* Re: what can be global aliases used for?
2023-02-17 14:54 ` what can be global aliases used for? Sebastian Gniazdowski
@ 2023-02-17 17:15 ` Roman Perepelitsa
2023-02-17 19:10 ` Bart Schaefer
2023-02-17 21:11 ` Lawrence Velázquez
2 siblings, 0 replies; 6+ messages in thread
From: Roman Perepelitsa @ 2023-02-17 17:15 UTC (permalink / raw)
To: Sebastian Gniazdowski; +Cc: Zsh hackers list
On Fri, Feb 17, 2023 at 3:59 PM Sebastian Gniazdowski
<sgniazdowski@gmail.com> wrote:
>
> I'm trying to get the suspected capabilities out of global aliases. Currently I'm using them for:
> - macro-like labels for exporting patterns like EMPTYSTR being [[:space:][:INVALID:]]# roughly, to a single place,
> - macro-like SNIP_EMULATE_OPTIONS_ZERO that invokes emulate, setopt and 0=...
>
> I wonder what else can global aliases do?
Global aliases are unhygienic macros. It's rarely a good idea to use
unhygienic macros in the code you share with others. If you must use
an unhygienic macro in shared code, give it a long and ugly name to
avoid clashes.
EMPTYSTR can be a parameter. You would have to use $~EMPTYSTR but
you'll avoid most of the pitfalls of unhygienic macros.
SNIP_EMULATE_OPTIONS_ZERO can also be a parameter, which you can use
via `eval $SNIP_EMULATE_OPTIONS_ZERO`. I do something like this in
zsh4humans:
typeset -gr _z4h_opt='emulate -L zsh &&
setopt typeset_silent pipe_fail extended_glob &&
setopt prompt_percent no_prompt_subst no_prompt_bang &&
setopt no_bg_nice no_aliases || return'
function foo() {
eval "$_z4h_opt"
# do stuff
}
function bar() {
eval "$_z4h_opt"
# do stuff
}
Roman.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: what can be global aliases used for?
2023-02-17 14:54 ` what can be global aliases used for? Sebastian Gniazdowski
2023-02-17 17:15 ` Roman Perepelitsa
@ 2023-02-17 19:10 ` Bart Schaefer
2023-02-17 21:11 ` Lawrence Velázquez
2 siblings, 0 replies; 6+ messages in thread
From: Bart Schaefer @ 2023-02-17 19:10 UTC (permalink / raw)
To: Sebastian Gniazdowski; +Cc: Zsh hackers list
On Fri, Feb 17, 2023 at 6:59 AM Sebastian Gniazdowski
<sgniazdowski@gmail.com> wrote:
>
> I wonder what else can global aliases do?
As Roman has already indicated, it's not a recommended practice to
rely on aliases of any kind in scripts. Aliasing is intended as an
interactive feature to reduce time spent typing commonly-used idioms.
That said, the most common use I've seen made of global aliases is
this kind of thing:
alias -g L='|less'
% ls -lLR L
That is, append L instead of "|less" to commands that are expected to
produce many pages of output.
Similarly stuff like
alias -g TODAYS_FILES='-lrt | fgrep "$(date +"%b %2d")" | awk '\''{print $NF}'\'
% ls TODAYS_FILES
(yes, there's a more zsh-ish way to do that, and it could also be a
command alias by sticking the "ls" in front, just using the pipeline
as an example).
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: what can be global aliases used for?
2023-02-17 14:54 ` what can be global aliases used for? Sebastian Gniazdowski
2023-02-17 17:15 ` Roman Perepelitsa
2023-02-17 19:10 ` Bart Schaefer
@ 2023-02-17 21:11 ` Lawrence Velázquez
2023-02-17 21:19 ` Roman Perepelitsa
2 siblings, 1 reply; 6+ messages in thread
From: Lawrence Velázquez @ 2023-02-17 21:11 UTC (permalink / raw)
To: Sebastian Gniazdowski; +Cc: zsh-workers
On Fri, Feb 17, 2023, at 9:54 AM, Sebastian Gniazdowski wrote:
> I wonder what else can global aliases do?
An esoteric but amusing example:
1) Autoconf uses ${1+"$@"} instead of "$@" to work around a bug
in pre-SVR3 Bourne shells.
2) This doesn't work properly in pre-4.3 zsh because SH_WORD_SPLIT
splits ${1+"$@"} too aggressively.
3) But zsh doesn't have a problem with "$@" in the first place,
so Autoconf defines a global alias that dynamically replaces
${1+"$@"} with "$@", undoing the original workaround.
https://www.gnu.org/software/autoconf/manual/autoconf-2.71/html_node/Shell-Substitutions.html#index-_0022_0024_0040_0022
--
vq
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: what can be global aliases used for?
2023-02-17 21:11 ` Lawrence Velázquez
@ 2023-02-17 21:19 ` Roman Perepelitsa
2023-02-17 23:27 ` Lawrence Velázquez
0 siblings, 1 reply; 6+ messages in thread
From: Roman Perepelitsa @ 2023-02-17 21:19 UTC (permalink / raw)
To: Lawrence Velázquez; +Cc: Sebastian Gniazdowski, zsh-workers
On Fri, Feb 17, 2023 at 10:13 PM Lawrence Velázquez <larryv@zsh.org> wrote:
>
> 1) Autoconf uses ${1+"$@"} instead of "$@" to work around a bug
> in pre-SVR3 Bourne shells.
Fascinating.
This made me Google SVR3. That's System V, Release 3, right? 1987.
Before the first release of bash and zsh.
Roman.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: what can be global aliases used for?
2023-02-17 21:19 ` Roman Perepelitsa
@ 2023-02-17 23:27 ` Lawrence Velázquez
0 siblings, 0 replies; 6+ messages in thread
From: Lawrence Velázquez @ 2023-02-17 23:27 UTC (permalink / raw)
To: Roman Perepelitsa; +Cc: zsh-workers
On Fri, Feb 17, 2023, at 4:19 PM, Roman Perepelitsa wrote:
> On Fri, Feb 17, 2023 at 10:13 PM Lawrence Velázquez <larryv@zsh.org> wrote:
>>
>> 1) Autoconf uses ${1+"$@"} instead of "$@" to work around a bug
>> in pre-SVR3 Bourne shells.
>
> Fascinating.
>
> This made me Google SVR3. That's System V, Release 3, right? 1987.
> Before the first release of bash and zsh.
That's right! Absolutely ancient, but -- to be fair -- downright
modern compared to its ancestors [1]. Sensible "$@" [2]? Functions
that don't trash the global positional parameters [3]? Sign me up.
[1]: https://www.in-ulm.de/~mascheck/bourne/
[2]: https://www.in-ulm.de/~mascheck/various/bourne_args/
[3]: https://www.in-ulm.de/~mascheck/bourne/function_parameters.html
--
vq
^ permalink raw reply [flat|nested] 6+ messages in thread