severity 649147 wishlist
tags 649147 + fixed-upstream
quit
Hi Frank,
Frank Sell wrote:
> date +"%y-%m-%d %H:%M:%S" | mawk '{ printf ("%s %s\n", $2, substr($2, 0, 5))
> }'
> 08:57:41 08:5
POSIX sayeth:
substr(s, m[, n ])
Return the at most n-character substring of s that begins at
position m, numbering from 1. If n is omitted, or if n
specifies more characters than are left in the string, the
length of the substring shall be limited by the length of the
string s.
So "substr($2, 1, 5)" is the portable way to express what you meant.
That said, some nonportable scripts in the wild also use the semantics
implied by your example. Therefore Thomas wrote the following patch.
-- >8 --
From: Thomas E. Dickey <dic...@invisible-island.net>
Date: Sun, 26 Jul 2009 12:39:02 +0000
Subject: tweak workaround for scripts that use substr(0, i)
makewhatis from man 1.6f uses (incorrectly...) substr(0,RSTART-1), and
that leaves mawk with a -1 initial index which it _adds_ to the length
rather than subtracting (probably not what anyone would expect).
Change the logic to subtract - and just for luck, account for the "1".
---
Hope that helps,
Jonathan
CHANGES | 9 +++++++--
bi_funct.c | 11 ++++++++---
2 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/CHANGES b/CHANGES
index 97f514b2..812e0d92 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,8 +1,13 @@
-- $MawkId$
Changes by Thomas E Dickey <dic...@invisible-island.net>
-20090725
+20090726
+ modify workaround for (incorrect) scripts which use a zero-parameter
+ for substr to ensure the overall length of the result stays the same.
+ For example, from makewhatis:
+ filename_no_gz = substr(filename, 0, RSTART - 1);
+
move regular-expression files into main directory to simplify building
using configure --srcdir and VPATH.
diff --git a/bi_funct.c b/bi_funct.c
index 7da2fbc2..9435aaff 100644
--- a/bi_funct.c
+++ b/bi_funct.c
@@ -10,7 +10,7 @@ the GNU General Public License, version 2, 1991.
********************************************/
/*
* $MawkId$
* @Log: bi_funct.c,v @
* Revision 1.9 1996/01/14 17:16:11 mike
* flush_all_output() before system()
@@ -258,12 +258,17 @@ bi_substr(CELL * sp)
}
i = d_to_i(sp[1].dval) - 1; /* i now indexes into string */
+ /*
+ * Workaround in case someone's written a script that does substr(0,last-1)
+ * by transforming it into substr(1,last).
+ */
if (i < 0) {
- n += i;
+ n -= i + 1;
i = 0;
}
- if (n > len - i)
+ if (n > len - i) {
n = len - i;
+ }
if (n <= 0) /* the null string */
{
--
1.7.8.rc2
--
To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org
with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
