get pid of process created with subprocess.check_call()

Question

I am currently trying to get the process id of a process started with subprocess.check_call.

i.e.

from subprocess import check_output

# I want to retrieve the PID of this process:
try:
    p = check_output(['some broken program']) 
except:
    if CalledProcessError: # but Popen does not throw me a CalledProcessError even if program crashes
        print("triage some stuff")
        print(p.pid) # this doesn't work unless its Popen

I have tried using Popen which works perfectly, however, it doesn't seem to be able to catch when a program is terminated i.e. CalledProcessError.

Can anyone advise, whether there is a way to get around either problem? Thanks!

For all of the `subprocess` functions other than `Popen()`, you don't get control back until the called process has exited, so there *is* no pid anymore. — jasonharper, Nov 22 '21 at 16:24

score 0 · Answer 1 · answered Nov 22 '21 at 16:17

You have to import CalledProcessError too. Code (with check_output): from subprocess import check_output, CalledProcessError

To detect a specific exception you have to use the following syntax:

 try:
     statement
 except ExceptionName:
     another_statement

In your situation:

 try:
     p = check_output(['some broken program']) 
 except CalledProcessError:
     print("triage some stuff")

You cannot reference p inside the except block as p may be undefined.
Moreover, as stated in this post, subprocess.run() is recommended over subprocess.check_output()

so... the question still stands. are there any methods that I can catch the `CalledProcessError` exception when using Popen? — caprinux, Nov 27 '21 at 09:45

get pid of process created with subprocess.check_call()

1 Answers1