Running c program with node.js and getting the response

Question

I am trying to get a secure "run-like" program in node.js that runs C programs. I understand that I must use a child process to achieve my goal... And I choose exec because it has a callback arguments:

exec.js

const { exec } = require('child_process');

var options = {
    timeout: 100,
    stdio: 'inherit',
    shell: true,
}

exec('gcc teste.c -o teste', (error, stdout, stderr) => {
    exec('./teste', options, (error,stdout,stderr)=>{
        console.log(`stdout: ${stdout}`);
        console.log(`stderr: ${stderr}`);

        if (error) {
            console.error(`exec error: ${error}`);
            return;
          }
    });  
});

teste.c

#include <stdio.h>
void main(){
    int i;
    printf("Hello World\n");
}

this is the output I am getting:

stdout: Hello World

stderr:
exec error: Error: Command failed: ./teste

Someone knows why this is happening? There is a better way of doing that? How can I really get timout working?

Thanks

@tadman The path it correct since the program does run, else there would be output to std out. Thassya Abreu can you try to add a return 0 to your c program? Edit: tadman was faster — Patrick Hollweck
– Patrick Hollweck, Commented Aug 27, 2018 at 18:36
@Thassya Abreu Your return type is still void, change it to int — Patrick Hollweck
– Patrick Hollweck, Commented Aug 28, 2018 at 10:44

tadman · Accepted Answer · 2018-08-27 18:34:25Z

4

Your executable should return a zero value (no error) on success:

#include <stdio.h>
int main(){
  int i;
  printf("Hello World\n");

  return 0;
}

If it doesn't you may have a random value assigned and that indicates some kind of error.

answered Aug 27, 2018 at 18:34

tadman

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3 Comments

John Bode Over a year ago

Now is a good time to point out that, per the language definition, main is supposed to return int, not void. The behavior of void main() is undefined.

Thassya Abreu Over a year ago

I put "return 0" but the error message is still there... picture

tadman Over a year ago

It's worth checking process.cwd() to see if the executable is being generated where you expect it, and if not, to specify the full path to the target. That it's running and still producing an error is odd, though.

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