CODEWITHSUNDEEP
pythonshellsubprocess
anexo
anexo

Reputation: 505

Subprocess result through shell instead of being saved into text file

I'm writing a Python script for my thesis research, and I'm having problems with the subprocess module.

What the script does is executing "perf" with lots of args (here is a simplified version):

cmd = 'sudo perf stat -C %s -I %s -x , -e "%s"' % (core_perf, interval, perf_event_text)

Then I split cmd into args, to have tokens to send to subprocess:

final_cmd = cmd.split()

with open('output.txt', 'w') as outfile:
    subprocess.Popen(final_cmd, stdout=outfile)

The problem is that this works well, but the output is shown through shell and not saved into file.

If I do it for "ls", it works like a charm:

with open('output.txt', 'w') as outfile:
    subprocess.Popen("ls", stdout=outfile)

Any ideas?

Any help would be appreciated!

Thanks in advance!

Upvotes: 0

Views: 69

Answers (2)

Corey Goldberg
Corey Goldberg

Reputation: 60604

another option is to pass the -o parameter to perf so it writes stderr output to the file you specify:

import shlex
import subprocess

cmd = shlex.split('perf stat -o outfile.txt ls')
subprocess.call(cmd)

Upvotes: 0

mata
mata

Reputation: 69042

perf stat doesn't use stdout for its output but stderr, many programs starting a command and reporting on it (e.g. time) do the same to not clobber the output of the executed command.

So in this case, instead of stdout=outfile use stderr=outfile.

Upvotes: 3

Related Questions