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Re: .ab oddity

From: John Gardner
Subject: Re: .ab oddity
Date: Mon, 6 Feb 2023 15:00:34 +1100

> Something I recommend to all serious Unix users is to put the exit status
> in the shell prompt.

Alternatively, you can indicate a non-zero exit status by displaying a
prompt symbol in a different colour than usual. This might be preferable
for folks who prefer fixed-width and/or minimalist prompt strings.

For example, my own prompt string
uses a dimmed “λ” in graphical (true colour) environments, and a red “$”
for purely-textual displays like fbdev(4) and wscons(4). It boils down to
something like this:

colour='\033[32m'; # Normal prompt-symbol colour
PS1="\$([ \$? -eq 0 ] && printf '$colour' || printf '\033[31m')\$${colour}"

Basically, if I care about the exit status, I can always run `echo $?`.
Most of the time, I don't (it's enough to know that an error occurred from
the colour alone), so it's not worth cluttering my terminal window with
unnecessary information.

— John

On Sun, 5 Feb 2023 at 08:56, G. Branden Robinson <> wrote:

> Hi Peter,
> At 2023-02-04T16:09:55-0500, Peter Schaffter wrote:
> > The reasoning makes sense but now you have to jump through a hoop
> > when you're using .ab for debugging.  I usually debug with the -z
> > flag.  Formerly,
> >
> >   echo -e ".nr foo 1\n.if r foo .ab\n" | groff -z
> >
> > would helpfully spit out "User abort."  Now there's no way to know
> > whether groff exited cleanly or aborted unless you add a string
> > after .ab.  (A minor annoyance, but I thought I should mention it.)
> There _is_ a way... :)
> Something I recommend to all serious Unix users is to put the exit
> status in the shell prompt.  I learned this trick early because too many
> times when working interactively, by the time I realize I want to know
> something's exit status, it is too late and $? has been clobbered.
> Here's an abbreviated form of my Bash prompt.  I note that the "($?)"
> part is thoroughly portable.  _All_ POSIX, Bourne-, or Korn-descended
> shells should support it.
> PS1='\D{%F} \t \s-\v [\l] {\j} ($?) \u@\h:\w !\!\$ '
> Regards,
> Branden

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