Error getting the output of child process in node

Question

I have a c program (I didn't code it) that prints some data in the terminal. I launch the program as a child process in node with the spawn function.

const child_process = spawn('./myProgram', ['--arg']);

After that, I code the event to get the printed data:

child_process.stdout.on('data', function(data) {
        console.log(data);
});

When I run the program I can't see the output data from my c program in my nodejs terminal. If I initialize the child process with stdio as inherit it works.

const child_process = spawn('./myProgram', ['--arg'], {stdio :'inherit'});

The key point here is that I need to process that data in my nodejs app. I suppose the way the c file prints the data is not the standard one, so my nodjs program does not get it.

Does this work with other programs? A simple test is like spawn('ls'). — tadman
– tadman, Commented Aug 13, 2020 at 1:02
Another thing to check is that you're not getting any errors, or that it's not outputting to stderr instead. — tadman
– tadman, Commented Aug 13, 2020 at 1:03
It works. The problem is with that c program. I have also created my own c program to test it and works. — Imanol
– Imanol, Commented Aug 13, 2020 at 1:04

Imanol · Accepted Answer · 2020-08-13 01:12:47Z

1

The file was outputting to stderr instead to stdout. It was fixed by adding the event to stderr:

child_process.stderr.on('data', function(data) {
        console.log(data);
});

@tadman got the answere.

answered Aug 13, 2020 at 1:12

Imanol

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