Question 171264 in PHP Question posted in
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Can’t read system call output in PHP?

I’m trying to read the hash of a torrent file, so I’m using a simple program called torrenttools.

When I run this php file on my localhost:

<html>
    <head>
<?php
ini_set('display_errors', '1');
ini_set('display_startup_errors', '1');
error_reporting(E_ALL);
$torrenthash = shell_exec ("./torrenttools info '/var/www/html/torrents/Elle -JP- (Sharp X68000).torrent' | grep hash | cut -b 20-59 2>&1");
echo "<pre>".$torrenthash."</pre>";
?>
</head>
</html>

the shell_exec call returns nothing, however, if I run it from command line:

root@milton:/var/www/html# php test.php 
<html>
    <head>
<pre>03b0c32a389c280213506becabf6bd61ca71c38a
</pre></head>
</html

the file permisson seems to be ok as far as I know:

root@milton:/var/www/html# ls -l
total 34596
-rw-r--r-- 1 www-data www-data    10701 May  8 11:48 index.html.bak
-rw-r--r-- 1 www-data www-data     2404 May 10 14:06 index.php
-rw-r--r-- 1 www-data www-data       21 May  8 11:53 phpinfo.php
-rw-r--r-- 1 www-data www-data      324 May 18 07:40 test.php
drwxr-xr-x 2 www-data www-data     4096 May 18 07:26 torrents
-rwxrwxrwx 1 www-data www-data 35390656 May 12 02:33 torrenttools
-rw-r--r-- 1 www-data www-data     3012 May 18 07:25 upload.php

what am I doing wrong? this is driving me crazy

When I try running the test.php file from a browser I get a blank page, however, when I try run it from commandline it works perfectly. I am using the function shell_exec to call the program torrenttools to get the hash of a torrent.

Thanks in advance.

Tags:

2

Answers


  1. 0

    Try the following perhaps?

    1. Use absolute file paths for the command tool, and the torrent file to ensure they can be located by the web server.
    2. Check the error logs for the Apache server and see if there is any error messages

    You can try this code to print errors

    $cmd = "./torrenttools info '/var/www/html/torrents/Elle -JP- (Sharp X68000).torrent' | grep hash | cut -b 20-59 2>&1";
$torrenthash = shell_exec($cmd);
echo "<pre>".$torrenthash."</pre>";

$errorOutput = shell_exec("echo $?");
echo "Error Output: ".$errorOutput;
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  2. 0

    Avoid shell_exec whenever possible, it often leads to lots of headaches and security problems.

    The method to generate a hash from the torrent file is documented here.

    You could use christeredvartsen/php-bittorrent to do this in pure PHP. From the shell, include the library in your project:

    composer require christeredvartsen/php-bittorrent

    Then just:

    require_once 'vendor/autoload.php';
$torrent = BitTorrentTorrent::createFromPath('/path/to/file.torrent');
$hash = $torrent->getHash();
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