php man page for system

SYSTEM(3)								 1								 SYSTEM(3)

system - Execute an external program and display the output

SYNOPSIS
       string system (string  $command, [int  &$return_var])

DESCRIPTION
       system(3) is just like the C version of the function in that it executes the given $command and outputs the result.

	The  system(3)	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(3)
       function.

PARAMETERS
	      o $command
		- The command that will be executed.

	      o $return_var
		- 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.

EXAMPLES
       Example #1

	      system(3) 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;
	      ?>

NOTES
       Warning

	      When allowing user-supplied data to be passed to this function, use escapeshellarg(3) or escapeshellcmd(3) to ensure that users can-
	      not trick the system into executing arbitrary commands.

       Note

	      If a program is started with this function, in order for it to continue running in the background, the output of the program must be
	      redirected to a file or another output stream. Failing to do so will cause PHP to hang until the execution of the program ends.

       Note

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

       Warning

	      With safe mode enabled, the command string is escaped with escapeshellcmd(3). Thus, echo y | echo x becomes echo y | echo x.

SEE ALSO
       exec(3), passthru(3), popen(3), escapeshellcmd(3), pcntl_exec(3), backtick operator.

PHP Documentation Group 														 SYSTEM(3)