PHP Execute Shell Command And Retrieve The Output

Question

I'm trying to retrieve the contents of a file on a remote server via SSH and display the results in a browser. The remote server's name and address is configured on my local server with the name "router", such that from the command line I can execute the following to successfully retrieve the results:

ssh router "cat /var/log/messages"

I'm having trouble getting this to execute in PHP - I can't get the quotes escaped properly. Here's my PHP script

<pre>
$command = 'ssh router \"cat /var/log/messages\"';
<?php system($command); ?>
</pre>

But this outputs the command string to the webpage instead of executing the command and returning the results.

Dolly Aswin · Accepted Answer · 2017-07-04 17:20:38Z

2

Use escapeshellarg() to escape command argument. Please try like this

$host       =  escapeshellarg("user@router");
$commandArg =  escapeshellarg("/var/log/messages");
$result     = shell_exec('ssh ' . $host . ' cat ' . $commandArg);
echo $result, PHP_EOL;

answered Jul 4, 2017 at 17:20

Dolly Aswin

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1 Comment

tadman Over a year ago

It's important to be extremely careful when executing arbitrary shell commands. It's great that you're using escapeshellarg, as this is really not optional.

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