How to redirect subprocess.Popen output to a file using in Python

Sonetimes you need to run shell commands in your Python script, there are few different modules in python for that and the subprocess is one of those . Then you might need to copy the output of your shell command to a log file . This can be usually done with the append (>>) method in shell . But in some cases, this won’t work especially if you have lots of dynamic variables using with the shell commands . For eg : I need to run a dulpcate IP scan specificially to a dynamic gateway IP .So this gateway IP is grepped from the interface uisng ‘awk’, ‘sed’ etc and then assign to a variable . I will be then using this variable in the shell command . So to append subprocess.Popen output to a file

First , assign a variable to your log file location and open the file in append mode

log = open("/var/log/name.log","a")

Then assign your shell command to another variable:

command = subprocess.Popen('your shell command' ,stdout=log, stderr=log, shell=True)

That’s it , your output will be appended to your log file . Its better to use the subprocess.wait to fnish the execution of the command . This is very useful in running commands in long python scripts where you need to wait until the first command finishes.

command.wait()