How Can I Get Live Output from Shell Commands in PHP?

Accessing Live Output via PHP with Shell Commands

PHP's shell_exec function provides a convenient way to execute shell commands from within PHP scripts. However, it can be challenging to retrieve the live output of these commands during runtime. This article explores two methods for achieving this functionality.

popen() and Interactivity

To interact with the process and read its output as it runs, use popen(). This function returns a file pointer that can be treated like any other file resource.

$proc = popen($cmd, 'r');
echo '<pre class="brush:php;toolbar:false">';
while (!feof($proc)) {
    echo fread($proc, 4096);
    @flush();
}
echo '

';

This script starts the command, reads its output in chunks of 4096 bytes, and prints it directly to the page. The flush() call ensures the output is displayed immediately.

Convenience with passthru()

If live interactivity is not required, passthru() provides an alternative approach. This function directly echoes the output of a command to the page.

echo '<pre class="brush:php;toolbar:false">';
passthru($cmd);
echo '

';

While passthru() is simpler, it outputs the entire command result at once, which may not be suitable for commands that generate a large amount of output.

Conclusion

Both popen() and passthru() offer different mechanisms for accessing live output from shell commands in PHP. popen() provides fine-grained control over data retrieval, allowing for real-time updates. passthru(), on the other hand, sacrifices interactivity for ease of use, making it suitable for scenarios where immediate output is desired.

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