Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. It only takes a minute to sign up.
Sign up to join this community
When I use kill on command line it works.
kill -SIGSTOP 1234
But if I use in bash script file I get this error:
kill: SIGSTOP: invalid signal specification
sh file is
#!/bin/sh
kill -SIGSTOP 1234
How can I use kill in bash script? I tried this:
#!/bin/sh
/bin/bash -c "kill -SIGSTOP 1234"
but it does not work.
The standard (POSIX) syntax is:
kill -s STOP "$pid"
That is, without the SIG prefix. Some shell implementations, support kill -s SIGSTOP or kill -SIGSTOP as an extension but that's not standard nor portable.
The UNIX specification (POSIX+XSI) also allows:
kill -STOP "$pid"
And
kill -19 "$pid"
Though which signal number is SIGSTOP is not specified and may change between systems and even architectures for a same system, so should be avoided.
set +o posix will allow the usage of SIGTERM, SIGSTOP etc. I do agree that set -o posix at the end is not necessary. It's more a habit. I'm not sure what the significance or the added value is in your answer.
Apr 29, 2015 at 11:18
set +o posix will only allow SIGTERM/SIGSTOP in bash when bash is started in posix mode, not with any other implementation of sh. So you rely on your /bin/sh being bash. Don't do that, use #! /bin/bash if you want to use bash specific features.
Apr 29, 2015 at 11:23
pdksh and yash also have a posix option. pdksh supports kill -SIGSTOP regardless of whether that option is enabled or not. yash, like bash also forbids kill -SIGSTOP when the posix option is off, and gives a more specific error message in that case: kill: SIGSTOP: the signal name must be specified without 'SIG'. dash and AT&T ksh kill builtins don't support kill -s SIGSTOP. zsh's and procps-ng's do.
Apr 29, 2015 at 12:09
-SIGSTOP I thought passing -s to kill was mandatory. Thanks for the explaination! Learnt something new today.
Apr 29, 2015 at 12:20
I am facing the same problem. All answers here did not address the true cause of the issue. Inside the script the kill used is the built-in provided by the shell, that is why you are having the error. While in your terminal, the kill used is the separate executable located at /bin/kill. To fix the issue, inside your script you must explicitly use the /bin/kill and not the built-in shell version. Therefore you write it like this:
#!/bin/sh
/bin/kill -s SIGHUP 14344
To start with: SIGSTOP will temporarily stop the process but keep in memory so it can be continued later on using SIGCONT system call. You can use the following little snippet to see what happens
#!/bin/bash
set -x
sleep 100 &
pid=$!
kill -s SIGSTOP "$pid"
sleep 2
kill -s SIGCONT "$pid"
You'll see what the script does interactively.
So to get your script working using #/bin/sh shebang you'd do something like
#!/bin/sh
set -x
set +o posix
sleep 100 &
pid=$!
kill -s SIGSTOP "$pid"
sleep 2
kill -s SIGCONT "$pid"
set -o posix
#!/bin/bash
bash option), and of course does not specify what would happen when you turn it off. Your answer doesn't make any sense. If you want to use a bash specific feature, start the script with #! /bin/bash, don't make it a sh script that assumes sh is bash and then disable the sh mode.
Apr 29, 2015 at 11:07
SIG in sh. So again instead of commenting on every answer I post you better edit the answer and provide the right one. How's that?
Apr 29, 2015 at 11:09
trap 'kill -s SIGSTOP 1234' EXITin a bash script. Also it is#!/bin/bashtrap 'kill -s SIGSTOP 1234' EXITbut I get same error#!/bin/shto#!/bin/bash. I always use#!/bin/shand now I really do not know why it does not work.set +o posix; kill -SIGSTOP 1234could solve the problem as well!