[SOLVED] Bash trap is to mean just some certain sequential lines

zeroone · 07-16-2023, 07:55 PM

How can we have Bash trap meaning some certain sequential code lines only not for the rest of script ?

grail · 07-16-2023, 10:08 PM

Maybe an example would help?

wpeckham · 07-16-2023, 11:06 PM

Your meaning is unclear. Please enlighten us.

pan64 · 07-17-2023, 01:29 AM

yes, would be nice to explain better what do you mean. By the way, here is the documentation: https://man7.org/linux/man-pages/man1/trap.1p.html, but obviously you can read the man page of bash (and look for the built-in command trap).

shruggy · 07-17-2023, 08:43 AM

Quote:

Originally Posted by zeroone

How can we have Bash trap meaning some certain sequential code lines only not for the rest of script ?

trap traps signals intended for the current process. So, as long as all your code runs as a single process you cannot trap signals only for parts of it. But you can start another process from inside your code. Something like this (untested):

Script a:

Code:

#!/bin/sh
trap 'echo Trapped on exit from a' EXIT
read -rp 'Start b (y/n) ' reply
[ 'y' = "$reply" ] && exec sh b
echo End of a

Script b:

Code:

#!/bin/sh
echo Inside b

Turbocapitalist · 07-17-2023, 09:18 AM

Or this will trap SIGINT for a little while and then go back to the default behavior.

Code:

#!/bin/sh

trapped () {
        echo "Trapped.  Exiting"
        exit
}

echo 1
sleep 2

echo 2
sleep 2

trap trapped INT

echo 3
sleep 2

echo 4
sleep 2

trap - INT

echo 5
sleep 2

echo 6
sleep 2

exit 0

If ctrl-C is pressed any time except between 3 and 4 then it will exit as normally. Between 3 and 4, ctrl-C will exit via the function trapped() instead.

See "man sh" under the section for "trap" and "man 7 signal" for more about signals.

NevemTeve · 07-30-2023, 01:18 AM

Subshell?

Code:

(
   trap code signal
   ..
)