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Re: Unquoted array slice address@hidden:0} expands to just one word if I


From: Robert Elz
Subject: Re: Unquoted array slice address@hidden:0} expands to just one word if IFS doesn't have a space
Date: Wed, 01 Aug 2018 21:52:20 +0700

    Date:        Wed, 1 Aug 2018 09:40:12 -0400
    From:        Greg Wooledge <address@hidden>
    Message-ID:  <address@hidden>

  | https://lists.gnu.org/archive/html/bug-bash/2017-06/msg00283.html

A bug in dash which as far as I can tell has since been fixed.

  | https://lists.gnu.org/archive/html/bug-bash/2017-09/msg00058.html

A bug in bash, but I don't have a recent enough version to know
if it has been fixed or not.

  | https://lists.gnu.org/archive/html/bug-bash/2018-01/msg00035.html

This one is fixed as well (seems to have been a transitory
bug as I don't see it in versions of bash I have on different
systems than are newer, or older, than the one shown as
affected.)

  | Unquoted $* or $@ is just a disaster.  Don't do it.

There are bugs in some shells (and just about everything else) in some
edge cases (the two above related to IFS='') which it is good to be aware of.

The solution is not to run away and hide, but to report the bugs and get them
fixed, which is what seems to have happed with dash and the first of
those three (and bash and the third) and perhaps for bash and the middle
one (it certainly should get fixed if it hasn't already.)

Then from the second message ...

        wooledg:/tmp/x$ set -- '* *'
        wooledg:/tmp/x$ args $*
        4 args: <file2.txt> <file one.txt> <file2.txt> <file one.txt>

exactly as it should be.   Field splitting comes first, so the unquoted $*
expands to two words, each containing a single character, '*', and
then filename expansion happens.   Each '*' expands to the two
filenames that exist.

This has nothing at all to do with $* the same happens ...
(in the same environment you set up, except here I'm using
the NetBSD sh rather than bash - I'm sure bash does the same)

[jinx]$ v='* *'
[jinx]$ args $v
4 args: <file one.txt> <file2.txt> <file one.txt> <file2.txt>

There are ways to code almost everything that one wants to do,
some of them hit bugs in some shells.

kre




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