Re: Weird set -u error

[Tim Woodall <debianuser@woodall.me.uk>]

On Fri, 26 Aug 2022, tomas@tuxteam.de wrote:

> On Fri, Aug 26, 2022 at 08:17:10AM +0100, Tim Woodall wrote:
> > $ cat Makefile.test
> > SHELL := /bin/bash -u
> > MAKEFLAGS += --no-builtin-rules
> > .SUFFIXES:
> >
> > all:
> >         echo done
> > $ make -f Makefile.test
> > echo done
> > done
> > $ make -f Makefile.test | cat
> > echo done
> > /etc/bash.bashrc: line 7: PS1: unbound variable
>                    ^^^^^^^^^^^
>
> [...]
>
> > Why do I get that unbound variable error? (I know how to fix it, I just
> > don't understand why it only happens when I pipe the output)
>
> If I were you, I'd  go looking at your /etc/bashrc and see what's around
> line 7. Mine says (line numbers added by me):

Yes, I know how to fix it. That is straight forward. SUDO_USER and
SUDO_PS1 have similar issues, debian_chroot works in the presence of set
-u

But I don't understand why /etc/bash.bashrc is being sourced by make
when piping make through cat. Make is doing something like:

source /etc/bash.bashrc; bash -c 'echo done' - but only when the output
is to a pipe.

bash -uc 'echo done'
doesn't have the problem whether or not it is outputting to a pipe.

Tim