Question

I want a Python script to grep for a particular process, extract its PID, and kill it. Here’s what I’m using:

def main():
    # Shutdown Tomcat
    shutdownCmd = "sh ${TOMCAT_HOME}/bin/shutdown.sh"
    subprocess.call([shutdownCmd], shell=True)

    # Check for PID
    grepCmd = "ps -aef | grep tomcat"
    grepResults = subprocess.check_output([grepCmd], shell=True)

    # Get PID(s) and kill it/them.
    for i in range(1, len(grepResults), 9):
    pid = grepResults[i]
    killPidCmd = "kill -9 " + pid
    subprocess.call([killPidCmd], shell=True)

    # Exit.
    sys.exit()

However, although it does shutdown my process (Apache Tomcat), I get the following “warnings” in the terminal whenever I run it:

kill -l [exitstatus]
/bin/sh: 1: kill: Operation not permitted

/bin/sh: 1: kill: Illegal number: h
/bin/sh: 1: kill: Illegal number: v
/bin/sh: 1: kill: Illegal number: l
/bin/sh: 1: kill: Operation not permitted

/bin/sh: 1: kill: Illegal number: .
/bin/sh: 1: kill: Illegal number: i
/bin/sh: 1: kill: Illegal number: D
/bin/sh: 1: kill: Illegal number: l
/bin/sh: 1: kill: Illegal number: .
/bin/sh: 1: kill: Illegal number: i
/bin/sh: 1: kill: Illegal number: /
/bin/sh: 1: kill: Illegal number: s
/bin/sh: 1: kill: Illegal number: r
/bin/sh: 1: kill: Illegal number: /
/bin/sh: 1: kill: Illegal number: .
/bin/sh: 1: kill: Illegal number: c
/bin/sh: 1: kill: Illegal number: t
/bin/sh: 1: kill: Illegal number: c
/bin/sh: 1: kill: Illegal number: i
/bin/sh: 1: kill: Illegal number: r
/bin/sh: 1: kill: Illegal number: a
/bin/sh: 1: kill: Illegal number: l
/bin/sh: 1: kill: Illegal number: a
/bin/sh: 1: kill: Illegal number: g
/bin/sh: 1: kill: Illegal number: j
/bin/sh: 1: kill: Illegal number: s
/bin/sh: 1: kill: Illegal number: g
/bin/sh: 1: kill: Illegal number: 
/bin/sh: 1: kill: Illegal number: X
/bin/sh: 1: kill: Illegal number: 
/bin/sh: 1: kill: Usage: kill [-s sigspec | -signum | -sigspec] [pid | job]... or
kill -l [exitstatus]
/bin/sh: 1: kill: Illegal number: n
/bin/sh: 1: kill: Illegal number: i
/bin/sh: 1: kill: Illegal number: /
/bin/sh: 1: kill: Illegal number: s
/bin/sh: 1: kill: Illegal number: r
/bin/sh: 1: kill: Illegal number: /
/bin/sh: 1: kill: Illegal number: .
/bin/sh: 1: kill: Illegal number: c
/bin/sh: 1: kill: Illegal number: t
/bin/sh: 1: kill: Illegal number: e
/bin/sh: 1: kill: Illegal number: 
/bin/sh: 1: kill: Illegal number: h
/bin/sh: 1: kill: Illegal number: h
/bin/sh: 1: kill: Illegal number: n
/bin/sh: 1: kill: Illegal number: /
/bin/sh: 1: kill: Illegal number: o
/bin/sh: 1: kill: Illegal number: .
/bin/sh: 1: kill: Illegal number: e
/bin/sh: 1: kill: Operation not permitted

/bin/sh: 1: kill: Illegal number: n
/bin/sh: 1: kill: Illegal number: a
/bin/sh: 1: kill: Illegal number: o
/bin/sh: 1: kill: Illegal number: e
/bin/sh: 1: kill: Illegal number: x
/bin/sh: 1: kill: Illegal number: c
/bin/sh: 1: kill: Illegal number: t
/bin/sh: 1: kill: Illegal number: a
/bin/sh: 1: kill: Illegal number: m
/bin/sh: 1: kill: Operation not permitted

/bin/sh: 1: kill: Illegal number: m
/bin/sh: 1: kill: Illegal number: .
/bin/sh: 1: kill: Illegal number: t
/bin/sh: 1: kill: Illegal number: s
/bin/sh: 1: kill: Illegal number: z
/bin/sh: 1: kill: Illegal number: a
/bin/sh: 1: kill: Illegal number: v
/bin/sh: 1: kill: Illegal number: t
Killed

Can any Python meastros take a look at the script and figure out why I’m getting all these /bin/sh: 1: kill: Illegal number: <whatever> warnings/errors/ouputs? Any suggestions as to how to fix them? Thanks in advance!

Answer 1

for i in range(1, len(grepResults), 9):
    pid = grepResults[i]
    killPidCmd = "kill -9 " + pid
    subprocess.call([killPidCmd], shell=True)

Looks like your grepResults is some plain string, and you’re picking single characters from it. That’s why kill complains about strange numbers (which are no numbers but chars) that you’re giving to it. Check the output of this command, then you should see, what’s going wrong:

grepResults = subprocess.check_output([grepCmd], shell=True)

Insert something like that and check, if pid fits for you. Also make sure, that the criterias (if 'grep' in line) fit and don’t match other processes. Maybe you have to add more if-clauses here.

import subprocess
grepCmd = "ps -aef | grep tomcat"
grepResults = subprocess.check_output([grepCmd], shell=True)
for line in grepResults.strip().split('\n'):
    if 'grep' in line: 
        continue
    pid = line.split()[1]
else:
    pid = None
# print pid

If pid is None, it should exit with error, as there was no running service found. And in case you want to kill more than one pid, of course you have to create some list, or directly kill the pid within this loop.