* Avoiding empty element when splitting NUL-separated string from command substitution @ 2011-08-16 12:13 Nikolai Weibull 2011-08-16 12:51 ` Peter Stephenson 0 siblings, 1 reply; 4+ messages in thread From: Nikolai Weibull @ 2011-08-16 12:13 UTC (permalink / raw) To: Zsh Users % b=(${(0)"$(print -n)"}) % echo $#b 1 How do I avoid b containing an empty element in this case? That is, when the command substitution generated no output. (The $(print -n) is, obviously, just an example. It can be the equivalent of, for example, $(print -n $'a\0\b\0c) as well.) ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Avoiding empty element when splitting NUL-separated string from command substitution 2011-08-16 12:13 Avoiding empty element when splitting NUL-separated string from command substitution Nikolai Weibull @ 2011-08-16 12:51 ` Peter Stephenson 2011-08-16 14:06 ` Nikolai Weibull 2011-08-16 14:53 ` Peter Stephenson 0 siblings, 2 replies; 4+ messages in thread From: Peter Stephenson @ 2011-08-16 12:51 UTC (permalink / raw) To: Zsh Users On Tue, 16 Aug 2011 14:13:58 +0200 Nikolai Weibull <now@bitwi.se> wrote: > % b=(${(0)"$(print -n)"}) > % echo $#b > 1 > > How do I avoid b containing an empty element in this case? That is, > when the command substitution generated no output. > > (The $(print -n) is, obviously, just an example. It can be the > equivalent of, for example, $(print -n $'a\0\b\0c) as well.) I think that's a bug. You can work around it by assigning the double-quoted expression to an intermediate parameter. The fix might be as simple as the following, but it probably needs a bit more investigation as to where the Nularg came from. If it was a nulstring, used in subst.c for reasons I can never remember (and, of course, aren't commented) this is fine; if it was something that should already have had remnulargs() applied to it the fix is somewhere else. Index: Src/utils.c =================================================================== RCS file: /cvsroot/zsh/zsh/Src/utils.c,v retrieving revision 1.261 diff -p -u -r1.261 utils.c --- Src/utils.c 4 Aug 2011 08:30:51 -0000 1.261 +++ Src/utils.c 16 Aug 2011 12:46:29 -0000 @@ -3176,6 +3176,10 @@ sepsplit(char *s, char *sep, int allownu int n, sl; char *t, *tt, **r, **p; + /* Null string? Treat as empty string. */ + if (s[0] == Nularg && !s[1]) + s++; + if (!sep) return spacesplit(s, allownull, heap, 0); -- Peter Stephenson <pws@csr.com> Software Engineer Tel: +44 (0)1223 692070 Cambridge Silicon Radio Limited Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, UK Member of the CSR plc group of companies. CSR plc registered in England and Wales, registered number 4187346, registered office Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom More information can be found at www.csr.com. Follow CSR on Twitter at http://twitter.com/CSR_PLC and read our blog at www.csr.com/blog ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Avoiding empty element when splitting NUL-separated string from command substitution 2011-08-16 12:51 ` Peter Stephenson @ 2011-08-16 14:06 ` Nikolai Weibull 2011-08-16 14:53 ` Peter Stephenson 1 sibling, 0 replies; 4+ messages in thread From: Nikolai Weibull @ 2011-08-16 14:06 UTC (permalink / raw) To: Peter Stephenson; +Cc: Zsh Users On Tue, Aug 16, 2011 at 14:51, Peter Stephenson <Peter.Stephenson@csr.com> wrote: > On Tue, 16 Aug 2011 14:13:58 +0200 > Nikolai Weibull <now@bitwi.se> wrote: >> % b=(${(0)"$(print -n)"}) >> % echo $#b >> 1 >> >> How do I avoid b containing an empty element in this case? That is, >> when the command substitution generated no output. >> >> (The $(print -n) is, obviously, just an example. It can be the >> equivalent of, for example, $(print -n $'a\0\b\0c) as well.) > > I think that's a bug. You can work around it by assigning the > double-quoted expression to an intermediate parameter. OK, thanks. ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Avoiding empty element when splitting NUL-separated string from command substitution 2011-08-16 12:51 ` Peter Stephenson 2011-08-16 14:06 ` Nikolai Weibull @ 2011-08-16 14:53 ` Peter Stephenson 1 sibling, 0 replies; 4+ messages in thread From: Peter Stephenson @ 2011-08-16 14:53 UTC (permalink / raw) To: Zsh Users On Tue, 16 Aug 2011 13:51:38 +0100 Peter Stephenson <Peter.Stephenson@csr.com> wrote: > On Tue, 16 Aug 2011 14:13:58 +0200 > Nikolai Weibull <now@bitwi.se> wrote: > > % b=(${(0)"$(print -n)"}) > > % echo $#b > > 1 > > I think that's a bug. > > The fix might be as simple as the following, but it probably needs a bit > more investigation as to where the Nularg came from. If it was a > nulstring, used in subst.c for reasons I can never remember (and, of > course, aren't commented) this is fine; if it was something that should > already have had remnulargs() applied to it the fix is somewhere else. This is indeed a specially created null string propagating up from readoutput() via multsub(), so I think the fix is legitimate. It's not clear if sepsplit() should be using null strings in its output, however, since I have no idea what they're for. That would be a different pre-existing bug with different effects. If you have any theories, you can post them to zsh-workers. Index: Test/D04parameter.ztst =================================================================== RCS file: /cvsroot/zsh/zsh/Test/D04parameter.ztst,v retrieving revision 1.59 diff -p -u -r1.59 D04parameter.ztst --- Test/D04parameter.ztst 3 Jun 2011 22:03:44 -0000 1.59 +++ Test/D04parameter.ztst 16 Aug 2011 14:50:13 -0000 @@ -1453,3 +1453,8 @@ print ${foo:5:-6} 1:Regression test for total length < 0 in array ?(eval):2: substring expression: 3 < 5 + + foo=(${(0)"$(print -n)"}) + print ${#foo} +0:Nularg removed from split empty string +>0 -- Peter Stephenson <pws@csr.com> Software Engineer Tel: +44 (0)1223 692070 Cambridge Silicon Radio Limited Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, UK Member of the CSR plc group of companies. CSR plc registered in England and Wales, registered number 4187346, registered office Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom More information can be found at www.csr.com. Follow CSR on Twitter at http://twitter.com/CSR_PLC and read our blog at www.csr.com/blog ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2011-08-16 15:37 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2011-08-16 12:13 Avoiding empty element when splitting NUL-separated string from command substitution Nikolai Weibull 2011-08-16 12:51 ` Peter Stephenson 2011-08-16 14:06 ` Nikolai Weibull 2011-08-16 14:53 ` Peter Stephenson
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