From: Eric Blake <ebb9@byu.net>
Date: Thu, 24 Jan 2008 03:24:47 +0000 (-0700)
Subject: * doc/autoconf.texi (Limitations of Usual Tools) <grep>: Document
X-Git-Tag: v2.62~75
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a0d6f350fee9d91382295e89d7cc50dc2a2cfadc;p=thirdparty%2Fautoconf.git

* doc/autoconf.texi (Limitations of Usual Tools) <grep>: Document
BSD behavior on binary input.

Signed-off-by: Eric Blake <ebb9@byu.net>
---

diff --git a/ChangeLog b/ChangeLog
index b8e7fb0d..a3f52fe1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2008-01-28  Eric Blake  <ebb9@byu.net>
 
+	Document grep peculiarity.
+	* doc/autoconf.texi (Limitations of Usual Tools) <grep>: Document
+	BSD behavior on binary input.
+
 	Minor testsuite improvements.
 	* lib/autotest/general.m4 (AT_INIT) <PREPARE_TESTS>: Use fewer
 	forks when sanitizing PATH.  Always output machine information,
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 59e6f97e..f6421d7a 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -14957,6 +14957,20 @@ Similarly, the following escape sequences should also be avoided:
 @samp{\<}, @samp{\>}, @samp{\+}, @samp{\?}, @samp{\`}, @samp{\'},
 @samp{\B}, @samp{\b}, @samp{\S}, @samp{\s}, @samp{\W}, and @samp{\w}.
 
+Posix does not specify the behavior of @command{grep} on binary files.
+An example where this matters is using @acronym{BSD} @command{grep} to
+search text that includes embedded @acronym{ANSI} escape sequences for
+colored output to terminals (@samp{\033[m} is the sequence to restore
+normal output); the behavior depends on whether input is seekable:
+
+@example
+$ @kbd{printf 'esc\033[mape\n' > sample}
+$ @kbd{grep . sample}
+Binary file sample matches
+$ @kbd{cat file | grep .}
+escape
+@end example
+
 
 @item @command{join}
 @c -----------------