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PHP : Function Reference : Program Execution Functions : system


Execute an external program and display the output (PHP 4, PHP 5)
string system ( string command [, int &return_var] )

system() is just like the C version of the function in that it executes the given command and outputs the result.

The system() call also tries to automatically flush the web server's output buffer after each line of output if PHP is running as a server module.

If you need to execute a command and have all the data from the command passed directly back without any interference, use the passthru() function.



The command that will be executed.


If the return_var argument is present, then the return status of the executed command will be written to this variable.

Return Values

Returns the last line of the command output on success, and FALSE on failure.


Example2015.system() example

echo '<pre>';

// Outputs all the result of shellcommand "ls", and returns
// the last output line into $last_line. Stores the return value
// of the shell command in $retval.
$last_line = system('ls', $retval);

// Printing additional info
echo '
<hr />Last line of the output: '
. $last_line . '
<hr />Return value: '
. $retval;



If you are going to allow data coming from user input to be passed to this function, then you should be using escapeshellarg() or escapeshellcmd() to make sure that users cannot trick the system into executing arbitrary commands.


If you start a program using this function and want to leave it running in the background, you have to make sure that the output of that program is redirected to a file or some other output stream or else PHP will hang until the execution of the program ends.


When safe mode is enabled, you can only execute executables within the safe_mode_exec_dir. For practical reasons it is currently not allowed to have .. components in the path to the executable.


With safe mode enabled, the command string is escaped with escapeshellcmd(). Thus, echo y | echo x becomes echo y \| echo x.

Related Examples ( Source code ) » system

Code Examples / Notes » system


z1a7n8g, your system logging to file function was really useful, but had two errors:
that line needs a second closing ')'
while ($line)
returns true until your script runs out of memory. Those two lines can be combined:


You probably want to check your system calls for errors. The convention is to return 0  for "no error" which is the same as FALSE which can be confusing. You need to do something like:
 $cmd = "/usr/bin/pngtopnm $png_file > $pnm_file";
 ($return_value == 0) or die("returned an error: $cmd");


Windows XP (IIS) users: (Unable to fork Problem)
If you receive something like:
Warning:  passthru() [function.passthru]: Unable to fork [dir] in c:\Inetpub\wwwroot\ping.php on line X
1. Copy CMD.EXE file from the Windows\System32\ folder to your PHP directory (c:\PHP\).
This should fix the problem.

a dot paul

Well system is a pretty interesting and useful function.
This might have been already pointed out by predessors but anyways, for anyone looking to execute command line queries from php or scripts in general, this function does the trick.
However while using the command, you have to always think in terms of the command you are using as the function and the parameters as the arguments.
So say I want to do a 'ls -ls' on /home/sites/sitexyz/www/$username
I could do a
system("ls -la \"/home/sites/sitexyz/www/$username\" ");
Its important to think of this as passing      /home/sites/sitexyz/www/$username     as an argument to the function ls -la .
Similarly, you could do a
system("cp -r \"/home/sites/sitexyz/www/$username\"  \"/home/sites/sitexyz/www/$username2\" ");
But you then need to use 'chmod -R 777 to the directory you want to copy it to, which can be done by a  
system("chmod -R 777   \"/home/sites/sitexyz/www/$username2\" ");
Now you can execute all the terminal commans via the php, however do realise the security concerns of using the same, especially when the operation is going to preceeded by some user input, so, you need to make sure you filter the inputs, or better not allow user intervention.


We were using system() to call a Cocoa command-line binary from PHP using Mac OS X. The Cocoa binary was simply not working -- no error message, no logging, nothing, it would just die within moments of  launching from the system() function and we'd get no results.
The answer now seems obvious -- we were hitting PHP's memory limit. We did not consider that PHP's memory limit would also extend to programs launched via system().
So, if your system() call is failing mysteriously and giving no results, after trying the obvious (permissions, executable, etc.) considering upping:
in your php.ini from 8M to something larger.


Under Linux
exec() doesnt follow symbolic link when interpret by httpd...
I have my /home/www/cgi-bin --> soft linked to a samba mounted directory under /mnt/Downloads/
exec("/home/www/cgi-bin/runProg $a $b");
works ok when I execute the script using > php myscript.php but fails to show the output when run via the web browser.
When I give it the exact full path without the symbolic link
exec("/mnt/Downloads/ $a $b");
everything works perfectly.

jim belton

To run a full screen program from a PHP CLI script, redirect input from and output to /dev/tty.  For example:
system("timeconfig > /dev/tty < /dev/tty");
System will wait for the program to finish before continuing.


To have system output from both the STDERR and STDOUT, I've modified the function posted above by
function mysystem($command) {
 if (!($p=popen("($command)2>&1","r"))) {
   return 126;
 while (!feof($p)) {
   $out .= $line;
 return $out;
Now you can use mysystem() like;
$var = "cat ".$file;
echo mysystem($var);
$catfile = mysystem($var);
if (ereg("text", $catfile)) {
 //stuff here;

18-jun-2002 04:29

The system() function does not consistently write to the int return_var.  I highly recommend using the code from the post above it worked well for me.
$a = `/bin/ls -a`;
note: the ` is a backtick, not a single quote
This also works well in Perl so it is rather useful to know.

shai coleman

The easiest way to run a process in the background under Windows, is to use system() with the bgrun.exe utility, available from

151408626 dot unique

The documentation notes that for making a program running in the background: ... you have to make sure that the output of that program is redirected to a file or some other output stream ...
But simply redirecting the command's output to a fifo will also cause PHP to wait for the command to terminate, even if it is started in background.
After quite a bit of trial & error, however I figured out that the trick (mentioned in some other note) using parenthesis to regain control over an already redirected STDOUT does work here, too:
// this will not execute the echo in background while continuing the PHP-script,
//    as one might expect
system("echo 'something' >$someFIFO &");
// however that will do the trick - the echo is run in background, waiting until the data is read
//    from the FIFO, while your PHP-script continues execution, e.g. being able to open that
//    FIFO for read without being blocked until some data will arrive!!
system("(echo 'something' >$someFIFO) >/dev/null &");


thanks to tr4nc3,
I'm trying to, from the explorer, run an access's macro and this example give me the solution:
You can execute a .bat file with the especifications that give us tr4nc3.
After, in this .bat file, you can execute msacces.exe and pass /x parameter with the name of the macro. like this:
"c:\windows\system32\cmd.exe /c <path or the msaccess.exe>" <path of the .mdb file> /x <name of the macro>"
At the end of the .bat file you have to put "exit" and the thread will end.
Thanks to tr4nc3!


Regarding the running of processes in the background.  i found that after a few different attempts that this worked fine and allowed the main script to continue unhindered.
Hope that this might help someone.
$arg1 = "arg1";
$arg2 = "arg2";
$page = "/path/tothe/script/scriptToRun.php";
$args = "--arg1='".urlencode($arg2)."' --arg2 ='".urlencode($arg2)."'";
$command = "(php -c /usr/local/lib/php.ini ".$page." ".$args." &) > /dev/null";


Regarding Billybob's comment about multi-line system commands like this:
$commandeDB1 = system ("cd \
                      cd mysql
                      cd bin
                      mysql -uroot -pedfdiver -P3307
                      use diver_1
                         insert into cdn_flv_8(flv_file,cdn_dn_or_ip,video_path,flv_groups
First things first, this kind of mysql interaction should be taken care of with the in-built mysql or mysqli PHP libraries, it make much more sense when you see it, loads and loads of tutorials online about this exact subject:
See how you can do exactly the same thing without using the system command:
$link = mysql_connect('localhost', 'root', 'edfdiver');
mysql_query("your insert sql here");
Also you no longer rely on MySQL being located in a certain folder, your script is cross-platform, easier to understand and generally far more robust.
Regarding multi-line statements using the system function, the only way I've done this in the past is to separate each command with a semi-colon which in some cases is useful but most of the time seems to be a really bad way of doing things (this is using Linux, BASH Shell, I expect Windows has similar mechanism).
Note that you don't seem to be able to set shell variables either, again using BASH:
x=10;echo $x
This works on the command line, running via system prints an empty line, may be possible but I've not managed it yet.
Also in your example, commands 1,2,3 and 4 are for the Operating System whilst commands 5 and 6 are for MySQL, try putting a semi-colon between each of your commands to see what happens.
My advice, if you are new-ish to PHP, is to try and avoid the system/exec/passthru functions and stick with in-built PHP libraries where-ever possible, most things you want to do can be handled by these libraries.
And additions to this are welcome, I'm no expert, just a few things I've noticed.


Re: cpmorris at hotmail dot com and WINNT.
I just spent some time learning to use the php system function.  I managed to get long file names to work for me.  It seems you need to take the same approach that batch files, WSH, and most other programming languages do under WinNT/2K/XP.  Putting double quotes around the Path+Filename seems to work.  So, something like this should have worked for you:
"c:\program files\apache group\apache2\bin\htpasswd"
Note that if you have parameters, they go OUTSIDE of the last quote.  Oh, and don't forget to escape the slashes and quotes!  
I don't know what htpasswd's params are, but let us pretend:
$cmd="\"c:\\program files\\apache group\\apache2\\bin\\htpasswd\" username password";
Hope this helps someone!


On Windows XP, (possibly others)
If you are getting the unable to fork error, make sure the internet guest user has permission to read and execute the \Windows\System32\cmd.exe file.


Note to the persons who suggested using backticks for gathering a return value from scripts via system().
Using Backticks is generally frowned upon for security sake.  They can be exploited more easily.
Instead, why not use the exec() function with a return parameter specified as an array type.  This will allow you to take the full string returned from your script (for example rsync) and return each line in an array.
like so:
$result = array();
exec( $cmd, &$result);
foreach ( $result as $v )
// parse, or do cool stuff
Hope this alternative brings you merriment.

stuart prescott

Note that for stderr redirection, you have to use double quotes (") not single quotes (') for the 2>&1 part at least.
//e.g. the this will NOT do what you expect:
exec('mysqldump -h localhost ...... 2>&1', $output);
//but this will:
exec("mysqldump -h localhost ...... 2>&1", $output);
(Sounds like a PHP bug to me..., or at least buggy docs!)


Just a note to dan at thecsl dot org
0 and FALSE are _NOT_ the same.
You can check for false like so:
if($return_val === FALSE) {
  // ....
} else if ($return_val == 0) {
  // ...
// Continue...


It's important to note that if you are running a series of system() commands in a loop, you need to include the second argument in order for them to run synchonously.
// this will execute process.php asynchronously; not waiting for completion before executing the next one.
$array = array('apple', 'banana', 'pear');
foreach($array as $i)
system("php process.php \"fruit=$i\"");
// this will execute process.php 3 times, waiting for the prior command to complete before starting a new one
$array = array('apple', 'banana', 'pear');
foreach($array as $i)
system("php process.php \"fruit=$i\"", $status);


It should be noted, too, that "unable to fork" error in Windows also occurs if you try to send a command that's too long for cmd.exe to process.


It is possible to only capture the error stream (STERR). Here it goes...
(some_command par1 par2 > /dev/null) 3>&1 1>&2 2>&3
-First STDOUT is redirected to /dev/null.
-By using parenthesis it is possible to gain control over STERR and STOUT again.
-Then switch STERR with STOUT.
The switch is using the standard variable switch method -- 3 variables (buckets) are required to swap 2 variables with each other. (you have 2 variables and you need to switch the contents - you must bring in a 3rd temporary variable to hold the contents of one value so you can properly swap them).
This link gave me this information:


In system($command), $command cannot contain no more than two doublequotes. (At least with 4.3.3, on Windows). IF the path+executable name contains any space (and thus enclosed in double quotes).
 * This example works fine, there is only 2 double quotes
 system ("\"c:\\program files\\myapp\\myapp.exe\" params_for_myapp");
 * This one will fail, php will complain sthg like c:\\program is not an executable
 system ("\"c:\\program files\\myapp\\myapp.exe\" \"One param for myapp that contains space\"");
  * If you want your script to be able to run with older version of PHP (like 4.3.3), this is a trick:
  * Save the command in a temporary file and call that file
 $tmpnam = tempname($writable_dir, "temp").".bat";
 $fp = fopen ($tmpnam, "w");
 fwrite($fp, $command);
 fclose ($fp);
 system($tmpnam, $status);
Note: In my preview, backslashes were gone!


In combination with Zend Optimizer and Windows 2K/XP some programs may not run with system(), exec(), etc.
I tried to use a small tool for ejecting the cd tray and it did just nothing. Disabling Zend Optimizer solved it.


If your PHP installation permits execution of commands through system() (e.g. you are not running in safe mode, or, if you are, safe_mode_exec_dir contains all the commands you need), you can trigger a backup of your MySQL database, just by pointing your browser to the following script:
 // Enter your MySQL access data  
 $host= 'dbhost';        
 $user= 'dbuser';              
 $pass= 'dbpassword';
 $db=   'db';
 $backupdir = 'backups';  
 // Compute day, month, year, hour and min.
 $today = getdate();
 $day = $today[mday];
 if ($day < 10) {
     $day = "0$day";
 $month = $today[mon];
 if ($month < 10) {
     $month = "0$month";
 $year = $today[year];
 $hour = $today[hours];
 $min = $today[minutes];
 $sec = "00";
 // Execute mysqldump command.
 // It will produce a file named $db-$year$month$day-$hour$min.gz
 // under $DOCUMENT_ROOT/$backupdir
   'mysqldump --opt -h %s -u %s -p%s %s | gzip > %s/%s/%s-%s%s%s-%s%s.gz',                                                  
 echo '+DONE';  
If you are not allowed cron access on the web server, you can set up your own cron job to periodically call the above script. If you don't have cron, or a similar functionality on your system, you can still modify the above script to inform the browser to reget the file every xxx hours. A poor man's cron, so to say ;-)
Of course, the $backupdir should at least be protected with a .htaccess file.
And of course, you are not going to backup a really large database this way, if your PHP has some timeout set (as is usually the case with web hosters).


If you're having problems with getting imagemagick/convert to work with ghostscript because the gs executable isn't in the apache PATH, do the following:
To create a thumb of the first pdf page:
$command= 'export PATH=$PATH:/sw/bin; convert "files/example.pdf[0]" -thumbnail 150x150 "files/thumbs/example.png"';
$lastline = system($command,$return);
Thanks and phpaladin!
Willy T. Koch
Oslo, Norway


If you need to run root-level commands, such as to reboot a service, the utility 'sudo' will let you handle linux permissions. In our example we use 'sudo' to allow apache temporary root access to restart a service. We can then use:
system("sudo service dhcpd restart")
You also need to examine the /etc/sudoers file to specify what permissions to grant. Hope this helps someone!


If you are trying to parse a CGI script to your webserver which needs arguments, take a look to the virtual() function .. it took me long before i found out it existed...
It's used like this:
And that works excellent now for me


If you are running PHP in a chroot environment then the system (and passthru) function needs /bin/sh to be located in the chroot as well.


If using Windows with IIS and you're having problems with the system() and related commands, I found the easiest way to solve it was to modify the Authentication Method for the file (or directory) that uses the call and change the anonymous access user from the default (IUSR_IMAGE) to a user with enough permissions to execute the commands in the system call.  This way, there is no need to give execute permissions to IUSR_IMAGE on cmd.exe (which opens up a security risk system-wide) or copy cmd.exe into your php directory (per the suggestions of others).  Hope this helps someone!


If the command printf("%s",system($cmd)); doesn't work, check the httpd.error_log file in your /var/log directory. At my home, the system command can just load binary files in the directory /usr/lib/apache/bin


If no headers have been printed, calling the system() function will flush the headers to the client and insert a newline; no further headers or cookies will be transferred to the browser.  In version 3.0.7, you will not be warned that the Header() function failed, but will be warned if trying to set a cookie.  If you want to continue to send headers after the function call, use exec() instead.


I've found a very useful technique for the system function. Say if you want to create a page of quotes and you have /usr/games/fortune available. Instead of spending time creating a database and populating it with thousands of quotes, you can just use:
likewise if you want to list the files in your directory, say for example, Mp3's?
system('ls /home/mp3 -l');


I was trying to use the system command, and I couldnt get it to work, then it occured to me, send the stderr to a file to see what is really happening.
system( $command . " &> /tmp/error " );


I am currently using a form driven administration
page to start an ftp server remotely from a web page in FreeBSD 4.5 using PHP 4.1.2 & apache 1.3.23. (Sorry guys, no CVS!!)
This code will emulate a CLI command from your browser (anywhere!!) and execute it if your PHP module/binary has the correct permissions...
//your front end
<form ..your form stuff here...>
<input type="text" name=command>
<your additional form stuff>
///the gutz
$arg=explode( " ", $command, 4 )
    if ($arg[0] = "system")
system($arg[1] . " " . $arg[2] . " " . $arg[3]..etc);
This works, however it is simple and lacks any error output.
<?system(command > /path/to/yourfile.php);
       while ($line)
       $formatted_line=ereg_replace("your favorite newline semantic","
       print $formatted_line;
Keep in mind the SECURITY implications with the use of this and like scripts. You've been warned.


I almost gave up trying to get Windows XP w/ Apache 2 to use either system(), or exec() to run a batch file.
If the batch file was this...
echo test > test.txt
it would work fine, creating test.txt...
but if the batch file was..
iexplore.exe ""
I would get nothing. After hours and hours of messing around with this I figured it must be some type of permission problem. (dugh!)
Long story a little shorter.. You have to give Apache permission to "interact with the desktop".
Here's how...
Right click "Apache...", select properties.
Click on the "LOG ON" tab
Check the box "Allow this service to interact with desktop"
Click OK
Restart Apache
Works great!
Too bad I didn't find a post like this before I figured it out myself. (I could have been working on something.)


I'm a newbie in php, and I was wondering if it's possible to use multiple line with "system". Here is an example:
$commandeDB1 = system ("cd \
      cd mysql
      cd bin
      mysql -uroot -pedfdiver -P3307
      use diver_1
                         insert into cdn_flv_8(flv_file,cdn_dn_or_ip,video_path,flv_groups


some tips for using a system()-call for batch files on a windows computer:
* Write the path to the executable with double back-slashes, like so:
* If you are refering to other pathes, e.g. as a parameter, one back-slash works fine.
* Do not use SET for declaring parameters - this does not work! Example:
  SET PATH="C:\path\to\lib"
  echo path is %PATH%
This works fine when started from the comand line, but when called from PHP, the variable is just empty.


Here's a neat trick that exploits an inherent php anomaly... if you want to run a shell command but not have it take up two processes for the entire life of the command (a child for the shell and a grandchild for the command), add a "&" at the end of the command to kill the shell and leave the grandchild command running... Though it's a bit counterintuitive, php will continue to listen for the orphanized grandchild command's STDOUT as long as it continues to run, provided STDOUT hasn't been been redirected with a ">/some/file"...
Very helpful if you're in a low-process-quota situation - I might even go so far as to say that this benefit might warrant ALWAYS using a "&" in php Unix system command situations - though the jury's still out on that one...


For your in-house pages, I recommend redirecting stderr to stdout so you'll know if something goes wrong.  Here's a real-life example:
system("/mysql_reboot 2>&1");

d dot kraft

For PHP running inside a Webserver:
When calling a process via
system("your_process &");
to make it running in background, note that this process is killed when the webserver is restarted.


Do not use "system" if you use the "php.ini" option:
   zlib.output_compression = On
Doing so will result in the browser receiving garbage (I'm guessing the headers/buffers get confused).
Use passthru in this case, it appears to work as intended.


BUGFIX for the mysystem() function, posted by n-jones.
function syscall($command){
if ($proc = popen("($command)2>&1","r")){
while (!feof($proc)) $result .= fgets($proc, 1000);
return $result;
Hello from Russia! :)


if (! system($cmd)) {
 print "error";
does not work!
if (system($cmd) === false) {


best use I have found for this function so far:
$fortune = `/usr/games/fortune -aeo`;

$var = eregi_replace("\n", "
", $fortune);
echo $var;
that's with all the fortune's installed, including the dirty ones. the reg expression replace formats them correctly


another reason to use shell_exec instead of system is when the result is multiple lines such as grep or ls
// this correctly sets answer string to all lines found
//$answer = shell_exec ("grep 'set of color names' *.php ");
//echo "answer = $answer";
// this passes all lines to output (they  show on page)
// and sets answer string to the final line
$sys = system ("grep 'set of color names' *.php ");
echo "sys =(($sys))";
here is view/source resulting from system call
setprefs.php:// The standard set of color names is:
setprefs.php:// Most browsers accept a wider set of color names
silly.php:  //$answer = shell_exec ("grep 'set of color names' *.php ");
silly.php: $sys = system ("grep 'set of color names' *.php ");
sys =((silly.php: $sys = system ("grep 'set of color names' *.php ");))
and here is view source from using shell_exec instead
answer = setprefs.php:// The standard set of color names is:
setprefs.php:// Most browsers accept a wider set of color names
silly.php:  $answer = shell_exec ("grep 'set of color names' *.php ");
silly.php:// $sys = system ("grep 'set of color names' *.php ");


An example of using the system to call the file command on a linux server. This script detects whether a user posted file is a jpeg, gif or png
$accepted_types=array("JPEG" , "GIF", "PNG");
   // The temporary filename of the file in which the uploaded file was stored on the server.
   $uploaddir = $_SERVER['DOCUMENT_ROOT']."/images/";
   $uploaddir.=basename( $_FILES['uploadedfile']['name']);
//verfiy file using linux FILE command
$last_line = system('file '.escapeshellarg($_FILES['uploadedfile']['tmp_name']), $retval);
//get the file extension returned through magic database
$splitvals=explode(' image data' ,  $last_line);
$vals=explode(':', $splitvals[0]);
$vals[1]=str_replace(' ','', $vals[1]);
if (in_array($vals[1], $accepted_types))
   echo $vals[1].' was accepted <br />';
   //Copy the file to some permanent location
   if(move_uploaded_file($_FILES["uploadedfile"]["tmp_name"], $uploaddir))
     echo $uploaddir." was uploaded! <br />";
     echo "There was a problem when uploding the new file, please contact admin about this.";
   else echo 'This file already exists in DB please rename file before uploading';
}else echo $_FILES['uploadedfile']['error'].'<br />';


a simple way to include a beep on the server-side whenever a page in viewed.
**contents of 'beeping' page**
require ("beep.php")
**contents of beep.php**
system ("/home/site/exe/beep.executable");
// on windows system ("c:\beep.exe");


a really useful use for import(); while running the server at ur own machine is taking a screenshot of you desktop and showing it to the guest !!!
echo system("/usr/X11R6/bin/import -window root -display localhost:0 /mnt/d/Desenvolvimento/Desenvolvimento\ WWW/import/cache/imagem.jpg -quality 30" ." 2>&1");
<img src="cache/imagem.jpg">
remember to set chmod 777 to your directory (called "cache" on my code). also do "xhost +" or you r gonna get a xlib error saying that it could not connect to x server at localhost...
the code is still too simple. i've just done it. e.g. you can improve a real cache system avoying more than one screenshot in a minute while...
that is it! hope u enjoy it ( rofl... =DDD ) ...

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