[TUHS] A few comments on porting the Bourne shell

[Bakul Shah]

On Jan 3, 2023, at 7:31 PM, Dan Cross <crossd at gmail.com> wrote:
> 
> On Tue, Jan 3, 2023 at 10:22 PM John Cowan <cowan at ccil.org> wrote:
>> Making shell scripts portable means not using pipelines, because given "foo | bar", kshNN and zsh execute foo in a subshell and bar in the top-level shell, whereas in other shells, both foo and bar execute in subshells.  (For this reason, Posix allows either behavior.)  Not having pipelines is a pretty drastic limitation.
> 
> This came up at work just the other day:
> 
> echo ' hi ' | sed 's/^ *//;s/ *$//' | read bummer
> echo $bummer
> 
> The behavior varies between ksh, zsh, bash, sh. Yay.

On this example sh, zsh, bash behave the same way on
freebsd. Rather than ban |, I think the lesson is to
*avoid* builtin commands in a pipeline that can affect
shell's environment. I only write /bin/sh scripts in
any case.

It is really unfortunate that infix | is so beguiling!
Except for that a Lisp or Scheme based shell would've
been fine and dandy! :-)/2