Re: [PATCH 1/2] help: add shell-path to --build-options

From: Emily Shaffer <emilyshaffer@google.com>
Date: May 13, 2020, 18:45 UTC
Message-ID: <20200513184507.GA196295@google.com>
In-Reply-To: <CAPig+cRGrExRsucs8pmmiP+Zc2CmR3AU=8ACuiyH9tkz9JSCgQ@mail.gmail.com>

On Wed, May 13, 2020 at 01:10:36AM -0400, Eric Sunshine wrote:

Show 19 quoted lines

> 
> On Wed, May 13, 2020 at 1:02 AM Junio C Hamano <gitster@pobox.com> wrote:
> > "brian m. carlson" <sandals@crustytoothpaste.net> writes:
> > > [...] A value of "/bin/sh" doesn't
> > > necessarily tell us very much on Debian (or on macOS, for that matter).
> >
> > Good point.  Perhaps readlink(3) on it, then?
> >
> > lrwxrwxrwx 1 root root 9 Mar 11  2018 /bin/sh -> /bin/bash
> 
> That wouldn't help on Mac OS:
> 
>     $ ls -l /bin/sh /bin/bash
>     -r-xr-xr-x  1 root  wheel  618448 Mar 18 22:04 /bin/bash
>     -r-xr-xr-x  1 root  wheel  618512 Mar 18 22:04 /bin/sh
> 
> Although /bin/sh is neither a hard link nor a symbolic link to
> /bin/bash, nor is the file size the same, it is nevertheless Bash (in
> some form or another).

Hum. It seems some useful things exist like $BASH_VERSION and $ZSH_VERSION, but I'm not terribly excited about the idea of making a list and checking each one in bugreport (as it's sure to be nonexhaustive). I found a few more heuristics in a SO post[1] but this approach generally looks like a pain, and somewhat unreliable.

Most other alternatives I found with a cursory Google involve checking the name of the shell, which I think will have the same issues as checking $SHELL:

 - `ps -p $$` for info about the current process (didn't reveal bash when I `cp
   /bin/bash ~/bin/nish && ~/bin/nish`)
 - `echo $0` since it's coming from the command line, of course will be
   the same as $SHELL

I suppose if we wanted to do the heuristics it'd be a better experience for us, the bugreport receivers, to have the bugreport library collect the heuristics and try to make a guess, rather than just dump all the heuristics and let the humans try to remember which shell has $PS4 and which shell has $version and so on. But to me that sounds prone to rot at best.

 - Emily

[1]: https://stackoverflow.com/a/3327022