Re: sh(1): POSIX "Command Search and Execution"

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Sun, 22 Sep 2024 09:09:06 +0200
    From:        tlaronde%kergis.com@localhost
    Message-ID:  <Zu_Cknt2-c_T29yZ%kergis.com@localhost>

  | (whether your test about the first two chars, or the more restricting
  | but simplest first an alphanumeric),

On that point, my reasoning is that I can imaging having 2 sets of
(some perhaps) of the utilities, a basic set, and an enhanced set,
living in sub-directories (of say, /usr/bin).   One of those would
be in PATH as the default to use, but sometimes a user might want
to use the other version as a test of something.

Those could be named basic/ls basic/cat ... and enhanced/ls enhanced/cat
(etc), but that would then be a lot to type, so if it were me, the
subdir names would be '-' and '+', so I might have /usr/bin/+
in PATH, and then simply run
	-/cat file ...
to use the basic one.   Not allowing non-alphanumerics as the first
char would prohibit that kind of thing.

kre

ps: Of course, one can almost accomplish this with functions...

PATH_TO_BASIC_UTILITIES=/usr/bin/-
PATH_TO_ENHANCED_UTILITIES=/usr/bin/+
-() { ${PATH_TO_BASIC_UTILITIES}/"$@" ; }
+() { ${PATH_TO_ENHANCED_UTILITIES}/"$@" ; }

and then use them as
	- cat ...
	+ ls
instead of
	-/cat ...
	+/ls

and in that the "cat" part *is* allowed to have '/' in its name.

And if this wouldn't be good enough, then you also need to be
concerned with how functions like execlp() etc work.   What you're
proposing isn't really just a small(ish) change to sh, everything
that does path searches needs to understand it (system(3) ...).