shell_exec
pthreads
Program execution Functions
PHP Manual

# 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.

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

`<?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 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.

> 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. Thus, echo y | echo x becomes echo y \| echo x.

### See Also

- exec
- passthru
- popen
- escapeshellcmd
- pcntl_exec
- backtick operator