system

(PHP 4, PHP 5, PHP 7, PHP 8)

system — Ejecutar un programa externo y mostrar su salida

Descripción

system(string $command, int &$result_code = null): string|false

system() es similar a la versión C de la función de mismo nombre, dado que ejecuta el command dado y muestra el resultado.

La llamada a system() también intenta volcar automáticamente el búfer de salida del servidor web después de cada línea de salida, si PHP está corriendo como un módulo de servidor.

Si necesita ejecutar un comando y recibir de vuelta todo los datos del mismo sin interferencias, use la función passthru().

Parámetros

comando: El comando que será ejecutado.
result_code: Si el argumento result_code se encuentra presente, entonces el status devuelto por el comando ejecutado será almacenado en esta variable.

Valores devueltos

Devuelve la última línea de la salida del comando en caso de tener éxito, y false si ocurre un error.

Ejemplos

Ejemplo #1 Ejemplo de system()

<?php
echo '<pre>';

// Muestra el resultado completo del comando "ls", y devuelve la
// ultima linea de la salida en $ultima_linea. Almacena el valor de
// retorno del comando en $retval.
$ultima_linea = system('ls', $retval);

// Imprimir informacion adicional
echo '
</pre>
<hr />Ultima linea de la salida: ' . $ultima_linea . '
<hr />Valor de retorno: ' . $retval;
?>

Notas

Advertencia

Si se va a permitir que datos provenientes del usuario sean enviados a esta función, habría que utilizar escapeshellarg() o escapeshellcmd() para asegurarse que el usuario no intenta engañar al sistema para que ejecute comandos arbitrarios.

Nota:
Si ejecutamos un programa con esta función y queremos dejarlo ejecutándose en segundo plano, hay que asegurarse que la salida del mismo es redireccionada a un fichero u otro flujo de salida o PHP se quedará esperando hasta que la ejecución del programa termine.

Ver también

exec() - Ejecutar un programa externo
passthru() - Ejecuta un programa externo y muestra la salida en bruto
popen() - Abre un proceso de un puntero a un fichero
escapeshellcmd() - Escapar meta-caracteres del intérprete de comandos
pcntl_exec() - Executes specified program in current process space
el operador de comillas invertidas

Found A Problem?

Learn How To Improve This Page • Submit a Pull Request • Report a Bug

＋add a note

User Contributed Notes 18 notes

down

no at mail dot com ¶

12 years ago

This is for WINDOWS users. I am running apache and I have been trying for hours now to capture the output of a command. 

I'd tried everything that is written here and then continued searching online with no luck at all. The output of the command was never captured. All I got was an empty array.

Finally, I found a comment in a blog by a certain amazing guy that solved my problems. 

Adding the string ' 2>&1' to the command name finally returned the output!! This works in exec() as well as system() in PHP since it uses stream redirection to redirect the output to the correct place!

system("yourCommandName 2>&1",$output) ;

down

dan at thecsl dot org ¶

18 years ago

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:

<?php
  $cmd = "/usr/bin/pngtopnm $png_file > $pnm_file";
  system($cmd,$return_value);
  ($return_value == 0) or die("returned an error: $cmd");
?>

down

mortoray at ecircle-ag dot com ¶

20 years ago

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.

down

timgolding_10 at hotmail dot com ¶

17 years ago

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

<?PHP

$accepted_types=array("JPEG" , "GIF", "PNG"); 

    // The temporary filename of the file in which the uploaded file was stored on the server. 
if(!empty($_FILES["uploadedfile"]))
  {
    $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 $vals[1].' was accepted <br />';
        if(!file_exists($uploaddir)){
            //Copy the file to some permanent location
            if(move_uploaded_file($_FILES["uploadedfile"]["tmp_name"], $uploaddir))
             {
              echo $uploaddir." was uploaded! <br />";
             }
            else
             {
              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 />';
?>

down

ccurtis at aet-usa dot com ¶

25 years ago

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.

down

nospam at php dot net ¶

24 years ago

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:

<?php

virtual("/cgi-bin/lastuser.cgi?argument");

?>

And that works excellent now for me

down

Jim Belton ¶

21 years ago

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.

down

Anonoymous ¶

5 years ago

Windows commands requiring a GUI.

Alot of the info on this topic is from the 2010-2012 time frame and referring to XP, and basically don't work.  I am using apache/php/mysql in windows 7.

When requiring a system command in windows with a GUI - such as a labview executable, notepad, etc..., others have mentioned the psexec command from sysinternals, since cmd /c wont work, but the specific use was not real clearly defined.  Here is what worked for me on windows 7:  

system('C:/nttools/2019/psexec \\\\10.100.100.101 -i  -u administrator -p password -accepteula -nobanner C:\\htdocs\\test\\test.bat');

The path to the psexec executable is with forward slashes, the remote PC network location (which was actually the local PC, not remote) was \\ip_address with an extra backslash for each backslash so that required the 4 \'s.

The path for the command to be executed by psexec required backslashes, which also requires double backslashes.

The -i option is for an interactive program, and is required for it to properly run, otherwise it show up in the taskmanager but not be visable or execute properly if given command line arguments.

The -accepteula -nobanner is to suppress the sysinternals message box about their license.

My command to execute is really long with multiple command line inputs with many surrounded in double quotes, so I thought it would be easiest to put that in a batch file and just call the bat file.  Works great, remote users loading the webpage causes the executable to pop up on the web server, do its analysis and disappear.  Labview can read native excel files with active-x functions and write to a mysql data base to store results etc, so thats a pretty powerful combination of functions.

down

vdweij at hotmail dot com ¶

19 years ago

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:
http://www.cpqlinux.com/redirect.html

down

morris_hirsch at hotmail dot com ¶

21 years ago

another reason to use shell_exec instead of system is when the result is multiple lines such as grep or ls 

<?php

// 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 ");

down

d dot kraft at szo dot de ¶

21 years ago

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.

down

kexianin at diyism dot com ¶

15 years ago

If you can't see any output or error from system(), shell_exec() etc, you could try this:



<?php

function my_exec($cmd, $input='')

         {$proc=proc_open($cmd, array(0=>array('pipe', 'r'), 1=>array('pipe', 'w'), 2=>array('pipe', 'w')), $pipes);

          fwrite($pipes[0], $input);fclose($pipes[0]);

          $stdout=stream_get_contents($pipes[1]);fclose($pipes[1]);

          $stderr=stream_get_contents($pipes[2]);fclose($pipes[2]);

          $rtn=proc_close($proc);

          return array('stdout'=>$stdout,

                       'stderr'=>$stderr,

                       'return'=>$rtn

                      );

         }

var_export(my_exec('echo -e $(</dev/stdin) | wc -l', 'h\\nel\\nlo'));

?>



For example, "echo shell_exec('ls');" will get nothing output,

"my_exec('ls');" will get "sh: ls: command not found",

"my_exec('/bin/ls');" will maybe get "sh: /bin/ls: Permission denied",

and the permission may be caused by selinux.

down

grytolle at gmail dot com ¶

15 years ago

This is a work-around that makes the program run in it's own directory instead of the script's.



example usage:

<?php runAsynchronously("c:\games\jazz2\jazz2.exe","-connect 1.2.3.4"); ?>



<?php

function runAsynchronously($path,$arguments) {

    $WshShell = new COM("WScript.Shell");

    $oShellLink = $WshShell->CreateShortcut("temp.lnk");

    $oShellLink->TargetPath = $path;

    $oShellLink->Arguments = $arguments;

    $oShellLink->WorkingDirectory = dirname($path);

    $oShellLink->WindowStyle = 1;

    $oShellLink->Save();

    $oExec = $WshShell->Run("temp.lnk", 7, false);

    unset($WshShell,$oShellLink,$oExec);

    unlink("temp.lnk");

}

?>

down

vlad dot sharanhovich at gmail dot com ¶

16 years ago

The double quote problem on Windows platform discussed earlier here in comments still present in PHP 5.2.5. You can't execute system($command) if $command contains more than 2 " chars. system('"echo" A'); works, while system('"echo" "A"'); does not. Search comment, that was a solution posted to overhaul this issue via temporary .bat file.

down

-1

Daniel Morris (danielxmorris.com) ¶

16 years ago

How to produce a system beep with PHP.

<?php
        function beep ($int_beeps = 1) {
            for ($i = 0; $i < $int_beeps; $i++): $string_beeps .= "\x07"; endfor;
            isset ($_SERVER['SERVER_PROTOCOL']) ? false : print $string_beeps; 
        }

?>

This will not do anything when running through a browser, if running through a shell it will produce an audible beep $int_beeps times.  This should work on Windows, Unix, etc.

down

-1

eric_REMOVE at movementmovement_REMOVE dot com ¶

20 years ago

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.

ie)

// 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);
}

down

-2

lc at _REMOVE__THIS_lc dot yi dot org ¶

21 years ago

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";
$str=system($cmd);

Hope this helps someone!

Leonard
http:\\www.lc.yi.org

down

-3

cnoelker at softpearls dot de ¶

21 years ago

Hi,
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:
   C:\\path\\to\\prog.exe
* 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.

＋add a note