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system> <proc_terminate
[edit] Last updated: Sat, 12 May 2012

view this page in

shell_exec

(PHP 4, PHP 5)

shell_execExecute command via shell and return the complete output as a string

Description

string shell_exec ( string $cmd )

This function is identical to the backtick operator.

Parameters

cmd

The command that will be executed.

Return Values

The output from the executed command or NULL if an error occurred.

Examples

Example #1 A shell_exec() example

<?php
$output 
shell_exec('ls -lart');
echo 
"<pre>$output</pre>";
?>

Notes

Note:

This function is disabled when PHP is running in safe mode.

See Also



system> <proc_terminate
[edit] Last updated: Sat, 12 May 2012
 
add a note add a note User Contributed Notes shell_exec
trev at dedicate.co.uk 21-Oct-2011 07:34
If you're trying to run a command such as "gunzip -t" in shell_exec and getting an empty result, you might need to add 2>&1 to the end of the command, eg:

Won't always work:
echo shell_exec("gunzip -c -t $path_to_backup_file");

Should work:
echo shell_exec("gunzip -c -t $path_to_backup_file 2>&1");

In the above example, a line break at the beginning of the gunzip output seemed to prevent shell_exec printing anything else. Hope this saves someone else an hour or two.
ilya at linemedia dot ru 16-Dec-2010 08:36
sudo can be executed without storing pass in a file

system('echo "PASS" | sudo -u root -S COMMAND');
fabjoa dot mwoz at gmail dot com 01-Nov-2010 04:02
I don't know how it goes in Windows, but in Linux, shell returns result with a line break at the end, I guess to make it more readable in shell, so don't forget to use trim() to encapsulate the returned result!

if(trim(shell_exec('whoami'))!='www-data')
nowayoutlive.de 26-Feb-2010 01:59
Today I needed a piece of code, which makes use of the shell_exec function. For those who want to scan 2 letter domains too, here is a nice linux and php5 way, using a character generator class.

<?php
define
("__USED_CHARS__", "abcdefghijklmnopqrstuvwxyz0123456789");
define("__CASE_SENSITIVE__", true); // Use string above or use uppercase / lowercase variant

$bf = new chargen(2); // new chargen object, length 2
$bf->generate("whois"); // generate chars and call whois function

function whois($str)
{
       
$domain = $str.".com";

       
$retval = shell_exec("whois $domain");

        if (
eregi("no match", $retval))
                echo
$domain." ist available\n";
        else
                echo
$domain." is unavailable\n";
}

class
chargen
{
        private
$chars = NULL;
        private
$maxlength = NULL;

        protected
$buffer = NULL;

        function
generate($mycallback = false)
        {
                foreach (
$this->buffer as $char)
                {
                        foreach (
$this->chars as $nextchar)
                        {
                               
$retval = $char.$nextchar;
                               
$this->buffer[$retval] = $retval;

                                if (
$mycallback && function_exists($mycallback))
                                       
$mycallback($retval);
                                else
                                        echo
$retval."\n";
                        }
                }

                if (
strlen($retval) == $this->maxlength)
                        return;

               
$this->generate($mycallback);
        }

        function
__construct($maxlength = 8)
        {
               
$chars = array();

               
$this->buffer = array();
               
array_push($this->buffer, "");

                for (
$i = 0; $i < strlen(__USED_CHARS__); $i++)
                {
                       
$index = substr(__USED_CHARS__, $i, 1);

                        if (
__CASE_SENSITIVE__)
                        {
                               
$this->chars[$index] = $index;
                        }
                        else
                        {
                               
$this->chars[strtolower($index)] = strtolower($index);
                               
$this->chars[strtoupper($index)] = strtoupper($index);
                        }
                }

               
$this->maxlength = $maxlength;
        }
}
?>
martin at intelli-gens dot com 17-Feb-2010 03:21
Also after lots of hair pulling why shell_exec didn't want to work for me I found out that in my case some things needed to be set (which normally are set by default).

the options -jo 
-j means: don't recreate the paths found in the archive
-o means: always overwrite files

And I needed to specify the destination path (even though it should unzip in the same directory when not specified), this is done by -d [path]

The strange thing was that I didn't have to put these options when I would give the command on the command-line, only when I would call it with shell_exec.

So the complete command in php would be for me:

shell_exec('unzip -jo /path_to_archive/archive.zip  -d /destination_path')

And putting en echo in front will help you a lot.
it should tell you something like this:
    

Archive:  /path_to_zip/archive.zip
  inflating: /destination_path/file1.jpeg 
  inflating: /destination_path/file2.jpeg
  inflating: /destination_path/file3.jpeg
codeslinger at compsalot dot com 13-Jan-2010 06:47
it took me a heck of a lot of head banging to finally solve this problem so I thought that I would mention it here.

If you are using Eclipse and you try to do something like

<?php

    $out
= shell_exec("php -s $File");   //this fails
?>

it will always fail when run inside of the Eclipse debugger.  This happens on both Linux and Windows.  I finally isolated the problem to changes that Eclipse makes to the environment when debugging.  

The fix is to force the ini setting.  If you don't need an ini then -n is sufficient.

<?php
   
    $out
= shell_exec("php -n -s $File");   //this works
?>

Of course if you run it outside of the debugger then it works fine without the -n.   You may want to use a debug flag to control this behavior.
joelhy 08-Apr-2009 06:29
Here is a easy way to grab STDERR and discard STDOUT:
    add  '2>&1 1> /dev/null' to the end of your shell command

For example:
<?php
$output
= shell_exec('ls file_not_exist 2>&1 1> /dev/null');
?>
dburles@NOSPAMgmailDOTcom 01-Feb-2009 03:07
Easy way to capture error output in windows

// we'll execute a php script as an example:
$out = shell_exec("php test.php 2> output");
print $out ? $out : join("", file("output"));

We assume in this case if the script produces output it has ran ok, the $out variable will then contain the output, if $out is empty then we read the captured error output from a file simply called 'output'.

Hope this helps someone
zd 16-Jan-2009 10:29
It's probably worth noting that shell_exec() return value seems binary safe, while the output array from exec() is not.

In either case, a more controlled way to launch and interact with a process is proc_open() which allows you to have streams and is also binary safe.
Rgemini 07-Jan-2009 03:46
A simple way to handle the problem of capturing stderr output when using shell-exec under windows is to call ob_start() before the command and ob_end_clean() afterwards, like this:

<?php
ob_start
()
$dir = shell_exec('dir B:');
if
is_null($dir)
{  
// B: does not exist
    // do whatever you want with the stderr output here
}
else
// B: exists and $dir holds the directory listing
   // do whatever you want with it here
}
ob_end_clean();   // get rid of the evidence :-)
?>

If B: does not exist then $dir will be Null and the output buffer will have captured the message:

  'The system cannot find the path specified'.

(under WinXP, at least). If B: exists then $dir will contain the directory listing and we probably don't care about the output buffer. In any case it needs to be deleted before proceeding.
dae3 22-Dec-2008 02:53
Beware of the following inconsistency: shell_exec() and the backtick operator will not return a string if the command's output is empty -- they'll return NULL instead.

This will make strict comparisons to '' return false.
redtuugii at yahoo dot com 12-Nov-2008 03:30
if you want get exit status

<?php
$command
= 'ls -lpas';
// Execute the shell command
$shellOutput = shell_exec($command.' > /dev/null; echo $?');
   
//return execute status;
echo trim($shellOutput);
?>
sa577 at gre dot ac dot uk 14-Aug-2008 04:59
The problem described by 'concept at conceptonline dot hu' was mine too (writing the output on the Apache error log instead of returning it). But I think the cause explanation is misleading: it is not due to running script in a different path. The clue for this behaviour as Apache documentation mention is:

"A very wide variety of different messages can appear in the error log. Most look similar to the example above. The error log will also contain debugging output from CGI scripts. Any information written to <i>stderr</i> by a CGI script will be copied directly to the error log." (http://httpd.apache.org/docs/1.3/logs.html#errorlog)

So the most probable cause for this problem is a running script which tends to write its output on stderr instead of stdout. You cannot even capture it by piping (e.g. [command]>[output] syntax of unix).
The smart trick to get rid of this situation (that can become a serious one as I experienced) is one suggested by Anatol Pomozov in his currently non-accessible weblog (I saw his post on archive.com!):
You should add after your command these characters within the qoutation mark:
" 2>&1"
I guess it forces OS to copy stderr on stdout.
sebastianstenzel AT googlemail DOT com 14-Aug-2008 06:06
I had some problems with the charset encoding. German chars like ö or ü have been transformed to some strange code.
This can be resolved by exporting the LANG environment variable (on unix-like systems) before performing the command.

Example:

<?php
shell_exec
('LANG=en_US.utf-8; somecommand -foo');
?>
sebastianstenzel at googlemail dot com 14-Aug-2008 06:06
I had some problems with the charset encoding. German chars like ö or ü have been transformed to some strange code.
This can be resolved by exporting the LANG environment variable (on unix-like systems) before performing the command.

Example:

<?php
shell_exec
('LANG=en_US.utf-8; somecommand -foo');
?>
ben at thelocust dot org 08-Aug-2008 10:59
For those running PHP on IIS under a 64-bit system, but running IIS in 32-bit mode, you will need to grant the IUSR_<machinename> user Read & Execute / Read permissions not on the C:\WINDOWS\SYSTEM32\cmd.exe file, but instead on the C:\WINDOWS\SysWOW64\cmd.exe - which is the 32-bit version of the command prompt.
saivert at saivert dot com 12-May-2008 08:48
How to get the volume label of a drive on Windows

<?php

function GetVolumeLabel($drive) {
 
// Try to grab the volume name
 
if (preg_match('#Volume in drive [a-zA-Z]* is (.*)\n#i', shell_exec('dir '.$drive.':'), $m)) {
   
$volname = ' ('.$m[1].')';
  } else {
   
$volname = '';
  }
return
$volname;
}

print
GetVolumeLabel("c");

?>

Note: The regular expression assumes a english version of Windows is in use. modify it accordingly for a different localized copy of Windows.
Anonymous 08-Apr-2008 08:35
In response to nathandehert and Paul Cook, rather than sudoing to execute a command, you might want to abstract the command(s) into a yet another script (php, perl, bash, whatever) and make use of the setuid bit.  then just execute that script from php.  of course, bear in mind the security implications of setuid.
gabekon at gmail dot com 03-Apr-2008 08:33
RE: kamermans note,

I was having a similar problem with the PATH variable when using shell_exec. Even with a hard-coded full path to a binary, I also got an error about a .so file that could not be found. After some reading up, I realized I had to set the LD_LIBRARY_PATH variable:

<?php

$command
= 'export LD_LIBRARY_PATH="' . $path_to_library_dir .'"; ' . $path_to_binary;
shell_exec($command);

?>

Hope this saves someone a headache,

- G
guenter at grodotzki dot ph 16-Jan-2008 08:07
If the return is empty, then command could not be executed or executed command returned an error.
mandor at mandor dot net 19-Nov-2007 02:02
Even when external program returns an ISO-8859-1 encoded string, PHP "parses" the encoded string as ASCII, expanding accented characters as their literal string form and not their binary form.
Basically, this mangles every accented character of the output from Windows external program.

Below is how I fixed it for french accented characters:

<?php

   
echo shell_exec('echo éêèëàâäîïùûüôöç');
   
// The output of this will be something like: ‚ˆŠ‰…ƒ„Œ‹—–“”‡
    // Not quite what was expected...

    // This is the function that fixes accented characters.
   
function fix_string($str) {
        return
strtr($str,
           
chr(130).chr(136).chr(138).chr(137).
           
chr(133).chr(131).chr(132).chr(140).
           
chr(139).chr(151).chr(150).chr(129).
           
chr(147).chr(148).chr(135),
           
chr(233).chr(234).chr(232).chr(235).
           
chr(224).chr(226).chr(228).chr(238).
           
chr(239).chr(249).chr(251).chr(252).
           
chr(244).chr(246).chr(231)
        );
    }

    echo
fix_string(shell_exec('echo éêèëàâäîïùûüôöç'));
   
// We now get a proper output!

?>
RoBorg 08-Nov-2007 07:45
The Subversion error "svn: Can't recode string" can be caused by the locale being wrong.  Try
<?php
putenv
('LANG=en_US.UTF-8');
?>
(or whatever your preferred locale is) before you call shell_exec()
kamermans at teratechnologies dot net 15-Oct-2007 08:01
I'm not sure what shell you are going to get with this function, but you can find out like this:

<?php
$cmd
= 'set';
echo
"<pre>".shell_exec($cmd)."</pre>";
?>

On my FreeBSD 6.1 box I get this:

USER=root
LD_LIBRARY_PATH=/usr/local/lib/apache2:
HOME=/root
PS1='$ '
OPTIND=1
PS2='> '
LOGNAME=root
PPID=88057
PATH=/etc:/bin:/sbin:/usr/bin:/usr/sbin
SHELL=/bin/sh
IFS='    
'

Very interesting.  Note that the PATH may not be as complete as you need.  I wanted to run Ghostscript via ImageMagik's "convert" and ended up having to add my path before running the command:

<?php
$cmd
= 'export PATH="/usr/local/bin/"; convert -scale 25%x25% file1.pdf[0] file2.png 2>&1';
echo
"<pre>".shell_exec($cmd)."</pre>";
?>

ALSO, note that shell_exec() does not grab STDERR, so use "2>&1" to redirect it to STDOUT and catch it.
eric dot peyremorte at iut-valence dot fr 05-Oct-2007 02:01
I had trouble with accented caracters and shell_exec.

ex :

Executing this command from shell :

/usr/bin/smbclient '//BREZEME/peyremor' -c 'dir' -U 'peyremor%*********' -d 0 -W 'ADMINISTRATIF' -O 'TCP_NODELAY IPTOS_LOWDELAY SO_KEEPALIVE SO_RCVBUF=8192 SO_SNDBUF=8192' -b 1200 -N 2>&1

gave me that :

Vidéos                             D        0  Tue Jun 12 14:41:21 2007
  Desktop                            DH        0  Mon Jun 18 17:41:36 2007

Using php like that :

shell_exec("/usr/bin/smbclient '//BREZEME/peyremor' -c 'dir' -U 'peyremor%*******' -d 0 -W 'ADMINISTRATIF' -O 'TCP_NODELAY IPTOS_LOWDELAY SO_KEEPALIVE SO_RCVBUF=8192 SO_SNDBUF=8192' -b 1200 -N 2>&1")

gave me that :

  Vid  Desktop                            DH        0  Mon Jun 18 17:41:36 2007

The two lines were concatenated from the place where the accent was.

I found the solution : php execute by default the command with LOCALE=C.

I just added the following lines before shell_exec and the problem was solved :

$locale = 'fr_FR.UTF-8';
setlocale(LC_ALL, $locale);
putenv('LC_ALL='.$locale);

Just adapt it to your language locale.
Woody/mC 12-Jul-2007 07:07
regarding the "ping" test that was mentioned by andy25it at hotmail dot it:

this might not work if the target server is behind a firewall which drops icmp packets. a better approach would be the use of fsockopen(), which doesn't use icmp. in the notes section of the function list, Alexander Wegener wrote a nice implementation of an isOnline() function which works with both http and https.
d-skyman at gmx dot de 08-Apr-2007 10:43
Got it! That was a "how does the windows scripting host work" problem.
Here's the answer:
<?php
$runCommand
= "C:\\WINDOWS\\system32\\shutdown.exe -t:30"; //Wrong by purpuse to get some good output
$WshShell = new COM("WScript.Shell");
$output = $WshShell->Exec($runCommand)->StdOut->ReadAll;
echo
"<p>$output</p>";
?>
RayJ 25-Feb-2007 09:07
After many failed attempts to find a way to run a php script in the background (the script had to be activated from a web browser). Since I create and test my scripts on a windows box, I need an automatic way to detect if the script was running on windows or the Linux server. The activated script will continue to run even if you close your browser.

<?php
  $runCommand
= 'php -q FULLPATH/FILE.php';

  if(isset(
$_SERVER['PWD'])//*nix (aka NOT windows)
 
{
   
$nullResult = `$runCommand > /dev/null &`;
  }
  else
//windowz
 
{
   
$WshShell = new COM("WScript.Shell");
   
$oExec = $WshShell->Run($runCommand, 7, false);
  }
?>

Also, to get the correct "basepath" from the script that runs in the background. try:

<?php
  ignore_user_abort
(true);
 
set_time_limit(0);

  if(isset(
$_SERVER['PWD']))
  {
$basepath = $_SERVER['PWD']; }
  else
  {
$basepath = ereg_replace('[^/]*$', '', $_SERVER['PHP_SELF']); }

 
$extendedpath = '/path1/path2/';
 
$basepath = preg_replace("|(?:{$extendedpath})$|i",'',$basepath);

  echo
'Start In: '.$basepath;
?>

Enjoy!

Later, RayJ
arturm at union dot com dot pl 29-Oct-2006 02:28
If someone has problems with IIS6 and CGI error message "The specified CGI application misbehaved by not returning a complete set of HTTP headers.", simply make sure that headers are already sent:
echo "<head>";
flush();
$result = shell_exec('C:\util\myprog.exe');
kees dot schepers at infolook dot nl 12-Oct-2006 05:27
If you are using a Windows server with IIS, and you try to execture a batch file with shell_exec() function, or his related functions you should do it like this:

<?
shell_exec
("C:\\path\\to\\cmd.exe /c C:\\batchfile.cmd");
?>

Note the parameter /c which says "Carries out the ommand specified by string and then terminates"

If you don't add the parameter /c the batch file will not be executed, only the cmd.exe file will.

As, also mentiod in these commants, put your cmd.exe file in your php folder, and your windows folder for security reasons.
Paul Cook 16-Sep-2006 11:00
The technique mentioned by Nathan De Hert below is rather insecure -- you should never leave a password lying around in a file readable by the apache user.

If you need this sort of functionality on *nix systems, have a look at the /etc/sudo file (edited with the command 'visudo'). The tag NOPASSWD allows specified commands to be run as root by another user, without needing to specify a password. It's a little extra configuration, but much more secure.
ruan at nospam dot tillcor dot com 24-Aug-2006 08:31
When following Kenneth's method for executing root scripts via the nanoweb server mentioned on this page you would most likely need to be able to run a text-mode browser like lynx and pass the php script to it (works great).

After struggling for a while (lynx kept asking me to download the file instead of executing it), I realised that I had to install php-cgi additionally and modify the nanoweb config file  to use that php interpreter instead of /usr/bin/php. (On Debian this is the CLI version).

On Ubuntu 6.06:

apt-get install php5-cgi

After editing /etc/nanoweb/nanoweb.conf and a quick restart of the web server, lynx and links will execute your PHP scripts properly.

Hope this helps somebody else out there :)

Ruan Fourie
nathandehert at no spam gmail dot com 07-Aug-2006 01:29
If you want to execute shell commands as root theres another workaround.

<?php
shell_exec
('sudo -u root -S command_goes_here < /home/$User/dir/dir/dir/passfile');
?>

It will readout the file 'passfile' that you've hidden under quite some dirs (to make it a bit less insecure) and use the content as password to login as root.

Note that storing your root password is far from secure but it's an easy way to execute commands under root in controlled environments.

Nathan De Hert
Kishan 04-Aug-2006 10:27
If you are on windows and has Cygwin, You can execute all your Cygwin binaries using shell_exec() as follows:

<?
$result
= shell_exec("C:\cygwin\bin\bash.exe --login  -c '/cygdrive/c/cygwin/bin/convert.exe --version'");
print(
$result);
?>

The key is the "--login"  option which appends all the required common cygwin binary and library paths to $PATH. Without this option some of the cygwin binaries that links to other libraries ( Like ImageMagick binaries which links to X11 ) will not work and you may see errors like "cygX11-6.dll not found, Could not start convert.exe"
doo_mangle_fus at by_mangle_u dizzot net 02-Aug-2006 12:00
If you're on a host that provides neither shell access nor a way to unzip uploaded archives, you can use PHP to call the unzip utility with shell_exec() (provided they're not also running in safe mode). Just make sure that PHP has write permission to the destination directory, or it won't work.

Here's an example script that accomplishes this, which you're free to use if you so chose:

<?php
$passwd
= 'censored';
$filename = 'archive.zip';
$options = '-o'//Overwrite existing files by default; this is mostly to suppress confirmations
$destDir = '';

if (isset (
$_POST['password']))  {
    if (
$_POST['password'] == $passwd)  {
        if (isset (
$_POST['filename']))  { $filename = escapeshellarg ($_POST['filename']); }
        if (isset (
$_POST['updateExisting']))  { $options .= "u"; }  //use with care, since a timezone mismatch may occur; see man unzip
       
if (isset ($_POST['destDir']))  { $destDir = ' -d '. escapeshellarg ($_POST['destDir']); }
       
        echo
"<pre>";
        echo
shell_exec ("unzip $options {$filename}{$destDir}");
        echo
"</pre>";
    }
    else  {
       
outputPage ("Your password didn't check out, mon. Better try it again, eh?");
    }
}
else  {
outputPage(); }

function
outputPage ($errorMessage = '')  {
    echo <<<HTML
        <html><head><title>Unzip password verification</title>
            <style type="text/css">
                td.left  { text-align: right; }
                td.right { text-align: left; }
               
                div  { color: red; border: 1px solid gray; padding: 4px; }
            </style>
        </head>
        <body>
HTML;

    if (!empty (
$errorMessage))  { echo "\n<div>$errorMessage</div>\n"; }
   
    echo <<<HTMLL
        <h1>Super Duper File Unzipper</h1>
        <form name="zipform" method="post" action="unzipper.php">
            <table>
                <tr>
                    <td class="left">Filename:</td>
                    <td class="right"><input type="text" name="filename" size="50" maxlength="255" /></td>
                </tr><tr>
                    <td class="left">Destination Directory:</td>
                    <td class="right"><input type="text" name="destdir" size="50" maxlength="1000" /></td>
                </tr><tr>
                    <td class="left">Password:</td>
                    <td class="right"><input type="password" name="password" size="15" maxlength="30" /></td>
                <tr>
                    <td colspan="2"><input type="checkbox" name="updateExisting" />Update existing files</td>
                </tr><tr>
                    <td class="right"><input type="reset" value="Reset" /></td>
                    <td class="left"><input type="submit" value="Unzip it!" /></td>
                </tr>
            </table>
           
        </form>
        </body>
        </html>
HTMLL;
}
?>
rustleb at hotmail dot com 05-Jun-2006 01:45
For capturing stdout and stderr, when you don't care about the intermediate files, I've had better results with . . .
<?php
function cmd_exec($cmd, &$stdout, &$stderr)
{
   
$outfile = tempnam(".", "cmd");
   
$errfile = tempnam(".", "cmd");
   
$descriptorspec = array(
       
0 => array("pipe", "r"),
       
1 => array("file", $outfile, "w"),
       
2 => array("file", $errfile, "w")
    );
   
$proc = proc_open($cmd, $descriptorspec, $pipes);
   
    if (!
is_resource($proc)) return 255;

   
fclose($pipes[0]);    //Don't really want to give any input

   
$exit = proc_close($proc);
   
$stdout = file($outfile);
   
$stderr = file($errfile);

   
unlink($outfile);
   
unlink($errfile);
    return
$exit;
}
?>

This isn't much different than a redirection, except it takes care of the temp files for you (you may need to change the directory from ".") and it blocks automatically due to the proc_close call.  This mimics the shell_exec behavior, plus gets you stderr.
squeegee 04-May-2006 10:36
Each time you call shell_exec, it operates in a completely new shell. So if you need to do different multiple things in it based on whatever criteria, assemble your command ahead of time:

instead of

<?php
shell_exec
("cd $path_to_dir");
shell_exec("ls -l");
?>

which, as you noted, won't work, do

<?php
$cmd
= "cd $path_to_dir; ";
if(
$a == true)$cmd .= "ls -l";
else
$cmd .= "du -h";
$result = shell_exec($cmd);
?>
notmespammers-iain at iaindooley dot com 19-Feb-2006 03:38
beware!

shell_exec('cd /path/to/dir');
shell_exec('ls -l');

will not give a listing of /path/to/dir!! use chdir() if you need to change directories, or group your commands with && (not always convenient/possible)

cheers

iain
rigsbr at yahoo dot com dot br 16-Feb-2006 06:24
If you need to execute a command without permission and could not execute it by ssh or install any extension, there is a way in Apache 1.3.x and PHP 4.
Create a file on cgi-bin directory, like this:

#!/usr/bin/php
<?
 
echo shell_exec('whoami');
?>

Don't forget to set the file you created the permission to execute it. Hence, call it from browser and you will se that this script will be executed by the shell user and not the user nobody (apache default user if running a PHP script).
andy25it at hotmail dot it 02-Jan-2006 09:06
As a webmaster i often deal with other servers with respect to the one that hosts my own site.
I actually had to face the following problem: some web pages depend directly from other webservers for example including a IMG SRC tag pointing to a remote image; but what if the remote server is temporary down? The download of the page remains in an incomplete state. It'd be better an error message for sure ! But how can i know whether the remote server is up or down? PING IT  is the answer..but how can i use a shell system function that outputs only text into some PHP scripting?..here the solution:

<?php

/*
the host whose service status has to be checked out
*/
$host_to_ping = "www.somehost.net" ;

/*
I ping twice the host (a higher number of ping would only result the execute script time to be MUCH high).
The result of the output ping command is stored into a variable. This can be done beacuse of the properties and features of the shell_exec() function, see above to know more.
*/
$outputShell = shell_exec("ping -c2 -w2 $host_to_ping") ;

/*
Now the only thing i have to do is to look up the '0 received' string into the output to know whether the server is down or up.
*/

if(strpos($outputShell, '0 received')) {
  
  
#SERVER is DOWN so i include an error message

}
else {

  
#SERVER is UP so i include the normal code that is meant to be included by default

}

?>

I used the shell_exec() function for 2 reasons:

1) the system() function is disabled in my webserver by the hosting company for security reasons

2) the shell_exec() function returns a string containing the output of the shell command.

Regards to the community. Hope to have given a hand.

Andrea from Italy
Ashraf Kaabi 19-Dec-2005 10:06
I've write a Full Class for Run in Background, Kill PID , check if is Running

<?php
/**
 * @author     Ashraf M Kaabi
 * @name       Advance Linux Exec
 */
class exec {
   
/**
     * Run Application in background
     *
     * @param     unknown_type $Command
     * @param     unknown_type $Priority
     * @return     PID
     */
   
function background($Command, $Priority = 0){
       if(
$Priority)
          
$PID = shell_exec("nohup nice -n $Priority $Command > /dev/null & echo $!");
       else
          
$PID = shell_exec("nohup $Command > /dev/null & echo $!");
       return(
$PID);
   }
  
/**
    * Check if the Application running !
    *
    * @param     unknown_type $PID
    * @return     boolen
    */
  
function is_running($PID){
      
exec("ps $PID", $ProcessState);
       return(
count($ProcessState) >= 2);
   }
  
/**
    * Kill Application PID
    *
    * @param  unknown_type $PID
    * @return boolen
    */
  
function kill($PID){
       if(
exec::is_running($PID)){
          
exec("kill -KILL $PID");
           return
true;
       }else return
false;
   }
};
?>
php [AT] jsomers [DOT] be 27-Sep-2005 06:00
<?php

/**
 * PHP Kill Process
 *
 * Sometimes, it can happen a script keeps running when it shouldn't, and it
 * won't stop after we close the browser, or shutdown the computer. Because it's
 * not always easy to use SSH there's a workaround.
 *
 * @author      Jensen Somers <php@jsomers.be>
 * @version     1.0
 */
 
class KillAllProcesses {
   
/**
     * Construct the class
     */
   
function killallprocesses() {
       
$this->listItems();
    }
   
   
/**
     * List all the items
     */
   
function listItems() {
       
/*
         * PS   Unix command to report process status
         * -x   Select processes without controlling ttys
         *
         * Output will look like:
         *      16479 pts/13   S      0:00 -bash
         *      21944 pts/13   R      0:00 ps -x
         *
         */
       
$output =   shell_exec('ps -x');
       
       
$this->output($output);
       
       
// Put each individual line into an array
       
$array  =   explode("\n", $output);
       
       
$this->doKill($array);
    }
   
   
/**
     * Print the process list
     * @param   string  $output
     */
   
function output($output) {
        print  
"<pre>".$output."</pre>";
    }
   
   
/**
     * Kill all the processes
     * It should be possible to filter in this, but I won't do it now.
     * @param   array   $array
     */
   
function doKill($array) {
       
/*
         * Because the first line of our $output will look like
         *        PID TTY      STAT   TIME COMMAND
         * we'll skip this one.
         */
       
for ($i = 1; $i < count($array); $i++) {
           
$id =   substr($array[$i], 0, strpos($array[$i], ' ?'));
           
shell_exec('kill '.$id);
        }
    }
}

new
KillAllProcesses();

?>

It's not the very best solution, but I've used it a couple of times when I needed to do it quick without to much trouble.
Make not I kill all the processes, on my server px -x will only return like 4 times /sbin/apache and it's pretty safe to kill them without any trouble.
concept at conceptonline dot hu 19-Sep-2005 02:02
Interestingly, if you execute a script which is not in your path (or you have made a typo, or if the script does no exist at all), you will get no return value. The error will be logged into the error_log of your webserver.

Someone could add a note how this can be (if it could be) overriden, as the standard behaviour is not really fool-proof.
ludvig dot ericson at gmail dot com 01-Sep-2005 11:50
(if you have any other way of doing this PLEASE send me a mail)
(The following note is interesting to *NIX administrators ONLY)
Jailing a PHP CLI session is not the easiest thing to do.

PHP has a gigantic list of dependencies, you can check it by
ldd `which php`
Each of these .so files (shared libraries) can have dependencies, and can depend on each other, making the list much bigger.
However, there are tools out there to copy all dependencies into a jailed directory, you just have to search for them - and I had no luck.

What I did was just to run these few commands:
su
mkdir /jailpath && mkdir /jailpath/lib
cp /lib/*.so* /jailpath/lib/
mkdir /jailpath/usr && mkdir /jailpath/usr/bin && mkdir /jailpath/usr/lib
cp /usr/lib/*.so* /jailpath/usr/lib
cp `which php` /jailpath/usr/bin
chmod -R 0755 /jailpath && chown -R root:root /jailpath && chmod 0000 /jailpath

Do note that this copies _all_ of your shared objects. There is one or two more libraries you have top copy, but chroot will tell you about which one it is.

Hope this helped somehow.
jesuse dot gonzalez at venalum dot com dot ve 15-Jul-2005 04:34
Here is an example of how you can execute a command in background an get the Process ID created by *NIX, for future reference or monitoring.

<?php
   
//Run linux command in background and return the PID created by the OS
   
function run_in_background($Command, $Priority = 0)
    {
        if(
$Priority)
           
$PID = shell_exec("nohup nice -n $Priority $Command > /dev/null & echo $!");
        else
           
$PID = shell_exec("nohup $Command > /dev/null & echo $!");
        return(
$PID);
    }
?>

There is also a trick which  I use to track if the background task is running using the returned PID

<?php
   
//Verifies if a process is running in linux
   
function is_process_running($PID)
    {
       
exec("ps $PID", $ProcessState);
        return(
count($ProcessState) >= 2);
    }
?>

I commonly use both functions in combination to batch copy big mysql tables in background and wait for the copy process to finish sending chunks to the client browser in the following way:

<?php
    $CopyTaskPid
= run_in_background("mysql --user=backup_user --password=backup_user_password --execute='INSERT INTO `backup-db`.`table` SELECT * FROM `online-db`.`table`'", "+20");
    while(
is_process_running($CopyTaskPid))
    {
        echo
".";
       
ob_flush(); flush();
       
sleep(2);
    }
?>
joanacosta at prodigy dot net dot mx 24-May-2005 05:25
Here is another good example of how to Create a File with some variables already defined by user, and creating a file with them. of course using shell_exec

<?php
$generatefile
= shell_exec("echo '$thisFOLIO','$thisREPORTO','$thisRESOLVIO','$thisVISTOB'  > datosmanda.txt");
echo
"<pre>$generatefile</pre>";
?>

Php Is Great.... cheers
dk at brightbyte dot de 13-May-2005 01:25
her's a function that is similar to shell_exec but captures both stdout and stderr. It's much more complicated than using 2>&1, but it's independent of the shell and should work on windows, too. It uses proc_open with stream_select and non-blocking streams to read stdout and stderr concurrently. It is not guarantied that the lines appear in the correct order or that they are not intermingeled - but it did not happened when I tested it. So, here goes:

<?php
   
function runExternal($cmd,&$code) {
       
$descriptorspec = array(
           
0 => array("pipe", "r"),  // stdin is a pipe that the child will read from
           
1 => array("pipe", "w"),  // stdout is a pipe that the child will write to
           
2 => array("pipe", "w") // stderr is a file to write to
       
);
       
       
$pipes= array();
       
$process = proc_open($cmd, $descriptorspec, $pipes);
       
       
$output= "";
       
        if (!
is_resource($process)) return false;
       
       
#close child's input imidiately
       
fclose($pipes[0]);
       
       
stream_set_blocking($pipes[1],false);
       
stream_set_blocking($pipes[2],false);
       
       
$todo= array($pipes[1],$pipes[2]);
       
        while(
true ) {
           
$read= array();
            if( !
feof($pipes[1]) ) $read[]= $pipes[1];
            if( !
feof($pipes[2]) ) $read[]= $pipes[2];
           
            if (!
$read) break;
           
           
$ready= stream_select($read, $write=NULL, $ex= NULL, 2);
           
            if (
$ready === false) {
                break;
#should never happen - something died
           
}
           
            foreach (
$read as $r) {
               
$s= fread($r,1024);
               
$output.= $s;
            }
        }
       
       
fclose($pipes[1]);
       
fclose($pipes[2]);
       
       
$code= proc_close($process);
       
        return
$output;
    }
?>

here is how to use it:

<?php
$result
= runExternal("ls -l some-file.txt",$code);

print
"<pre>";
print
$result;
print
"</pre>\n";

print
"<b>code: $code</b>\n";
?>

enjoy :-)
phillipberry at NOSPAM dot blisswebhosting dot com 11-Apr-2005 01:13
I found something odd.

If you run exec then straight after shell_exec the shell_exec will simply not run and will return NULL.

To get it to work i put a sleep(5) after the exec and now shell_exec works fine.
Kenneth 09-Mar-2005 09:19
Sometimes it's needed to be able to execute shell commands as root using PHP. For instance, restarting named after adding or changing zones, or adding new alliases for sendmail.

My approach is to run a server called Nanoweb, available from  http://nanoweb.si.kz/. It's a webserver written in PHP, and needs only the pcntl extension extra to operate. Nanoweb is configured to only listen for connections on localhost, port 81 for example. From my normal PHP scripts running inside Apache I simply call scripts in Nanoweb to get the messy 'root' tasks done. Much more secure and safer.

Hope this helps
03-Jan-2005 09:10
Be careful as to how you elevate privileges to your php script.  It's a good idea to use caution and planing.  It is easy to open up huge security holes.  Here are a couple of helpful hints I've gathered from experimentation and Unix documentation.

Things to think about:

1. If you are running php as an Apache module in Unix then every system command you run is run as user apache.  This just makes sense.. Unix won't allow privileges to be elevated in this manner.  If you need to run a system command with elevated privileges think through the problem carefully!

2. You are absolutely insane if you decide to run apache as root.  You may as well kick yourself in the face.  There is always a better way to do it.

3. If you decide to use a SUID it is best not to SUID a script.  SUID is disabled for scripts on many flavors of Unix.  SUID scripts open up security holes, so you don't always want to go this route even if it is an option.  Write a simple binary and elevate the privileges of the binary as a SUID.  In my own opinion it is a horrible idea to pass a system command through a SUID-- ie have the SUID accept the name of a command as a parameter.  You may as well run Apache as root!
snoj-wwwposter at latitude dot li 29-Sep-2004 02:53
if the script you want to run from shell_exec needs more permissions than the webserver has (for example script needs root priviliges, do:

# chown root:root
# chmod 4711!

of course, replace root:root with the user that the script needs to run as and tweek the chmod for your security policy.

!! be careful about what the script does!  remember it has root privilige!
James McCormack 05-Aug-2004 01:50
I had a perl program which ran fine from command line but not using shell_exec(), exec() or system() - nothing was being returned. I was using the full path and permissions were set correctly.

It turned out the perl program was using more memory than my PHP.INI file was set to allow. Increasing "memory_limit" solved the problem.
leaetherstrip at inbox dot ru 08-Jul-2004 02:23
Note on XP users: XP-Home edition does not allow to set rights directly on files and folders. You should use 'cacls' command-line utility to do this.

For example:

cacls c:\windows\system32\cmd.exe /E /G IUSR_ADMIN2003:F

gives IIS user full access to cmd.exe (potential security hole!), so PHP can fork and execute external programs.
vsuarez at vorealis dot com 30-Jun-2004 06:34
Got the error "Unable to execute..." when trying to run an external program with shell_exec under Windows XP, IIS 5, php 4.3.7  Solved by giving the IIS user (IUSR_...) execution privileges on the system file %systemroot%\system32\cmd.exe  This should be used carefully because may represent a server's security hole.
dj-bj at gmx dot net 17-Mar-2004 05:22
shell_exec passes the result to a variable only if the result of the command is true.

When the result is false the generated page contains the error string in clear text at the position the result was fetched (which can differ from reload to reload).

If you would like to recieve also the error messages append 2>&1 to the end of the command you are executing.
However, the result is also passed to the page directly.

To avoid page destruction you should not fetch the result in your script.
By appending >nul to the shell command you can hide any output.
Hope this helps.
Martin Rampersad 11-Jan-2004 01:13
I have PHP (CGI) and Apache. I also shell_exec() shell scripts which use PHP CLI. This combination destroys the string value returned from the call. I get binary garbage.  Shell scripts that start with #!/usr/bin/bash return their output properly.

A solution is to force a clean environment.  PHP CLI no longer had the CGI environment variables to choke on.

<?php

// Binary garbage.
$ExhibitA = shell_exec('/home/www/myscript');

// Perfect.
$ExhibitB = shell_exec('env -i /home/www/myscript');

?>

-- start /home/www/myscript
#!/usr/local/bin/phpcli
<?php

echo("Output.\n");

?>
-- end /home/www/myscript
spagmoid at yahoo dot NOSPAMcom 17-Dec-2003 02:52
Note that whatever you run with this function seems to use PHP memory, so it will die if it exceeds the limit (usually 8 megs)  To do database dumps or other memory-hogging operations use something like system() instead.
jessop <AT> bigfoot <DOT> com 03-Dec-2003 12:19
Just a quick reminder for those trying to use shell_exec on a unix-type platform and can't seem to get it to work. PHP executes as the web user on the system (generally www for Apache), so you need to make sure that the web user has rights to whatever files or directories that you are trying to use in the shell_exec command. Other wise, it won't appear to be doing anything.
ericphp at shepard dot com 23-Nov-2003 02:45
I had major problems getting sell_exec() to work from PHP. It was working fine via the Telnet command line.

Turns out (for me anyway) it was a pathing problem. I'm set up on a VPS FreeBSD server the does not (technically) have root access.

PHP needs to reference the FULL PATH to the app it's calling. But it gets more tricky than that. There may be more than one full path on a server. For instance, on mine there is:

>find ~/ -name mysqldump (VPS non-root search method)

/usr/local/bin/mysqldump
/usr/home/myusername/usr/local/bin/mysqldump
/usr/home/myusername/usr/local/mysql-3.23.41/bin/mysqldump
/usr/home/myusername/usr/local/mysql-3.23.43/bin/mysqldump

Turns out (after 5 hours of hair pulling fun) that /usr/home/myusername/usr/local/mysql-3.23.43/bin/mysqldump was the winner.

The same applies to using cURL and PHP via Cron. /usr/home/myusername/usr/local/curl-7.10.5/bin/curl  works for me there.

And tar wouldn't work until I dug up PHPTAR /usr/home/myusername/usr/local/bin/phptar. Never new that existed ...

Good luck.
moneyboi at fuckwindows dot com 16-Jul-2003 06:46
shell_exec("yourscript.sh") is great for opening shell scripts.
eremi at eremi dot net 09-Jun-2003 10:29
To output the command has it should be, you can do the str_replace trick above, or you can put the output in a <pre> tag.

Example:
<?php
  $output
= shell_exec("[command]");
  echo
"<pre>$output</pre>";
?>
Ben 04-Jun-2003 10:01
When running subprocesses via shell_exec (and maybe others) from Apache/mod_php4, Apache's environment variables don't seem to be passed on to the subprocess environment unless you specifically force them by using putenv something like this:

$remaddr = getenv("REMOTE_ADDR");
putenv("REMOTE_ADDR=$remaddr");
shell_exec("/path/to/subprocess");
dan at mathjunkies.com 15-Apr-2003 09:02
Just a note for anybody who's box is involuntarily running in safemode (i.e. you buy space on a server), or just not working right.  Shell commands won't work.  You can, however, use PHPs FTP functions to FTP in.  I was copying files and making directories, but I assume there might be a way to do something more complex.
mcbeth at broggs dot org 14-Apr-2003 02:18
As far as error checking on the last example.  Several of the shells have the && operator, so you just string your commands together using it instead of ; If at any time any of the programs fail, you will return without running the rest
ron dot petty at unigeek dot com 21-Mar-2003 11:40
Here is an example on how to install software using php

shell_exec("cd /usr/local/src/; gunzip program.tar.gz; tar xvf program.tar; cd program; ./configure; make; make install);

Now depending if your root or not some commands like "make install" may fail.  This doesn't do any error checking, the reason for that is I do not know how to cd to a directory and then execute another command unless they are in the same shell. 

So basically, take what you type on the command line and string them together.
bruce at accumatics dot com 01-Feb-2003 09:24
If you're not getting any output from echo shellexec( "count.pl" ) [for instance], at least try "./count.pl" before bothering with the full path.
flame 29-Jan-2003 06:21
add  '2>&1' to the end of your shell command to have STDERR returned as well as STDOUT.

$shell_return = shell_exec($shell_command." 2>&1");
ryon -at- ryon labaw -dot- com 17-Jan-2003 12:47
Note: You cant used shell_exec() when safemode = on (its disabled), instead use
exec() and copy the needed program into the /nonexec directory (by default, set in php.ini).
dj-bj at gmx dot net 17-Dec-2002 06:27
Running PHP 4.2.3 on Windows 2000 Server shell_exec works fine and passes its output to the variable when the result of the executed command is true.
However, if the command fails and the DOS-shell returns an error the result is no longer availiable in the variable but is passed directly to the page.
yaacov at pleasedontspamme dot spam 29-Oct-2002 10:46
If you're running scripts or commands and can't figure out what's not working, check to make sure that you're not using an alias in place of a command. PHP (quite reasonably) doesn't seem to recognise aliases.
php at chris-decker dot com 24-Jun-2002 11:12
I have found it easiest to use the following code to execute a shell command and return all of it's output (not just the last line) to the user as if he/she were sitting at the terminal:

$output = shell_exec("$command");
echo(nl2br($output));
matt_smith&uconn_edu 18-Jun-2002 09:51
Re: executing scripts that work on command line, but not from PHP system() calls -- Make sure you include the full path to the executable.
tonysb at gmx dot net 30-Mar-2002 12:57
shell_exec is extremely useful as a substitute for the virtual() function where unavailable (Microsoft IIS for example). All you have to do is remove the content type string sent in the header:

<?
$mstrng
= shell_exec('yourcgiscript.cgi');
$mstrng = ereg_replace( "Content-type: text/html", "", $mstrng );
echo
$mstrng;
?>

This works fine for me as a substitute for SSI or the virtual() func.

Anton Babadjanov
http://www.vbcn.com.ar

 
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