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From: gentoo_eshoes@tutanota.com
Newsgroups: gnu.bash.bug
Subject: Re: looking for consistent C-c trap behavior
Date: Sat, 18 Apr 2020 00:00:59 +0200 (CEST)
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Apr 17, 2020, 22:14 by gentoo_eshoes@tutanota.com:

>
>
>
> Apr 17, 2020, 22:02 by dualbus@gmail.com:
>
>> On Fri, Apr 17, 2020 at 12:59 PM gentoo_eshoes--- via Bug reports for
>> the GNU Bourne Again SHell <bug-bash@gnu.org> wrote:
>>
>>>
>>> I've noticed that if I trap SIGINT in a bash script, the behavior when =
encountering C-c depends on whether an external command (eg. 'sleep 100') o=
r a builtin command (like 'read -p') was encountered.
>>>
>>> I attach an example script which requires me to press C-c twice to inte=
rrupt the builtin 'read -p' command, and it only works because I'm restorin=
g the trap via 'trap - SIGINT' the first time.
>>>
>>> My goal is to have C-c interrupt and use that exit code (130 most likel=
y) to exit with from script, regardless or whether or not the interrupted c=
ommand in the script was an internal or external one.
>>>
>>> How to do?
>>>
Let me put some effort into it: (attached anew script, prev. was had extra =
'sleep 100' which was supposed to be commented out)

To break from the builtin 'read', I have to use C-c twice: the first time I=
 restore SIGINT trap so that the second C-c can actually make 'read' break/=
exit

$ ./sigintread.bash=20
Press C-c here...^Cinterrupted sees exit code '0'
^C

Maybe I should paste it rather than attach it, here:

#!/bin/bash

#C-c won't break the builtin read unless default SIGINT trap is restored, t=
hus needing two C-c to exit

interrupted() {
=C2=A0=C2=A0=C2=A0 local ec=3D"$?"
=C2=A0=C2=A0=C2=A0 trap - SIGINT=C2=A0 #this restores prev. behaviour, so n=
ow another C-c will stop 'read -rp'
=C2=A0 =C2=A0 echo "interrupted sees exit code '$ec'"
=C2=A0=C2=A0=C2=A0 #=C2=A0 exit "$ec"=C2=A0 #this is needed ONLY for when '=
sleep' is used and interrupted, or else it will continue running and hit 'N=
ormal exit', if used with 'read' then it will exit without breaking 'read' =
thus exit code is 0 instead of 130 (128+2 aka SIGINT=3D=3D2)
}

trap interrupted SIGINT
builtin read -rp "Press C-c here..."=C2=A0 #can use 'sleep 100' instead of =
this 'read...' here, for testing how the behaviour is different with an ext=
ernal command instead of a builtin one.
#sleep 100
#ping 127.0.0.1=C2=A0 #ping will ec=3D0 on C-c
ec=3D"$?"
echo
echo "Normal exit sees ec=3D$ec"
exit "$ec"


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