326831 | I've got the following problem regarding to sed command. What I wish to do is:sed '1 d' filename.fa | sed 1i\>filename\n > filename_Edited.fawhere the file frist line is replaced by >filename. This is done in 2 steps: deleting first line and then inserting a new one which contains the desired >text. The command works as it is wirtten above if it is typed directly into the console (w/o variables). However, I need this command integrated in the following script where filename is now depending on a variable:#!/bin/bashCODE=`cut -c 7-21 Data.txt`cd ../FASTA_SEC/ for i in ${CODE} do sed '1 d' ${CODE}.fa | sed 1i\>${CODE}\n > ${CODE}_Edited.fa doneI get the following error when this script is ran for each for loop iteration:try: line 8: ${CODE}_Edited.fa: ambiguous redirectI dont get whats wrong in sed sintaxis orin the overall script, Aparently it should work but it does not. Any clue?I have also tried to run the script without pipped part, only executing the sed which deletes first line from the text:#!/bin/bashCODE=`cut -c 7-21 Data.txt`cd ../FASTA_SEC/ for i in ${CODE} do sed '1 d' ${CODE}.fa > ${CODE}_Edited.fa doneHowever, it returns the former error again!Thank you for yr help!!**.fa format are known as fasta which are a kind of plain text format used in DNA sequences | sed in bash scripting troubleshooting | bash;sed;scripting;variable | null |
_softwareengineering.323592 | I'm looking at the alternative that can substitute the use of eval() and new Function() javascript techniques. I'm developing a solution build with javascript and the platform on which it is built (Salesforce) recently has announced they're introducing CSP (content security policy) that will block the use of eval(), and other unsafe functions.My solution is using eval function to evaluate string expressions and do some other magic stuff. I'm looking for some alternative, ideally without writing my own parser.As I have mentioned, I use eval to evaluate expressions. Expressions that should be to be supported are usually like:String comparison eval('something' == 'something') // return trueCalculations eval(2 + 2 * 3) // return 8&& and || support eval(1 == 1 && 'cat' == 'dog') // return falseConditional operators,at least ternary eval((1 == 2 ? 'dog' : 'cat')) // return catfull if-else would be really great: eval(if(1 == 2) { 'dog' } else if (1 == 3) { 'dog' } else { 'nothing' }) // return nothingSome basic Math class methods, e.g.: eval(Math.ceil(12.313)); // return 13Capabilities that would be really great to haveInject variable new Function(var item = this; item.number = 10;, item); // item is variable defined outside of eval and I want to dynamically modify it within eval()Inject function definition eval(invert('123')) // return 321, invert() is a function defined somewhere elseI'm looking for something that is:Relatively close to Javascript syntax (but I would accept if it would be some different language that can be interpreted by some js library compliant with CSP)Not too much dependent on other librariesCan be loaded without node.js etc (standalone js library) | Alternative for eval() in javascript for expression evaluation | javascript;parsing;computation expressions | null |
_codereview.48097 | I am not sure if I should be using recursion or not or if it even helps in increasing the performance of my algorithm. I feel as though I am creating and replacing too many arrays by calling my inner rotate() function.Should I add a check to convert rotation -270 to 90 and vice-versa so that I am rotating less often?Please refer to the JSFiddle I have provided for details and clarification on the functions involved in the code below: JSFiddle Demovar rotateMatrix = function (matrix, n, direction) { var ret = matrix.slice(); var rotate = function(direction, matrix) { var r = zeroArr(n, n); for (var i = 0; i < n; i++) { for (var j = 0; j < n; j++) { if (direction < 0) { r[i][j] = matrix[n - j - 1][i]; } else { r[i][j] = matrix[j][n - i - 1]; } } } return r; }; for (var turn = Math.abs(direction); turn > 0; turn -= 90) { ret = rotate(direction, ret); } return ret;};var tile = [ ['A', 'B', 'C'], ['D', 'E', 'F'], ['G', 'H', 'I']];trace2('Rotate +180', printMatrix(rotateMatrix(tile, 3, 180)));trace2('Rotate +90', printMatrix(rotateMatrix(tile, 3, 90)));trace2('Orginal', printMatrix(tile));trace2('Rotate -90', printMatrix(rotateMatrix(tile, 3, -90)));trace2('Rotate -180', printMatrix(rotateMatrix(tile, 3, -180)));Output:Rotate +180: I| H| G--+--+-- F| E| D--+--+-- C| B| ARotate +90: C| F| I--+--+-- B| E| H--+--+-- A| D| GOrginal: A| B| C--+--+-- D| E| F--+--+-- G| H| IRotate -90: G| D| A--+--+-- H| E| B--+--+-- I| F| CRotate -180: I| H| G--+--+-- F| E| D--+--+-- C| B| A | Matrix rotation efficiency | javascript;optimization;matrix | null |
_unix.251799 | After sshing (using putty with X11 enabled) into my virtual box VM, I tried to open an xterm window. However the following command:xterm -sb 500or even /usr/bin/xterm -sb 500returns the error:xterm: No absolute path found for shell: 500I cant seem to figure out what the error even means!EDIT:ls -la /usr/bin/xterm-rwxr-xr-x 1 root root 450888 Sep 28 2012 /usr/bin/xtermalias xterm-bash: alias: xterm: not foundDISTRIB_DESCRIPTION=Ubuntu 12.10NAME=UbuntuVERSION=12.10, Quantal Quetzal | Xterm: No absolute path found for shell: 500 | ubuntu;xterm | null |
_unix.386352 | i want to create a template for multiple vm deployment from a existing image ,,i basically have template vm ready with image in qcow2 format at path /kvm/template.qcow2. I have heard about virt-sysprep which can modiy hostname,ssh host keys, and etc,, all packages are installed.when i try to do basic virt-sysprep cmd i get no operating system found error. My Host Machine is Centos 6.9 , and guest vm is Centos7[root@ns0 kvm]# virt-sysprep --format qcow2 -a template.qcow2Examining the guest ...virt-sysprep: no operating systems were found in the guest image[root@ns0 kvm]#[root@ns0 kvm]#[root@ns0 kvm]# ls -lh | grep template.qcow2-rw-r--r-- 1 root root 16G Aug 16 05:27 template.qcow2 | kvm template creation issue | linux;virtual machine;kvm;libvirtd | null |
_softwareengineering.228410 | A suggestion has been made by a team member to leave all debug code intact in our web pages... and then to create a variable that can be turned on / off to enable / disable debugging. This is a technique we use in some of our low level, non web code.Just wondering if anyone had any comments on how they've implemented something similar for web applications? Some of our web applications are written in lua, and others in PHP. I like the idea and I've seen it used in different types of solutions. However, my knee-jerk reaction is that for web apps, it might not be such a great idea. I don't want to have a tonn of logs generated on the web server. At the same time, it'd be nice to simply enable a variable and then start collecting information. The alternative could be to always have a test page that calls the same methods that the production page does, but the test page dumps a bunch of data to the screen. Just wondering if anyone has any experience / comments on doing this for the web as far as how to build it in, how difficult it is to maintain etc.Thanks. | debugging web applications using debug parameter | php;debugging;logging;lua | null |
_webmaster.71296 | When the user goes to the Cart page, we have a CTA button that allows then to 'upgrade' their product to a more deluxe version. Whether they decide to upgrade or not, they will be sent to an Information page where they enter their credit card and account information. Finally, the will reach an Order Confirmation page.I have already applied analytics to the 'upgrade' CTA button to track when they have used this feature. Now I am trying to track whether the user has successfully went through the entire checkout flow with the an upgraded product. I was thinking of tracking this with a Google Analytics Custom Dimension, but I am unsure if this will work. I was hoping to get feedback before I implement my idea.Requirements:Tracks if the user reaches the Order Confirmation page with an 'upgraded' product they have upgraded in the Cart pageProposed Solution:Fire a Custom Dimension when the user upgrades the product in the Cart page. I am unsure how to verify if the user reaches the Order Confirmation page with the 'upgraded' product though. | Google Analytics - Track Products Through Checkout Flow | google analytics | null |
_codereview.158704 | I have implemented a queue data structure using linked list in C#. I have also associated my implementation with unit tests. Is this implementation correct? Any suggestion? namespace QueueDataStructure{ internal class Node { internal int value; internal Node next; } public class Queue { private Node head; private int size; public Queue(){} public void Enqueue(int n) { if(head == null) // queue is empty { head = new Node{ value = n, next = null }; } else // queue has items { var oldHead = head; head = new Node { value = n, next = oldHead }; } size++; } public int? Dequeue() { if (size == 0) return null; var node = head; Node previous = node; while (node.next != null) { previous = node; node = node.next; } previous.next = null; size--; return node.value; } public int Count { get { return size; } } public string PrintElements() { var node = head; int[] elements = new int[size]; int i = 0; while (node != null) { elements[i++] = node.value; node = node.next; } return string.Join( , elements); } }}using Microsoft.VisualStudio.TestTools.UnitTesting;using QueueDataStructure;namespace TestQueue{ [TestClass] public class Tests { [TestMethod] public void TestQueue() { var queue = new Queue(); Assert.AreEqual(0, queue.Count); Assert.AreEqual(null, queue.Dequeue()); queue.Enqueue(1); queue.Enqueue(2); queue.Enqueue(3); Assert.AreEqual(3, queue.Count); Assert.AreEqual(3 2 1, queue.PrintElements()); Assert.AreEqual(1, queue.Dequeue()); Assert.AreEqual(2, queue.Dequeue()); Assert.AreEqual(3, queue.Dequeue()); Assert.AreEqual(0, queue.Count); } }} | Queue implementation using linked list | c#;unit testing;linked list;queue | null |
_unix.339973 | I work on arm cortex-m3 microcontrollers for 3,5 months.I made several projects and programmed directly with st arm debugger for real time operations(motor drive, sensor and actuator applications....).But nowadays I am searching for running linux on arm processors and design embedded board for it.According to my research, there are several embedded Linux kernel that can be used in arm processors and it is possible to install.But I couldn't find any instruction about installing these linux kernels on arm processor.Is there any complete tutorial to explain how to install any example Linux kernel to arm step by step.What type of toolchains should i use ?Should I use any programmer for installation and what type(JTAG/SWD/USART)?Is there any restrictive situations?(I am not planning to use 8-bit simple processor.I am considering to use Arm v8 cortex A-53 )Also I would like to inform you that I already used Raspberry pi,Intel Galileo.. Unix based embedded controller board for many applications.(I just would like to create new bride development board to obtain flexible hardware).Any help will be appreciated. | How to install Linux on arm processors | linux;embedded;arm | null |
_cs.54253 | I have a structure. that consist of the following:Athlete A Athlete B Athlete Cspeed=10 speed=12 speed=6endurance=60 endurance=59 endurance=64I would like to rank the strength of those three Athletes based on their speed and endurance. I would like to give a slightly greater weight (0.6) to the endurance. Is there any algorithm that have a good complexity to solve this problem? | Rank athletes by weighted criteria | algorithms;sorting | I would like to rank the strength of those three Athletes based on their speed and endurance. There is an infinite number of ways of doing that. The two lexicographic orders and weighted sums are only a few examples.What do you really want?I would like to give a slightly greater weight (0.6) to the endurance.This suggests that you want (linear) weighted sums. If that is to make sense, you need to normalize your values to a shared scale. You don't give units or ranges, so I'll have to guess.Normalizing with the maximum values in the sample and assuming that values $0$ are possible, a weighted sum that gives weight $p \in [0,1]$ to endurance and $1-p$ to speed looks like this:$\qquad\displaystyle w(a) = p \cdot \frac{\operatorname{end}(a)}{64} + (1-p) \cdot \frac{\operatorname{speed}(a)}{12}$.Implementing this is so straight-forward that it's barely worth being called algorithm; you'll certainly find nothing in a textbook that lays out the details for your. Just code it down. |
_webmaster.32803 | I have some images in a section of a site that require the user to be logged in in order to view. These images are served by a PHP script, which checks the user's login state and if valid, serves the binary data with the appropriate headers. This all works fine. The issue comes when a user tries to print one of these images. In Internet Explorer, when they go to print preview, they get the broken image box with a red cross in the corner instead of the actual file. This is also what gets printed. All other browsers can print the images without issue.I have some images elsewhere on the site that are also served via. PHP but these don't require a login. These print fine.The PHP-powered HTML pages on the site that require a login also print fine in IE. It's just login-required images.When the user hits 'print preview', this does not seem to result in additional HTTP request to the server for the file. However I do see an additional HTTP request a few seconds later that comes from the same IP (may or may not be related), This request includes no host header, no REQUEST_URI and no user agent. The 'please login' page sends an appropriate 403 header. I've also added a far-in-future expires header to the image response itself to ensure that browsers can serve/print the files from their own cache but this hasn't made any difference.Why can't IE print the images and what else can I do to investigate or fix the problem? | Unable to print login-required images in IE | php;internet explorer;print | null |
_unix.304145 | in Kaffeine <1.3 is bug with samba, I try to build version 1.3.x. But after call cmake, I get an error:-- The C compiler identification is GNU 4.9.2-- The CXX compiler identification is GNU 4.9.2-- Check for working C compiler: /usr/bin/cc-- Check for working C compiler: /usr/bin/cc -- works-- Detecting C compiler ABI info-- Detecting C compiler ABI info - done-- Check for working CXX compiler: /usr/bin/c++-- Check for working CXX compiler: /usr/bin/c++ -- works-- Detecting CXX compiler ABI info-- Detecting CXX compiler ABI info - doneCMake Error at CMakeLists.txt:6 (qt5_add_resources): **Unknown CMake command qt5_add_resources.**-- Configuring incomplete, errors occurred!I test version and settings:$ qtchooser -print-envQT_SELECT=defaultQTTOOLDIR=/usr/lib/x86_64-linux-gnu/qt5/binQTLIBDIR=/usr/lib/x86_64-linux-gnu$ qmake -vQMake version 3.0Using Qt version 5.3.2 in /usr/lib/x86_64-linux-gnu$ cmake --versioncmake version 3.0.2 | Error (qt5_add_resources) when build kaffeine in debian jessie | debian;compiling;qt | null |
_unix.85115 | I have a Linux server that gets a time offset for some strange reason. I set up cron job to run and update the time using the following command:/usr/sbin/ntpdate pool.ntp.orgThe problem is the command would not run because I have a firewall (iptables).I have always used IP to allow traffic in my network:iptables -A INPUT -p tcp -m tcp -i eth0 -s 11.11.11.11 --dport 5060 -j ACCEPTI would like to know how to do it using a domain name in this case would be pool.ntp.org, or maybe someone could tell me a better way to keep the clocks in sync. | Allowing a domain name in my IP Tables | linux;iptables;clock;ntp | To allow a NTP client to talk to a server you can use these rules:$ sudo iptables -A OUTPUT -p udp --dport 123 -j ACCEPT$ sudo iptables -A INPUT -p udp --sport 123 -j ACCEPTTo act as a NTP server and accept client connections:$ sudo iptables -A INPUT -p udp --dport 123 -j ACCEPT$ sudo iptables -A OUTPUT -p udp --sport 123 -j ACCEPTReferencesWhat are the iptables rules to permit ntp? |
_unix.352355 | I was just installing arch linux on my pc, besides windows 7.Accidentally I unmounted the boot partition of windows and tried to mount it again with the command mount /dev/sda1 /mnt (sda1 = windows boot partition)and as i tried to boot windows it said Missing operating system.Is it possible to remount the windows partition, and if yes, how? | Mount windows 7 boot partition via. arch linux | arch linux | null |
_unix.362518 | I would like to do some music composition on my linux mint pc, but I have run into instabilities while trying to install and use a low-latency kernel (system freezes, possibly due to conflicts with the nvidia proprietary graphics drivers). So as I see it, I have three options:Either use my current system, i.e. the normal, generic kernelInstall a dedicated audio distribution like UbuntustudioInstall the low-latency kernel on my current system but disable my graphics card.Option 2 involves repartitioning etc so I'd like to avoid that, and option 3 is pretty ugly and tedious to work with. So I would like to know, if I go with option 1, what am I missing out on by not using a low-latency kernel for music production? (both in general, and w.r.t. the linux toolchain in particular)?If I choose to use a generic kernel for music production, what side-effects, problems can I expect that a low-latency kernel is supposed to solve? Will I not be able to use JACK effectively? Will I be able to record? Will there be a lag in my recordings? Noise / skips / screetches? Will midi input accuracy via piano keyboard suffer?PS. This question is crossposted from music.SE as per a comment there suggesting this may be a more appropriate forum. I'd be interested in people's opinion here on whether a linux workflow for music production is a suitable topic for this forum. | Linux music production workflow without a low-latency kernel | linux;linux mint;linux kernel;music | null |
_unix.291370 | I have been reading about performance tuning of Linux to get the fastest packet processing times when receiving financial market data. I see that when the NIC receives a packet, it puts it in memory via DMA, then raises a HardIRQ - which in turn sets some NAPI settings and raises a SoftIRQ. The SoftIRQ then uses NAPI/device drivers to read data from the RX Buffers via polling, but this is only run for some limited time (net.core.netdev_budget, defaulted to 300 packets). These are in reference to a real server running ubuntu, with a solarflare NICMy questions are below:If each HardIRQ raises a SoftIRQ, and the Device Driver reads multiple packets in 1 go (netdev_budget), what happens to the SoftIRQs raised by each of the packets that were drained from the RX buffer in 1 go (Each pack received will raise a hard and then soft irq)? Are these queued? Why does the NAPI use polling to drain the RX_buffer? The system has just generated a SoftIRQ and is reading the RX buffer, then why the polling?Presumably, draining of the RX_Buffer via the softirq, will only happen from 1 specific RX_Buffer and not across multiple RX_Buffers? If so, then increasing the netdev_budget can delay the processing/draining of other RX_buffers? Or can this be mitigated by assigning different RX_buffers to different cores?There are settings to ensure that HardIRQs are immediately raised and handled. However, SoftIRQs may be processed at a later time. Are there settings/configs to ensure that SoftIRQs related to network RX are also handled at top priority and without delays? | SoftIRQs and Fast Packet Processing on Linux network | linux;networking;network interface;high performance | null |
_unix.153484 | I am installing this tool to Debian GNU/Linux 7.5 x64 (wheezy) and when I run install_mnemosyne.sh I get this error when the pycrypto installation is running: Downloading/unpacking pycrypto (from -r requirements.txt (line 8)) Downloading pycrypto-2.6.1.tar.gz (446kB): 446kB downloadedCleaning up...Exception:Traceback (most recent call last): File /opt/mnemosyne/env/local/lib/python2.7/site-packages/pip/basecommand.py status = self.run(options, args) File /opt/mnemosyne/env/local/lib/python2.7/site-packages/pip/commands/instal requirement_set.prepare_files(finder, force_root_egg_info=self.bundle, bundl File /opt/mnemosyne/env/local/lib/python2.7/site-packages/pip/req.py, line 1 do_download, File /opt/mnemosyne/env/local/lib/python2.7/site-packages/pip/req.py, line 1 self.session, File /opt/mnemosyne/env/local/lib/python2.7/site-packages/pip/download.py, l unpack_file(temp_location, location, content_type, link) File /opt/mnemosyne/env/local/lib/python2.7/site-packages/pip/util.py, line untar_file(filename, location) File /opt/mnemosyne/env/local/lib/python2.7/site-packages/pip/util.py, line destfp.close()IOError: [Errno 28] No space left on deviceStoring debug log for failure in /root/.pip/pip.logBut df -i shows this:Filesystem Inodes IUsed IFree IUse% Mounted onrootfs 85344 20381 64963 24% /udev 214285 350 213935 1% /devtmpfs 216800 287 216513 1% /run/dev/disk/by-uuid/aa26072b-e0f4-4962-ba44-76d5e65346de 85344 20381 64963 24% /tmpfs 216800 3 216797 1% /run/locktmpfs 216800 2 216798 1% /run/shm/dev/sda9 35323904 576 35323328 1% /home/dev/sda8 97536 270 97266 1% /tmp/dev/sda5 549440 57132 492308 11% /usr/dev/sda6 183264 8085 175179 5% /varand du -sh /*:6,0M /bin16M /boot0 /dev3,5M /etc14M /home0 /initrd.img94M /lib12K /lost+found3,0K /media1,0K /mnt158M /opt19M /pokus0 /proc294K /root808K /run5,6M /sbin1,0K /selinux1,0K /srv0 /sys6,7M /tmp1,7G /usr2,2G /var0 /vmlinuzIf I run df -i during installation increase is about 1%: Filesystem Inodes IUsed IFree IUse% Mounted on rootfs 85344 20381 64963 25% / udev 214285 350 213935 1% /dev tmpfs 216800 287 216513 1% /run /dev/disk/by-uuid/aa26072b-e0f4-4962-ba44-76d5e65346de 85344 20381 64963 25% / tmpfs 216800 3 216797 1% /run/lock tmpfs 216800 2 216798 1% /run/shm /dev/sda9 35323904 576 35323328 1% /home /dev/sda8 97536 270 97266 1% /tmp /dev/sda5 549440 57132 492308 11% /usr /dev/sda6 183264 8085 175179 5% /varBut df -h:Filesystem Space Used Free Use% Mounted onrootfs 323M 311M 0 100% /udev 10M 0 10M 0% /devtmpfs 406M 832K 405M 1% /run/dev/disk/by-uuid/aa26072b-e0f4-4962-ba44-76d5e65346de 323M 311M 0 100% /tmpfs 5,0M 0 5,0M 0% /run/locktmpfs 2,4G 0 2,4G 0% /run/shm/dev/sda9 531G 211M 504G 1% /home/dev/sda8 368M 18M 332M 5% /tmp/dev/sda5 8,3G 1,9G 6,0G 24% /usr/dev/sda6 2,8G 2,3G 402M 85% /varSo how can I expand rootfs please? | Install of pycrypto [Errno 28] No space left on device | debian;software installation | Based on the output of your df commands you're running out of disk space on your root partition, which is the reason why installing your software package fails with the descriptive error: IOError: [Errno 28] No space left on device.Try installing your software in larger partition like /usr with sufficient empty space instead of /opt which is on your tiny and full rootfs. Regardless your solution should at least consist of creating some free space on the root filesystem, as a full rootfs is bad. The majority of the majority of the root filesystem seems to be occupied by the contents of /opt, maybe you can move that directory to another partition and create a symlink in its place?Because you're using hard partitions and not something more flexible like LVM resizing the root partition appears a bit difficult, so I don't have an easy solution at hand. You have a sizeable disk (600GB or larger even based on /home), why did you limit the root filesystem to 300 MB in the first place? |
_opensource.5422 | I am using a library that is under the MIT license. I never used a library that I needed to include the license before, so I have no idea where to add them. I read that I should add them in my file, but the thing is my project is a site constituting of php files, is there a certain file that I need to add the license to or all the files? Also what should I add? The project came with a LICENSE.txt file and contains text.The project I am using is jsModal. | Using an MIT licensed library in my project | licensing;mit | I am not a lawyer, but here are my recommendations.The main requirement of the MIT license can be found on the jsModal license pageThe above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.If your project is a website, you should state that you are using jsModal that it is licensed under the MIT license. You need to make the entire text of the jsModal license page (including the copyright information) available directly on your site. I do NOT think a simple hyperlink the the jsModal page is sufficient. The text must be a part of your web site.If the web site is the only place you are using jsModal, you do not need to add any licensing information to any other files. A single page stating you are using jsModal with the entire text of the MIT license is sufficient.Edit:You should make sure that this license/copyright information is visible to the end user. Typical users won't look at your code comments, so code comments by themselves are not sufficient. You only need a single page for this license & copyright information. You don't need to add it to every page of your website. |
_webmaster.88348 | I have 2 domains let say redd.it and reddit.com.Now how might I let google index the reddit.com but have users browse redd.it?The purpose of this would allow the address bar to be shorter and automatically give the users a shorter domain(although not technically a url shortner) while allowing Google to use reddit.com for indexing and Google links. As explained here it appears country code extensions are penalized(not exactly but being ccTLD certainly hurts you results outside your specific country).They only way I could see this working is 2 sites with duplicate, but I'm not quit sure if this would work. Would duplicate sites decrease ratings for one or the other site?How might I display a short domain in address bar while indexing and displaying the reddit.com link on Google? | Display short domain (country code) in the address bar while still having the site served on a global .com | indexing;google index | null |
_softwareengineering.83929 | I need to implement flexible AND simple (if such thing exist) and at the same time utilize built-on means if possibleSo far I have MembershipProvider and RoleProviders implemented. This is cool but where do I go next? I feel like I need to add term Priviledge and than hardcode those inside application. Users will configure roles to add Privilidges to Roles and assign Roles to users.Does that sound like a good model? Should I think about adding priviledges at User level on top of adding them to Roles? I might but I envision problems with setup (confusing) and following support. If I don't do that and some specific users will need lesser priviledges - admin will have to create another role, etc.. Any silver bullet for system like this? And why Microsoft didn't go further then just Membership and Role providers?Another idea:Leave Roles as priviledge holder and hardcode them. Then I can code to those roles inside app using all available markups/attributes, etc - all Microsoft.Add new entity Group and create relationship like thisUsers UserGroups Groups RoleGroupsRolesThis way I can collect Roles into groups and assign those groups to Users. Sounds great and matches other software patterns. But then I can't really implement things inside RoleProvider like:AddUsersToRolesRemoveUsersFromRolesAnd some things do not really make sense anymore because they will be hard-codedDeleteRole CreateRole | Permissions/right model/pattern for .NET application | design patterns;security | If role-based authorization isn't granular enough for you then consider using Claims-Based Authorization.A claim describes a resource and activity - sort of like an entry in an ACL, but more flexible, because the resource doesn't have to be a physical object, it can be anything you want it to be and can contain any information you want.In this model, a claim is equivalent to what you call a privilege, and you group claims into claim sets, which is roughly equivalent to what you're calling a role. All of these APIs and more are already in the System.IdentityModel namespace.Of course you mention MembershipProvider and RoleProvider and if you are trying to cram this all into the ASP.NET membership model (as those names imply), then just forget about it. If you want to use those provider APIs then you have to do it their way, and their way does not get any more granular than the concept of a role.Instead, in ASP.NET, the concept of a privilege is actually encoded at the action or operation level, where you declare which roles are allowed to execute that action. This is really a lot easier to deal with in ASP.NET MVC where you just slap an [AuthorizeAttribute] on controllers or controller actions; in old-school ASP.NET, you're handling events, so authorization either tends to be either ad-hoc or at the page level (or both). |
_unix.340693 | My router has a public IP and my computer is in my LAN. So naturally I'm going to masquerade outbound(me -> Internet) traffic to make it possible to access the Internet. My settings:(I can't embed images yet...so please follow the link)Pic: Firewall Zone SettingsIn the picture, if I uncheck Masquerading in the second line, I'll lose my access to the Internet. And through iptables-save I found that the MASQUERADE target for the chain zone_nat_wan in the table nat is gone.So here's my question: doesn't wan lan mean the traffic from WAN to LAN? If not, what does it mean?P.S. My router runs OpenWrt Attitude Adjustment 12.09. | Confused about OpenWRT's Firewall Zone Settings Definition | networking;openwrt;router | It depends(tm). The WAN Zone (WAN->LAN in your example) is about traffic from WAN to LAN for Forward (established connections), from LAN to WAN for Output and from WAN to LAN (all other packets) for Input. Masquerading is applied on outgoing packets of a specific interface by setting the source address of that packet to the interface address and using conntrack to save the state, therefore the developers opted to interpret this as Masquerade WAN = Masquerade outgoing packets on the WAN interface. Of course one can argue that it would make more sense to enable masquerading on the LAN interface, since this is the network that is being masqueraded, so it's more a matter of perspective. |
_cs.14419 | Consider the following sequence $a_n$:\begin{align*} a_0 &= \alpha \\ a_k &= \beta a_{k-1} + \kappa\end{align*}Now consider the implementation of this sequence via lisp:(defun an (k) (if (= k 0) alpha (+ (* beta (an (- k 1))) kappa)))What is the running time to compute (an k) just as it is written? Also, what would be the maximum stack depth reached? My hypothesis would be that both the running time and stack depth are $O(k)$ because it takes $k$ recursive calls to get to the base case and there is one call per step and one stack push per step.\.Is this analysis corect? | Running time and stack depth of a lisp recurrence | algorithm analysis;programming languages;recurrence relation | The time and other resources (such as stack consumption) needed to run an with the argument $x \in \mathbb{N}^*$ is the sum of:the resources needed to compute (- k 1) with k bound to $x$;the resources needed to compute an with the argument $x-1$;the resources needed to compute (if (= k 0) alpha (+ (* beta$y$`) kappa))` where $y$ is the value returned by the recursive call to an.Let $T(x)$ be the running time of this computation. For $x \gt 0$, by the analysis above, $T(x) = T(x-1) + C$ for some constant $C$ (assuming that the arithmetic operations take constant time). A very simple induction shows that $T(x) = C \, x + T(0)$, i.e. $T(x) = \Theta(x)$. The same goes for stack consumption.There is more than one stack push per recursive call, (3 in a naive interpreted Lisp such as Emacs Lisp), but that doesn't affect the $O$ or $\Theta$ analysis. Other than this minor detail your analysis is correct.Are you sure that you typed the right code? Emacs has a fairly low limit on stack usage but even it can sustain more recursive calls (up to 123 in Emacs 23 where max-lisp-eval-depth is 500). |
_unix.193638 | Let's say we have a string and its delimiter is ?:Leslie Cheung April 1 ? Elvis August 16 ? Leonard Nimoy February 27I know how to grep the first substring between delimiters:echo $above_string | grep -oP ^[^?]*Leslie Cheung April 1How should I change the Regex in order to grep the second or third substring? | How to grep the n-th substring between given delimiters? | command line;grep;regular expression | echo $above_string | grep -oP ^([^?]*\?){2}\K[^?]*Change 2 to the n - 1 value in order to obtain the nth string.This assumes that you want the nth string in that line. You have n - 1 strings with no ? ending with a literal '?' (\? since it's a special character in perl regex). Then with \K you state you are not interested in the previous contents, thus extracting just the following text until the next separator. |
_softwareengineering.319264 | My question: is there a canonical way of creating a dictionary of dictionaries and providing an outer/inner key pair? Is there a NugetPackage out there with an implementation?In my code, I have now a few places where I have a property like thisprivate readonly IDictionary<string, IDictionary<string, SomeType>> _nestedDict = new Dictionary<string, IDictionary<string, SomeType>>();and I've created extension methods like thispublic static V AddOrUpdate<T, U, V>( [NotNull] this IDictionary<T, IDictionary<U, V>> dictionary, [NotNull] T outerKey, [NotNull] U innerKey, [NotNull] Func<V> addValueFactory, [NotNull] Func<V, V> updateValueFactory, [CanBeNull] IEqualityComparer<U> innerDictionaryComparer = null){ IDictionary<U, V> dict; if (dictionary.TryGetValue(outerKey, out dict)) { V currentValue; if (dict.TryGetValue(innerKey, out currentValue)) { var updatedValue = updateValueFactory(currentValue); if (!object.ReferenceEquals(updatedValue, currentValue)) dict[innerKey] = updatedValue; return updatedValue; } var addedValue1 = addValueFactory(); dict[innerKey] = addedValue1; return addedValue1; } var addedValue = addValueFactory(); if (innerDictionaryComparer != null) dictionary[outerKey] = new Dictionary<U, V>(innerDictionaryComparer) {{innerKey, addedValue}}; else dictionary[outerKey] = new Dictionary<U, V> {{innerKey, addedValue}}; return addedValue;}This is powerful, but I'm starting to feel like I should just make a class for nested dictionaries. Here's my thinking:The addValueFactory and updateValueFactory are sort of clumsy and it feels like it's breaking OO principles.I am thinking about creating a ConcurrentDictionary of Dictionarys (or perhaps of ConcurrentDictionarys), and this would require some more extension methods. I sort of thought if I'm using it this much that I should just create the darn class and be done with it.What say you? | Dictionary of dictionaries design in C# | c#;class;dictionary | null |
_scicomp.5551 | I was reading this paper related to Multiclass Classication withMulti-Prototype Support Vector Machines - paperHowever, I am having difficulty in understanding why they have mentioned the following problem non convex.I am really struggling figuring out the convexity/concavity of the functions. Can anyone just skim through the paper to help me out. The paper is about SVM (multi class classification) where each class can have multiple weight vectors/prototypes. | Confusion related to convexity of a problem | machine learning;support vector machines | Sounds too simple so maybe I've misunderstood you, but they have binary variables, hence obviously a nonconvex problem (a binary variable is either 0 or 1, which is a nonconvex set) |
_softwareengineering.355414 | I understand Web API. I understand websites, how they call a web API and all the good stuff. My question is, how do you control the user view in the website consuming the API, based on the API permissions. The goal would be to not have the view in the website if the user is not authorized to preform such action. Not just do a trick and hide it the HTML (Tech-savey user can see html code for actions/data forms they shouldn't).Simplified Scenario: User has access to API to create other users, but not delete. They can technically send the delete verb to the URI, but they would get access denied. The goal would be for the HTML website to not show the delete option in the first place, as they cannot preform the action anyway. As well as no way of knowing via the website HTML/JS to see where the delte option is/how it works (Of course the delete view shows to users with that permission set)Idea's:Have API support sending the HTML code for views on the site based off permissions. -Not a big fan of this as I feel it sorta breaks the idea of the API. What if I need to do something similar on a mobile app?Use server side code as intermediary to call the API and build the view. -Im not sure about this because I feel it will require a redundant amount of work, but may be the best option.I am using c# .net for this, if that matters. Preferably strictly HTML JS for the website, but don't believe thats possible unless sending HTML from the API. | Consuming Web API in website with role based views | c#;javascript;api;asp.net;html | The goal would be to not have the view in the website if the user is not authorized to preform such action. Not just do a trick and hide it the HTML (Tech-savey user can see html code for actions/data forms they shouldn't).I agree with you. That would be the ideal case to me too. However, I consider this to be implementation details. There's nothing wrong in hidding the HTML code, as soon as the API implements authorization and authentication.A tech-savey doesn't need to look into the code. For example, he/she can track the browser connections and try for each URI of the API, different HTTP methods. Basically, he/she can bypass the client and attack the API from any other application (curl, Postman, java client, etc...)how do you control the user view in the website consuming the API, based on the API permissionsAnyways, if the API stick with REST, there should be possible for us to achieve what we want. What we need first is to know what actions are we allowed to perform. This should be possible with the method OPTIONS. 1AuthorizedOPTIONS /rest/api/product HTTP/1.1Host: example.netAuthentication: ...HTTP/1.1 200 OK Allow: HEAD,GET,DELETE,OPTIONSUnauthorizedOPTIONS /rest/api/product HTTP/1.1Host: example.net HTTP/1.1 401 UnauthorizedThis is easier to say than done. It might result in many more calls to the API than the initially expected.A way to solve the previous problem with OPTIONS could be implementing HATEOAS. In other words, we could make the API more descriptive.Implementing HATEOAS the API response doesn't only provides resource representations. It also provides links to more resources. Links can be as descriptive as we deem it appropriated. For example, look at the PayPal API model.The view would populate its controls according with the links. No link, no control (button, form, etc.)Regarding your ideas, I agreed too. I would not mix API and views. Every client has its own concerns and these concerns -IMO- should be addressed independently. The more agnostic is the API to these problems, the better.As well as no way of knowing via the website HTML/JS to see where the delte option is/how it works (Of course the delete view shows to users with that permission set)I will assume that we already solved the problem with the HTML block. According with your conocerns, the user still could look at the JS code. Yes, and we can obfuscate the code too.On the other hand, if we don't want users bulding their own clients, we can (should) provide them one. For example, like Google does.1: According with the Allowed methods, we decide what to do. Just remember that Javascript can hide DOM elements by altering styles, but it can also add/remove elements dynamically too. |
_unix.211416 | I have file1.txt with string values such asNew Drug ApplicationDrug ProductDosing instructionsI need to count how often these strings occur in file2.txt with data such asRegulatory New Drug Application for Drug Product after testing of Dosing instructions for all new studies.The commands I have used are;foreach string ( `cat terms.txt` )foreach? echo $string >>out.txtforeach? grep $string data.txt | wc >>out.txtendThe out.txt will not return the complete string with spaces. Instead it returns data such as:The -1New -2Application -1etc.I have tried adding quotes and forward slashes to the terms in my data files, egrep, fgrep - to no avail. How do I get the data I want from these two files? | Find strings in file1, count occurrences in file2 | shell script;search;string | null |
_softwareengineering.133020 | What is your methodology when you need to determine the cost of UI design if you know the cost (work hours) of programming in some project?Let's say, programming of logic in some project cost X dollars. Is there some general percentage (like 30% of programming costs) which can help determine the cost of design?The area of interest is mobile phones development (mainly business tools and 2D games, not 3D at all). There is less design work here comparing to a web design or a PC game design. | Cost of design based on the cost of programming | programming languages;business;user interface | There is no such percentage. In the same way, there is no percentage of time you'll work on security, for example. One application must be secure and will require half of your staff to work on it. Another application doesn't have any security concerns, so the impact on your schedule will be minimal.The time required to do visual design depends on the requirements. It's not about the type of software (you quoted business tools, web applications and games).If my customer doesn't care about visual design of a website, I'll spend a few hours creating something basic, and use the remaining two months of work for other, more important aspects.If my customer cares about user interaction, I'll spend a few weeks creating carefully the different aspects of interaction design, polishing the visual aspect, etc., while caring less about the aspects which don't matter for this customer for this project.In both cases, it's still a web application.In general, you have two ways to group tasks when creating an application.The first one is sequential: it's the states you need to do in order to achieve success in your project. You start by gathering functional and non-functional requirements, you work on the specification, architecture and application design, you create tests, you write the actual code, you deploy and maintain the application.Here, depending on the level of seriousness and the scale of the project, you have the similar percentages from project to project. For a home-made tiny application, you'll always have 0% to 5% for requirements. For a large-scale enterprise application requiring exemplary QA, the time you'll actually write code will be 15% to 20%.The second one is parallel: it's the things you have to do, given that they are nearly independent from the point of view of project management and the things you may do or skip. It includes security, visual design, portability, performance, etc.Here, percentages are irrelevant. It's more a question of priorities, not the scale of the application and the required QA level. A business app may have an outstanding user experience, because the stakeholders know that the project will fail otherwise or that the UX is a competitive edge. Another business app may have nearly no design at all, because there is nothing to innovate in terms of design. |
_unix.334344 | I have a command for bashfind /any/directory/ -type f -printf %f\n >> data.txtthat a put all filenames, (as example 5r32a.xml and 5r343.xml) present in specified directory, to data.txt. I want to add filenames (using a command) in order to such code in .txt, for example:cat ../raw_orig/5r32a.xml tmp_file ../raw_orgg/bab-aux-cal.xml > ./5r32a.xmlcat ../raw_orig/5r343.xml tmp_file ../raw_orgg/bab-aux-cal.xml > ./5r343.xml# And etcHow can I do this using terminal? How can I specify the row and column? | Batch, add filenames to txt in bash | bash;text;printf | This is what you are looking for.find /any/directory/ -type f -printf cat ../raw_orig/%f tmp_file ../raw_orgg/bab-aux-cal.xml > ./%f\n >> data.txt |
_unix.168640 | Due to a bug in another script, there were 1000's of mails in var/spool/mqueue.I read somewhere that one should delete /var/spool/mqueue to prevent the messages from being sent.Unfortunately, after doing so it seems that sendmail can't send mail! When I tried to send mail, I would never receive it.Running mailq gave the following output:MSP Queue status... /var/spool/mqueue-client (4 requests)-----Q-ID----- --Size-- -----Q-Time----- ------------Sender/Recipient-----------sAID7J0d003724 13 Tue Nov 18 13:07 me (Deferred: 421 4.3.0 collect: Cannot write ./dfsAID7JS9003725) [email protected] 15 Tue Nov 18 13:09 me (Deferred: 421 4.3.0 collect: Cannot write ./dfsAID99Xx003776) [email protected] 116 Tue Nov 18 13:07 me (Deferred: 421 4.3.0 collect: Cannot write ./dfsAID7sQr003749) [email protected] 117 Tue Nov 18 13:06 me (Deferred: 421 4.3.0 collect: Cannot write ./dfsAID6Qda003701) [email protected] Total requests: 4MTA Queue status.../var/spool/mqueue is empty Total requests: 0me@mycomp:/var/spool/mqueue$ How do I fix this ?EDIT: I normally send mail by doing: echo My message | sendmail [email protected] | What to do if you accidentally delete /var/spool/mqueue | ubuntu;email;sendmail | null |
_cs.72214 | I read somewhere that the Apollo Guidance Computer was designed in such a way, that, although it is hugely less powerful than the average smartphone, it was dependable to the point that it never crashed. My questions pertaining to this were:Is designing such a digital system possible, even in the '60's ?What are the constraints that one would want to look out for when attempting to design such a digital system that never crashed, using today's technology? | How does one go about designing a system that never crashes? | computer architecture | null |
_webmaster.5230 | I have a site hosted at: http://41.223.52.100/ which i used jbar to display certain text on the page. The same page looks great in Firefox & google crome but not in IE8, Can't figure-out why! Please share your kind inputs, on this.Thanks. | Same page looks great in Firefox & crome But Not in IE8 | php;internet explorer;firefox;javascript;jquery | Position should be absolute in the message id tag, not fixed. As for the rounded corners, it is currently not supported in IE. |
_unix.338330 | I wrote the following code to determine which files a program writes to. I want to capture the filenames of course. strace -f -t -e trace=file -p 8804 2>&1 | grep -oP \(.*)\.*O_WRONLYThis outputs something like/tmp/11111111.txt, O_WRONLYThe problem is I can't pipe the output of all this to any commandstrace -f -t -e trace=file -p 8804 2>&1 | grep -oP \(.*)\.*O_WRONLY | echo# does not show anythingAnd also I can't save the output of all this for later use:strace -f -t -e trace=file -p 8804 2>&1 | grep -oP \(.*)\.*O_WRONLY > asd.out# file is emptyYour help is appreciated. :) | Grepping strace output gets hard | grep;pipe;strace | You can write the output to a file (with strace -o asd.out) and then grep it:From strace manual:-o filename Write the trace output to the file filename rather than to stderr. Use filename.pid if -ff is used. If the argument begins with`|' or with `!' then the rest of the argument is treated as a commandand all output is piped to it. This is convenient for piping thedebugging output to a program without affecting the redirections of executed programs. |
_scicomp.1574 | I'm simulating two phase immiscible drainage (air displacing water) in a rectangular domain of size .6mm x 2.4mm (2 dimensions) using Ansys FLUENT software. I am using an implicit Volume of Fluid formulation with a PRESTO pressure solver and PISO pressure-velocity coupling, with 2nd order upwind schemes for momentum and volume fraction. The problem is that even with a highly refined mesh, my scheme diverges very quickly (within the first few timesteps, using an algebraic multigrid solver). When I try taking smaller timesteps (about $10^{-6}$ s), the solution takes a lot longer to diverge, but still diverges nonetheless.I'm not sure if the problem is with the choice of solver itself or if the boundary conditions were not set correctly. I chose to use a constant inlet velocity of .0001m/s, and zero pressure conditions at the outlet. I used no-slip boundary conditions at the other two walls, with wall adhesion and a constant air-to-water contact angle of 135 degrees. Any help with this would be greatly appreciated! :) | What numerical methods are recommendable for simulating two phase immiscible fluid flow through a pipe with high capillary pressure? | linear solver;fluid dynamics;boundary conditions | It sounds like you are using Ansys Fluent. As I recall from some VOF articles most of them were using projection methods with explicit time stepping. If you are using Fluent you could try finding Non-iterative time advancement (NITE) option for time stepping.I would also suggest you trying to write your own solver! There are really good algorithms that you could try in that case. One of those is Moment of fluid (MOF) interface reconstruction developed by researchers from LANL. Here are some links that might be helpful:A paper from Int. J. Numer. Methods in Fluids, and a short note about the method from LANL web site |
_unix.157689 | I have explored almost all available similar questions, to no avail.Let me describe the problem in detail:I run some unattended scripts and these can produce standard output and standard error lines, I want to capture them in their precise order as displayed by a terminal emulator and then add a prefix like STDERR: and STDOUT: to them.I have tried using pipes and even epoll-based approach on them, to no avail. I think solution is in pty usage, although I am no master at that. I have also peeked into the source code of Gnome's VTE, but that has not been much productive. Ideally I would use Go instead of Bash to accomplish this, but I have not been able to. Seems like pipes automatically forbid keeping a correct lines order because of buffering.Has somebody been able to do something similar? Or it is just impossible? I think that if a terminal emulator can do it, then it's not - maybe by creating a small C program handling the PTY(s) differently?Ideally I would use asynchronous input to read these 2 streams (STDOUT and STDERR) and then re-print them second my needs, but order of input is crucial!NOTE: I am aware of stderred but it does not work for me with Bash scripts and cannot be easily edited to add a prefix (since it basically wraps plenty of syscalls).Update: added below two gistsExample program that generates mixed stdout/stderrExpected output from program above(sub-second random delays can be added in sample script I provided to prove a consistent result)Update: solution to this question would also solve this other question, as @Gilles pointed out. However I have come to the conclusion that it's not possible to do what asked here and there. When using 2>&1 both streams are correctly merged at the pty/pipe level, but to use the streams separately and in correct order one should indeed use the approach of stderred that involes syscall hooking and can be seen as dirty in many ways.I will be eager to update this question if somebody can disproof the above. | How to capture ordered STDOUT/STDERR and add timestamp/prefixes? | bash;shell;io redirection;pipe | null |
_softwareengineering.1849 | If you've always loved unit testing, good for you! But for the unfortunate ones who weren't born with a liking for it, how have you managed to make this task more enjoyable ? This is not a what is the right way to unit test question. I simply want to know little personal tricks that reduce the boredom (dare I say) of writing unit tests. | How have you made unit testing more enjoyable? | productivity;unit testing | Firstly, I agree with you - if you are writing your unit tests on already completed code, or you are manually unit testing your code, I find that extremely boring too.I find there are two ways of unit testing for me that really make it enjoyable:By using Test Driven Development (TDD) - writing the tests first allows me to think about the next piece of functionality or behaviour that I need in my code. I find driving towards my end goal in tiny steps and seeing tangible progress towards that goal every few minutes extremely rewarding and enjoyable.When there are bugs, rather than going straight to the debugger, it's a fun challenge to figure out a way to write a failing unit test that reproduces the bug. It's extremely satisfying to finally figure out the circumstances that make your code fail, then fix it and watch the bar turn green for the new failing test (and stay green for all of your existing tests). |
_codereview.60026 | By adding more and more features to my websites, I am now up to 7 different hard coded queries.I have read a lot about SQL injections and possible flaws and security issues, and wanted to make sure that it was secure enough.This is one of my regular UPDATE queries :Using thisConnection As New OleDbConnection(Provider=Microsoft.ACE.OLEDB.12.0;Data Source=Striped Source) Using thisCommand As OleDbCommand = thisConnection.CreateCommand ' Open connection object thisConnection.Open() ' Initialize SQL UPDATE command to update the desired data With thisCommand .CommandText = UPDATE Login SET ClientName = @ClientName, Fonction = @Fonction, CompanyName = @CompanyName, Address = @Address, Country = @Country, & _ [Phone Number] = @Phone, [Fax Number] = @Fax, [I prefer to be contacted] = @Contacted & _ WHERE Username = @Username With .Parameters .AddWithValue(@ClientName, VB_Name) .AddWithValue(@Fonction, VB_Fonction) .AddWithValue(@CompanyName, VB_Company) .AddWithValue(@Address, VB_Address) .AddWithValue(@Country, VB_Country) .AddWithValue(@Phone, VB_Phone) .AddWithValue(@Fax, VB_Fax) .AddWithValue(@Contacted, VB_Preference) .AddWithValue(@Username, LBL_Welcome.Text) End With End With thisCommand.ExecuteNonQuery() thisConnection.Close() End UsingEnd UsingAnd this is one of my non-regular double SELECT queries (Lengthy) :Using thisConnection As New OleDbConnection(Provider=Microsoft.ACE.OLEDB.12.0;Data Source=Striped source) Using thisCommand As OleDbCommand = thisConnection.CreateCommand thisConnection.Open() 'This query is to get the information thisCommand.CommandText = SELECT [Minimum Length] & _ FROM Stats & _ WHERE ([N Cylinder] = @cylinder) AND ([N Section] = 0) thisCommand.Parameters.AddWithValue(@cylinder, cylinder Dim thisReader As OleDbDataReader = thisCommand.ExecuteReader() If (thisReader.Read()) Then cylinderLengthMin = thisReader.GetValue(0) End If thisReader.Close() 'This query is to get the number of stages of the cylinder thisCommand.CommandText = SELECT Stroke & _ FROM (Stats) & _ WHERE ([N Cylinder] = @cylinder) & _ ORDER BY [N Section] thisCommand.Parameters.AddWithValue(@cylinder, cylinder) thisReader = thisCommand.ExecuteReader() count = -1 Dim condition As Boolean = True Dim temp As String 'This loop gets the strokes of the stages While (thisReader.Read()) And condition temp = thisReader.GetValue(0).ToString() If thisReader.GetValue(0).ToString() = Then condition = False Else count += 1 End If End While countMax = count 'This is used later for array formatting thisReader.Close() If countMax = -1 Then Throw New SQLException(There has been an error with the database query.) End If 'This query is to gather the data. It is stored in Imperial in the DataBase. ReDim cylinderOutsideDiameter(countMax) ReDim cylinderInsideDiameter(countMax) ReDim cylinderSectionStroke(countMax) ReDim cylinderSectionRetracted(countMax) ReDim cylinderIDStopRing(countMax) thisCommand.CommandText = SELECT Stroke, [Retracted Length], [Inside Diameter], [Outside Diameter], [Non-contact Diameter] & _ FROM (Stats) & _ WHERE ([N Cylinder] = @cylinder) & _ ORDER BY [N Section] thisCommand.Parameters.AddWithValue(@cylinder, cylinder) thisReader = thisCommand.ExecuteReader() count = 0 While (thisReader.Read()) AndAlso count <= countMax 'Scans each row and adds it to respective string/double array For i = 0 To 4 If thisReader.GetValue(i).ToString() = Then Throw New SQLException(There has been an error with the database query.) End If Next cylinderSectionStroke(count) = thisReader.GetValue(0) cylinderSectionRetracted(count) = thisReader.GetValue(1) cylinderInsideDiameter(count) = thisReader.GetValue(2) cylinderOutsideDiameter(count) = thisReader.GetValue(3) cylinderIDStopRing(count) = thisReader.GetValue(4) count += 1 End While thisReader.Close() thisConnection.Close() End UsingEnd UsingQuestionsAre my SQL queries secure?Should I make a function for the queries (as I am up to 7 queries now and I should never repeat the same code multiple times). If yes, how? (I'm not asking for a code dump, just a descriptive explanation on how I could do it would be awesome)If there is anything I could improve in the code, don't hesitate. I would love to have feedback on how to improve it. | Security issues in a SQL query and possible function? | security;vb.net;ms access | Make your code DRY (don't repeat yourself). Extract out your whole code of data retrieving to helper classCommandBehavior.CloseConnection will avoid closing the connection so you need to explicitly close the connection. so use using keyword for VB. it will close the connection automatically you are using parameterized query so it will make your SQL safer in case of SQL Injection.Public Shared Function ExecuteReader(ByVal commandtext As String, ByVal parameters As Dictionary(Of String, Object)) As IDataReader Using thisConnection As New OleDbConnection(Provider=Microsoft.ACE.OLEDB.12.0;Data Source=Striped source) Using thisCommand As OleDbCommand = thisConnection.CreateCommand thisConnection.Open() thisCommand.CommandText = commandtext For Each parameter In parameters thisCommand.Parameters.AddWithValue(parameter.Key, parameter.Value) Next 'CommandBehavior.CloseConnection will avoid closing the connection so you need to explicity close the connection Return thisCommand.ExecuteReader(CommandBehavior.CloseConnection) End Using End UsingEnd FunctionPublic Function HowToUseExecuteReader() Dim parameters As New Dictionary(Of String, Integer) parameters.Add(@cylinder, cylinder) Dim query As String = SELECT [Minimum Length] FROM Stats WHERE ([N Cylinder] = @cylinder) AND ([N Section] = 0) Dim dataReader As IDataReader = ExecuteReader(query, New Dictionary(Of String, Object)) Using dataReader While dataReader.Read Dim cylinderLengthMin = dataReader.GetValue(0) End While End UsingEnd Function |
_cs.44149 | Suppose we have the graph of a social network with symmetric connections (e.g. Facebook or LinkedIn). Suppose we would like to find all pairs of people who have at least k friends in common, in order to show them friend recommendations.What is the most efficient way to do this? Does this problem have a name?Apart from the naive solution (check all pairs - complexity $O(N^2 d)$ where $d$ is the average degree), the best I could come up with is the following:For every vertex, gather all pairs of its neighbors. The current vertex is one of their friends in common.Count pairs that occur more than k times.The complexity is something like $O(N d^2)$ which is strictly better.It seems that there should be a more efficient solution (though obviously not better than $O(N^2)$ in the worst case), but I can't see any particular structure in the problem pointing toward it. | Computing the at least k friends in common graph | algorithms;graph theory;graphs;social networks;network analysis | null |
_codereview.146247 | I wrote this MATLAB/Octave function to use along with the Bayes Classifier.Is this the correct approach? Is the following logic correct?if(feat>1) mu = mean(train(clidx,feat)); sigma = std(train(clidx,feat));else mu = 1; sigma = 1;endpdfindep.mfunction pdfmx = pdfindep(train, test)classnb = rows(unique(train(:,1)));pdfmx = ones(rows(test), classnb);for cl=1:classnb clidx = train(:,1) == cl; indiv = zeros(rows(test), columns(test)); for feat=1:columns(test) %%strcat(num2str(clidx),',', num2str(feat)) if(feat>1) mu = mean(train(clidx,feat)); sigma = std(train(clidx,feat)); else mu = 1; sigma = 1; end indiv(:,feat) = normpdf(test(:,feat), mu, sigma); end pdfmx(:,cl) = prod(indiv,2);endTest data you can usetrain.txttest.txt | Finding the density of multidimensional random vectors (independence) | matlab;octave | null |
_unix.308927 | I'm trying to test if an archive has all its files. All I need to do is a simple unzip and then make. The shell keeps trying to interpret arguments like -aoq as a program. Other errors exist as well, but I'll spare readers each and every way not to do it. Here are some of the failed attempts:Failed:RESULT=$(unzip -aoq cryptopp563.zip -d $TMP/cryptopp563-zip/)if [[ $RESULT -eq 0 ]]; then ... fi;RESULT=$(unzip (-aoq cryptopp563.zip -d $TMP/cryptopp563-zip/))if [[ $RESULT -eq 0 ]]; then ... fi;RESULT=$(unzip (-aoq cryptopp.zip -d $TMP/cryptopp-zip/))if [[ $RESULT -eq 0 ]]; then ... fi;RESULT=$(unzip -aoq cryptopp563.zip -d $TMP/cryptopp563-zip/)if [[ $RESULT -eq 0 ]]; then ... fi;RESULT=$(unzip {-aoq cryptopp563.zip -d $TMP/cryptopp563-zip/})if [[ $RESULT -eq 0 ]]; then ... fi;RESULT=$(unzip (-aoq cryptopp563.zip -d $TMP/cryptopp563-zip/))if [[ $RESULT -eq 0 ]]; then...If I see one more question and answer that says just use parenthesis, just use quotes or just use curly braces I think I am going to scream...How do I call unzip with arguments so that Bash does not try to interpret the arguments as commands?Here's a couple of the more comical error messages:unzip: cannot find or open {-aoq cryptopp563.zip -d /tmp/cryptopp563-zip/}, {-aoq cryptopp563.zip -d/tmp/cryptopp563-zip/}.zip or {-aoq cryptopp563.zip -d /tmp/cryptopp563-zip/}.ZIP.unzip: cannot find or open (-aoq cryptopp563.zip -d /tmp/cryptopp563-zip/), (-aoq cryptopp563.zip -d/tmp/cryptopp563-zip/).zip or (-aoq cryptopp563.zip -d /tmp/cryptopp563-zip/).ZIP.Here are a few questions/answers that did not work for me. I'm fairly certain I have visited U&L.SE, Stack Overflow and Super User multiple times.Bash: convert command line arguments into arrayPassing arrays as parameters in bashhow to pass an array argument to the bash scriptPassing array values to command args | How to provide command arguments as an array? | bash;command;arguments | The first one:RESULT=$(unzip -aoq cryptopp563.zip -d $TMP/cryptopp563-zip/)should run unzip just fine, and drop its output to the variable RESULT. However, unzip doesn't print much in its standard output (well, unless with unzip -l), so I think you actually want the return value. Which can be found in $? after the assignment and command substitution, or just after running the program as normal:unzip -aoq cryptopp563.zip -d $TMP/cryptopp563-zip/if [ $? -eq 0 ] ; then echo ok ; fi(And yes, you could just if unzip ... ; then ....)You don't really have an array there, though, just a bunch of normal parameters to the command. This would make an array, print its length and pass it as arguments to unzip:A=(-aoq cryptopp563.zip -d $TMP/cryptopp563-zip/)echo ${#A[@]}unzip ${A[@]} # note the quotes |
_unix.128158 | I am trying to create a simple alias that will allow me to create a new screen and set its name simple by typing newscreen {screenname} where {screenname} is set at the prompt.For example, I would like to be able to create the following alias:alias newscreen='screen -D -R -S {screenname}'Then at the command prompt, type:$ newscreen clientThis would then start a new screen for me, and give it a name of clientThat way, I could resume the screen with screen -r client.Can someone point out to me the best way to do that.Thanks. | Set a screen session name at the command prompt | gnu screen | null |
_unix.105032 | Is there any way for me to symlink a particular file so that it appears in every directory on the system?So if I symlink /tmp/scratchNo matter where I am I can type vi scratch? | Symlink everywhere | command line;vim;symlink;vi | null |
_cs.69960 | According to Wikipedia,A $\rho$-approximation algorithm $A$ is defined to be an algorithm for which it has been proven that the value/cost, $f(x)$, of the approximate solution $A(x)$ to an instance $x$ will not be more (or less, depending on the situation) than a factor $\rho$ times the value, $OPT$, of an optimum solution.I am interested in a situation where we would like to measure the performance of $A$ by how often it finds the optimal solution. For example, the algorithm $A$ finds the optimal value $R$ % of the time and finds a strictly larger (or less) solution $100-R$ % of the time. What would such algorithm be called? Is this notion known in the literature? | What would you call an algorithm that finds $R$ % of the time the optimal solution to an NP-hard problem? | terminology;reference request | null |
_unix.354096 | I am installing a custom package to /opt/package_name, storing configuration files in /etc/opt/package_name and static files in /var/opt/package_name/static/ - all following the conventions suggested by FHS. [1] [2] [3]I also need to store some logfiles. I want them to be discoverable by analysis tools, so they should also be in a conventional location. Should these go in:/var/log/package_name (like a system package, even though this is a custom package)/var/opt/package_name/log (following the /var/opt convention - but is this discoverable?)something else? | Where should an /opt package write logs? | logs;fhs | I would place them in /var/log/package_name; it satisfies the principle of least surprise better than /var/opt/package_name/opt. I don't have a citation for this; it simply matches where I'd look for logs.I might also forego writing my own log files, and instead log to syslog with an appropriate tag and facility; if I'm looking for clean integration with established analysis tools, I don't believe I can do better for a communications channel:Every generic tool with log analysis as a listed feature already watches syslog.Log file release and rotation semantics are handled for me; I don't have to set up a mechanism for logrotate to tell me to let go of the file and open a new one. I don't even have to tell logrotate about new files to rotate!Offloading logs to central logging servers is handled for me, if the site demands it; Existing established tools like rsyslog will be in use if needed, so I don't have to contemplate implementing that feature myself.Access controls (POSIX and, e.g. SELinux) around the log files are already handled, so I don't need to pay as much attention to distribution-specific security semantics.Unless I'm doing some custom binary format for my log—and even then, I prefer syslog-friendly machine-parseable text formats like JSON—I have a hard time justifying my own separate log files; analysis tools already watch syslog like a hawk. |
_webmaster.100604 | I have user generated questions and answers on my site. Should we add https://schema.org/Question schema on this ?What would be the SEO implications of adding this schema ? Any example site that is using this schema and getting benefit would be of great help. | Does adding schema.org questions schema enhance SEO of my page? | seo;schema.org;rich snippets;google ranking | Simple answer is no... however additional information appearing in the serps can indirectly improve your SEO because people are more inclined to click things that shows additional information, particularly review stars as a good example.Obviously the more traffic your site receives the higher the chance of someone linking to the site or sharing it on social media which effectively increases your SEO directly, and naturally. SOURCEWhether structured data affects rankings has been the subject of much discussion and many experiments. As of yet, there is no conclusive evidence that this markup improves rankings. But there are some indications that search results with more extensive rich snippets (like those created using Schema) will have a better click-through rate. For best results, experiment with Schema markup to see how your audience responds to the resulting rich snippets. |
_codereview.78191 | Lately I have been learning about serialization so I decided to write a little helper class for my application to make it easy to use this feature in multiple places. I actually mixed some generics in the code and want to hear your feedback on my overall approach. SerializationService.cspublic class SerializationService{ /// <summary> /// This method Serializes the given Obj into an XML file. /// </summary> /// <param name=myObject>The obj to be serialized.</param> /// <param name=fileFullPath>The file name with the full /// path for the output serialized XML file.</param> public static void SerializeToFile(Object myObject, string fileFullPath) { var xmlDoc = new XmlDocument(); var xmlSerializer = new XmlSerializer(myObject.GetType()); using (var fs = new FileStream(fileFullPath, FileMode.Create)) { var writer = new XmlTextWriter(fs, Encoding.Unicode); xmlSerializer.Serialize(writer, myObject); writer.Close(); } } /// <summary> /// This method deserializes the XML file into an Obj. /// </summary> /// <param name=fuleFullPath>The XML file to read.</param> /// <returns>Deserialized obj of a type T.</returns> public static T DeserializeToObj<T>(string fuleFullPath) { var xmlSerializer = new XmlSerializer(typeof(T)); using (var reader = new FileStream(fuleFullPath, FileMode.Open)) { return (T) xmlSerializer.Deserialize(reader); } }}And here is how I use it in my code:SerializationSerializationService.SerializeToFile( _partRepository.GetParts().Where(p => p.IsIgnored).ToList(), fileFullPath);De-serializationvar ignoredParts = SerializationService.DeserializeToObj<List<Part>>(ignoredPartsXml); | Simple Generic output for Deserializer | c#;generics;serialization | Here are a few remarks. I'm not perfect or write perfect code but I hope these tips will help write better code:Naming consistency:It would be easier to understand if the names of your two methods had opposing names. For example: SerializeToFile and DeserializeFromFile. It's obvious that deserialization will return an object, omit that in the name.Also, if you're using the same type/kind of parameter or variable in one method, give it the same name in the other method.Truly generic:You should make your serialize method generic too:public static void SerializeToFile<T>(T obj, string fullPath)In the point Type constraint a bit further you'll see why.Scoping variables:You should define variables as close to their usage as possible. In your case you can instantiate the XmlSerializer class inside the using statement since you don't need it outside the statement. Example:using (var stream = new FileStream(fullPath, FileMode.Open)){ var xmlSerializer = new XmlSerializer(typeof(T));}Checking for the file:In both methods an exception can be thrown in certain situations. In the serialize method, if the path doesn't exist you'll get a DirectoryNotFoundException and in the deserialize method you'll get a FileNotFoundException if the file doesn't exist. This can easily be solved://Check for directory in serialize:var directoryPath = Path.GetDirectory(fileFullPath);var directoryExists = Directory.Exists(directoryPath);//Check for file in deserializevar fileExists = File.Exists(fileFullPath);You should decide whether you want positive or negative evaluation on this. For example, only perform the method if the checks are positive or throw an argument exception if the checks are negative. That is up to you.Also, like Heslacher stated: what if the file already exists? As for now, the content of the file will be overwritten by the new content.using statement:Following:using (var fs = new FileStream(fileFullPath, FileMode.Create)){ var writer = new XmlTextWriter(fs, Encoding.Unicode); xmlSerializer.Serialize(writer, myObject); writer.Close();}can be replaced by:using (var stream = new FileStream(fullPath, FileMode.Create))using (var writer = new XmlTextWriter(stream, Encoding.Unicode)){ var xmlSerializer = new XmlSerializer(obj.GetType()); xmlSerializer.Serialize(writer, obj);}Type constraint:Remember my point for making the serialize method generic too? For now, you don't validate the incoming and outgoing object. What if I pass an instance of a class that has no public parameterless constructor? During runtime I'll get an InvalidOperationException with a message like:... cannot be serialized because it does not have a parameterless constructor.The solution is to place type constraints on your methods. Definition from MSDN:When you define a generic class, you can apply restrictions to the kinds of types that client code can use for type arguments when it instantiates your class, these restrictions are called constraints.You should use the class and new() type constraints. Here's their definition:class: the type argument must be a reference type; this applies also to any class, interface, delegate, or array type.new(): the type argument must have a public parameterless constructor. When used together with other constraints, the new() constraint must be specified last.Now you'll get a compile-time exception when trying to serialize an instance of a clas without a public parameterless constructor. You can read more on this here: Constraints on Type Parameters (C# Programming Guide).public static void SerializeToFile<T>(T obj, string fullPath) where T : class, new(){ //method body}public static T DeserializeFromFile<T>(string fullPath) where T : class, new(){ //method body}Final code:With all this applied, your code might look like following:public class SerializationService{ public static void SerializeToFile<T>(T obj, string fullPath) where T : class, new() { if(Directory.Exists(Path.GetDirectoryName(fullPath))) { using (var stream = new FileStream(fullPath, FileMode.Create)) using (var writer = new XmlTextWriter(stream, Encoding.Unicode)) { var xmlSerializer = new XmlSerializer(obj.GetType()); xmlSerializer.Serialize(writer, obj); } } } public static T DeserializeFromFile<T>(string fullPath) where T : class, new() { if(File.Exists(fullPath)) { using (var stream = new FileStream(fullPath, FileMode.Open)) { var xmlSerializer = new XmlSerializer(typeof(T)); return (T) xmlSerializer.Deserialize(stream); } } return default(T); }} |
_cstheory.19013 | It's been known for a long time that any claim in NP has a zero-knowledge proof for it. Has anybody actually implemented a zero-knowledge proof system for a NP-complete language? Using a search engine, the most relevant thing I could find is this:www.usenix.org/event/sec10/tech/full_papers/Meiklejohn.pdfI'm not exactly sure what the scope of ZKPDL, but it looks like it's a combination of many special-purpose zero-knowledge protocols, and that it is not intended to NP-complete. It might turn out to be NP-complete with clauses like x in [0,1] and x*y=z allowing a reduction from SAT to the languages described there. However, the reduction doesn't seem natural or efficient.The reason I'm asking this is that I'm currently working on an implementation of a NP-complete zero-knowledge protocol and I want to know what the prior work is. | Are there any implementations for zero-knowledge proofs of NP-complete problems? | zero knowledge;implementation;np complete | The answer is yes, check the following paper:SNARKs for C: Verifying Program Executions Succinctly and in Zero KnowledgeEli Ben-Sasson and Alessandro Chiesa and Daniel Genkin and Eran Tromer and Madars Virzahttp://eprint.iacr.org/2013/507(also published at Crypto 2013) |
_webapps.18713 | I have a set of filters that auto add emails sent within a particular domain as 'internal'e.g. if [email protected] sends an email to [email protected], it is tagged internalThe problem is, my filter is not truely internal, because say I send an email to [email protected] and CC [email protected], it picks the latter up and flags it internal, but this is not an internal email.I need to filter emails sent to a particular domain, and only that domain. | Filter messages sent to a particular domain, and only that domain | gmail;gmail filters | (Converting my comment to an answer, as requested.)I'm afraid that Gmail's filters aren't sophisticated enough for that. |
_webmaster.45027 | I have a problem with Google indexing our site in different languages using the alternate hreflang.It's a forum and every thread is translated in the background and based on the language, the user choose in his options, the original text is replaced by the one in the right language.So every User can write in his own language and the other users can still read it (somehow - I know it's not the best solution, but it was not my idea :D )So - now we have the forum in many languages and of course we want the users form every language to find us via google.So i created some php-files, which get the right language by php and not by javascript.So the head in the original file looks like this:<link rel=alternate hreflang=de href=myurl/printthread.php?t=2967&lang=de/><link rel=alternate hreflang=en href=myurl/printthread.php?t=2967&lang=en/><link rel=alternate hreflang=fr href=myurl/printthread.php?t=2967&lang=fr/><link rel=alternate hreflang=es href=myurl/printthread.php?t=2967&lang=es/>On this pages the language is shown in the right language based on the url not on the users choice so that google can index it.But you guess it - For some reason it does not work. Google only saves the content from the original file - not the alternate files for the different languages :(You have any idea? | Google does not find/ignore alternate hreflang content | google;seo | Google announced as part of this video that text that is automatically translated by a computer (machine translated) is webspam. Google does not want to index this content, and it will penalize sites that try to get machine translated text indexed.If you do get text well translated by an actual human translator, you should put the translated text onto a new site. This can be either a new domain, new sub-domain, or even a new folder. Google does best at indexing different languages when it is set up as a different site. Google usually has problems identifying the language and indexing it correctly when a URL parameter is used like you have done. See: How should I structure my urls for both SEO and localization?. |
_codereview.36482 | I went with what I know and can use well, not what I know and can't figure the syntax out to make it look good.So please enjoy the code and prepare to school me (probably in the basics) in C#public static void Main (string[] args){ /* Here are your rules: Scissors cuts paper, paper covers rock, rock crushes lizard, lizard poisons Spock, Spock smashes scissors, scissors decapitate lizard, lizard eats paper, paper disproves Spock, Spock vaporizes rock. And as it always has, rock crushes scissors. -- Dr. Sheldon Cooper */ List<string> listOfGestures = new List<string>(); listOfGestures.Add(rock); listOfGestures.Add (paper); listOfGestures.Add (scissors); listOfGestures.Add (lizard); listOfGestures.Add (spock); int win = 0; int lose = 0; int tie = 0; var newGame = true; while (newGame) { var playerGesture = ; var validInput = false; while (!validInput) { var playerChoice = -1; Console.WriteLine(Please choose your Gesture ); gameSetup(listOfGestures); try { playerChoice = Convert.ToInt32 (Console.ReadLine()); } catch (FormatException e) { validInput = false; } if (playerChoice > 0 && playerChoice <= listOfGestures.Count) { playerGesture = listOfGestures[playerChoice - 1]; validInput = true; } else { validInput = false; } } var computerPlay = ComputerGesture(listOfGestures); Console.WriteLine (Computer: + computerPlay); Console.WriteLine (your Gesture: + playerGesture); if (playerGesture == computerPlay) { tie++; Console.WriteLine (you have tied with the computer); Console.WriteLine (Computer: + computerPlay); Console.WriteLine (your Gesture: + playerGesture); } else { if (playerGesture == rock) { if (computerPlay == lizard || computerPlay == scissors) { Console.WriteLine (You Win, + playerGesture + Crushes + computerPlay); win++; } else if (computerPlay == paper) { Console.WriteLine (You Lose, Paper Covers Rock); lose++; } else if (computerPlay == spock) { Console.WriteLine (You Lose, Spock Vaporizes Rock); lose++; } } else if (playerGesture == paper) { if (computerPlay == spock) { Console.WriteLine (You Win, Paper Disproves Spock); win++; } else if (computerPlay == rock) { Console.WriteLine (You Win, Paper Covers Rock); win++; } else if (computerPlay == lizard) { Console.WriteLine (You Lose, Lizard Eats Paper); lose++; } else if (computerPlay == scissors) { Console.WriteLine (You Lose, Scissors Cut Paper); lose++; } } else if (playerGesture == scissors) { if (computerPlay == paper) { Console.WriteLine (You Win, Scissors Cut Paper); win++; } else if (computerPlay == lizard) { Console.WriteLine (You Win, Scissors Decapitate Lizard); win++; } else if (computerPlay == rock) { Console.WriteLine (You Lose, Rock Crushes Scissors); lose++; } else if (computerPlay == spock) { Console.WriteLine (You Lose, Spock Smashes Scissors); lose++; } } else if ( playerGesture == lizard) { if (computerPlay == paper) { Console.WriteLine (You Win, Lizard Eats Paper); win++; } else if (computerPlay == spock) { Console.WriteLine (You Win, Lizard Poisons Spock); win++; } else if (computerPlay == scissors) { Console.WriteLine (You Lose, Scissors Decapitates Lizard); lose++; } else if (computerPlay == rock) { Console.WriteLine (You Lose, Rock Crushes Lizard); lose++; } } else if (playerGesture == spock) { if (computerPlay == rock) { Console.WriteLine(You Win, Spock Vaporizes Rock); win++; } else if (computerPlay == scissors) { Console.WriteLine (You Win, Spock Smashes Scissors); win++; } else if (computerPlay == paper) { Console.WriteLine (You Lose, Paper Disproves Spock); lose++; } else if (computerPlay == lizard) { Console.WriteLine(You Lose, Lizard Poisons Spock); lose++; } } } Console.WriteLine (Your Score is (W:L:T:) : {0}:{1}:{2}, win, lose, tie); Console.WriteLine (Again? Type 'n' to leave game.); if (Convert.ToString (Console.ReadLine ().ToLower ()) == n) { Console.WriteLine (would you like to reset your Score?); if (Convert.ToString (Console.ReadLine ().ToLower ()) == y) { win = 0; lose = 0; tie = 0; } Console.WriteLine (would you like to play another game?); Console.WriteLine (if you type 'n' the game will end.); if (Convert.ToString(Console.ReadLine().ToLower()) == n) { newGame = false; } } } Console.WriteLine(Goodbye); Console.ReadLine ();}Helper Methods that I used. I could probably use a couple more.public static void gameSetup (List<string> List){ for (int i=0; i<List.Count; i++) { Console.WriteLine ((i+1) + : + List[i]); } }With Random here I am not sure that I am using it correctly or if Random should be a static variable in the class scope and I should just be calling rand.next() everytime that I need to use it.public static string ComputerGesture (List<string> options){ Random rand = new Random(); return options[rand.Next(0,options.Count)];} | RPSLS Game in C# | c#;beginner;game;community challenge;rock paper scissors | Some minor syntax detail: C# has collection initializers so one can write:List<string> listOfGestures = new List<string> { rock, paper, scissors, lizard, spock }You use magic strings for the gestures all over the place. This can pose a problem if you want to change them. You could do a find and replace but this could inadvertently change a part of a method or variable name which happens to include rock if you are not careful. In other solutions to the problem posted before enums were used instead. If you insist on using strings then make them named constants and use those insteadconst string Rock = rock;const string Paper = paper;... etc.The main problem is that the entire implementation is basically just one big blob of code in the main method. Logic and input/output are totally intertwined. Assume you have to write an automated test case for this - it will drive you insane. If I were to encounter code like this in production I would very likely kill it and rewrite it - the problem is fairly simple and given it's untestable there aren't any unit tests anyway. If the code were too much to rewrite then I'd start refactoring it. Possible steps:Create a Game class which effectively encapsulates the main while loop up until the line Console.WriteLine (Your Score is (W:L:T:) : {0}:{1}:{2}, win, lose, tie);Dump everything into one method into that class for starters.The Game class should also keep track of the score.Override ToString to print out the current scores.Move the ask user if he wants to play another round into a method on the Game classAfter that the Main should look somewhat like this:var game = new Game();var continuePlaying = true;while (continuePlaying){ game.Play(); Console.WriteLine(game.ToString()); continuePlaying = game.ShouldContinue();}Next step would be to start refactoring the Game class and the methods within.Move the decision logic into it's own internal private method to reduce the bulk of the Play() method.Define an interface for getting user input and another one for writing output. Pass these interfaces into the Game constructor. Provide a console implementation for both interfaces. Change all the input and output to use the interfaces rather than the console.Now Game is decoupled from the specific input and output methods and you can start writing unit tests for the Play() and the ShouldContinue() methods. Once you have done that you can continue refactoring those methods. And because you have just created unit tests you should be able to detect if you create any regressions (introducing bugs) while doing so.Wash, Rinse, Repeat |
_unix.308259 | I need to run performance testing of database systems using C++ client (console). C++ client and database system should be run on the same computer under Linux. Unfortunately my main system is Windows (I cannot change it) and Linux is run in Virtual Box. I'd like to measure time in C++ program using the client.I'd like to ask you what Linux distribution should I use? I'd like to have as good tests as it possible (I mean I would like to eliminate any unwanted processes and behaviors from system). I think it should by some light system. And maybe you can recommend some settings of the system? | Distribution and configuration of linux for performance testing of system | linux;testing;distributions | null |
_softwareengineering.212152 | During 1990s when there were no advanced frameworks/paradigms available for S/W development , knowledge on data structures was critical... which I can comprehend.But nowadays, for most of the problems (at least from Java/Android development) we can rely on an existing class to provide solution.As such I believe, an in depth knowledge of data structures is not needed for someone who is stepping into programming now.Is my belief right ?. | Importance of data structures in modern S/W development | java;android;data structures | You are partially right. Nowadays, only a few people need to be able to correctly and efficiently implement algorithms and a lot of tasks can be completed successfully without knowing all that much about algorithms.On the other hand, knowing about the different algorithms that are commonly used in the kind of software you usually write and their strengths and weaknesses can also be a tremendous advantage in creating better performing software (or at least, avoiding writing complete crap) and in understanding some of the bottlenecks. |
_unix.324850 | I can visualize data transfer with# watch dfFilesystem 1K-blocks Used Available Use% Mounted onudev 4015776 0 401234 0% /devtmpfs 805936 9744 79651 2% /run/dev/sda1 21836624 11527716 917120 56% /tmpfs 4029672 152 4022520 1% /dev/shmHow can I have the byte rate for each column instead of the absolute value? | How to get the transfer rate of my devices? | disk usage;monitoring;devices | null |
_codereview.79613 | I have a paid app on the app engine. At the moment, usually there is only one instance. The app has a download handler that sends an image after re-sizing it if it is too big. The problem is: if a web page contains many big images (60 or more) the app engine creates another instance. I'm trying to keep the app as cheap as possible and creating too many instances is probably not good for that. Is there a way to improve this code? Or my concerns are just unfounded?The application settings are:automatic_scaling: min_idle_instances: 1 max_pending_latency: 10sThe code:class ServeHandler(blobstore_handlers.BlobstoreDownloadHandler): def get(self, resource): resource = str(urllib.unquote(resource)) blob_info = blobstore.BlobInfo.get(resource) if not blob_info: pass else: data = blobstore.fetch_data(blob_info.key(), 0, 50000) img0 = images.Image(image_data=data) img = images.Image(blob_key=blob_info.key()) if img0.width >= 800: img.resize(width=800) img = img.execute_transforms(output_encoding=images.JPEG) self.response.headers['Content-Type'] = 'image/jpeg' self.response.out.write(img) else: self.send_blob(blob_info) | Image download handler app | python;image;google app engine;network file transfer | null |
_cs.32598 | What is the lower bound for finding the third largest in a set of $n$ distinct elements? For the case of finding the second largest, we have the tight lower bound of $n + \lceil \lg n \rceil -2$. The adversary argument can be found in this lecture, which also provides an optimal algorithm using the Tournament Method.Edit (04-04-2017): Removing the algorithm for finding the third largest element which turns out to be wrong. | What is the lower bound for finding the third largest in a set of $n$ distinct elements? | complexity theory;reference request;time complexity;lower bounds;search problem | Answer my own question:At the end of Lecture 28: Adversary Arguments by Jeff Erickson, I foundA similar argument implies that at least $n - k + \lceil \lg {n \choose k-1} \rceil = \Omega \big( (n - k) + k \log (n / k) \big)$ comparisons are required to find the $k$-th largest element in an $n$-element set. This bound is tight up to constant factors for all $k \le n/2$; there is an algorithm that uses at most $O \big( n+k \log(n/k) \big)$ comparisons. Moreover, this lower bound is exactly tight when $k = 1$ or $k = 2$. In fact, these are the only values of $k \le n/2$ for which the exact complexity of the selection problem is known. Even the case $k = 3$ is still open!Therefore, the current answer to the question is that it is still unknown. |
_cs.24593 | I am reading Computational Complexity book and specifically Grovers search algorithm. I am aware that if we knew in advance exact number of solutions $K$, then the basic algorithm can be tweaked to find an input $x$ in $O(\sqrt{2^{|x|}/K})$ time. I found some material but, as I am new to quantum computing, I have problem connecting it to the explanation given in this book. Can anybody present the basic idea? | Grover algorithm for known number of solutions | complexity theory;time complexity;search algorithms;quantum computing | null |
_unix.23265 | I am running busy box on an embedded platform. I would like to set the date on the box properly each time I reboot the hardware. I have no way to save the time persistently, so am reduced to setting the time each time. I have LAN connectivity for it, but no SSH. My current hack for this is to redirect the output of 'date' to a file on my PC, access that file from my hardware platform through tftp, and then somehow parse the file, use its contents and then to set the date. I have no idea how to get the string from the file and then set it using the 'date' command. Any help would be appreciated. Any other way to set the date would be get. I have tried using ntpd, but that fails due to lack of internet connectivity | Trying to set date on a Linux based machine from another machine | date;busybox | Using a cron job, you could write a file to your /tftp directory with a granularity of 1 minute.* * * * * date +%m%d%H%M%Y.%S > /tftp/currdate.txt 2>/dev/nullThe contents of that file are a single value, which is formatted conveniently in the same format the date command needs to set the date/time.bash$ cat currdate.txt102600052011.00On the busybox side of things, you could just tftpget the file, and process itcat currdate.txt | while read date; do date $datedoneIf HTTP is an option, you could set up a php script that just returned the date when called, and have your script on the busybox side poll that URL, and process the result. The granularity of the date would be closer, in that case.With TFTP, you'll be within 1 minute. Hopefully that's close enough. |
_softwareengineering.326286 | I've looked for the solution of my problem but I've failed in finding a suitable answer.I've been trying to develop an Android application with heavy asyncronous networking capabilities. The problem is syncronizing async parts at some point.What I want to do is to create a service, download big amounts of data from several links, parse them as soon as I get a response and finally show them IF the activity is present. The service should be functional even when the application is closed and should be able to sync itself with the corresponding views in the activity. User should be pause, stop or continue network tasks from within the activity. Also, the activity or the service can exist independent from each other.I've thought about buffering the network responses via a queue implementation and reading from that buffer when the activity is present.One example for such operations could be the uTorrent application. It leaves a notification while running the service and as soon as you touch it, the application starts an activity and shows the situation of the torrents. I aim to build a similar structure.Problems:The activity can easily read from that buffer but after that how will it know that there are new items in the buffer?How will the service know if the application is terminated while reading the buffer or not?There is a GenerateSummary function for the completed downloads but where will it read the finished network operation data?TL,DR: What is the best practice while executing network tasks with coexisting independent user interface for an Android application? | Android Activitiy and Service Sync | android;synchronization;asynchronous programming;service;activity | null |
_unix.253544 | i have installed tmux on my pi (raspbian jessie) it has installed ok but when I ssh from osx command + b + doesn't work, or any other command for that matter. Do I need to create a config file? | Tmux raspbian installation | osx;tmux;raspberry pi | null |
_softwareengineering.342220 | Imagine I have a set of choices having different set of values but also the chance to input a free value (usually a number)e.g.<select name=choiceA> <option value=One> <option value=Two> .... <option value=Nth></select>or<input name=freeNumChoice type=number/>Not all combinations are possible so I need to represent rules of exclusion in some data structure.I'm not asking for language syntax but more on how to data strcture my rules for combinations.Programming language would be javascript and data for rules would be expressed as JSON documents.Example (pseudo code) possible ruleschoiceA whitelist only o1,o2,o3 (options) for choiceBchoiceE blacklists choiceA's o1choiceC if greater than 5 then whitelist only o1 for choiceBwhat would you suggest? is there around ant theory about this problem (looks like to be a common one)thanks | What's the best data structure to represent rules limitations? | data structures | null |
_unix.40304 | When I try any other finger with:%> fprintd-enroll left-index-fingerUsing device /net/reactivated/Fprint/Device/0failed to claim device: Not Authorized: net.reactivated.fprint.device.setusernameIt doesn't work for me;But if I don't specify finger (which uses right-index by default):%> fprintd-enroll Using device /net/reactivated/Fprint/Device/0Enrolling right index finger.It worksRunning on Arch Linux , and packages installed from aur:fprintd 0.4.1-4libfprint 0.4.0-3UPDATE%> fprintd-enroll -f left-index-fingerUsing device /net/reactivated/Fprint/Device/0Enrolling right index finger. | fprintd-enroll works with right-index finger only | security | I think this is only supported as of fprintd 0.5.1: http://cgit.freedesktop.org/libfprint/fprintd/commit/?id=7eb1f0fd86a4168cc74c63b549086682bfb00b3eWhen I build fprintd 0.5.1, the -f option does work correctly. |
_unix.78947 | I am using ArchLinux on an HP Pavilion dv9000t which has overheating problems. I did all what I can do to get a better air flow in the laptop and put a better thermal paste but there is still a problem:the fan stops spinning when the CPU temperature is low (even if the GPU temperature is high, which is problematic).I found out I can get the fan running by launching some heavy processing commands (like the yes command). However, it is not a solution because I need to stop this command when the CPU gets too hot and launch it again when the fan stops (so that the GPU does not get hot).I tried to control the fan using this wiki, but when I run pwmconfig, I get this error:/usr/bin/pwmconfig: There are no pwm-capable sensor modules installedDo you know what can I do to get the fan always spinning?Edit:The sensors-dectect output is the following:~/ sudo sensors-detect # sensors-detect revision 6170 (2013-05-20 21:25:22 +0200)# System: Hewlett-Packard HP Pavilion dv9700 Notebook PC [Rev 1] (laptop)# Board: Quanta 30CBThis program will help you determine which kernel modules you needto load to use lm_sensors most effectively. It is generally safeand recommended to accept the default answers to all questions,unless you know what you're doing.Some south bridges, CPUs or memory controllers contain embedded sensors.Do you want to scan for them? This is totally safe. (YES/no): Module cpuid loaded successfully.Silicon Integrated Systems SIS5595... NoVIA VT82C686 Integrated Sensors... NoVIA VT8231 Integrated Sensors... NoAMD K8 thermal sensors... NoAMD Family 10h thermal sensors... NoAMD Family 11h thermal sensors... NoAMD Family 12h and 14h thermal sensors... NoAMD Family 15h thermal sensors... NoAMD Family 15h power sensors... NoAMD Family 16h power sensors... NoIntel digital thermal sensor... Success! (driver `coretemp')Intel AMB FB-DIMM thermal sensor... NoVIA C7 thermal sensor... NoVIA Nano thermal sensor... NoSome Super I/O chips contain embedded sensors. We have to write tostandard I/O ports to probe them. This is usually safe.Do you want to scan for Super I/O sensors? (YES/no): Probing for Super-I/O at 0x2e/0x2fTrying family `National Semiconductor/ITE'... NoTrying family `SMSC'... NoTrying family `VIA/Winbond/Nuvoton/Fintek'... NoTrying family `ITE'... NoProbing for Super-I/O at 0x4e/0x4fTrying family `National Semiconductor/ITE'... NoTrying family `SMSC'... NoTrying family `VIA/Winbond/Nuvoton/Fintek'... NoTrying family `ITE'... NoSome hardware monitoring chips are accessible through the ISA I/O ports.We have to write to arbitrary I/O ports to probe them. This is usuallysafe though. Yes, you do have ISA I/O ports even if you do not have anyISA slots! Do you want to scan the ISA I/O ports? (YES/no): Probing for `National Semiconductor LM78' at 0x290... NoProbing for `National Semiconductor LM79' at 0x290... NoProbing for `Winbond W83781D' at 0x290... NoProbing for `Winbond W83782D' at 0x290... NoLastly, we can probe the I2C/SMBus adapters for connected hardwaremonitoring devices. This is the most risky part, and while it worksreasonably well on most systems, it has been reported to cause troubleon some systems.Do you want to probe the I2C/SMBus adapters now? (YES/no): Using driver `i2c-i801' for device 0000:00:1f.3: Intel 82801H ICH8Module i2c-dev loaded successfully.Next adapter: nouveau-0000:01:00.0-0 (i2c-0)Do you want to scan it? (yes/NO/selectively): Next adapter: nouveau-0000:01:00.0-1 (i2c-1)Do you want to scan it? (yes/NO/selectively): Next adapter: nouveau-0000:01:00.0-2 (i2c-2)Do you want to scan it? (yes/NO/selectively): Now follows a summary of the probes I have just done.Just press ENTER to continue: Driver `coretemp': * Chip `Intel digital thermal sensor' (confidence: 9)Do you want to overwrite /etc/conf.d/lm_sensors? (YES/no): Unloading i2c-dev... OKUnloading cpuid... OKThe file /etc/conf.d/lm_sensors contains:HWMON_MODULES=coretempAnd the file /etc/modules-load.d/lm_sensors.conf contains:coretempacpi-cpufreqThe command sensors outputs this:~/ sensorscoretemp-isa-0000Adapter: ISA adapterCore 0: +46.0C (high = +85.0C, crit = +85.0C)Core 1: +47.0C (high = +85.0C, crit = +85.0C)acpitz-virtual-0Adapter: Virtual devicetemp1: +49.0C nouveau-pci-0100Adapter: PCI adaptertemp1: +60.0C (high = +95.0C, hyst = +3.0C) (crit = +115.0C, hyst = +5.0C) (emerg = +115.0C, hyst = +5.0C) | How to force the fan to always spin? | temperature;fan;gpu | I finally decided to choose a hardware solution.I cut two wires from the fan and now the fan always spin (at the max level though).I found this solution in this blog post. |
_webmaster.93335 | I made some changes to the files on a website and now Search Console is showing me 404 errors for some URLs.The normal setup, which works fine is like this:the user-friendly URL mywebsite.com/modeles-voiture/Volvo/XC60is rewritten to get to the PHP script as: RewriteCond %{REQUEST_URI} ^/?modeles-voiture [NC] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule \/([A-Z][\-A-Za-z]+)\/([\-A-Za-z0-9\.]+$) /models.php?brand=$1&model=$2 [L]Now, I do have some old URLs out there, that are generating the 404 errors and that look like:mywebsite.com/modeles.php?brand=Volvo&model=XC60So, I came up with the following redirect to send them to the right place.This first step would redirect the old URLs to the new, user-friendly ones:RewriteCond %{REQUEST_URI} \/modeles\.php [NC]RewriteCond %{REQUEST_FILENAME} !-fRewriteCond %{REQUEST_FILENAME} !-dRewriteRule brand=([A-Z][\-A-Za-z]+)&model=([\-A-Za-z0-9\.]+$) http://www.soeezauto.com/modeles-voiture/$1/$2 [R=301,L]Then, the existing code ( below ), would do its regular job of sending over to the proper PHP script.So ( just repeating what I stated up on the top ): RewriteCond %{REQUEST_URI} ^/?modeles-voiture [NC] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule \/([A-Z][\-A-Za-z]+)\/([\-A-Za-z0-9\.]+$) /models.php?brand=$1&model=$2 [L]My this is not working. Still getting a 404 error.I did test all the individual regexps ( at regex101.com ) and they seem to do what they are supposed to.I may just have made the wrong assumption concerning the chaining, but in that case, what is the solution to this? | combined 301 redirects not working | htaccess;301 redirect;mod rewrite;user friendly | RewriteCond %{REQUEST_URI} \/modeles\.php [NC]RewriteCond %{REQUEST_FILENAME} !-fRewriteCond %{REQUEST_FILENAME} !-dRewriteRule brand=([A-Z][\-A-Za-z]+)&model=([\-A-Za-z0-9\.]+$) http://www.soeezauto.com/modeles-voiture/$1/$2 [R=301,L]You can't match the query string with the RewriteRule pattern. The RewriteRule only matches against the URL-path (less the query string). To match the query string you need to use a RewriteCond directive and check against the QUERY_STRING server variable.It is also more efficient to match the URL-path in the RewriteRule, rather than using a condition to match against REQUEST_URI (where possible).Try something like:RewriteCond %{REQUEST_FILENAME} !-fRewriteCond %{REQUEST_FILENAME} !-dRewriteCond %{QUERY_STRING} ^brand=([A-Z][-A-Za-z]+)&model=([-A-Za-z0-9.]+)$RewriteRule ^modeles\.php http://www.example.com/modeles-voiture/%1/%2? [R=301,L]This matches the exact query string, eg. brand=Volvo&model=XC60 - if there are other URL params then this will not match.EDIT: The ? on the end of the substitution effectively removes the query string from the redirected URL. Alternatively, on Apache 2.4, you can use the QSD (Query String Discard) flag.You don't need to escape slashes in Apache config regex. (Apache regex does not use slash delimiters.) In a regex character class you also don't need to escape literal dots, or hyphens if they occur at the start or end of the character class.The RewriteRule substitution uses %1 and %2 (as opposed to $1, etc) as a backreference to the last captured group(s) in the RewriteCond directive. |
_reverseengineering.8078 | I usually work with two or three IDBs open at the same time which are linked between themselves (basically the main .exe, and DLLs it loads).However, every now and then I open different files to take a look, and my recently used IDBs quickly gets filled up and the IDBs I work with disappear.Is there any way I can make IDA stick those IDBs at the top of the recently opened files so I can access them easily? | Is there any way to make IDA permanently save recently used files in a list? | ida;idapro plugins | Assuming you're on Windows, you could write a script that regularly restores HKEY_CURRENT_USER\Software\Hex-Rays\IDA\History.On Linux or Mac OS, I'm sure there's something similar than can be easily restored via a simple script. |
_softwareengineering.208319 | I have experience developing software and web applications and I have decided to do some freelance work on the side. Well, I met with my first client and they are requesting a relatively simple, custom system that (without being long winded) tracks clients paperwork as it progresses through the businesss different manual processes. It is a small business that has about 10 employees, but all of the employees will interact with the clients paperwork, therefore everyone would need access to the new system. When I say track I literally mean that the employees will check as complete on a simple page the increases a progress bar at different stages for the paperwork. Now I am %110 capable of coding the custom system that meets their needs, but I am unsure about how I should go about doing it.The information that is being tracked in the new system and stored in the DB is confidential information that they are very protective of. My main question is how should I be developing this to be as secure as I can?They have their own server in house, so should I develop an application (VB and SQL) for the server and require employees to log on remotely to use it? Can more than one person access/use the application at a time?Or should I develop a web application (ASP.Net/VB and SQL) that is only accessible on their network to their employees? They plan to expand offices, could they set up a VPN to access the site?Im leaning towards a web application, but I have not done too much in term of security. What specific options do I have for security that aren't too complex. Basically Im looking for pros and cons for either option or any suggestions on what I should. | VB stand alone application or ASP web application | asp.net;security;web;applications;visual basic | null |
_webmaster.89426 | I'm managing an interactive community website for a video game.The video game is about cards which are bundled as decks. One can construct multiple decks with different cards. The website I've built allows to build & share such decks.The website name actually includes the word decks.One problem I see is that the majority of users is calling decks builds. Analytics is confirming this.So my problem is: the competition is using the word build over and over again while I'm using deck. And as I said build is apparently the preferred (even when wrong) term.I don't want to lose rankings / want to improve rankings to my page with the term build.The actual question: what can I do to teach search machines that deck and build are synonyms in my case?I've already used both terms as meta keywords like<game> decks, <game> buildsWhat I don't want to do is using the term build on my actual page since it's kinda contradictory with decks in the site name/domain | How to improve SEO for synonyms? | seo;keywords | Synonyms and plural versions of words are not needed. You do not have to tell search engines what they already know. The schema.org mark-up would be correct to use for something that is not normally recognized by the various ontologies that exist.Why do I say this? Because ontologies have been used in Google since the days when it was a research project. Ontologies are a form of a database that can be a dictionary, thesaurus, fact knowledge base, language translation, etc. Ontologies for plural terms and synonyms have existed since 1975. That is not a typo! The various open ontologies have been significantly improved over the years with huge leaps made in 2007 and 2008 and continuing. As well, Google uses AI to derive synonyms not already known. This is based upon linguistics fist and corroboration second and works extremely well.You do not need to create a site for machines so please stop.As well, it appears that you are operating on the apprehension that you must compete for keywords and placement in search. One thing is true. You must compete for placement in search, but not keywords. Search engines do not match keywords. Google never has and never will. Any match is incidental to the semantic analysis that exists. This is why sites and pages can compete for terms that do not exist. It is a matter of linguistics and not keywords, density, or how well you play hacky sack.Create fan-freakin-tastic content for users and not machines.Lastly, the keywords meta-tag is completely ignored. The reasons are simple. It can be manipulated and it does not add value. It does not give any additional semantic clues that support what search engines can already know about your site. Period. It is utterly useless to search engines and therefore utterly useless to you. Do not waste your time. |
_unix.113895 | I use Red Hat Enterprise in my school and I want to compile some c++11 code but the gcc --version is 4.4.7 which is not compatible.Is that one the latest version in the red hat repositories?is there any compiler that can be installed quickly using yum and that supports c++11? | Is there a newer version of gcc in red hat? | rhel;gcc;c++ | null |
_datascience.11247 | I am currently doing sentiment analysis using Python. Here I am taking all the reviews from movie dataset and using Naive Bayes algorithm to predict whether the review is positive or negative. From the input dataset, I am using a logic to remove stopwords and after that training my dataset to predict the result. As of now, my test results are predicted, but few results are predicted wrongly. This was a great film. Jack Halley is comical as usual and Bela Lugos is hilarious even in his tiny role. I love this flick.Example, the above sentence is positive, but it is predicting as negative. Similar instance occurs to many other scenarios. If it has some sarcasm, then there are chances that it may predict the other way. But for few direct reviews, it is predicting the other way. Could you suggest other ways to better my algorithm, so that it increases the accuracy of prediction. Any other efficient methods apart from removal of stopwords? I have been looking for various suggestions through internet but I am new to this topic and hence couldn't find an effective way to proceed. Any good suggestions would be greatly appreciated. | Sentiment Analysis of Movie Reviews using Python | python;data mining;bigdata;pandas;nltk | null |
_cs.54778 | Today at lunch, I brought up this issue with my colleagues, and to my surprise, Jeff E.'s argument that the problem is decidable did not convince them (here's a closely related post on mathoverflow). A problem statement that is easier to explain (is P = NP?) is also decidable: either yes or no, and so one of the two TMs that always output those answers decides the problem. Formally, we can decide the set $S :=\{|\{P, NP\}|\}$: either the machine that outputs $1$ only for input $1$ and otherwise $0$ decides it, or the machine that does so for input $2$.One of them boiled it down to basically this objection: if that's how weak the criterion of decidability is - which implies that every question which we can formalize as a language that we can show to be finite is decidable - then we should formalize a criterion that doesn't render any problem with finitely many possible answers that's formalizable in this way decidable. While the following is possibly a stronger criterion, I suggested that maybe this could be made precise by requiring that decidability should depend on being able to show a TM, basically proposing an intuitionist view of the matter (which I don't incline towards - nor do any of my colleagues, all of them accept the law of excluded middle).Have people formalized and possibly studied a constructive theory of decidability? | Constructive version of decidability? | computability;undecidability | I think the question you are trying to ask is is computability theory constructive?. And this is an interesting question, as you may see by this discussion on the Foundations of Mathematics mailing list.Unsurprisingly, it has been considered, since a lot of recursion theory was developed by people with constructive sensibilities and vice versa. See e.g. Besson's book and the venerable Introduction to Metamathematics. It's pretty clear that the first couple of chapters of recursion theory survive moving to a constructive setting with minimal changes: e.g. the s-n-m theorem, Rice's theorem or the Kleene recursion theorems survive unchanged.After the first chapters though, things get a bit tougher. In particular, the higher levels of the arithmetic hierarchy are usually defined by a notion of truth. In particular, widely used theorems such as the Low Basis Theorem seem to be explicitly non-constructive.Perhaps a more pragmatic response, though, is that these paradoxically computable languages are simply an idiosyncrasy, that can (and have!) been studied at great length, like non-measurable sets of reals, but that once the initial surprise has been overcome, one can move on to more interesting things. |
_codereview.25971 | Why does this Erlang code take about one minute on my machine?On Pascal something like this took less then second on my machine.What I can do to speed it up?-module(slow).-export([slow/0]).pyth(N) -> [{A, B, C} || A <- lists:seq(1, N - 2), B <- lists:seq(A + 1, N - 1), C <- lists:seq(B + 1, N), A + B + C =< N, A * A + B * B == C * C].slow() -> io:format(~p\n, [pyth(1000)]). | Slow Erlang code to find Pythagorean triplets | performance;erlang | Erlang runs on a VM, so you will get better performance on such a pure arithmetic computation by compiling it into native code using HIPE.From the command line:erlc +native slow.erlOr from the Erlang shell:1> hipe:c(slow).Or:1> c(slow, [native]). |
_unix.361116 | I installed Google Chrome for linux opensuse, but when I tried to open the browser it is showing error as Please start Google Chrome as a normal user. If you need to run as root for development, rerun with the --no-sandbox flag . Please help me how to solve this. | Linux opensuse - google chrome setup | linux;chrome | null |
_unix.251057 | I read a lot of articles and watch videos on How people can connect two computers with a ethernet cable but a lot of the instructions was more / windows to windows/mac to mac /windows to mac/ but yet I never came across anything like Windows to Linux so is it possible to connect a Windows to a Linux via ethernet cable? | Can I contect a Ubuntu Linux laptop to a Windows 10 laptop via ethernet cable | linux;windows;ethernet;connection sharing | null |
_softwareengineering.231018 | I've already read this question on CodeReview. I was hoping for general advice. I'm writing a service which will go to numerous data sources. Each source requires getting copious amounts of data and changing it to a single format. What is the best pattern for a task like this?I currently have a base class which exposes a static GetData method, which the other classes inherit from and implement. This doesn't seem like the cleanest approach, so I was wondering what other approaches might suit my needs? | Pattern for multiple datasources | c#;design;design patterns;object oriented;.net | null |
_softwareengineering.76627 | When we say that Dennis Ritchie developed C language, do we mean that he has created a compiler (using an 'already' developed other language) which can compile the source code written in C language?if yes, what was language he used to write first C compiler? I understand a compiler is a program and we can create another compiler for C language using presently available C compiler. Is that correct? | What is the history of the C compiler? | c;compiler | From wiki:Ritchie is best known as the creator of the C programming language and a key developer of the Unix operating system, and as co-author of the definitive book on C.Also from wiki:The first C compiler written by Dennis Ritchie used a recursive descent parser, incorporated specific knowledge about the PDP-11, and relied on an optional machine-specific optimizer to improve the assembly language code it generated.The first C compiler was also written by him, in assembly.This page from bell-labs answers most of your questions. |
_unix.314419 | We run an application which creates a lot of directories. Once the application completes we do not need those directories. Hence we want to delete them as they are consuming lots of space. The problem is this application is running on a remote server. I have to write a shell script that will delete those directories from the remote server. I tried the ssh commandssh [email protected] 'rm /some/where/some_file.war' but it asked for a password. Then I followed the below stepSetup password-less keys then add the command as part of the ssh command. See: http://www.dotkam.com/2009/03/10/run-commands-remotely-via-ssh-with-no-password/I am able to to do all steps as described but at last it is again asking for a password. How can I use ssh without a password? | automate file delete in remote server | ssh;authentication | null |
_unix.353714 | I'm pretty new to the bash shell scripting game but have been catching on fairly well. I'm writing a script right now for the automated id3 data editing or mp3 files. I'm currently using the id3v2 command line program. These are mp3 files that are coming from a police scanner program I have recording. I'm wondering if there is a way to make a variable related to the number the file...you know I'm not sure how to word this. Sorry, been battling a headache for the last couple of days. I can explain it like this.So if I were in a directory of recordings I can easily get them listed in order because the time they were recorded is a part of the file name. So a general ls command would produce something likeFile_012030.mp3File_012040.mp3File_012045.mp3I would like to use a variable to assign the track number to each files id3 data. My first thought is to somehow use the number of how far down it is in the list of files in that directory. So the above example would be. File_012030.mp3 <- 01File_012040.mp3 <- 02File_012045.mp3 <- 03Is this something that would be possible? | Create variable based on the order a file is in an alphabetical list of files | bash;shell script;variable | Just use a for loop and a counter:k=1; for file in *mp3; do id3v2 --track $k $file ((k++)) doneThat will iterate over all files and directories whose name ends in mp3, saving each as $file. Then, the $k variable is incrementing once per iteration (((k++))) so $k will be the number of the file in the order you process them and you can use --track $k to set the track number. |
_unix.264943 | I've just finished installing a fresh installation of syslog-ng on CentOS 7, but syslog-ng.service failed to start.It says:Failed to issue method call: Unit syslog.service failed to load: No such file or directory.Any ideas? | install syslog-ng on CentOS 7 | centos;syslog ng | null |
_codereview.171404 | I've written some script in python using lxml library which is capable of dealing with a webpage with complicatedly layed-out next page links. My scraper is able to parse all the next page links without going to the next page and hardcoding any number to the lastmost link and scrape the required fields flawlessly. Although I tried to do the whole thing specklessly, any improvement on this will be highly appreciable. Here is what I've tried with:import requestsfrom lxml import htmlmain_link = https://www.yify-torrent.org/search/1080p/base_link = https://www.yify-torrent.orgdef get_links(item_link): response = requests.get(item_link).text tree = html.fromstring(response) last_page = tree.cssselect('div.pager a:contains(Last)')[0].attrib[href].split(/)[-2].replace('t-','') links = [item_link +t-{0}/.format(page) for page in range(int(last_page) +1)] for link in links: process_docs(link)def process_docs(nextpage_link): response = requests.get(nextpage_link).text tree = html.fromstring(response) for items in tree.cssselect('div.mv'): name = items.cssselect('h3 a')[0].text try: genre = items.xpath('.//div[@class=mdif]//li[b=Genre:]/text()')[0] # I don't know If css selector could do this except IndexError: genre = try: imd = items.xpath('.//div[@class=mdif]//li[b=Rating:]/text()')[0] # Used xpath in lieu of css selector except IndexError: imd = print(name, genre, imd)get_links(main_link) | Scraping required fields exhausting a full website | python;performance;python 3.x;web scraping;lxml | This is quite clean and understandable.I would pinpoint only a couple of things:to avoid code repetition and to generalize getting search result properties, what if you would collect all the properties (genre, quality, size etc) into a dictionary:properties = { label.text: label.xpath(following-sibling::text())[0] for label in items.xpath(.//div[@class=mdif]//li/b)}As a bonus, you would not need the try/except part at all.as usual, you may reuse a session to boost your HTTP requests part performanceSome other minor notes:it looks like that you make an extra request to the page number 0, adjust your range if this is the caseitems variable name is probably a bit misleading, at the very least it should be item since you are iterating over search result items one by oneput get_links() call to under the if __name__ == '__main__' to avoid the code being executed if the module is ever importedI would also return or yield from the get_links and process_docs functions instead of printing things out |
_unix.340168 | I am trying to convert a text file containing ASCII art into an image.When using the command below, i get the following error message:convert: non-conforming drawing primitive definition `OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO00OOkxxkkxxoloxOOkolONMMMMMMM' @ error/draw.c/DrawImage/3184.The code I am using is convert: convert -size 360x360 xc:white -font FreeMono -pointsize 12 -fill black -draw @ascii.txt image.png | non-conforming drawing primitive definition error when converting ascii text to an image using imagemagick | linux;imagemagick;ascii | null |
_unix.268167 | I would like to know if there is any command line tool to search text files preloaded with some well-known regexes (IP, email, date, path, url, xml tags, etc) so you could do something like:grep -A 5 '443: open' somefile.log | getregexmatch --ipTo extract all the IP addresses from the output of grep. | Is there any text search tool preloaded with well-known regexes? | regular expression;utilities | Yes, perl is your friend. In this case perl's Regexp::Common in particular. It provides predefined regex definitions (see the documentation for more details : http://search.cpan.org/~abigail/Regexp-Common-2016020301/lib/Regexp/Common.pm).An IPv4 example would be :$ perl -MRegexp::Common -lne 'print $1 if /($RE{net}{IPv4})/g' file172.18.0.1172.17.0.1127.0.0.1 |
_unix.382220 | I am training de deep learning model with tensorflow basically. As you may know numpy is a dependency for tensorflow, and numpy has blas(openblas/atlas/lapack) as optional dependency to improve performance. In my case I am using CUDA and cuDNN, so basically most of the computation is done in GPU through tensorflow/libcudnn(and therefore cuda), my doubt here is if should I care about if numpy have been built(or not) with blas/atlas/lapack/openblas support ?OBS: I am not sure if this question is appropriated here in U&L, but I hope you may help me. | Does it matter if numpy uses blas/atlas/lapack when using Tensorflow (with GPU support)? | libraries;gpu | null |
_softwareengineering.206317 | When should I use one versus the other? For instance, let's say I have 20 comma delimited, denormalized text files and I want to transform the data and load it into normalized SQL Server tables. | SQL Server: When to use SSIS vs T-SQL for ETL Tasks | .net;sql server;database development;ssis | What are the size of the files? T/SQL is pretty fast, I've done million record imports in less than three seconds. Is this 'once' or 'scheduled'?SSIS is for complicated scenarios. SSIS can schedule FTPs, external commands (such as ZIP and unZIP), branching paths on step failures, etc. Therefore it isn't as simple as importing data, it's the entire 'overnight data exchange process'.Given that you have CSVs (presumably with column names) much of your work would appear to have been done already. If you don't need to filter out bad records you're just doing 'group bys' to generate validation fact tables.More information is needed. |
_webmaster.19397 | Every website I've ever been to has links to legal, privacy, tos, etc on the bottom of every page.Is this required?Can I have all that info on a specific about page rather than on every page? | Where to place privacy, legal, etc info on a website? | legal | null |
_codereview.33245 | Someone posted a question on http://math.stackexchange.com earlier because their program to tranpose a matrix wasn't working. I copied the code they posted (which was just the transpose method) and added the code necessary to check if it worked on their example matrix and it does, so there's obviously a problem elsewhere in their code. I've posted my code below. I don't have much programming experience and I suspect my style is unconventional. I implement most of the main program in the constructor, because every time I try to do it in the main method, I get lots of errors because I'm referencing non-static variables and methods from a static context. Maybe there are good reasons for using the static keyword, but I just wanted to write quickly a program to check whether the other person's method was correct and it seemed like the fact that the main method was static was getting in the way, so I just transferred most of the program to the constructor. I have 9 questions (question 8 is actually 2 questions), but question 8 is the most important: Is my program ok? Could it be better and if so, why?What would be the conventional way to write the program?How would the program be written with the main method in the main method rather than the constructor?How does having the main method static help? Someone wrote 'It is good to move code into on or more classes instead of having everything in the main method!'. If I do this, it seems like I get lot of errors because I'm referencing a static variable from a non-static context (since I must at least instantiate one class in the static main method). How would I best overcome this? Someone else suggested changing everything to static, but that can't be normal, can it? I know that's a lot of questions. I think the following 2 questions could pin down what I want to find out: where would printMatrix() be in a conventional program (presumably not in the constructor like it is in mine)? If there wouldn't even be such a method in a conventional program, how would the printing of the matrix and its transpose be implemented?public class Matrix { double[][] M = new double[3][3]; static int mat_size=3; public Matrix() { M[0][0]=1; M[0][1]=0; M[0][2]=0; M[1][0]=5; M[1][1]=1; M[1][2]=0; M[2][0]=6; M[2][1]=5; M[2][2]=1; System.out.println(M); printMatrix(); transpose(); System.out.println(M'); printMatrix(); } public static void main(String[] args) { // TODO Auto-generated method stub new Matrix(); } public void transpose() { System.out.println(); for(int i = 0; i < mat_size; ++i) { for(int j = 0; j < i ; ++j) { double tmpJI = get(j, i); put(j, i, get(i, j)); put(i, j, tmpJI); } } } public void printMatrix() { System.out.println(); for(int i = 0; i < mat_size; ++i) { for(int j = 0; j < mat_size ; ++j) { System.out.print((int)get(i,j)+ ); } System.out.println(); } } private void put(int i, int j, double d) { // TODO Auto-generated method stub M[i][j]=d; } private double get(int i, int j) { // TODO Auto-generated method stub return M[i][j]; }} | How to overcome static referencing errors in Java/basic programming? | java;static | Is my program ok?Well, I guess it works. However, it can be structured far better.Basic Object Oriented Programming in JavaIn Java (and all of this is also true for C#), every object has a type which is represented by a so-called class. We can define operations on each type, which we call methods. Some methods operate on an individual instance of a type. Other operations are not inherently bound to instances, and operate on the whole class. We call this second kind of operations static methods.Likewise, data can either belong to a specific instance, or is shared across all instances, in which case it's called static. Every method (static and non-static) can refer to static data, because that is shared. However, static methods cannot reference instance data, because a static method can't tell from which instance you'd like the data and sometimes, no instance may exist at all. Static methods are mostly useful for general helpers.It is really important to grok the difference between static and non-static methods in order to use Java effectively (the same holds for any other class-based programming language).Meaning of the mainWhat is the main and why do we need it? The main originated as a feature of the C programming language. It defines an entry point into the program. At startup, your classes are initialized and then the main methods gets called with the command line arguments in an array as parameter. The main method doesn't return a value (it is void), because returning from it aborts the process.The main is static because it's a helper method to get your control flow going it is not coupled to any instance. It is therefore common in a main to create an instance of the surrounding class, and work with that.ConstructorsA constructor is a special method used to initialize a fresh instance. All it usually does is assigning its arguments to the corrects data fields of the instance. It isn't recommended to do the actual work here put that into another method.In your code, everything after the initialization can be moved into the main method where it belongs. Note that methods are invoked on a specific instance with the dot operator. The main now looks like:public static void main(String[] args) { Matrix matrix = new Matrix(); System.out.println(M); matrix.printMatrix(); matrix.transpose(); System.out.println(M'); matrix.printMatrix();}Now we are already getting into the code review zone of this answer.Design spotlightsA method should do one thing only and no and!Every method should do one thing only. Exaggerated: While a description of your method uses the word and, it is doing to much. Split the functionality into more methods. For example, your transpose method does this: It prints an empty line and swaps columns with rows of the matrix. Is printing an empty line really necessary in a method called transpose?The same goes for your version of the constructor: It initialized the matrix and prints it out and transposes it and prints it out again but we already cleaned that up above.ComposabilityAn advantage of having each method doing one concept only makes it easier to compose them in a different way to do new things. There are a few important things that can make this easier:Don't hardcode stuff parameterize itDon't hardcode things that aren't universal constants. Actually, don't hardcode things at all. For example, you assign static int mat_size = 3 but what if I want to use a 55 matrix? You don't provide any functionality that actually depends on the number three. Instead, the size is a property of each instance. Therefore, we'll remove the static modifier, and initialize it in the constructor.The constructor is another example of hardcoding: The whole test matrix is specified there. It would be better to move that data out of the constructor, and have the constructor take an array as argument instead. I'd rather initialize a new matrix like:// array literals :) however, I'm unsure about the exact syntaxdouble[3][3] testData = { { 1, 0, 0 }, { 5, 1, 0 }, { 6, 5, 1 } };Matrix matrix = new Matrix(3, testData);We can now initialize a matrix with arbitrary other values, not only that specific data set.ImmutabilityWhen objects don't change their internal state over time, programs often get a bit simpler. Mathematics does this as well: When we transpose a matrix M, the M still has its old values. The transposition produces a new and distinct matrix, which we can call M' (you even do this in your printout). There is no reason our transpose method shouldn't return a new matrix either. Now we get something along the lines of:public Matrix transpose() { double[size][size] newData = new double[size][size]; for(int i = 0; i < size; i++) { for(int j = 0; j < i ; j++) { newData[i][j] = get(j, i); newData[j][i] = get(i, j); } newData[i][i] = get(i, i); } return new Matrix(size, newData);}This changes our main:public static void main(String[] args) { Matrix matrix = new Matrix(); System.out.println(M); matrix.printMatrix(); Matrix transposed = matrix.transpose(); System.out.println(M'); transposed.printMatrix();}No side effectsWhen a method has any effect except returning some data, it has side effects. Such effects might be changing the state of some object (thus voiding the point about immutability), or printing out some data. These side effects make it more difficult to combine these methods in a new way.Specifically, printMatrix is an offender here. Also because it can't be changed to print to anything other than System.out. What happens when I want a string representation to display on a GUI? I can't simply use your awesome Matrix class :(Here, it would be better to implement the toString() function, which returns a string representation of your object. There is already a default implementation for every object, but we can override it. Then, our main will look like:public static void main(String[] args) { Matrix matrix = new Matrix(); System.out.println(M); System.out.println(matrix.toString()); Matrix transposed = matrix.transpose(); System.out.println(M'); System.out.println(transposed.toString());}That is more ugliness here, but massively clears up the rest of your code. The toString might be:public String toString() { StrinBuilder sb = new StringBuilder(); for(int i = 0; i < size; i++) { for(int j = 0; j < size ; j++) { sb.append( + (int) get(i, j)); } sb.append(\n); } return sb.toString();}// apologies if I mixed up the StringBuilder APIA closing note on naming thingsIn Java, names are written in camelCase. Class names are capitalized. Any other names start with a lowercase letter: Matrix refers to a class, while matrix is a local variable, field, or method. As an exception, constants are written all-uppercase and seperated by underscores. Because for normal names the parts of a word are distinguished by capitalization, no underscores are ever used.It is advisable to use meaningful names like matrix or transformedMatrix, not shortcuts like m or t or m_. Choosing longer names makes it easier to read a piece of code for someone who isn't used to your shortcut notation. |
_unix.289407 | Probably a basic question but I did not manage to find a clear answer to it:Let's say I am compiling a code (with some parts in C) on a build server and run it on a different server. The build server has gcc version X and glibc version Y. What are the constraints on the gcc and glibc versions on the run server, in order for my code to run properly ? | Constraints on gcc / glibc versions between build and run | linux;gcc;glibc | null |
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