PHP shell_exec() vs exec() Function

In PHP, shell_exec() and exec() are functions used to execute external commands from within a script. While shell_exec() returns the entire output of the command as a string, exec() only returns the last line, offering more control over output handling.

shell_exec() Function

The shell_exec() function in PHP executes a command via the shell and returns the complete output as a string. It allows running shell commands directly from a PHP script, capturing the full output, which can be useful for automating system tasks.

Syntax:

string shell_exec( $cmd )

Parameters: This function accepts a single parameter $cmd which is used to hold the command that will be executed.

Return Value: This function returns the executed command or NULL if an error occurred.

Note: This function is disabled when PHP is running in safe mode.

Example: In this example we use the shell_exec() function to execute the ls command, listing files and directories.

<?php

// Use ls command with shell_exec function
$output = shell_exec('ls');

// Display the list of all files and directories
echo "<pre>$output</pre>";

?>

Output:

gfg.php
index.html
geeks.php

exec() Function

The exec() function in PHP executes an external command via the shell but only returns the last line of the output as a string. It allows capturing command results, handling outputs through references, and provides more control over the command's execution status.

Syntax:

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

Parameters:

This function accepts three parameters as mentioned above and described below:

• $command: This parameter is used to hold the command which will be executed.
• $output: This parameter is used to specify the array which will be filled with every line of output from the command.
• $return_var: The $return_var parameter is present along with the output argument, then it returns the status of the executed command will be written to this variable.

Return Value:

This function returns the executed command, be sure to set and use the output parameter.

Example: In this example we use the exec() function to run the command iamexecfunction from the system shell. It echoes the last line of the command's output

<?php
// (on a system with the "iamexecfunction" executable in the path)
echo exec('iamexecfunction');
?>

Output:

geeks.php

PHP is a server-side scripting language designed specifically for web development. You can learn PHP from the ground up by following this PHP Tutorial and PHP Examples.

Difference table between PHP shell_exec() vs exec() Function