   #PHP Manual Program Execution functions shell_exec Printer functions

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                                    system

   (PHP 3, PHP 4 )
   system -- Execute an external program and display the output

Description

   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. If a variable is
   provided as the second argument, then the return status code of the
   executed command will be written to this variable.

   Warning

   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.

     Note: 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.

   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.

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

   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.

   Example 1. system() example
   <?php
   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 '
   </pre>
   <hr />Last line of the output: ' . $last_line . '
   <hr />Return value: ' . $retval;
   ?>

   See also exec(), passthru(), popen(), escapeshellcmd(), and the
   backtick operator.
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