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Re: Revisiting Error handling (errexit)

From: Yair Lenga
Subject: Re: Revisiting Error handling (errexit)
Date: Sat, 9 Jul 2022 22:39:54 +0300

Hi Martin,

Long answer - my own view: The old 'errexit' logic was spec'ed many years
ago. As far as I can tell, it existed in bash 2.0, from 1996. I think
requirements/expectations are different now. The 'exit on error' error
handling was good for 1996 - does not meet today's requirement - using bash
to glue complex systems together. For that reason, I do not think that
replicating the errexit small details is a good strategy. In fact, I think
that most developers are looking for something that is closer to the "try
... catch" that they have in other environments. The 'errfail' is my
proposal to get there, without introducing lsignificant changes, or risk.

Re: command prefaced by ! which is important:
* The '!' operator 'normal' behavior is to reverse the exit status of a
command ('if ! check-something ; then ...').
* I do not think it's a good idea to change the meaning of '!' when running
with 'error checking'.
* I think that the existing structures ('|| true', or '|| :') to force
success status are good enough and well understood by beginner and advanced

Question: What is the penalty for "|| true" ? true is bash builtin, and in
bash it's equivalent to ':'. (see:

Re: yet another global setting is perpetuating the "wrong direction".
I prefer not to get into "flame war" on the issue of dynamic scope vs.
lexical scope. Most other scripting solutions that I'm familiar with are
using dynamic (rather than lexical) scoping for 'try ... catch.'.
Considering that bash is stable, I do not think that it is realistic to try
to expect major changes to 'bash'. Also, Bash code was developed with
specific design/requirements in mind. It can not be easily stretched to
integrate new ideas - sometimes it is better to go for practical solutions
than for the best solution. There is a big range of applications where bash
can play an important role. For a more sophisticated environment, python,
groovy, javascript or (your favorite choice) might be a better solution.

Question: Out of curiosity, can you share your idea for a better solution ?

Thanks for taking the time !

Sent from my iPad

On Jul 8, 2022, at 3:31 PM, Martin D Kealey <martin@kurahaupo.gen.nz> wrote:

The old errexit explicitly exempts any command prefaced by ! which is
important so that one can write ! (( x++ )) without it blowing up when x is
0 and without paying the penalty for  "|| true".
Does this new proposal honour that?

Aside from that, I still think that yet another global setting is
perpetuating the "wrong direction"; "local -" has the same dynamic scope as
any other "local", which means magic action at a difference, and makes
brittle code that can abort unexpectedly in production.


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