Web page does not run shell script

Question

I've made a simple webpage that has to run some simple bash scripts. I run apache2 on Jetson Nano and I have three files in /var/www/html folder:

index.html
testexec.php
test.sh

First one looks like:

<!DOCTYPE html>
<html>
     <head>
        <meta charset="UTF-8">
        <title>TEST</title>
     </head>
  <body>
    <form action="testexec.php">
        <input type="submit" value="Create file">
    </form>
  </body>
</html>

the php file:

<?php
$output = shell_exec("test.sh");
header('Location: http://192.168.25.16/index.html?success=true');
?>

script:

#!/bin/bash


touch file.txt

My problem is that everything looks good, but the scrit doesn't run. In future it will be used to run program written in python, but for now I can't run even that simple one. Is the problem with location of files or with something else?

I've already tried to change php file

$output = shell_exec("test.sh");

with

$output = exec("test.sh");

with or without $output

My browser (firefox) returns no errors in console.

Script works fine when I run it from shell. It is executable.

I've already tried to look for similar problems, but there were no solutions.

Try echoing `$output` to see. Also add `2>&1` to the end of the command so you get error messages. — Barmar, Jan 04 '22 at 18:18
echoing `$output` doesn't print anything. In the end of which command should I put `2>&1`? — Master1521, Jan 04 '22 at 18:23
Then it should be working. What happens if the shell script prints something, do you see that in the `echo $output;`? — Barmar, Jan 04 '22 at 18:24
When script echos something I can see it but i had to comment line `header('Location: http://192.168.25.16/index.html?success=true');` — Master1521, Jan 04 '22 at 18:27
Of course, if you redirect you don't see the output. But that means the script is running. Try using the absolute path to the file you want to touch, it's probably doing it in an unexpected directory. — Barmar, Jan 04 '22 at 18:29
So the script is running, it's just that the `touch` command doesn't work? — Barmar, Jan 04 '22 at 19:57
I don't think so, script works straight from shell, with other scripts, which are supposed to run simple python programs, I have same problems — Master1521, Jan 04 '22 at 20:02
I'm just trying to understand exactly what's going wrong when you run this script from PHP. If you put echo commands in the script, you see the output. But if you put a `touch` command in the script, it doesn't work, and doesn't print an error message, either. — Barmar, Jan 04 '22 at 20:04
If you put echo commands before and after the touch command, you see both of them? — Barmar, Jan 04 '22 at 20:05
Put this in the shell script: `echo before touch; touch file.txt; echo after touch` — Barmar, Jan 04 '22 at 20:17
Put `$output = shell_exec("./test.sh 2>&1"); echo $output;` in the PHP script, and remove the redirect. — Barmar, Jan 04 '22 at 20:18
it prints only before and after touch. Only what's on shell script, any output from php. Also file wasn't created — Master1521, Jan 04 '22 at 20:37
Add `pwd` to the shell script, so you're sure that it's creating the file in the directory you expect. — Barmar, Jan 04 '22 at 20:38
Oh, I've made some changes and now output is like: before touch: cannot touch 'file.txt': Permission denied after — Master1521, Jan 04 '22 at 20:45
That means the web userid doesn't have write permission to the directory where you're trying to create the file. — Barmar, Jan 04 '22 at 20:46
The file already exists? I thought you were tryiing to create the file. — Barmar, Jan 04 '22 at 20:49
The permission problem is with the directory where you're trying to create the file, not the script. — Barmar, Jan 04 '22 at 20:50
Directory write permission controls who can create/delete/rename files in the directory. — Barmar, Jan 04 '22 at 20:51
so should I change tej ownership od whole folders on Path `/var/www/html/`? because html is owned by my user on Jetson — Master1521, Jan 04 '22 at 20:59

Zlatov · Answer 1 · 2022-01-04T18:53:56.330

0

Very often the problem is with user rights, first try installing chmod 777 test.sh to just check if this is the problem. In addition, you should go back to the exec documentation

exec(string $command, array &$output = null, int &$result_code = null): string|false

and check what $result_code is equal to.

If we get echo result!:

$output=null;
$retval=null;
exec('echo $(pwd);', $output, $retval);
echo "${retval} with value:\n";
print_r($output);

edited Jan 04 '22 at 18:53

answered Jan 04 '22 at 18:27

Zlatov

126
1
6

He says in a comment he's getting output from the script if he adds an echo, so it's not a permission problem. – Barmar Jan 04 '22 at 18:30
if we get a response from echo then it is worth checking echo $(pwd). – Zlatov Jan 04 '22 at 18:50
*0 with value: Array ( [0] => /var/www/html ) * <-- this is response to your script – Master1521 Jan 04 '22 at 19:10
but `exec('touch file.txt', $output, $retval);` the file is not created? – Zlatov Jan 04 '22 at 19:18
it didn't create file – Master1521 Jan 04 '22 at 20:05
Please show output `stat /var/www/html` and `systemctl | grep php` and `systemctl status phpX.X-fpm.service`. I have replicated your code on my local server. My file is being created. I am sure that the reason is precisely the lack of rights for the user to create files. You need to check the php-fpm user. – Zlatov Jan 05 '22 at 08:35

Web page does not run shell script

1 Answers1