UNIX for Dummies Questions & Answers

I want to test if script.sh is being run with nohup ... but $0 does not contain nohup part...

purpose: script.sh should only be ran with nohup if user forgets nohup then it should echo "run with nohup" && exit.......

One way to achieve this is by creating an alias

Code:

alias script.sh="nohup /path/script.sh"

So if someone tries to run script.sh, it will actually call the alias.

Code:

script.sh

But this approach will fail if the script is ran with path specified like below (You can put a check in your script to make sure everyone is calling the alias):-

Code:

./script.sh

Code:

/path/script.sh

I'm not sure if there are any other ways to enforce use of nohup. I hope this helps.

Inside a shell script it is hard to determine if it was started by the nohup utility. However, if STDOUT or STDERR for your script is a TTY device, you will know that it was not started by nohup. If being immune to SIGHUP signals and not having STDOUT directed to a TTY device and not having STDERR directed to a TTY device is sufficient for your script to continue running, the following code may help:

Code:

#!/bin/ksh
trap '' HUP
if [ "x$(tty <&1)" != "xnot a tty" ] || [ "x$(tty <&2)" != "xnot a tty" ]
then    printf '%s: This script must be started by "nohup %s ..."\n' "$0" "$0"
        exit 1
fi
printf '%s SIGHUP ignored and STDIN & STDERR directed to non-TTYs\n' "$0"
. . . other shell commands . . .

This was written and tested with the Korn shell, but should work with bash, ksh, or sh with no changes. It won't work with csh or similar shells.