GNU bug report logs -
#12115
Please add tip about using tac to reverse a file byte-by-byte
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Reported by: Reuben Thomas <rrt <at> sc3d.org>
Date: Wed, 1 Aug 2012 21:46:01 UTC
Severity: normal
Done: Paul Eggert <eggert <at> cs.ucla.edu>
Bug is archived. No further changes may be made.
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Your message dated Fri, 01 Feb 2013 13:36:00 -0800
with message-id <510C3540.2010806 <at> cs.ucla.edu>
and subject line Re: bug#12115: Please add tip about using tac to reverse a file byte-by-byte
has caused the debbugs.gnu.org bug report #12115,
regarding Please add tip about using tac to reverse a file byte-by-byte
to be marked as done.
(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)
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12115: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=12115
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Patch:
From 3c1b7d442dc6161e3c88703c9acc3f768f9ba689 Mon Sep 17 00:00:00 2001
From: Reuben Thomas <rrt <at> sc3d.org>
Date: Wed, 1 Aug 2012 22:35:38 +0100
Subject: [PATCH] doc: Add tip on reversing a file byte-by-byte
* doc/coreutils.texi: Note how to use tac to reverse a file
byte-by-byte.
---
doc/coreutils.texi | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 516ec73..66b0838 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -1625,6 +1625,12 @@ Use @var{separator} as the record separator,
instead of newline.
@end table
+To reverse a file byte by byte, use:
+
+@example
+tac -r -s '.\| ' @var{file}
+@end example
+
@exitstatus
--
1.7.9.5
--
http://rrt.sc3d.org
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On 02/01/13 11:14, Reuben Thomas wrote:
> Given how long it took how many experts to come up with a valid
> incantation, it seems to me it *is* a useful documentation example.
Sure, but the valid incantation is a bit confusing, and it's not
documented correctly (it reverses characters, not bytes).
As far as I know there's no portable way to use 'tac' to
reverse a file byte-by-byte.
I installed this:
From dad0a3c743464664ed6a7ae8445cb58b8326db6d Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert <at> cs.ucla.edu>
Date: Fri, 1 Feb 2013 13:32:48 -0800
Subject: [PATCH] doc: say how to tac char-by-char
This fixes Bug#12115, reported by Reuben Thomas.
* doc/coreutils.texi (tac invocation): Document how to reverse a
file character by character. Break out MS-DOS into a separate
section, like 'cat' does.
---
doc/coreutils.texi | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index eac8d52..e29af8b 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -1613,10 +1613,7 @@ precedes in the file.
@itemx --regex
@opindex -r
@opindex --regex
-Treat the separator string as a regular expression. Users of @command{tac}
-on MS-DOS/MS-Windows should note that, since @command{tac} reads files in
-binary mode, each line of a text file might end with a CR/LF pair
-instead of the Unix-style LF.
+Treat the separator string as a regular expression.
@item -s @var{separator}
@itemx --separator=@var{separator}
@@ -1626,8 +1623,18 @@ Use @var{separator} as the record separator, instead of newline.
@end table
+On systems like MS-DOS that distinguish between text and binary files,
+@command{tac} reads and writes in binary mode.
+
@exitstatus
+Example:
+
+@example
+# Reverse a file character by character.
+tac -r -s 'x\|[^x]'
+@end example
+
@node nl invocation
@section @command{nl}: Number lines and write files
--
1.7.11.7
This bug report was last modified 12 years and 114 days ago.
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