CODEWITHSUNDEEP
shellsubshellbash-trap
Teodoro
Teodoro

Reputation: 1474

Trap signals both in script and subshells

I know there's a lot of questions similar to mine, but I didn't found any about trapping signals sent when a subshell is taking place on the terminal. Let me explain:

#!/bin/sh

trap 'echo "exiting.."; exit 0;' INT

var1=$(echo "ab\nab" | fzf)
var2=$(echo "cd\ncd" | fzf)

fzf is a tool to display a selector of items of a list, so when the program reaches var1 a pretty selector covers my terminal screen prompting ab in one line and ab in the second, with the arrow keys I select the desired one and the result gets printed. Looks a lot like dmenu using this way.

The problem is that Ctrl-C doesn't get trapped by the script when fzf is prompting those lines. Instead, Ctrl-C kills fzf but the script keeps running.
So the question here is more about how to propagate this signal to the parent process.

Upvotes: 4

Views: 859

Answers (1)

Gre-san
Gre-san

Reputation: 391

There is no easy way to propagate the particular signal from child to parent. However, exit code is 130 if the program is terminated by Ctrl-C in many cases. fzf follows it also. Checking exit status and sending signal to own process is one of the workaround.

#!/bin/sh
trap 'echo "exiting.."; exit 0;' INT

var1=$(echo "ab\nab" | fzf)
[ $? -eq 130 ] && kill -INT $$
var2=$(echo "cd\ncd" | fzf)
[ $? -eq 130 ] && kill -INT $$

However, it is not common way. If it needs to do something when terminated with any errors, using set -e and trapping EXIT or other signals is general way.

#!/bin/sh
set -e
trap 'echo "exiting.."; exit 0;' EXIT

var1=$(echo "ab\nab" | fzf)
var2=$(echo "cd\ncd" | fzf)

Upvotes: 3

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