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Changes to grep/manual/grep.html,v
|
From: |
Jim Meyering |
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Subject: |
Changes to grep/manual/grep.html,v |
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Date: |
Tue, 21 Sep 2010 06:07:08 +0000 |
CVSROOT: /webcvs/grep
Module name: grep
Changes by: Jim Meyering <meyering> 10/09/21 06:07:07
Index: grep.html
===================================================================
RCS file: /webcvs/grep/grep/manual/grep.html,v
retrieving revision 1.5
retrieving revision 1.6
diff -u -b -r1.5 -r1.6
--- grep.html 2 Apr 2010 10:26:52 -0000 1.5
+++ grep.html 21 Sep 2010 06:07:05 -0000 1.6
@@ -1,8 +1,8 @@
<html lang="en">
<head>
-<title>GNU Grep 2.6.3</title>
+<title>GNU Grep 2.7</title>
<meta http-equiv="Content-Type" content="text/html">
-<meta name="description" content="GNU Grep 2.6.3">
+<meta name="description" content="GNU Grep 2.7">
<meta name="generator" content="makeinfo 4.13">
<link title="Top" rel="top" href="#Top">
<link href="http://www.gnu.org/software/texinfo/"; rel="generator-home"
title="Texinfo Homepage">
@@ -33,7 +33,7 @@
--></style>
</head>
<body>
-<h1 class="settitle">GNU Grep 2.6.3</h1>
+<h1 class="settitle">GNU Grep 2.7</h1>
<div class="contents">
<h2>Table of Contents</h2>
<ul>
@@ -91,7 +91,7 @@
<p><samp><span class="command">grep</span></samp> prints lines that match a
pattern.
- <p>This manual is for version 2.6.3 of GNU Grep.
+ <p>This manual is for version 2.7 of GNU Grep.
<p>This manual is for <samp><span class="command">grep</span></samp>, a
pattern matching engine.
@@ -786,12 +786,8 @@
by default,
such options are permuted to the front of the operand list
and are treated as options.
-Also,
-<span class="sc">posix.2</span> requires that unrecognized options be
diagnosed as “illegal”,
-but since they are not really against the law the default
-is to diagnose them as “invalid”.
-<code>POSIXLY_CORRECT</code> also disables
<code>_</code><var>N</var><code>_GNU_nonoption_argv_flags_</code>,
-described below.
+Also, <code>POSIXLY_CORRECT</code> disables special handling of an
+invalid bracket expression. See <a
href="#invalid_002dbracket_002dexpr">invalid-bracket-expr</a>.
<br><dt><samp><span class="env">_</span><var>N</var><span
class="env">_GNU_nonoption_argv_flags_</span></samp><dd><a
name="index-g_t_005f_0040var_007bN_007d_005fGNU_005fnonoption_005fargv_005fflags_005f-_0040r_007benvironment-variable_007d-165"></a>(Here
<var>N</var> is <samp><span class="command">grep</span></samp>'s numeric
process ID.)
If the <var>i</var>th character of this environment variable's value is
‘<samp><span class="samp">1</span></samp>’,
@@ -1037,6 +1033,7 @@
<br><dt>‘<samp><span
class="samp">[:space:]</span></samp>’<dd><a
name="index-space-_0040r_007bcharacter-class_007d-231"></a><a
name="index-space-characters-232"></a><a
name="index-whitespace-characters-233"></a>Space characters:
tab, newline, vertical tab, form feed, carriage return, and space.
+See <a href="#Usage">Usage</a>, for more discussion of matching newlines.
<br><dt>‘<samp><span
class="samp">[:upper:]</span></samp>’<dd><a
name="index-upper-_0040r_007bcharacter-class_007d-234"></a><a
name="index-upper_002dcase-letters-235"></a>Upper-case letters:
<code>A B C D E F G H I J K L M N O P Q R S T U V W X Y Z</code>.
@@ -1052,6 +1049,12 @@
part of the symbolic names, and must be included in addition to
the brackets delimiting the bracket expression.)
+ <p><a name="invalid_002dbracket_002dexpr"></a>If you mistakenly omit the
outer brackets, and search for say, ‘<samp><span
class="samp">[:upper:]</span></samp>’,
+GNU <samp><span class="command">grep</span></samp> prints a diagnostic and
exits with status 2, on
+the assumption that you did not intend to search for the nominally
+equivalent regular expression: ‘<samp><span
class="samp">[:epru]</span></samp>’.
+Set the <code>POSIXLY_CORRECT</code> environment variable to disable this
feature.
+
<p>Most meta-characters lose their special meaning inside bracket
expressions.
<dl>
@@ -1109,6 +1112,10 @@
<br><dt>‘<samp><span class="samp">‘</span><samp><span
class="samp">\W</span></samp><span
class="samp">’</span></samp>’<dd>Match non-word constituent, it is
a synonym for ‘<samp><span class="samp">[^[:alnum:]]</span></samp>’.
+ <br><dt>‘<samp><span class="samp">‘</span><samp><span
class="samp">\s</span></samp><span
class="samp">’</span></samp>’<dd>Match whitespace, it is a synonym
for ‘<samp><span class="samp">[[:space:]]</span></samp>’.
+
+ <br><dt>‘<samp><span class="samp">‘</span><samp><span
class="samp">\S</span></samp><span
class="samp">’</span></samp>’<dd>Match non-whitespace, it is a
synonym for ‘<samp><span class="samp">[^[:space:]]</span></samp>’.
+
</dl>
<p>For example, ‘<samp><span
class="samp">\brat\b</span></samp>’ matches the separate word
‘<samp><span class="samp">rat</span></samp>’,
@@ -1362,7 +1369,29 @@
as there is no ‘<samp><span class="samp">aa</span></samp>’ in the
input, so the ‘<samp><span class="samp">\1</span></samp>’ in the
second alternate
has nothing to refer back to, meaning it will never match anything.
(The second alternate in this example can only match
-if the first alternate has matched – making the second one superfluous.)
+if the first alternate has matched—making the second one superfluous.)
+
+ <li>How can I match across lines?
+
+ <p>Standard grep cannot do this, as it is fundamentally line-based.
+Therefore, merely using the <code>[:space:]</code> character class does not
+match newlines in the way you might expect. However, if your grep is
+compiled with Perl patterns enabled, the Perl ‘<samp><span
class="samp">s</span></samp>’
+modifier (which makes <code>.</code> match newlines) can be used:
+
+ <pre class="example"> printf 'foo\nbar\n' | grep -P
'(?s)foo.*?bar'
+</pre>
+ <p>With the GNU <samp><span class="command">grep</span></samp> option
<code>-z</code> (see <a href="#File-and-Directory-Selection">File and Directory
Selection</a>), the input is terminated by null bytes. Thus,
+you can match newlines in the input, but the output will be the whole
+file, so this is really only useful to determine if the pattern is
+present:
+
+ <pre class="example"> printf 'foo\nbar\n' | grep -z -q
'foo[[:space:]]\+bar'
+</pre>
+ <p>Failing either of those options, you need to transform the input
+before giving it to <samp><span class="command">grep</span></samp>, or turn to
<samp><span class="command">awk</span></samp>,
+<samp><span class="command">sed</span></samp>, <samp><span
class="command">perl</span></samp>, or many other utilities that are
+designed to operate across lines.
<li>What do <samp><span class="command">grep</span></samp>, <samp><span
class="command">fgrep</span></samp>, and <samp><span
class="command">egrep</span></samp> stand for?
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