Execution failing while running from browser

Question

I am building online compiler for C and C++ using php, so we are using gcc compiler to execute using "shell_exec" function ,

test.php

<?php $output = shell_exec("gcc /var/www/test/main.c 2>&1"); print_R($output); ?>

If I execute in terminal like php test.php, is working fine and it is creating a.out compiled file.

But If I try to run in the browser like localhost/test.php, its giving below error

gcc: error trying to exec 'cc1': execvp: No such file or directory

I gave full permission (0777) to test.php,

$ whereis cc1 // cc1:

Please find below version I am using

gcc version 5.4.0

PHP 7.0.32

OS: ubuntu 16.04

server : Nginx

Is there any alternate to run C and C++ using PHP or how to resolve this issue whille running from the browser.

It becouse gcc is root's program. In terminal you can run it (your profile can run root's programs). But brouser starts other user (like www-data, or other). And it user cant run root's programs — Vasyl Zhuryk, Oct 20 '18 at 08:01
@Vasyl Zhuryk, thanks for the reply, is there anyway to fix this or any alternate method for this? — Abhi, Oct 20 '18 at 08:03
That is not secure, but you can try: `ln -s /usr/bin/gcc /usr/local/bin/gcc` It creates symbolic link to program without root privileges — Vasyl Zhuryk, Oct 20 '18 at 08:09
Does this `gcc /var/www/test/main.c` complete successfully when executed from a shell on the server itself? — alk, Oct 20 '18 at 08:17
@alk, yes it execute successfully while running from terminal — Abhi, Oct 20 '18 at 08:20
@Vasyl, I created sym link in /usr/local/bin/gcc, still error gcc: error trying to exec 'cc1': execvp: No such file or directory — Abhi, Oct 20 '18 at 08:21
@Abhi can you try this code? `shell_exec("/usr/bin/gcc /var/www/test/main.c 2>&1");` — Vasyl Zhuryk, Oct 20 '18 at 08:24
@Vasyl , its giving now error as , collect2: fatal error: cannot find 'ld' compilation terminated — Abhi, Oct 20 '18 at 08:32
@ Vasyl Zhuryk , #include int main() { printf("Hello...."); return 0; } — Abhi, Oct 20 '18 at 11:38
@Abhi I tried to do it in my computer - all done right. In your case can help this: https://stackoverflow.com/questions/11912878/gcc-error-gcc-error-trying-to-exec-cc1-execvp-no-such-file-or-directory — Vasyl Zhuryk, Oct 20 '18 at 12:22
@Abhi `$ gcc -v ... Thread model: posix gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.10)` — Vasyl Zhuryk, Oct 21 '18 at 11:42
@Abhi `PHP 7.1.23-2+ubuntu16.04.1+deb.sury.org+1 (cli) (built: Oct 15 2018 11:36:43) ( NTS )` Also I added my user to apache user (in your case nginx user) — Vasyl Zhuryk, Oct 21 '18 at 12:00

Mathieu · Answer 1 · 2018-10-20T08:42:02.233

0

Reading the error message, the problem comes from two issues:

php cannot find gcc since $path variable is not correctly set, in php file, you should type something like PATH=/usr/bin && gcc /var/www/test/main.c. In this example, gcc and other stuff are in /usr/bin directory. To know where are located cc1 for instance, type find / -name cc1 and add it to $PATH: PATH=/some/path:/some/other/path
Current directory of php could no be writtable, so indicate where the generated file must be created: gcc /var/www/test/main.c -o /var/www/test/main
Directory /var/www/test must be writable by user running php program.

Note that the user running the php program is not necessary the root...

So your php file should looks like:

<?php
 $output = shell_exec("PATH=/usr/bin && gcc /var/www/test/main.c -o/var/www/test/main 2>&1");    
 print_R($output);
?>

edited Oct 20 '18 at 08:42

answered Oct 20 '18 at 08:18

Mathieu

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Hello purplepsycho, still I am getting same error gcc: error trying to exec 'cc1': execvp: No such file or directory – Abhi Oct 20 '18 at 08:36
@ purplepsycho, I updated path as , PATH=/usr/bin:/usr/lib/gcc/x86_64-linux-gnu/5/cc1, still the same error – Abhi Oct 20 '18 at 08:53
@Abhi Do not put the `cc1` in path – Mathieu Oct 20 '18 at 08:54
still the same for shell_exec("PATH=/usr/bin:/usr/lib/gcc/x86_64-linux-gnu/5/ && gcc /var/www/test/compiler/test/main.c -o/var/www/test/compiler/test/main 2>&1"); – Abhi Oct 20 '18 at 08:56

Execution failing while running from browser

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