Path: csiph.com!feeder.erje.net!2.us.feeder.erje.net!nntp.club.cc.cmu.edu!micro-heart-of-gold.mit.edu!bloom-beacon.mit.edu!bloom-beacon.mit.edu!171.64.64.130.MISMATCH!usenet.stanford.edu!not-for-mail From: Greg Wooledge Newsgroups: gnu.bash.bug Subject: Re: Unset array doesn't work Date: Wed, 28 Feb 2018 15:00:51 -0500 Lines: 57 Approved: bug-bash@gnu.org Message-ID: References: <21679c48-4064-5683-2d5f-91bfb76687d0@case.edu> <790ade74-690f-541c-9ab4-6359917442d0@case.edu> <755d61fa-d2bc-8855-bc30-4388aff40691@gmail.com> <9974.1519637469@jinx.noi.kre.to> <15717.1519764581@jinx.noi.kre.to> <24248.1519844400@jinx.noi.kre.to> NNTP-Posting-Host: lists.gnu.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: usenet.stanford.edu 1519848060 32521 208.118.235.17 (28 Feb 2018 20:01:00 GMT) X-Complaints-To: action@cs.stanford.edu To: bug-bash@gnu.org Envelope-to: bug-bash@gnu.org Mail-Followup-To: bug-bash@gnu.org Content-Disposition: inline In-Reply-To: <24248.1519844400@jinx.noi.kre.to> User-Agent: NeoMutt/20170113 (1.7.2) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 139.137.100.1 X-BeenThere: bug-bash@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Bug reports for the GNU Bourne Again SHell List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Xref: csiph.com gnu.bash.bug:13775 I think most people will agree that unset is extremely surprising, though they may point to different parts of it as the source of their surprise. 8 years after Freddy Vulto's initial investigations, there are many things I still don't understand. For example, consider this code straight from his web site[1]: ===================================================================== wooledg:~$ cat freddy #!/bin/bash a=0 b=0 c=0 d=0 e=0 _unset() { unset -v b c c d d d e; } t1() { local a=1 b=1 c=1 d=1 t2 } t2() { local a=2 b=2 c=2 d=2 e=2 _unset echo a:$a b:$b c:$c d:$d e:$e } t1 wooledg:~$ ./freddy a:2 b:1 c:0 d: e:0 ===================================================================== But if I make a tiny change to it (eliminating the _unset function which *appears* to have no purpose), it has entirely different behavior: ===================================================================== wooledg:~$ cat freddy2 #!/bin/bash a=0 b=0 c=0 d=0 e=0 t1() { local a=1 b=1 c=1 d=1 t2 } t2() { local a=2 b=2 c=2 d=2 e=2 unset -v b c c d d d e echo a:$a b:$b c:$c d:$d e:$e } t1 wooledg:~$ ./freddy2 a:2 b: c: d: e: ===================================================================== I don't understand the difference. Does unset create some kind of "placeholder" in the current function (but not in a caller)? [1] http://fvue.nl/wiki/Bash:_Unset