Kill process by pid file

Question

I try to kill a process by pid file:

kill -9 $(cat /var/run/myProcess.pid)

The pid file contains the process number. However executing the kill gives me no stdout and the processes is still alive. But this works:

kill -9 PID

What is wrong with the first kill command? Does it fail to extract the PID from the file?

Example content of pid file:

and

kill -9 5424

works.

I'm guessing, but try `cat /var/run/myProcess.pid | xargs kill -9`; my assumption is that you have trailing white-space in the pid file. — Elliott Frisch, Sep 29 '14 at 19:11
@artworkadシ Does ``kill -9 `cat /var/run/myProcess.pid` `` work? (had to figure out how to print backticks inside of backticks, heh) — admdrew, Sep 29 '14 at 19:16
Is this in a script, or at the command line? If it's a script what is your shebang line and are you on Ubuntu? — Elliott Frisch, Sep 29 '14 at 19:20
@admdrew this works, can you explain where the difference is? — DarkLeafyGreen, Sep 29 '14 at 19:30
@ElliottFrisch I am on debian, and the command is called from a nodejs script. The problem was solved with kill -9 `cat /var/run/myProcess.pid` — DarkLeafyGreen, Sep 29 '14 at 19:30
@artworkadシ I actually didn't know; looks like they're equivalent, but `$()` is the newer [POSIX standard](http://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_03) ([source1](http://stackoverflow.com/questions/9405478/command-substitution-backticks-or-dollar-sign-paren-enclosed), [source2](http://stackoverflow.com/questions/4708549/shell-programming-whats-the-difference-between-command-and-command)) — admdrew, Sep 29 '14 at 19:32
Be aware most of the times `-9` is not required and not recommended. Give process a chance to properly cleanup its resources. — Umur Gedik, Feb 03 '19 at 04:46

score 89 · Accepted Answer · edited May 23 '17 at 10:31

I believe you are experiencing this because your default shell is dash (the debian almquist shell), but you are using bash syntax. You can specify bash in the shebang line with something like,

#!/usr/bin/env bash

Or, you could use the dash and bash compatible back-tick expression suggested by admdrew in the comments

kill -9 `cat /var/run/myProcess.pid`

Regardless, you can't rely on /bin/sh to be bash.

score 84 · Answer 2 · answered Jun 03 '16 at 07:33

In some situations, the more compact:

pkill -F /var/run/myProcess.pid

is the way to go. I've had trouble with the varieties:

kill $(cat /var/run/myProcess.pid)
# Or
kill `cat /var/run/myProcess.pid`

when I had to put the command into something else which might parse it using different rules, like Monit does for its start/stop commands.

score 4 · Answer 3 · answered Jan 22 '20 at 22:39

4

cat /var/run/myProcess.pid | sudo xargs kill -9

answered Jan 22 '20 at 22:39

ehsan houshmand

373
3
6

3

While this may answer the question, providing additional context regarding why and/or how this code answers the question improves its long-term value. – leopal Jan 23 '20 at 07:13

score 0 · Answer 4 · answered May 22 '21 at 12:24

0

There is very simple method.

fuser -k /path/filename

example lets say you wanna kill apt lock file in linux.

sudo fuser -k /var/lib/dpkg/lock

and it will kill the process that holds the file.

answered May 22 '21 at 12:24

Ry Van

311
2
9

Kill process by pid file

4 Answers4