Re: interactive shell detection in shrc

Robert Elz wrote in
 <[email protected]>:
 |    Date:        Tue, 24 Sep 2024 03:06:49 +0300
 |    From:        Valery Ushakov <[email protected]>
 |    Message-ID:  <[email protected]>
 |
 || I also wanted to drop the ${1+"$@"} workaroud for the v7 shell bug
 || which I'm pretty sure we are not going to hit in this day and age on a
 || NetBSD system, but I won't to get down that rabbit hole.
 |
 |That one isn't a rabbit hole, by all means, go ahead and delete that
 |usage, you are unlikely to find broken "$@" in any shell anyone would
 |actually want to use any more - that was a truly ancient bug being
 |worked around, as distinct from a difference from what is required,
 |which return being ignored in a script is.

Sven Maschek [1]:

  Which Bourne shells exactly need the workaround?
  
  These shells behave the old way and need ${1+"$@"}:
  
      Certainly: /bin/sh on 7th edition (aka Version 7). And thus also /bin/sh on original BSDs, until these shipped the Almquist shell (after 4.3BSD-Reno)
      HP-UX 8, 9 /bin/sh, HP-UX 10.x, 11.x /usr/old/bin/sh (as /bin/sh has become a ksh)
      OSF1/V4 and V5 aka Tru64 /bin/sh
      Ultrix /bin/sh and /bin/sh5
      Sinix 5.20 /bin/sh in both the "ucb" and the "sie" universe 
  
  In contrast, these Bourne shell variants behave the modern way:
  
      8th edition (aka Version 8) /bin/sh
      SunOS 4.1.x and SunOS 5.x /bin/sh
      IRIX 5 - IRIX 6.3 /bin/sh, IRIX 6.4+x /usr/bin/bsh (as /usr/bin/sh has become a ksh)
      AIX 3.2.4 /bin/sh, AIX 4.x /usr/bin/bsh (as /usr/bin/sh has become a ksh)
      OpenServer 3 ff. /usr/bin/sh
      MUNIX 3.1 (Cadmus, SVR3.1) /bin/sh
      Sinix 5.20 /bin/sh in the "xopen" universe 
  
  Oh wait, there's another meaning
  
  It's also a workaround for a problem in some shells if you want to use the flag u ("error upon using empty variables")
  and "$@" (or $@, "$*", $*) is used without arguments. Example:
  
      $ shell -cu 'echo     "$@";  echo not reached'
      @: parameter not set
      $ shell -cu 'echo ${1+"$@"}; echo ok'
      ok
  
  At least these shells need that workaround:
  
      bash-4.0.0 ... -4.0.27

^ Somewhere around 2010.

      dash-0.4.6 ... -0.4.18
      all ksh88
      ksh93 until release t+20090501
      pdksh-5.1.3, -5.2.14
      mksh before R39 (as pdksh descendant)
      posh < 0.10 (as pdksh descendant)
      NetBSD 2 ff. /bin/sh
      all traditional Bourne shells 

  [1] https://www.in-ulm.de/~mascheck/various/bourne_args/

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)