Re: FYI: fix-bootstrap-translation-download-on-darwin

[Eric Blake-1]

> It appears that only gawk saves $3 from the last input line for use in
> the END clause, where darwin awk (maybe others too, I haven't looked
> elsewhere) discards it.

On Solaris 8, /usr/bin/awk and /usr/bin/nawk leave $3 empty,
while /usr/xpg4/bin/awk leaves it populated.  POSIX states that
inside END, $NF must retain at the value it had for the last
record read (which would imply that $3 should do likewise),
but I saw nothing that actually required $3 remain populated.

At any rate, it is a definite portability pitfall, so how about the
following patch?


2007-09-12  Eric Blake  <address@hidden>

        Document another awk pitfall.
        * doc/autoconf.texi (Limitations of Usual Tools) <awk>: Document
        limitation of field variables in END.
        Reported by Gary V. Vaughan.

Index: doc/autoconf.texi
===================================================================
RCS file: /sources/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.1174
diff -u -p -r1.1174 autoconf.texi
--- doc/autoconf.texi   13 Sep 2007 03:21:18 -0000      1.1174
+++ doc/autoconf.texi   13 Sep 2007 03:51:47 -0000
@@ -13361,6 +13361,23 @@ input in this case.  Portable scripts ca
 awk 'BEGIN @{print "hello world"@}' </dev/null
 @end example
 
+Posix says that in an @samp{END} action, @samp{$NF} (and presumably,
address@hidden) retain their value from the last record read, if no
+intervening @samp{getline} occurred.  However, some implementations
+(such as Solaris 10 @samp{/usr/bin/awk}, @samp{nawk}, or Darwin
address@hidden) reset these variables.  A workaround is to use an
+intermediate variable prior to the @samp{END} block.  For example:
+
address@hidden
+$ @kbd{cat end.awk}
address@hidden tmp = $1 @}
+END @{ print "a", $1, $NF, "b", tmp @}
+$ @kbd{echo 1 | awk -f end.awk}
+a   b 1
+$ @kbd{echo 1 | gawk -f end.awk}
+a 1 1 b 1
address@hidden example
+
 If you want your program to be deterministic, don't depend on @code{for}
 on arrays:
 


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