CODEWITHSUNDEEP
pythonpython-3.x
lonelymo
lonelymo

Reputation: 4192

How do I check for error code from os.system?

I have a python system call that takes a while to finish.

os.system("call_that_takes_quite_some_time")

In the meanwhile I want to keep throwing a message that says "waiting..." every now and then till the os.system returns 0 or an error. / How do I do this? Is there something in python that I can "listen" to in a while loop?

Upvotes: 3

Views: 9287

Answers (2)

justhalf
justhalf

Reputation: 9117

You can use threading

import os
import time
import threading

def waiter():
    waiter.finished = False
    while not waiter.finished:
        print 'Waiting...'
        time.sleep(1)
os_thread = threading.Thread(target=waiter)
os_thread.daemon = True
os_thread.start()
return_value = os.system('sleep 4.9')
return_value >>= 8  # The return code is specified in the second byte
waiter.finished = True
time.sleep(3)
print 'The return value is', return_value

This will print "Waiting..." message every 1 second, and it stops after waiter.finished is set to True (in this case there will be 5 "Waiting..." messages)

But os.system is not recommended. The documentation recommends using subprocess module.

Upvotes: 1

venpa
venpa

Reputation: 4318

os.system waits till your command execution is complete. use subprocess.Popen you can check output or error. Popen gives handle and you can check return code using wait to find out command is successful/failure. For ex:

proc = subprocess.Popen(command, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
while proc.poll() is None:
      print proc.stdout.readline() #give output from your execution/your own message
 self.commandResult = proc.wait() #catch return code

Upvotes: 8

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