subprocess.call exit code in python

Question

I have a use case where I execute a java jar through python subprocess. How can I get to know if the subprocess completed successfully or terminated because of some exception. Subprocess does return an exit code but the jar does not handle returning appropriate exit codes. Is there some other way to do this?

class Test(object):
     #constructor
     .
     .
     def execute(self):
         exit_code = subprocess.call(['jar_path'])
         if not exit_code:
             return True
         else:
             return False

does the jar report correct exceptions to stdout or stderr ? — Anand S Kumar
– Anand S Kumar, Commented Sep 1, 2015 at 5:06

Community · Accepted Answer · 2020-06-20 09:12:55Z

3

Since you say -

Ques : does the jar report correct exceptions to stdout or stderr ?

Ans : yes it does support.

You can use subprocess.Popen() along with .communicate() and subprocess.PIPE to get the data from stdout/stderr and parse that appropriately to determine whether there was any exception.

Example -

 def execute(self):
     proc = subprocess.Popen(['jar_path'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     pout,perr = proc.communicate()
     if not perr:  #or however you want to check stderr/stdout
         return True
     else:
         return False

edited Jun 20, 2020 at 9:12

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answered Sep 1, 2015 at 6:12

Anand S Kumar

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10 Comments

Abhi Over a year ago

will it not make subprocess non blocking if I use Popen instead of call?

Anand S Kumar Over a year ago

Well, .communicate() is blocking, it would block the process till the proc completes.

Abhi Over a year ago

I tried with communicate. Both stderr and stdout outputs are being redirected to a file instead of PIPE. Probably because of that pout and perr seems to be none.

Anand S Kumar Over a year ago

when you directly run that jar file in command line do you get any output in the console?

Abhi Over a year ago

yes I do. but now inside Popen I am using file to dump stdout and stderr results. I am getting these log in a file. But pout and perr seems to be null. Is it because I am redirecting the output to a file instead of PIPE?

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