KeyError: 'print $2' when I use subprocess.call("ps -ef | grep wget | grep {0} | awk '{print $2}'

Question

In my macOS, I using a wget downloading the www.test.com index page.

then I have below python code:

#-*- coding:utf-8 -*-
import subprocess

url = "https://www.test.com"

subprocess.call("ps -ef | grep wget | grep {0}  | awk '{print $2}'".format(url), shell=True)

when I run it, I get issue:

subprocess.call("ps -ef | grep wget | grep {0}  | awk '{print $2}'".format(url), shell=True)
KeyError: 'print $2'

and I switch the subprocess.call() to os.system() , still get this issue.

Answer 1

Your error is not caused by subprocess, rather the string format.

"ps -ef | grep wget | grep {0}  | awk '{print $2}'".format(url)

you can use %s to forming string.

"ps -ef | grep wget | grep %s  | awk '{print $2}'"%(url)

Answer 2

You need to use subprocess.run()

From Docs

Code needing to capture stdout or stderr should use run() instead

Note : Do not use stdout=PIPE or stderr=PIPE with this function. The child process will block if it generates enough output to a pipe to fill up the OS pipe buffer as the pipes are not being read from.