Running “Last” Linux Command

Question

I'm trying to execute a linux command in PHP, here is my sample code:

$command = "last -F";
$o = shell_exec($command);
print_r($o);

Most of the Linux commands gives me an output, but for the Last -F command, I have no output. Why is it so?

Answer 1

Try This Explaination . Your issue MAY be that the last line of last -F is a new-line. shell_exec() only returns the last line of the command, and therefore, if that line is empty, you get nothing, nada.

As an alternative, try exec() , this will allow you to capture the return value (success or failure of execution) as well as the entirety of the command's output. Check it out here

Answer 2

You are executing that command as web user ( nobody or www-data ), which is a limited privileged user.You have to execute that command as root. Unfortunately giving sudo permission or full permission to web user is really a bad idea. So I recommend make a cron or background script that execute last -F and write output to a file. You can read that file from your PHP script.

You can make a script runs in background like this.

   #!/bin/bash

    while [ true ]; do
         last -F > /tmp/myfile
    done

save the code as mycron.sh

chmod +x mycron.sh
mycron.sh &

Read the file /tmp/myfile from your PHP Program. It will give the exact output of that command.