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According to Jim Meyering on 3/22/2008 12:20 PM:
|>> $ busybox sed -n '/^g''l_INCLUDE_EXCLUDE_PROG(.*
\[\(.*\)\])/{s//\1/;s/,/ /gp
|>> }' configure.ac
|>> sed: No previous regexp.
|>> [Exit 1]
|
| This appears to be a busybox "limitation".
| I expect to work around it with this patch:
|
| portability: work around a "busybox sed" limitation
| * configure.ac: While every other sed tested supports usage like
| '/\(re\)/{s//\1/;...<NEWLINE>}', and POSIX appears to requires this,
| busybox's sed does not support it. So duplicate the regexp:
| '/\(re\)/{s/\(re\)/\1/;...<NEWLINE>}'. Reported by Vincent Lefevre:
| <http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/13013>.
Thanks for this portability analysis. I agree that it is a violation of
POSIX; perhaps someone should report this to the busybox maintainers.
Meanwhile, I'm documenting it for future reference:
- --
Don't work too hard, make some time for fun as well!
Eric Blake [EMAIL PROTECTED]
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>From 5c55fb1f4db4ce31263d71744014eddde28071fd Mon Sep 17 00:00:00 2001
From: Eric Blake <[EMAIL PROTECTED]>
Date: Tue, 25 Mar 2008 21:19:58 -0600
Subject: [PATCH] Document busybox sed bug.
* doc/autoconf.texi (Limitations of Usual Tools): Mention
restrictions when using back-references.
Reported by Vincent Lefevre:
<http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/13013>.
Signed-off-by: Eric Blake <[EMAIL PROTECTED]>
---
ChangeLog | 6 ++++++
doc/autoconf.texi | 14 ++++++++++++++
2 files changed, 20 insertions(+), 0 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 0aab398..7f82ee2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
2008-03-26 Eric Blake <[EMAIL PROTECTED]>
+ Document busybox sed bug.
+ * doc/autoconf.texi (Limitations of Usual Tools): Mention
+ restrictions when using back-references.
+ Reported by Vincent Lefevre:
+ <http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/13013>.
+
Document Automake interaction with AC_CONFIG_MACRO_DIR.
* doc/autoconf.texi (Input): Mention ACLOCAL_AMFLAGS for automake
users.
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 17b9045..b72d875 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -15389,6 +15389,20 @@ flushleft
indented
@end example
+Posix requires that with an empty regular expression, the last non-empty
+regular expression from either an address specification or substitution
+command is applied. However, busybox 1.6.1 complains when using a
+substitution command with a replacement containing a back-reference to
+an empty regular expression; the workaround is repeating the regular
+expression.
+
[EMAIL PROTECTED]
[EMAIL PROTECTED] {echo abc | busybox sed '/a\(b\)c/ s//\1/'}
+sed: No previous regexp.
[EMAIL PROTECTED] {echo abc | busybox sed '/a\(b\)c/ s/a\(b\)c/\1/'}
+b
[EMAIL PROTECTED] example
+
@item @command{sed} (@samp{t})
@c ---------------------------
--
1.5.4
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