Re: GROUPS

[Greg Wooledge]

On Fri, Aug 13, 2021 at 10:10:42AM -0400, Chet Ramey wrote:
> As long as you stick to things POSIX standardizes. Relevant here, the
> standard even includes a list of variables you should avoid using because
> various shells and applications use them.

Just out of curiosity, where is that?  It's not under section
2.5.3 Shell Variables, which is where I looked first.

The closest thing I could find is a section in the Rationale that
describes some variables that are no longer covered by the standard,
but either used to be, or are commonly used as extensions:

https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xcu_chap02.html#tag_23_02_05_03

Is there another section that I've missed?

> Obviously not, since they never tested it on bash. It's more likely they
> expected it to run on Debian's /bin/sh -- hence the hashbang -- which is
> dash.

For the record, Debian uses dash as /bin/sh by default in modern versions,
but historically, it used bash.  And it still offers the user a supported
means of switching "back" to bash as /bin/sh, for systems that require it.

A Debian shell script which uses #!/bin/sh should be written to work
under bash *or* dash (at the very minimum).  If it fails under either
of those shells, it's a bug.