The PHP shell_exec() and exec() Functions

1. the PHP shell_exec() Function
2. the PHP exec() Function

This article will discuss the PHP shell_exec() and exec() functions. While differentiating the two functions, we will see how each function performs and its practical use.

the PHP shell_exec() Function

We use the shell_exec() function to execute commands in the shell and return the output as a string. The shell_exec is the alias for the backtick operator, *nix.

Syntax:

string shell_exec( $cmd )

This function accepts one parameter, $cmd. It contains the command to be executed.

In case of errors, the function returns NULL.

It is important to note that the function does not run when PHP is in safe mode.

Example:

<?php
// Use ls command
$output = shell_exec('ls');

//List all files and directories
echo "<pre>$output</pre>";
?>

Output:

Insert.php
index.html
delft.php

the PHP exec() Function

The exec() function executes external programs and returns the last line of the output. If the command fails, it returns NULL.

Syntax:

string exec( $command, $output, $return_var )

Parameters:

1. $command contains the command to be executed.
2. $output specifies the array to be filled.
3. $return_var comes with the output argument.

Example:

<?php
echo exec('iamexecfunction');
?>

Output:

delft.php