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I'm learning how to run shell commands through the os module and the subprocess module. The following is my code.

from subprocess import call
call('/usr/lib/mailman/bin/find_member -w user_email')
import os
os.system('/usr/lib/mailman/bin/find_member -w user_email')

The second one works very well, while on the other hand, the first one does not work, and I got the following errors. 

Traceback (most recent call last):
  File "fabfile.py", line 6, in <module>
    call('/usr/lib/mailman/bin/find_member -w user_email')
  File "/usr/lib64/python2.6/subprocess.py", line 478, in call
    p = Popen(*popenargs, **kwargs)
  File "/usr/lib64/python2.6/subprocess.py", line 639, in __init__
    errread, errwrite)
  File "/usr/lib64/python2.6/subprocess.py", line 1228, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory

I thought those two methods have the same effect. Could you point to me what's the possible errors here? Many thanks.

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  • Try: call('/usr/lib/mailman/bin/find_member -w user_email', shell=True) or, better yet: call(['/usr/lib/mailman/bin/find_member', '-w', 'user_email']). Commented Jun 12, 2017 at 20:21

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One difference between the two is documented (Here)

os.system(command)

Execute the command (a string) in a subshell.

While subprocess.call() looks like:

subprocess.call(args, *, stdin=None, stdout=None, stderr=None, shell=False)

Run the command described by args. Wait for command to complete, then return the returncode attribute.

To make subprocess.call() behave the same as os.system() you need to pass shell=True. So something like:

from subprocess import call
call('/usr/lib/mailman/bin/find_member -w user_email', shell=True)
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