What's the Difference Between PHP's `shell_exec()` and `exec()` Functions?

Distinguishing PHP's shell_exec() and exec() Functions

The PHP functions shell_exec() and exec() both facilitate the execution of server-side commands. However, there are subtle differences in their behavior and usage.

Key Difference: Output Handling

The primary distinction between shell_exec() and exec() lies in how they handle output from the executed command.

• shell_exec(): Retrieves all of the command's output as a single string and returns it.
• exec(): By default, returns only the last line of the output. However, it can return the entire output as an array if you specify the second parameter as true.

Usage Considerations

Choosing which function to use depends on your specific needs:

• shell_exec(): Ideal for capturing the entire output of a command, such as lengthy logs or multiple lines of text.
• exec(): Useful when only the last line of output is relevant, or when you need the output to be an array (e.g., for parsing or further processing).

Example Usage:

To demonstrate the difference:

// Use shell_exec() to capture the entire output of a command
$output = shell_exec('echo "Hello World"');
echo $output; // Prints "Hello World"

// Use exec() to retrieve the last line of output
exec('echo "Last Line Output"');
echo $output; // Prints "Last Line Output"

// Use exec() to return the entire output as an array
$output = [];
exec('echo "Line 1\nLine 2\nLine 3"', $output);
echo implode("\n", $output); // Prints "Line 1\nLine 2\nLine 3"

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