Re: Question on unintuitive behaviour for function execution and parameter assignment

[Peter Stephenson <p.w.stephenson@ntlworld.com>]

> On 12 October 2021 at 09:20 Jett Husher <jetthusher@pm.me> wrote:
> 
> 
> Good day!
> 
> Does a function `assign-hello` treat parameter assignment on simple command as local parameter in the following code snipped?
> 
> ```
> HELLO=WORLD
> 
> function assign-hello() HELLO=$1
> 
> assign-hello THERE
> echo $HELLO # Prints 'THERE', as expected
> 
> # This part trips me up
> HELLO= assign-hello WHY
> echo $HELLO # Why does it still print 'THERE'?
> ```

This is covered by the POSIX_BUILTINS option.  Generally, the POSIX_* options are
the place to look for this sort of think --- granted that can be a bit of hunt.

Usually an easy test to see if zsh does have the POSIX behaviour available is
to start a new shell as

ARGV0=sh zsh

and see what behaviour that gives you.  That should be maximally compatible,
although it doesn't help you find which option controls  the behaviour.

POSIX_BUILTINS <K> <S>
    When this option is set the command builtin can be used  to  execute  shell
    builtin  commands.   Parameter assignments specified before shell functions
    and special builtins are kept after the command completes unless  the  spe‐
    cial builtin is prefixed with the command builtin.  Special builtins are .,
    :, break, continue, declare, eval, exit, export, integer, local,  readonly,
    return, set, shift, source, times, trap and unset.

pws