1'' 1'' - 1 year ago 122
Bash Question

Process substitution not allowed by Python's subprocess with shell=True?

Here is a toy example of process substitution that works fine in Bash:

$ wc -l <(pwd)
1 /proc/self/fd/11

So why does the same command give a syntax error when invoked from Python's subprocess with shell=True?

>>> subprocess.check_call('wc -l <(pwd)', shell=True)
/bin/sh: 1: Syntax error: "(" unexpected
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/path/to/my/python/lib/python3.5/subprocess.py", line 581, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command 'wc -l <(pwd)' returned non-zero exit status 2

dsh dsh
Answer Source

/bin/sh: 1: Syntax error: "(" unexpected

You have a bashism. It is not valid according to POSIX, which is what /bin/sh implements.

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