Problems running terminal command via Python

Question

I'm working on a small project where I need to control a console player via python. This example command works perfectly on the Linux terminal:

mplayer -loop 0 -playlist <(find "/mnt/music/soundtrack" -type f | egrep -i '(\.mp3|\.wav|\.flac|\.ogg|\.avi|\.flv|\.mpeg|\.mpg)'| sort)

In Python I'm doing the following:

command = """mplayer -loop 0 -playlist <(find "/mnt/music/soundtrack" -type f | egrep -i '(\.mp3|\.wav|\.flac|\.ogg|\.avi|\.flv|\.mpeg|\.mpg)'| sort)""" 
os.system(command)

The problem is when I try it using Python it gives me an error when I run it:

sh: 1: Syntax error: "(" unexpected

I'm really confused here because it is the exact same string. Why doesn't the second method work?

Thanks.

score 3 · Accepted Answer · 2013-07-11 02:43:20Z

3

Your default user shell is probably bash. Python's os.system command calls sh by default in linux.

A workaround is to use subprocess.check_call() and pass shell=True as an argument to tell subprocess to execute using your default user shell.

import subprocess
command = """mplayer -loop 0 -playlist <(find "/mnt/music/soundtrack" -type f | egrep -i '(\.mp3|\.wav|\.flac|\.ogg|\.avi|\.flv|\.mpeg|\.mpg)'| sort)"""
subprocess.check_call(command, shell=True)

edited Jul 11, 2013 at 2:43

answered Jul 11, 2013 at 2:37

user849425

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3 Comments

computer10171 Over a year ago

I tried what you suggested however a different error is occurring: /bin/sh: 1: Syntax error: "(" unexpected with a traceback ...returned non-zero exit status 2. Also tried this subprocess.Popen(command, shell=True, stdout=subprocess.PIPE, stdin=subprocess.PIPE) but I get /bin/sh: 1: Syntax error: "(" unexpected. Tried a bunch of things and nothing seems to be working...

user849425 Over a year ago

A non-zero exit normally indicates a command failed in Linux. I would check the mplayer documentation to find out what the error is (if any).

computer10171 Over a year ago

Ok, I'm sure I'll get this working soon enough. At least I now know why it isn't working. Thank you.

Community · Accepted Answer · 2017-05-23 12:05:28Z

1

Your python call 'os.system' is probably just using a different shell than the one you're using on the terminal: os.system() execute command under which linux shell?

The shell you've spawned with os.system may not support parentheses for substitution.

edited May 23, 2017 at 12:05

CommunityBot

11 silver badge

answered Jul 11, 2013 at 2:37

Stephen Crosby

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2 Comments

Barmar Over a year ago

He's using <(...) for process substitution, not grouping.

Stephen Crosby Over a year ago

Thanks for the correction. I just learned something new. Here's an explanation for anyone else who wants it: en.wikipedia.org/wiki/Process_substitution

mousetail · Accepted Answer · 2021-06-21 13:10:06Z

0

import subprocess  
 
COMND=subprocess.Popen('command',shell=True,stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=subprocess.PIPE)
COMND_bytes = COMND.stdout.read() + COMND.stderr.read()  
print(COMND_bytes)

edited Jun 21, 2021 at 13:10

mousetail

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answered Jun 21, 2021 at 12:35

user15082770

1 Comment

mousetail Over a year ago

Please add some explanation. Right now it is unclear why this works while the original code doesn't

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