Executing A complex Shell command read as String from a File in Python

Question

I have a configuration file where user can specify a set of shell commands. Commands are basically a chain of pipe-separated shell commands.

CMD1 = grep "SomeOtherString" | grep "XX" | cut -d":" -f9 | cut -d"," -f1

CMD2 = grep "SomeOtherString" | tail -1| cut -d":" -f9 | cut -d"," -f1 | cut -d"[" -f2 | cut -d"]" -f1

I am able to read the commands in my Python scripts. My question is how will I be able to run these read command strings in Python and get the output.

Any solution with subprocess, plumbum, sh will be acceptable.

Answer 1

Use subprocess.check_output()

output = subprocess.check_output(output)

Something to be aware of is that unlike the other subprocess commands, a subprocess.CalledProcessError will be raised if a non-zero error code is returned.

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You shouldn't need to do this, but in case it comes in handy to somebody out there, I did run into an experience once where for some reason the above solution did not work, and so, instead, I did the following.

    stdout_fh = io.StringIO()
    stderr_fh = io.StringIO()
    with redirect_stderr(stderr_fh):
        with redirect_stdout(stdout_fh):
            subprocess.run(command, shell=True)
    stderr = stderr_fh.getvalue()
    stdout = stderr_fh.getvalue()