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phpcommand-lineexecshell-exec

exec('top', $output) is returning an empty array?

I am writing a PHP-Script to be used to check the cpu-usage of my system but it won't work as I want.

I have seen a lot of similar questions here on stackoverflow, but i havent found a solution for my problem yet.

public static function checkCurrentCpuUsage()
{
    $load = sys_getloadavg();
    if (true) {
        $output = '';
        exec('top', $output, $return_var);

        echo "<br>";
        echo 'print_r($load) --> ';
        print_r($load);
        echo "<br>";
        echo 'var_dump($output) --> ';
        var_dump($output);
        echo "<br>";
        echo 'print_r($output) --> ';
        print_r($output);
        echo "<br>";
        echo 'print_r($return_var) --> ';
        print_r($return_var);
    }
}

This code returns this output:

print_r($load) --> Array ( [0] => 0.53 [1] => 0.41 [2] => 0.41 ) 
var_dump($output) --> array(0) { } 
print_r($output) --> Array ( ) 
print_r($return_var) --> 1

Why is $output empty ?

I have tried a lot of things to get the output of the top-command as an array in $output, but nothing worked.

Some answers i found told me that "exec('top', $output, $return_var);" will get stuck in the "top-command", so i tried using "top -n 1" instead but this didn't work for me.

I also tried a lot of versions with "passthru()" and "shell-exec()" instead of "exec()", but nothing worked for me.

Can you tell me how to get the output of the "top-command" as an array?

Solution

  • Top is an interactive program and sends output to video by default. In order to get the output you can run it in batch mode with -b and -n 1, as per man page 

    -b  :Batch-mode operation
        Starts top in Batch mode, which could be useful for sending output from top to other  pro‐
        grams or to a file.  In this mode, top will not accept input and runs until the iterations
        limit you've set with the `-n' command-line option or until killed.

    and

    -n  :Number-of-iterations limit as:  -n number
        Specifies the maximum number of iterations, or frames, top should produce before ending.