PHP shell_exec command doesn't work

Question

I am trying learn to execute shell scripts from within PHP code. So, I made a test program to execute a bash script from within PHP. However, it has no effect. The relevant code is shown below.

<?php 
.......
shell_exec('/bin/bash /var/www/html/just_touch.sh');
?>

The just_touch.sh script just creates a new file, like as shown below.

touch /home/user/some.txt

I was expecting to have file /home/user/some.txt after execution, but no, it isn't made. What mistake, am I doing?

P.S: The following code works though.

$output = shell_exec('ls /home/user');
echo $output;

Does this have anything to do with permissions?

Moreover, I notice that while this prints "Can you see me?".

$output = shell_exec('echo Can you see me?');
echo $output;

This doesn't!

shell_exec('echo Can you see me?')

What is going on here?

It still doesn't work. Is there a way to see what error occurs from Mozilla? — pythonic
– pythonic, Commented Jul 18, 2016 at 16:14
To see something in Mozilla use passthru() instead of shell_exec(). php.net/manual/en/function.passthru.php — Jay Blanchard
– Jay Blanchard, Commented Jul 18, 2016 at 16:15
Most likelely /home/user/some.txtis not writable by webservers userid — Jürgen Hötzel
– Jürgen Hötzel, Commented Jul 18, 2016 at 16:50
How can I make that writable then? How can I even check if its writable or not through webservers userid? — pythonic
– pythonic, Commented Jul 18, 2016 at 16:53

Jürgen Hötzel · Accepted Answer · 2016-07-18 17:26:22Z

3

Stderr is lost when using shell_exec. You might wan't to use:

shell_exec('/bin/bash /var/www/html/just_touch.sh 2>&1');

answered Jul 18, 2016 at 17:26

Jürgen Hötzel

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3 Comments

pythonic Over a year ago

Very useful indeed, because now I see the message, touch: cannot touch '/home/user/some.txt': Permission denied. These permission rights are killing me though :(! Do, you know anyway to solve these permission rights?

Jürgen Hötzel Over a year ago

Make the target directory /home/user writable by the webserver user. I.e make it group-writable: chmod g+w /home/user and set the group of the home directory to the same group the webserver is running: chgrp wwwrun /home/user

pythonic Over a year ago

I see. At the moment I got away by setting permissions to 777. But I think that would be very insecure. I'll checkout with your approach.

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