Re: [RFC PATCH] Allow trap to override permanently-ignored signals in background shells

From: Harald van Dijk <harald@gigawatt.nl>
To: Johannes Altmanninger <aclopte@gmail.com>, dash@vger.kernel.org
Subject: Re: [RFC PATCH] Allow trap to override permanently-ignored signals in background shells
Date: Fri, 8 Mar 2024 11:48:11 +0000	[thread overview]
Message-ID: <b42dbf13-989d-4609-bbcb-8b9eababbe65@gigawatt.nl> (raw)
In-Reply-To: <20240308110158.2459219-1-aclopte@gmail.com>

Hi,

On 08/03/2024 11:01, Johannes Altmanninger wrote:
> TL;DR: I think this job should exit on Control-C.
> 
> 	( trap - INT; sleep inf ) &

The TL;DR is oversimplified: Control-C would not result in SIGINT being 
sent to the sleep command, because it runs in the background.

Your fuller version, I agree, I think that is a bug in dash. There are 
some more known bugs in its handling of the trap command in subshells 
that require a bigger rework (particularly the one where, despite traps 
being reset in subshells, the 'trap' command should print the parent 
shell's traps if called in a subshell) that maybe should be looked at at 
the same time.

> In general, I wonder if SIGINT is only for actual shells, and SIGTERM
> is the signal to use in our situation.

SIGINT is not limited to shells. At first glance, sending SIGINT to 
another process or process group upon receipt of SIGINT, because that 
other process or process group is what it was intended for, seems like 
an appropriate use to me.

Cheers,
Harald van Dijk