Php/docs/function.system

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system

(PHP 4, PHP 5, PHP 7)

systemExecute an external program and display the output


Description

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

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.


Parameters

command
The command that will be executed.
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() example

<?phpecho '<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 infoecho '</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() or escapeshellcmd() to ensure that users cannot 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.

See Also