Re: Avoiding empty element when splitting NUL-separated string from command substitution

[Peter Stephenson <Peter.Stephenson@xxxxxxx>]

On Tue, 16 Aug 2011 14:13:58 +0200
Nikolai Weibull <now@xxxxxxxx> 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@xxxxxxx>            Software Engineer
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