Question

I want to run a command like this

grep -w 1 pattern <(tail -f mylogfile.log)

basically from a python script i want to monitor a log file for a specific string and continue with the python script as soon as i found that.
I am using os.system(), but that is hanging. The same command in bash works good.

I have a very old version of python (v2.3) and so don’t have sub-process module.

do we have a way to acheive this

Answer 1

In Python 2.3, you need to use subprocess from SVN

import subprocess
import shlex
subprocess.call(shlex.split("/bin/bash -c 'grep -w 1 pattern <(tail -f mylogfile.log)'"))

To be explicit, you need to install it from the SVN link above.

You need to call this with /bin/bash -c due to the shell redirection you’re using

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EDIT

If you want to solve this with os.system(), just wrap the command in /bin/bash -c since you’re using shell redirection…

os.system("/bin/bash -c 'grep -w 1 pattern <(tail -f mylogfile.log)'")