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1 @c -*-texinfo-*-
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2 @c This is part of the XEmacs Lisp Reference Manual.
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3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
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4 @c See the file lispref.texi for copying conditions.
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5 @setfilename ../../info/searching.info
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6 @node Searching and Matching, Syntax Tables, Text, Top
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7 @chapter Searching and Matching
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8 @cindex searching
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9
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10 XEmacs provides two ways to search through a buffer for specified
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11 text: exact string searches and regular expression searches. After a
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12 regular expression search, you can examine the @dfn{match data} to
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13 determine which text matched the whole regular expression or various
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14 portions of it.
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15
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16 @menu
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17 * String Search:: Search for an exact match.
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18 * Regular Expressions:: Describing classes of strings.
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19 * Regexp Search:: Searching for a match for a regexp.
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20 * POSIX Regexps:: Searching POSIX-style for the longest match.
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21 * Search and Replace:: Internals of @code{query-replace}.
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22 * Match Data:: Finding out which part of the text matched
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23 various parts of a regexp, after regexp search.
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24 * Searching and Case:: Case-independent or case-significant searching.
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25 * Standard Regexps:: Useful regexps for finding sentences, pages,...
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26 @end menu
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27
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28 The @samp{skip-chars@dots{}} functions also perform a kind of searching.
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29 @xref{Skipping Characters}.
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30
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31 @node String Search
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32 @section Searching for Strings
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33 @cindex string search
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34
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35 These are the primitive functions for searching through the text in a
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36 buffer. They are meant for use in programs, but you may call them
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37 interactively. If you do so, they prompt for the search string;
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38 @var{limit} and @var{noerror} are set to @code{nil}, and @var{repeat}
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39 is set to 1.
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40
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41 @deffn Command search-forward string &optional limit noerror repeat
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42 This function searches forward from point for an exact match for
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43 @var{string}. If successful, it sets point to the end of the occurrence
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44 found, and returns the new value of point. If no match is found, the
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45 value and side effects depend on @var{noerror} (see below).
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46 @c Emacs 19 feature
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47
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48 In the following example, point is initially at the beginning of the
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49 line. Then @code{(search-forward "fox")} moves point after the last
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50 letter of @samp{fox}:
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51
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52 @example
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53 @group
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54 ---------- Buffer: foo ----------
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55 @point{}The quick brown fox jumped over the lazy dog.
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56 ---------- Buffer: foo ----------
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57 @end group
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58
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59 @group
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60 (search-forward "fox")
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61 @result{} 20
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62
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63 ---------- Buffer: foo ----------
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64 The quick brown fox@point{} jumped over the lazy dog.
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65 ---------- Buffer: foo ----------
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66 @end group
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67 @end example
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68
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69 The argument @var{limit} specifies the upper bound to the search. (It
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70 must be a position in the current buffer.) No match extending after
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71 that position is accepted. If @var{limit} is omitted or @code{nil}, it
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72 defaults to the end of the accessible portion of the buffer.
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73
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74 @kindex search-failed
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75 What happens when the search fails depends on the value of
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76 @var{noerror}. If @var{noerror} is @code{nil}, a @code{search-failed}
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77 error is signaled. If @var{noerror} is @code{t}, @code{search-forward}
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78 returns @code{nil} and does nothing. If @var{noerror} is neither
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79 @code{nil} nor @code{t}, then @code{search-forward} moves point to the
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80 upper bound and returns @code{nil}. (It would be more consistent now
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81 to return the new position of point in that case, but some programs
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82 may depend on a value of @code{nil}.)
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83
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84 If @var{repeat} is supplied (it must be a positive number), then the
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85 search is repeated that many times (each time starting at the end of the
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86 previous time's match). If these successive searches succeed, the
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87 function succeeds, moving point and returning its new value. Otherwise
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88 the search fails.
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89 @end deffn
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90
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91 @deffn Command search-backward string &optional limit noerror repeat
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92 This function searches backward from point for @var{string}. It is
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93 just like @code{search-forward} except that it searches backwards and
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94 leaves point at the beginning of the match.
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95 @end deffn
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96
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97 @deffn Command word-search-forward string &optional limit noerror repeat
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98 @cindex word search
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99 This function searches forward from point for a ``word'' match for
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100 @var{string}. If it finds a match, it sets point to the end of the
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101 match found, and returns the new value of point.
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102 @c Emacs 19 feature
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103
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104 Word matching regards @var{string} as a sequence of words, disregarding
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105 punctuation that separates them. It searches the buffer for the same
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106 sequence of words. Each word must be distinct in the buffer (searching
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107 for the word @samp{ball} does not match the word @samp{balls}), but the
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108 details of punctuation and spacing are ignored (searching for @samp{ball
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109 boy} does match @samp{ball. Boy!}).
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110
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111 In this example, point is initially at the beginning of the buffer; the
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112 search leaves it between the @samp{y} and the @samp{!}.
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113
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114 @example
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115 @group
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116 ---------- Buffer: foo ----------
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117 @point{}He said "Please! Find
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118 the ball boy!"
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119 ---------- Buffer: foo ----------
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120 @end group
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121
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122 @group
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123 (word-search-forward "Please find the ball, boy.")
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124 @result{} 35
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125
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126 ---------- Buffer: foo ----------
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127 He said "Please! Find
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128 the ball boy@point{}!"
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129 ---------- Buffer: foo ----------
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130 @end group
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131 @end example
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132
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133 If @var{limit} is non-@code{nil} (it must be a position in the current
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134 buffer), then it is the upper bound to the search. The match found must
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135 not extend after that position.
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136
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137 If @var{noerror} is @code{nil}, then @code{word-search-forward} signals
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138 an error if the search fails. If @var{noerror} is @code{t}, then it
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139 returns @code{nil} instead of signaling an error. If @var{noerror} is
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140 neither @code{nil} nor @code{t}, it moves point to @var{limit} (or the
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141 end of the buffer) and returns @code{nil}.
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142
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143 If @var{repeat} is non-@code{nil}, then the search is repeated that many
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144 times. Point is positioned at the end of the last match.
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145 @end deffn
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146
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147 @deffn Command word-search-backward string &optional limit noerror repeat
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148 This function searches backward from point for a word match to
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149 @var{string}. This function is just like @code{word-search-forward}
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150 except that it searches backward and normally leaves point at the
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151 beginning of the match.
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152 @end deffn
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153
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154 @node Regular Expressions
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155 @section Regular Expressions
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156 @cindex regular expression
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157 @cindex regexp
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158
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159 A @dfn{regular expression} (@dfn{regexp}, for short) is a pattern that
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160 denotes a (possibly infinite) set of strings. Searching for matches for
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161 a regexp is a very powerful operation. This section explains how to write
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162 regexps; the following section says how to search for them.
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163
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255
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164 To gain a thorough understanding of regular expressions and how to use
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165 them to best advantage, we recommend that you study @cite{Mastering
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166 Regular Expressions, by Jeffrey E.F. Friedl, O'Reilly and Associates,
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167 1997}. (It's known as the "Hip Owls" book, because of the picture on its
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168 cover.) You might also read the manuals to @ref{(gawk)Top},
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169 @ref{(ed)Top}, @cite{sed}, @cite{grep}, @ref{(perl)Top},
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170 @ref{(regex)Top}, @ref{(rx)Top}, @cite{pcre}, and @ref{(flex)Top}, which
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171 also make good use of regular expressions.
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172
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173 The XEmacs regular expression syntax most closely resembles that of
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174 @cite{ed}, or @cite{grep}, the GNU versions of which all utilize the GNU
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175 @cite{regex} library. XEmacs' version of @cite{regex} has recently been
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176 extended with some perl--like capabilities, described in the next
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177 section.
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178
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179 @menu
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180 * Syntax of Regexps:: Rules for writing regular expressions.
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181 * Regexp Example:: Illustrates regular expression syntax.
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182 @end menu
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183
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184 @node Syntax of Regexps
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185 @subsection Syntax of Regular Expressions
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186
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187 Regular expressions have a syntax in which a few characters are
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188 special constructs and the rest are @dfn{ordinary}. An ordinary
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189 character is a simple regular expression that matches that character and
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190 nothing else. The special characters are @samp{.}, @samp{*}, @samp{+},
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191 @samp{?}, @samp{[}, @samp{]}, @samp{^}, @samp{$}, and @samp{\}; no new
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192 special characters will be defined in the future. Any other character
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193 appearing in a regular expression is ordinary, unless a @samp{\}
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194 precedes it.
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195
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196 For example, @samp{f} is not a special character, so it is ordinary, and
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197 therefore @samp{f} is a regular expression that matches the string
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198 @samp{f} and no other string. (It does @emph{not} match the string
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199 @samp{ff}.) Likewise, @samp{o} is a regular expression that matches
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200 only @samp{o}.@refill
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201
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202 Any two regular expressions @var{a} and @var{b} can be concatenated. The
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203 result is a regular expression that matches a string if @var{a} matches
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204 some amount of the beginning of that string and @var{b} matches the rest of
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205 the string.@refill
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206
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207 As a simple example, we can concatenate the regular expressions @samp{f}
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208 and @samp{o} to get the regular expression @samp{fo}, which matches only
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209 the string @samp{fo}. Still trivial. To do something more powerful, you
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210 need to use one of the special characters. Here is a list of them:
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211
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212 @need 1200
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213 @table @kbd
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214 @item .@: @r{(Period)}
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215 @cindex @samp{.} in regexp
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216 is a special character that matches any single character except a newline.
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217 Using concatenation, we can make regular expressions like @samp{a.b}, which
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218 matches any three-character string that begins with @samp{a} and ends with
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219 @samp{b}.@refill
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220
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221 @item *
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222 @cindex @samp{*} in regexp
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255
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223 is not a construct by itself; it is a quantifying suffix operator that
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224 means to repeat the preceding regular expression as many times as
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225 possible. In @samp{fo*}, the @samp{*} applies to the @samp{o}, so
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226 @samp{fo*} matches one @samp{f} followed by any number of @samp{o}s.
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227 The case of zero @samp{o}s is allowed: @samp{fo*} does match
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228 @samp{f}.@refill
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229
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230 @samp{*} always applies to the @emph{smallest} possible preceding
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231 expression. Thus, @samp{fo*} has a repeating @samp{o}, not a
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232 repeating @samp{fo}.@refill
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233
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234 The matcher processes a @samp{*} construct by matching, immediately, as
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235 many repetitions as can be found; it is "greedy". Then it continues
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236 with the rest of the pattern. If that fails, backtracking occurs,
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237 discarding some of the matches of the @samp{*}-modified construct in
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238 case that makes it possible to match the rest of the pattern. For
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239 example, in matching @samp{ca*ar} against the string @samp{caaar}, the
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240 @samp{a*} first tries to match all three @samp{a}s; but the rest of the
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241 pattern is @samp{ar} and there is only @samp{r} left to match, so this
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242 try fails. The next alternative is for @samp{a*} to match only two
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243 @samp{a}s. With this choice, the rest of the regexp matches
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244 successfully.@refill
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245
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246 Nested repetition operators can be extremely slow if they specify
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247 backtracking loops. For example, it could take hours for the regular
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248 expression @samp{\(x+y*\)*a} to match the sequence
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249 @samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz}. The slowness is because
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250 Emacs must try each imaginable way of grouping the 35 @samp{x}'s before
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251 concluding that none of them can work. To make sure your regular
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252 expressions run fast, check nested repetitions carefully.
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253
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254 @item +
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255 @cindex @samp{+} in regexp
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255
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256 is a quantifying suffix operator similar to @samp{*} except that the
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257 preceding expression must match at least once. It is also "greedy".
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258 So, for example, @samp{ca+r} matches the strings @samp{car} and
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259 @samp{caaaar} but not the string @samp{cr}, whereas @samp{ca*r} matches
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260 all three strings.
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261
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262 @item ?
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263 @cindex @samp{?} in regexp
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255
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264 is a quantifying suffix operator similar to @samp{*}, except that the
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265 preceding expression can match either once or not at all. For example,
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266 @samp{ca?r} matches @samp{car} or @samp{cr}, but does not match anyhing
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267 else.
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268
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255
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269 @item *?
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270 @cindex @samp{*?} in regexp
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271 works just like @samp{*}, except that rather than matching the longest
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272 match, it matches the shortest match. This is known as a "non-greedy"
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273 quantifier. It is a syntax that comes to us from perl. It is very
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274 useful for situations where you want to match the text inside a pair of
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275 delimiters.
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276 @c Did perl get this from somewhere? What's the real history of *? ?
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277
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278 @lisp
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279 @group
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280 (setq s "/ blah / / blah2 /")
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281 @result{} "/ blah / / blah2 /"
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282 (string-match "/.*/" s)
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283 @result{} 0
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284 (match-string 0 s)
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285 @result{} "/ blah / / blah2 /"
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286 (string-match "/.*?/" s)
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287 @result{} 0
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288 (match-string 0 s)
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289 @result{} "/ blah /"
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290 @end group
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291 @end lisp
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292
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293 @item +?
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294 @cindex @samp{+?} in regexp
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295 is the @samp{+} analog to @samp{*?}.
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296
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297 @item \@{n,m\@}
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298 @c Note the spacing after the close brace is deliberate.
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299 @cindex @samp{\@{n,m\@} }in regexp
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300 this is an interval quantifier, which is analogous to @samp{*} or
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301 @samp{+}, but specifies that the expression must match at least @samp{n}
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302 times, but no more than @samp{m} times. This syntax comes to us from
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303 @cite{ed}, @cite{grep}, and @cite{perl}. The @cite{etags} utility also
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304 supports it.
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305
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306 @lisp
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307 @group
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308 (setq s "12 123 1234 12345")
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309 @result{} "12 123 1234 12345"
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310 (string-match "[0-9]\\@{2,4\\@}" s)
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311 @result{} 0
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312 (match-string 0 s)
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313 @result{} "12"
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314 (string-match "[0-9]\\@{3,4\\@}" s)
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315 @result{} 3
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316 (match-string 0 s)
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317 @result{} "123"
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318 @end group
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319 @end lisp
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320
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321 @item [ @dots{} ]
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322 @cindex character set (in regexp)
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323 @cindex @samp{[} in regexp
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324 @cindex @samp{]} in regexp
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325 @samp{[} begins a @dfn{character set}, which is terminated by a
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326 @samp{]}. In the simplest case, the characters between the two brackets
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327 form the set. Thus, @samp{[ad]} matches either one @samp{a} or one
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328 @samp{d}, and @samp{[ad]*} matches any string composed of just @samp{a}s
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329 and @samp{d}s (including the empty string), from which it follows that
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330 @samp{c[ad]*r} matches @samp{cr}, @samp{car}, @samp{cdr},
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331 @samp{caddaar}, etc.@refill
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332
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333 The usual regular expression special characters are not special inside a
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334 character set. A completely different set of special characters exists
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335 inside character sets: @samp{]}, @samp{-} and @samp{^}.@refill
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336
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337 @samp{-} is used for ranges of characters. To write a range, write two
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338 characters with a @samp{-} between them. Thus, @samp{[a-z]} matches any
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339 lower case letter. Ranges may be intermixed freely with individual
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340 characters, as in @samp{[a-z$%.]}, which matches any lower case letter
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341 or @samp{$}, @samp{%}, or a period.@refill
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342
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343 To include a @samp{]} in a character set, make it the first character.
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344 For example, @samp{[]a]} matches @samp{]} or @samp{a}. To include a
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345 @samp{-}, write @samp{-} as the first character in the set, or put it
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346 immediately after a range. (You can replace one individual character
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347 @var{c} with the range @samp{@var{c}-@var{c}} to make a place to put the
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348 @samp{-}.) There is no way to write a set containing just @samp{-} and
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349 @samp{]}.
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350
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351 To include @samp{^} in a set, put it anywhere but at the beginning of
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352 the set.
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353
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354 @item [^ @dots{} ]
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355 @cindex @samp{^} in regexp
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356 @samp{[^} begins a @dfn{complement character set}, which matches any
|
|
|
357 character except the ones specified. Thus, @samp{[^a-z0-9A-Z]}
|
|
|
358 matches all characters @emph{except} letters and digits.@refill
|
|
|
359
|
|
|
360 @samp{^} is not special in a character set unless it is the first
|
|
|
361 character. The character following the @samp{^} is treated as if it
|
|
|
362 were first (thus, @samp{-} and @samp{]} are not special there).
|
|
|
363
|
|
|
364 Note that a complement character set can match a newline, unless
|
|
|
365 newline is mentioned as one of the characters not to match.
|
|
|
366
|
|
|
367 @item ^
|
|
|
368 @cindex @samp{^} in regexp
|
|
|
369 @cindex beginning of line in regexp
|
|
|
370 is a special character that matches the empty string, but only at the
|
|
|
371 beginning of a line in the text being matched. Otherwise it fails to
|
|
|
372 match anything. Thus, @samp{^foo} matches a @samp{foo} that occurs at
|
|
|
373 the beginning of a line.
|
|
|
374
|
|
|
375 When matching a string instead of a buffer, @samp{^} matches at the
|
|
|
376 beginning of the string or after a newline character @samp{\n}.
|
|
|
377
|
|
|
378 @item $
|
|
|
379 @cindex @samp{$} in regexp
|
|
|
380 is similar to @samp{^} but matches only at the end of a line. Thus,
|
|
|
381 @samp{x+$} matches a string of one @samp{x} or more at the end of a line.
|
|
|
382
|
|
|
383 When matching a string instead of a buffer, @samp{$} matches at the end
|
|
|
384 of the string or before a newline character @samp{\n}.
|
|
|
385
|
|
|
386 @item \
|
|
|
387 @cindex @samp{\} in regexp
|
|
|
388 has two functions: it quotes the special characters (including
|
|
|
389 @samp{\}), and it introduces additional special constructs.
|
|
|
390
|
|
|
391 Because @samp{\} quotes special characters, @samp{\$} is a regular
|
|
|
392 expression that matches only @samp{$}, and @samp{\[} is a regular
|
|
|
393 expression that matches only @samp{[}, and so on.
|
|
|
394
|
|
|
395 Note that @samp{\} also has special meaning in the read syntax of Lisp
|
|
|
396 strings (@pxref{String Type}), and must be quoted with @samp{\}. For
|
|
|
397 example, the regular expression that matches the @samp{\} character is
|
|
|
398 @samp{\\}. To write a Lisp string that contains the characters
|
|
|
399 @samp{\\}, Lisp syntax requires you to quote each @samp{\} with another
|
|
|
400 @samp{\}. Therefore, the read syntax for a regular expression matching
|
|
|
401 @samp{\} is @code{"\\\\"}.@refill
|
|
|
402 @end table
|
|
|
403
|
|
|
404 @strong{Please note:} For historical compatibility, special characters
|
|
|
405 are treated as ordinary ones if they are in contexts where their special
|
|
|
406 meanings make no sense. For example, @samp{*foo} treats @samp{*} as
|
|
|
407 ordinary since there is no preceding expression on which the @samp{*}
|
|
|
408 can act. It is poor practice to depend on this behavior; quote the
|
|
|
409 special character anyway, regardless of where it appears.@refill
|
|
|
410
|
|
|
411 For the most part, @samp{\} followed by any character matches only
|
|
|
412 that character. However, there are several exceptions: characters
|
|
|
413 that, when preceded by @samp{\}, are special constructs. Such
|
|
|
414 characters are always ordinary when encountered on their own. Here
|
|
|
415 is a table of @samp{\} constructs:
|
|
|
416
|
|
|
417 @table @kbd
|
|
|
418 @item \|
|
|
|
419 @cindex @samp{|} in regexp
|
|
|
420 @cindex regexp alternative
|
|
|
421 specifies an alternative.
|
|
|
422 Two regular expressions @var{a} and @var{b} with @samp{\|} in
|
|
|
423 between form an expression that matches anything that either @var{a} or
|
|
|
424 @var{b} matches.@refill
|
|
|
425
|
|
|
426 Thus, @samp{foo\|bar} matches either @samp{foo} or @samp{bar}
|
|
|
427 but no other string.@refill
|
|
|
428
|
|
|
429 @samp{\|} applies to the largest possible surrounding expressions. Only a
|
|
|
430 surrounding @samp{\( @dots{} \)} grouping can limit the grouping power of
|
|
|
431 @samp{\|}.@refill
|
|
|
432
|
|
|
433 Full backtracking capability exists to handle multiple uses of @samp{\|}.
|
|
|
434
|
|
|
435 @item \( @dots{} \)
|
|
|
436 @cindex @samp{(} in regexp
|
|
|
437 @cindex @samp{)} in regexp
|
|
|
438 @cindex regexp grouping
|
|
|
439 is a grouping construct that serves three purposes:
|
|
|
440
|
|
|
441 @enumerate
|
|
|
442 @item
|
|
|
443 To enclose a set of @samp{\|} alternatives for other operations.
|
|
|
444 Thus, @samp{\(foo\|bar\)x} matches either @samp{foox} or @samp{barx}.
|
|
|
445
|
|
|
446 @item
|
|
|
447 To enclose an expression for a suffix operator such as @samp{*} to act
|
|
|
448 on. Thus, @samp{ba\(na\)*} matches @samp{bananana}, etc., with any
|
|
|
449 (zero or more) number of @samp{na} strings.@refill
|
|
|
450
|
|
|
451 @item
|
|
|
452 To record a matched substring for future reference.
|
|
|
453 @end enumerate
|
|
|
454
|
|
|
455 This last application is not a consequence of the idea of a
|
|
|
456 parenthetical grouping; it is a separate feature that happens to be
|
|
|
457 assigned as a second meaning to the same @samp{\( @dots{} \)} construct
|
|
|
458 because there is no conflict in practice between the two meanings.
|
|
|
459 Here is an explanation of this feature:
|
|
|
460
|
|
|
461 @item \@var{digit}
|
|
|
462 matches the same text that matched the @var{digit}th occurrence of a
|
|
|
463 @samp{\( @dots{} \)} construct.
|
|
|
464
|
|
|
465 In other words, after the end of a @samp{\( @dots{} \)} construct. the
|
|
|
466 matcher remembers the beginning and end of the text matched by that
|
|
|
467 construct. Then, later on in the regular expression, you can use
|
|
|
468 @samp{\} followed by @var{digit} to match that same text, whatever it
|
|
|
469 may have been.
|
|
|
470
|
|
|
471 The strings matching the first nine @samp{\( @dots{} \)} constructs
|
|
|
472 appearing in a regular expression are assigned numbers 1 through 9 in
|
|
|
473 the order that the open parentheses appear in the regular expression.
|
|
|
474 So you can use @samp{\1} through @samp{\9} to refer to the text matched
|
|
|
475 by the corresponding @samp{\( @dots{} \)} constructs.
|
|
|
476
|
|
|
477 For example, @samp{\(.*\)\1} matches any newline-free string that is
|
|
|
478 composed of two identical halves. The @samp{\(.*\)} matches the first
|
|
|
479 half, which may be anything, but the @samp{\1} that follows must match
|
|
|
480 the same exact text.
|
|
|
481
|
|
255
|
482 @item \(?: @dots{} \)
|
|
|
483 @cindex @samp{(?:} in regex
|
|
|
484 @cindex regexp grouping
|
|
|
485 is called a "shy" grouping operator, and it is used just like @samp{\(
|
|
|
486 @dots{} \)}, except that it does not cause the matched substring to be
|
|
|
487 recorded for future reference. This can be useful at times when a
|
|
|
488 program wants to refer to a specific @samp{\( @dots{} \)} group's number
|
|
|
489 (eg. in a @code{match-string} or @code{match-beginning} function
|
|
|
490 application) and you need to use grouping constructs for an alternation
|
|
|
491 or multi--character repetition inside a regular expression string that
|
|
|
492 can change each time the code is run, but you don't want those groups
|
|
|
493 counting because they'd change the reference number of the group you
|
|
|
494 want to refer to that is inside the static part of your generated
|
|
|
495 regular expression.
|
|
|
496
|
|
|
497 @lisp
|
|
|
498 ;; @r{Here `dynamic-regex' might contain shy groups.}
|
|
|
499 (re-search-forward
|
|
|
500 (concat "\\(" dynamic-regex "\\)\\(-?[0-9]\\@{2,4\\@}\\)"))
|
|
|
501 ;; @r{and this `match-string' will still refer to the integer}
|
|
|
502 ;; @r{captured by the second group in the `concat' string.}
|
|
|
503 (match-string 2)
|
|
|
504 @end lisp
|
|
|
505
|
|
|
506 Using @samp{\(?: @dots{} \)} rather than @samp{\( @dots{} \)} when you
|
|
|
507 don't need the captured substrings ought to speed up your programs some,
|
|
|
508 since it shortens the code path followed by the regular expression
|
|
|
509 engine, as well as the amount of memory allocation and string copying it
|
|
|
510 must do. The actual performance gain to be observed has not been
|
|
|
511 measured or quantified as of this writing.
|
|
|
512 @c This is used to good advantage by the font-locking code, and by `regexp-opt.el'.
|
|
|
513 @c ... It will be. It's not yet, but will be.
|
|
|
514
|
|
0
|
515 @item \w
|
|
|
516 @cindex @samp{\w} in regexp
|
|
|
517 matches any word-constituent character. The editor syntax table
|
|
|
518 determines which characters these are. @xref{Syntax Tables}.
|
|
|
519
|
|
|
520 @item \W
|
|
|
521 @cindex @samp{\W} in regexp
|
|
|
522 matches any character that is not a word constituent.
|
|
|
523
|
|
|
524 @item \s@var{code}
|
|
|
525 @cindex @samp{\s} in regexp
|
|
|
526 matches any character whose syntax is @var{code}. Here @var{code} is a
|
|
|
527 character that represents a syntax code: thus, @samp{w} for word
|
|
|
528 constituent, @samp{-} for whitespace, @samp{(} for open parenthesis,
|
|
|
529 etc. @xref{Syntax Tables}, for a list of syntax codes and the
|
|
|
530 characters that stand for them.
|
|
|
531
|
|
|
532 @item \S@var{code}
|
|
|
533 @cindex @samp{\S} in regexp
|
|
|
534 matches any character whose syntax is not @var{code}.
|
|
|
535 @end table
|
|
|
536
|
|
|
537 The following regular expression constructs match the empty string---that is,
|
|
|
538 they don't use up any characters---but whether they match depends on the
|
|
|
539 context.
|
|
|
540
|
|
|
541 @table @kbd
|
|
|
542 @item \`
|
|
|
543 @cindex @samp{\`} in regexp
|
|
|
544 matches the empty string, but only at the beginning
|
|
|
545 of the buffer or string being matched against.
|
|
|
546
|
|
|
547 @item \'
|
|
|
548 @cindex @samp{\'} in regexp
|
|
|
549 matches the empty string, but only at the end of
|
|
|
550 the buffer or string being matched against.
|
|
|
551
|
|
|
552 @item \=
|
|
|
553 @cindex @samp{\=} in regexp
|
|
|
554 matches the empty string, but only at point.
|
|
|
555 (This construct is not defined when matching against a string.)
|
|
|
556
|
|
|
557 @item \b
|
|
|
558 @cindex @samp{\b} in regexp
|
|
|
559 matches the empty string, but only at the beginning or
|
|
|
560 end of a word. Thus, @samp{\bfoo\b} matches any occurrence of
|
|
|
561 @samp{foo} as a separate word. @samp{\bballs?\b} matches
|
|
|
562 @samp{ball} or @samp{balls} as a separate word.@refill
|
|
|
563
|
|
|
564 @item \B
|
|
|
565 @cindex @samp{\B} in regexp
|
|
|
566 matches the empty string, but @emph{not} at the beginning or
|
|
|
567 end of a word.
|
|
|
568
|
|
|
569 @item \<
|
|
|
570 @cindex @samp{\<} in regexp
|
|
|
571 matches the empty string, but only at the beginning of a word.
|
|
|
572
|
|
|
573 @item \>
|
|
|
574 @cindex @samp{\>} in regexp
|
|
|
575 matches the empty string, but only at the end of a word.
|
|
|
576 @end table
|
|
|
577
|
|
|
578 @kindex invalid-regexp
|
|
|
579 Not every string is a valid regular expression. For example, a string
|
|
|
580 with unbalanced square brackets is invalid (with a few exceptions, such
|
|
|
581 as @samp{[]]}), and so is a string that ends with a single @samp{\}. If
|
|
|
582 an invalid regular expression is passed to any of the search functions,
|
|
|
583 an @code{invalid-regexp} error is signaled.
|
|
|
584
|
|
|
585 @defun regexp-quote string
|
|
|
586 This function returns a regular expression string that matches exactly
|
|
|
587 @var{string} and nothing else. This allows you to request an exact
|
|
|
588 string match when calling a function that wants a regular expression.
|
|
|
589
|
|
|
590 @example
|
|
|
591 @group
|
|
|
592 (regexp-quote "^The cat$")
|
|
|
593 @result{} "\\^The cat\\$"
|
|
|
594 @end group
|
|
|
595 @end example
|
|
|
596
|
|
|
597 One use of @code{regexp-quote} is to combine an exact string match with
|
|
|
598 context described as a regular expression. For example, this searches
|
|
|
599 for the string that is the value of @code{string}, surrounded by
|
|
|
600 whitespace:
|
|
|
601
|
|
|
602 @example
|
|
|
603 @group
|
|
|
604 (re-search-forward
|
|
|
605 (concat "\\s-" (regexp-quote string) "\\s-"))
|
|
|
606 @end group
|
|
|
607 @end example
|
|
|
608 @end defun
|
|
|
609
|
|
|
610 @node Regexp Example
|
|
|
611 @subsection Complex Regexp Example
|
|
|
612
|
|
|
613 Here is a complicated regexp, used by XEmacs to recognize the end of a
|
|
|
614 sentence together with any whitespace that follows. It is the value of
|
|
|
615 the variable @code{sentence-end}.
|
|
|
616
|
|
|
617 First, we show the regexp as a string in Lisp syntax to distinguish
|
|
|
618 spaces from tab characters. The string constant begins and ends with a
|
|
|
619 double-quote. @samp{\"} stands for a double-quote as part of the
|
|
|
620 string, @samp{\\} for a backslash as part of the string, @samp{\t} for a
|
|
|
621 tab and @samp{\n} for a newline.
|
|
|
622
|
|
|
623 @example
|
|
|
624 "[.?!][]\"')@}]*\\($\\| $\\|\t\\| \\)[ \t\n]*"
|
|
|
625 @end example
|
|
|
626
|
|
|
627 In contrast, if you evaluate the variable @code{sentence-end}, you
|
|
|
628 will see the following:
|
|
|
629
|
|
|
630 @example
|
|
|
631 @group
|
|
|
632 sentence-end
|
|
|
633 @result{}
|
|
|
634 "[.?!][]\"')@}]*\\($\\| $\\| \\| \\)[
|
|
|
635 ]*"
|
|
|
636 @end group
|
|
|
637 @end example
|
|
|
638
|
|
|
639 @noindent
|
|
|
640 In this output, tab and newline appear as themselves.
|
|
|
641
|
|
|
642 This regular expression contains four parts in succession and can be
|
|
|
643 deciphered as follows:
|
|
|
644
|
|
|
645 @table @code
|
|
|
646 @item [.?!]
|
|
|
647 The first part of the pattern is a character set that matches any one of
|
|
|
648 three characters: period, question mark, and exclamation mark. The
|
|
|
649 match must begin with one of these three characters.
|
|
|
650
|
|
|
651 @item []\"')@}]*
|
|
|
652 The second part of the pattern matches any closing braces and quotation
|
|
|
653 marks, zero or more of them, that may follow the period, question mark
|
|
|
654 or exclamation mark. The @code{\"} is Lisp syntax for a double-quote in
|
|
|
655 a string. The @samp{*} at the end indicates that the immediately
|
|
|
656 preceding regular expression (a character set, in this case) may be
|
|
|
657 repeated zero or more times.
|
|
|
658
|
|
|
659 @item \\($\\|@ $\\|\t\\|@ @ \\)
|
|
|
660 The third part of the pattern matches the whitespace that follows the
|
|
|
661 end of a sentence: the end of a line, or a tab, or two spaces. The
|
|
|
662 double backslashes mark the parentheses and vertical bars as regular
|
|
|
663 expression syntax; the parentheses delimit a group and the vertical bars
|
|
|
664 separate alternatives. The dollar sign is used to match the end of a
|
|
|
665 line.
|
|
|
666
|
|
|
667 @item [ \t\n]*
|
|
|
668 Finally, the last part of the pattern matches any additional whitespace
|
|
|
669 beyond the minimum needed to end a sentence.
|
|
|
670 @end table
|
|
|
671
|
|
|
672 @node Regexp Search
|
|
|
673 @section Regular Expression Searching
|
|
|
674 @cindex regular expression searching
|
|
|
675 @cindex regexp searching
|
|
|
676 @cindex searching for regexp
|
|
|
677
|
|
|
678 In XEmacs, you can search for the next match for a regexp either
|
|
|
679 incrementally or not. Incremental search commands are described in the
|
|
|
680 @cite{The XEmacs Reference Manual}. @xref{Regexp Search, , Regular Expression
|
|
|
681 Search, emacs, The XEmacs Reference Manual}. Here we describe only the search
|
|
|
682 functions useful in programs. The principal one is
|
|
|
683 @code{re-search-forward}.
|
|
|
684
|
|
|
685 @deffn Command re-search-forward regexp &optional limit noerror repeat
|
|
|
686 This function searches forward in the current buffer for a string of
|
|
|
687 text that is matched by the regular expression @var{regexp}. The
|
|
|
688 function skips over any amount of text that is not matched by
|
|
|
689 @var{regexp}, and leaves point at the end of the first match found.
|
|
|
690 It returns the new value of point.
|
|
|
691
|
|
|
692 If @var{limit} is non-@code{nil} (it must be a position in the current
|
|
|
693 buffer), then it is the upper bound to the search. No match extending
|
|
|
694 after that position is accepted.
|
|
|
695
|
|
|
696 What happens when the search fails depends on the value of
|
|
|
697 @var{noerror}. If @var{noerror} is @code{nil}, a @code{search-failed}
|
|
|
698 error is signaled. If @var{noerror} is @code{t},
|
|
|
699 @code{re-search-forward} does nothing and returns @code{nil}. If
|
|
|
700 @var{noerror} is neither @code{nil} nor @code{t}, then
|
|
|
701 @code{re-search-forward} moves point to @var{limit} (or the end of the
|
|
|
702 buffer) and returns @code{nil}.
|
|
|
703
|
|
|
704 If @var{repeat} is supplied (it must be a positive number), then the
|
|
|
705 search is repeated that many times (each time starting at the end of the
|
|
|
706 previous time's match). If these successive searches succeed, the
|
|
|
707 function succeeds, moving point and returning its new value. Otherwise
|
|
|
708 the search fails.
|
|
|
709
|
|
|
710 In the following example, point is initially before the @samp{T}.
|
|
|
711 Evaluating the search call moves point to the end of that line (between
|
|
|
712 the @samp{t} of @samp{hat} and the newline).
|
|
|
713
|
|
|
714 @example
|
|
|
715 @group
|
|
|
716 ---------- Buffer: foo ----------
|
|
|
717 I read "@point{}The cat in the hat
|
|
|
718 comes back" twice.
|
|
|
719 ---------- Buffer: foo ----------
|
|
|
720 @end group
|
|
|
721
|
|
|
722 @group
|
|
|
723 (re-search-forward "[a-z]+" nil t 5)
|
|
|
724 @result{} 27
|
|
|
725
|
|
|
726 ---------- Buffer: foo ----------
|
|
|
727 I read "The cat in the hat@point{}
|
|
|
728 comes back" twice.
|
|
|
729 ---------- Buffer: foo ----------
|
|
|
730 @end group
|
|
|
731 @end example
|
|
|
732 @end deffn
|
|
|
733
|
|
|
734 @deffn Command re-search-backward regexp &optional limit noerror repeat
|
|
|
735 This function searches backward in the current buffer for a string of
|
|
|
736 text that is matched by the regular expression @var{regexp}, leaving
|
|
|
737 point at the beginning of the first text found.
|
|
|
738
|
|
|
739 This function is analogous to @code{re-search-forward}, but they are not
|
|
|
740 simple mirror images. @code{re-search-forward} finds the match whose
|
|
|
741 beginning is as close as possible to the starting point. If
|
|
|
742 @code{re-search-backward} were a perfect mirror image, it would find the
|
|
|
743 match whose end is as close as possible. However, in fact it finds the
|
|
|
744 match whose beginning is as close as possible. The reason is that
|
|
|
745 matching a regular expression at a given spot always works from
|
|
|
746 beginning to end, and starts at a specified beginning position.
|
|
|
747
|
|
|
748 A true mirror-image of @code{re-search-forward} would require a special
|
|
|
749 feature for matching regexps from end to beginning. It's not worth the
|
|
|
750 trouble of implementing that.
|
|
|
751 @end deffn
|
|
|
752
|
|
|
753 @defun string-match regexp string &optional start
|
|
|
754 This function returns the index of the start of the first match for
|
|
|
755 the regular expression @var{regexp} in @var{string}, or @code{nil} if
|
|
|
756 there is no match. If @var{start} is non-@code{nil}, the search starts
|
|
|
757 at that index in @var{string}.
|
|
|
758
|
|
|
759 For example,
|
|
|
760
|
|
|
761 @example
|
|
|
762 @group
|
|
|
763 (string-match
|
|
|
764 "quick" "The quick brown fox jumped quickly.")
|
|
|
765 @result{} 4
|
|
|
766 @end group
|
|
|
767 @group
|
|
|
768 (string-match
|
|
|
769 "quick" "The quick brown fox jumped quickly." 8)
|
|
|
770 @result{} 27
|
|
|
771 @end group
|
|
|
772 @end example
|
|
|
773
|
|
|
774 @noindent
|
|
|
775 The index of the first character of the
|
|
|
776 string is 0, the index of the second character is 1, and so on.
|
|
|
777
|
|
|
778 After this function returns, the index of the first character beyond
|
|
|
779 the match is available as @code{(match-end 0)}. @xref{Match Data}.
|
|
|
780
|
|
|
781 @example
|
|
|
782 @group
|
|
|
783 (string-match
|
|
|
784 "quick" "The quick brown fox jumped quickly." 8)
|
|
|
785 @result{} 27
|
|
|
786 @end group
|
|
|
787
|
|
|
788 @group
|
|
|
789 (match-end 0)
|
|
|
790 @result{} 32
|
|
|
791 @end group
|
|
|
792 @end example
|
|
|
793 @end defun
|
|
|
794
|
|
|
795 @defun looking-at regexp
|
|
|
796 This function determines whether the text in the current buffer directly
|
|
|
797 following point matches the regular expression @var{regexp}. ``Directly
|
|
|
798 following'' means precisely that: the search is ``anchored'' and it can
|
|
|
799 succeed only starting with the first character following point. The
|
|
|
800 result is @code{t} if so, @code{nil} otherwise.
|
|
|
801
|
|
|
802 This function does not move point, but it updates the match data, which
|
|
|
803 you can access using @code{match-beginning} and @code{match-end}.
|
|
|
804 @xref{Match Data}.
|
|
|
805
|
|
|
806 In this example, point is located directly before the @samp{T}. If it
|
|
|
807 were anywhere else, the result would be @code{nil}.
|
|
|
808
|
|
|
809 @example
|
|
|
810 @group
|
|
|
811 ---------- Buffer: foo ----------
|
|
|
812 I read "@point{}The cat in the hat
|
|
|
813 comes back" twice.
|
|
|
814 ---------- Buffer: foo ----------
|
|
|
815
|
|
|
816 (looking-at "The cat in the hat$")
|
|
|
817 @result{} t
|
|
|
818 @end group
|
|
|
819 @end example
|
|
|
820 @end defun
|
|
|
821
|
|
|
822 @node POSIX Regexps
|
|
|
823 @section POSIX Regular Expression Searching
|
|
|
824
|
|
|
825 The usual regular expression functions do backtracking when necessary
|
|
|
826 to handle the @samp{\|} and repetition constructs, but they continue
|
|
|
827 this only until they find @emph{some} match. Then they succeed and
|
|
|
828 report the first match found.
|
|
|
829
|
|
|
830 This section describes alternative search functions which perform the
|
|
|
831 full backtracking specified by the POSIX standard for regular expression
|
|
|
832 matching. They continue backtracking until they have tried all
|
|
|
833 possibilities and found all matches, so they can report the longest
|
|
|
834 match, as required by POSIX. This is much slower, so use these
|
|
|
835 functions only when you really need the longest match.
|
|
|
836
|
|
|
837 In Emacs versions prior to 19.29, these functions did not exist, and
|
|
|
838 the functions described above implemented full POSIX backtracking.
|
|
|
839
|
|
|
840 @defun posix-search-forward regexp &optional limit noerror repeat
|
|
|
841 This is like @code{re-search-forward} except that it performs the full
|
|
|
842 backtracking specified by the POSIX standard for regular expression
|
|
|
843 matching.
|
|
|
844 @end defun
|
|
|
845
|
|
|
846 @defun posix-search-backward regexp &optional limit noerror repeat
|
|
|
847 This is like @code{re-search-backward} except that it performs the full
|
|
|
848 backtracking specified by the POSIX standard for regular expression
|
|
|
849 matching.
|
|
|
850 @end defun
|
|
|
851
|
|
|
852 @defun posix-looking-at regexp
|
|
|
853 This is like @code{looking-at} except that it performs the full
|
|
|
854 backtracking specified by the POSIX standard for regular expression
|
|
|
855 matching.
|
|
|
856 @end defun
|
|
|
857
|
|
|
858 @defun posix-string-match regexp string &optional start
|
|
|
859 This is like @code{string-match} except that it performs the full
|
|
|
860 backtracking specified by the POSIX standard for regular expression
|
|
|
861 matching.
|
|
|
862 @end defun
|
|
|
863
|
|
|
864 @ignore
|
|
|
865 @deffn Command delete-matching-lines regexp
|
|
|
866 This function is identical to @code{delete-non-matching-lines}, save
|
|
|
867 that it deletes what @code{delete-non-matching-lines} keeps.
|
|
|
868
|
|
|
869 In the example below, point is located on the first line of text.
|
|
|
870
|
|
|
871 @example
|
|
|
872 @group
|
|
|
873 ---------- Buffer: foo ----------
|
|
|
874 We hold these truths
|
|
|
875 to be self-evident,
|
|
|
876 that all men are created
|
|
|
877 equal, and that they are
|
|
|
878 ---------- Buffer: foo ----------
|
|
|
879 @end group
|
|
|
880
|
|
|
881 @group
|
|
|
882 (delete-matching-lines "the")
|
|
|
883 @result{} nil
|
|
|
884
|
|
|
885 ---------- Buffer: foo ----------
|
|
|
886 to be self-evident,
|
|
|
887 that all men are created
|
|
|
888 ---------- Buffer: foo ----------
|
|
|
889 @end group
|
|
|
890 @end example
|
|
|
891 @end deffn
|
|
|
892
|
|
|
893 @deffn Command flush-lines regexp
|
|
|
894 This function is the same as @code{delete-matching-lines}.
|
|
|
895 @end deffn
|
|
|
896
|
|
|
897 @defun delete-non-matching-lines regexp
|
|
|
898 This function deletes all lines following point which don't
|
|
|
899 contain a match for the regular expression @var{regexp}.
|
|
|
900 @end defun
|
|
|
901
|
|
|
902 @deffn Command keep-lines regexp
|
|
|
903 This function is the same as @code{delete-non-matching-lines}.
|
|
|
904 @end deffn
|
|
|
905
|
|
|
906 @deffn Command how-many regexp
|
|
|
907 This function counts the number of matches for @var{regexp} there are in
|
|
|
908 the current buffer following point. It prints this number in
|
|
|
909 the echo area, returning the string printed.
|
|
|
910 @end deffn
|
|
|
911
|
|
|
912 @deffn Command count-matches regexp
|
|
|
913 This function is a synonym of @code{how-many}.
|
|
|
914 @end deffn
|
|
|
915
|
|
|
916 @deffn Command list-matching-lines regexp nlines
|
|
|
917 This function is a synonym of @code{occur}.
|
|
|
918 Show all lines following point containing a match for @var{regexp}.
|
|
|
919 Display each line with @var{nlines} lines before and after,
|
|
|
920 or @code{-}@var{nlines} before if @var{nlines} is negative.
|
|
|
921 @var{nlines} defaults to @code{list-matching-lines-default-context-lines}.
|
|
|
922 Interactively it is the prefix arg.
|
|
|
923
|
|
|
924 The lines are shown in a buffer named @samp{*Occur*}.
|
|
|
925 It serves as a menu to find any of the occurrences in this buffer.
|
|
|
926 @kbd{C-h m} (@code{describe-mode} in that buffer gives help.
|
|
|
927 @end deffn
|
|
|
928
|
|
|
929 @defopt list-matching-lines-default-context-lines
|
|
|
930 Default value is 0.
|
|
|
931 Default number of context lines to include around a @code{list-matching-lines}
|
|
|
932 match. A negative number means to include that many lines before the match.
|
|
|
933 A positive number means to include that many lines both before and after.
|
|
|
934 @end defopt
|
|
|
935 @end ignore
|
|
|
936
|
|
|
937 @node Search and Replace
|
|
|
938 @section Search and Replace
|
|
|
939 @cindex replacement
|
|
|
940
|
|
|
941 @defun perform-replace from-string replacements query-flag regexp-flag delimited-flag &optional repeat-count map
|
|
|
942 This function is the guts of @code{query-replace} and related commands.
|
|
|
943 It searches for occurrences of @var{from-string} and replaces some or
|
|
|
944 all of them. If @var{query-flag} is @code{nil}, it replaces all
|
|
|
945 occurrences; otherwise, it asks the user what to do about each one.
|
|
|
946
|
|
|
947 If @var{regexp-flag} is non-@code{nil}, then @var{from-string} is
|
|
|
948 considered a regular expression; otherwise, it must match literally. If
|
|
|
949 @var{delimited-flag} is non-@code{nil}, then only replacements
|
|
|
950 surrounded by word boundaries are considered.
|
|
|
951
|
|
|
952 The argument @var{replacements} specifies what to replace occurrences
|
|
|
953 with. If it is a string, that string is used. It can also be a list of
|
|
|
954 strings, to be used in cyclic order.
|
|
|
955
|
|
|
956 If @var{repeat-count} is non-@code{nil}, it should be an integer. Then
|
|
|
957 it specifies how many times to use each of the strings in the
|
|
|
958 @var{replacements} list before advancing cyclicly to the next one.
|
|
|
959
|
|
|
960 Normally, the keymap @code{query-replace-map} defines the possible user
|
|
|
961 responses for queries. The argument @var{map}, if non-@code{nil}, is a
|
|
|
962 keymap to use instead of @code{query-replace-map}.
|
|
|
963 @end defun
|
|
|
964
|
|
|
965 @defvar query-replace-map
|
|
|
966 This variable holds a special keymap that defines the valid user
|
|
|
967 responses for @code{query-replace} and related functions, as well as
|
|
|
968 @code{y-or-n-p} and @code{map-y-or-n-p}. It is unusual in two ways:
|
|
|
969
|
|
|
970 @itemize @bullet
|
|
|
971 @item
|
|
|
972 The ``key bindings'' are not commands, just symbols that are meaningful
|
|
|
973 to the functions that use this map.
|
|
|
974
|
|
|
975 @item
|
|
|
976 Prefix keys are not supported; each key binding must be for a single event
|
|
|
977 key sequence. This is because the functions don't use read key sequence to
|
|
|
978 get the input; instead, they read a single event and look it up ``by hand.''
|
|
|
979 @end itemize
|
|
|
980 @end defvar
|
|
|
981
|
|
|
982 Here are the meaningful ``bindings'' for @code{query-replace-map}.
|
|
|
983 Several of them are meaningful only for @code{query-replace} and
|
|
|
984 friends.
|
|
|
985
|
|
|
986 @table @code
|
|
|
987 @item act
|
|
|
988 Do take the action being considered---in other words, ``yes.''
|
|
|
989
|
|
|
990 @item skip
|
|
|
991 Do not take action for this question---in other words, ``no.''
|
|
|
992
|
|
|
993 @item exit
|
|
|
994 Answer this question ``no,'' and give up on the entire series of
|
|
|
995 questions, assuming that the answers will be ``no.''
|
|
|
996
|
|
|
997 @item act-and-exit
|
|
|
998 Answer this question ``yes,'' and give up on the entire series of
|
|
|
999 questions, assuming that subsequent answers will be ``no.''
|
|
|
1000
|
|
|
1001 @item act-and-show
|
|
|
1002 Answer this question ``yes,'' but show the results---don't advance yet
|
|
|
1003 to the next question.
|
|
|
1004
|
|
|
1005 @item automatic
|
|
|
1006 Answer this question and all subsequent questions in the series with
|
|
|
1007 ``yes,'' without further user interaction.
|
|
|
1008
|
|
|
1009 @item backup
|
|
|
1010 Move back to the previous place that a question was asked about.
|
|
|
1011
|
|
|
1012 @item edit
|
|
|
1013 Enter a recursive edit to deal with this question---instead of any
|
|
|
1014 other action that would normally be taken.
|
|
|
1015
|
|
|
1016 @item delete-and-edit
|
|
|
1017 Delete the text being considered, then enter a recursive edit to replace
|
|
|
1018 it.
|
|
|
1019
|
|
|
1020 @item recenter
|
|
|
1021 Redisplay and center the window, then ask the same question again.
|
|
|
1022
|
|
|
1023 @item quit
|
|
|
1024 Perform a quit right away. Only @code{y-or-n-p} and related functions
|
|
|
1025 use this answer.
|
|
|
1026
|
|
|
1027 @item help
|
|
|
1028 Display some help, then ask again.
|
|
|
1029 @end table
|
|
|
1030
|
|
|
1031 @node Match Data
|
|
|
1032 @section The Match Data
|
|
|
1033 @cindex match data
|
|
|
1034
|
|
|
1035 XEmacs keeps track of the positions of the start and end of segments of
|
|
|
1036 text found during a regular expression search. This means, for example,
|
|
|
1037 that you can search for a complex pattern, such as a date in an Rmail
|
|
|
1038 message, and then extract parts of the match under control of the
|
|
|
1039 pattern.
|
|
|
1040
|
|
|
1041 Because the match data normally describe the most recent search only,
|
|
|
1042 you must be careful not to do another search inadvertently between the
|
|
|
1043 search you wish to refer back to and the use of the match data. If you
|
|
|
1044 can't avoid another intervening search, you must save and restore the
|
|
|
1045 match data around it, to prevent it from being overwritten.
|
|
|
1046
|
|
|
1047 @menu
|
|
|
1048 * Simple Match Data:: Accessing single items of match data,
|
|
|
1049 such as where a particular subexpression started.
|
|
|
1050 * Replacing Match:: Replacing a substring that was matched.
|
|
|
1051 * Entire Match Data:: Accessing the entire match data at once, as a list.
|
|
|
1052 * Saving Match Data:: Saving and restoring the match data.
|
|
|
1053 @end menu
|
|
|
1054
|
|
|
1055 @node Simple Match Data
|
|
|
1056 @subsection Simple Match Data Access
|
|
|
1057
|
|
|
1058 This section explains how to use the match data to find out what was
|
|
|
1059 matched by the last search or match operation.
|
|
|
1060
|
|
|
1061 You can ask about the entire matching text, or about a particular
|
|
|
1062 parenthetical subexpression of a regular expression. The @var{count}
|
|
|
1063 argument in the functions below specifies which. If @var{count} is
|
|
|
1064 zero, you are asking about the entire match. If @var{count} is
|
|
|
1065 positive, it specifies which subexpression you want.
|
|
|
1066
|
|
|
1067 Recall that the subexpressions of a regular expression are those
|
|
|
1068 expressions grouped with escaped parentheses, @samp{\(@dots{}\)}. The
|
|
|
1069 @var{count}th subexpression is found by counting occurrences of
|
|
|
1070 @samp{\(} from the beginning of the whole regular expression. The first
|
|
|
1071 subexpression is numbered 1, the second 2, and so on. Only regular
|
|
|
1072 expressions can have subexpressions---after a simple string search, the
|
|
|
1073 only information available is about the entire match.
|
|
|
1074
|
|
|
1075 @defun match-string count &optional in-string
|
|
|
1076 This function returns, as a string, the text matched in the last search
|
|
|
1077 or match operation. It returns the entire text if @var{count} is zero,
|
|
|
1078 or just the portion corresponding to the @var{count}th parenthetical
|
|
|
1079 subexpression, if @var{count} is positive. If @var{count} is out of
|
|
|
1080 range, or if that subexpression didn't match anything, the value is
|
|
|
1081 @code{nil}.
|
|
|
1082
|
|
|
1083 If the last such operation was done against a string with
|
|
|
1084 @code{string-match}, then you should pass the same string as the
|
|
|
1085 argument @var{in-string}. Otherwise, after a buffer search or match,
|
|
|
1086 you should omit @var{in-string} or pass @code{nil} for it; but you
|
|
|
1087 should make sure that the current buffer when you call
|
|
|
1088 @code{match-string} is the one in which you did the searching or
|
|
|
1089 matching.
|
|
|
1090 @end defun
|
|
|
1091
|
|
|
1092 @defun match-beginning count
|
|
|
1093 This function returns the position of the start of text matched by the
|
|
|
1094 last regular expression searched for, or a subexpression of it.
|
|
|
1095
|
|
|
1096 If @var{count} is zero, then the value is the position of the start of
|
|
|
1097 the entire match. Otherwise, @var{count} specifies a subexpression in
|
|
|
1098 the regular expresion, and the value of the function is the starting
|
|
|
1099 position of the match for that subexpression.
|
|
|
1100
|
|
|
1101 The value is @code{nil} for a subexpression inside a @samp{\|}
|
|
|
1102 alternative that wasn't used in the match.
|
|
|
1103 @end defun
|
|
|
1104
|
|
|
1105 @defun match-end count
|
|
|
1106 This function is like @code{match-beginning} except that it returns the
|
|
|
1107 position of the end of the match, rather than the position of the
|
|
|
1108 beginning.
|
|
|
1109 @end defun
|
|
|
1110
|
|
|
1111 Here is an example of using the match data, with a comment showing the
|
|
|
1112 positions within the text:
|
|
|
1113
|
|
|
1114 @example
|
|
|
1115 @group
|
|
|
1116 (string-match "\\(qu\\)\\(ick\\)"
|
|
|
1117 "The quick fox jumped quickly.")
|
|
|
1118 ;0123456789
|
|
|
1119 @result{} 4
|
|
|
1120 @end group
|
|
|
1121
|
|
|
1122 @group
|
|
|
1123 (match-string 0 "The quick fox jumped quickly.")
|
|
|
1124 @result{} "quick"
|
|
|
1125 (match-string 1 "The quick fox jumped quickly.")
|
|
|
1126 @result{} "qu"
|
|
|
1127 (match-string 2 "The quick fox jumped quickly.")
|
|
|
1128 @result{} "ick"
|
|
|
1129 @end group
|
|
|
1130
|
|
|
1131 @group
|
|
|
1132 (match-beginning 1) ; @r{The beginning of the match}
|
|
|
1133 @result{} 4 ; @r{with @samp{qu} is at index 4.}
|
|
|
1134 @end group
|
|
|
1135
|
|
|
1136 @group
|
|
|
1137 (match-beginning 2) ; @r{The beginning of the match}
|
|
|
1138 @result{} 6 ; @r{with @samp{ick} is at index 6.}
|
|
|
1139 @end group
|
|
|
1140
|
|
|
1141 @group
|
|
|
1142 (match-end 1) ; @r{The end of the match}
|
|
|
1143 @result{} 6 ; @r{with @samp{qu} is at index 6.}
|
|
|
1144
|
|
|
1145 (match-end 2) ; @r{The end of the match}
|
|
|
1146 @result{} 9 ; @r{with @samp{ick} is at index 9.}
|
|
|
1147 @end group
|
|
|
1148 @end example
|
|
|
1149
|
|
|
1150 Here is another example. Point is initially located at the beginning
|
|
|
1151 of the line. Searching moves point to between the space and the word
|
|
|
1152 @samp{in}. The beginning of the entire match is at the 9th character of
|
|
|
1153 the buffer (@samp{T}), and the beginning of the match for the first
|
|
|
1154 subexpression is at the 13th character (@samp{c}).
|
|
|
1155
|
|
|
1156 @example
|
|
|
1157 @group
|
|
|
1158 (list
|
|
|
1159 (re-search-forward "The \\(cat \\)")
|
|
|
1160 (match-beginning 0)
|
|
|
1161 (match-beginning 1))
|
|
|
1162 @result{} (9 9 13)
|
|
|
1163 @end group
|
|
|
1164
|
|
|
1165 @group
|
|
|
1166 ---------- Buffer: foo ----------
|
|
|
1167 I read "The cat @point{}in the hat comes back" twice.
|
|
|
1168 ^ ^
|
|
|
1169 9 13
|
|
|
1170 ---------- Buffer: foo ----------
|
|
|
1171 @end group
|
|
|
1172 @end example
|
|
|
1173
|
|
|
1174 @noindent
|
|
|
1175 (In this case, the index returned is a buffer position; the first
|
|
|
1176 character of the buffer counts as 1.)
|
|
|
1177
|
|
|
1178 @node Replacing Match
|
|
|
1179 @subsection Replacing the Text That Matched
|
|
|
1180
|
|
|
1181 This function replaces the text matched by the last search with
|
|
|
1182 @var{replacement}.
|
|
|
1183
|
|
|
1184 @cindex case in replacements
|
|
|
1185 @defun replace-match replacement &optional fixedcase literal string
|
|
|
1186 This function replaces the text in the buffer (or in @var{string}) that
|
|
|
1187 was matched by the last search. It replaces that text with
|
|
|
1188 @var{replacement}.
|
|
|
1189
|
|
|
1190 If you did the last search in a buffer, you should specify @code{nil}
|
|
|
1191 for @var{string}. Then @code{replace-match} does the replacement by
|
|
|
1192 editing the buffer; it leaves point at the end of the replacement text,
|
|
|
1193 and returns @code{t}.
|
|
|
1194
|
|
|
1195 If you did the search in a string, pass the same string as @var{string}.
|
|
|
1196 Then @code{replace-match} does the replacement by constructing and
|
|
|
1197 returning a new string.
|
|
|
1198
|
|
|
1199 If @var{fixedcase} is non-@code{nil}, then the case of the replacement
|
|
|
1200 text is not changed; otherwise, the replacement text is converted to a
|
|
|
1201 different case depending upon the capitalization of the text to be
|
|
|
1202 replaced. If the original text is all upper case, the replacement text
|
|
|
1203 is converted to upper case. If the first word of the original text is
|
|
|
1204 capitalized, then the first word of the replacement text is capitalized.
|
|
|
1205 If the original text contains just one word, and that word is a capital
|
|
|
1206 letter, @code{replace-match} considers this a capitalized first word
|
|
|
1207 rather than all upper case.
|
|
|
1208
|
|
|
1209 If @code{case-replace} is @code{nil}, then case conversion is not done,
|
|
|
1210 regardless of the value of @var{fixed-case}. @xref{Searching and Case}.
|
|
|
1211
|
|
|
1212 If @var{literal} is non-@code{nil}, then @var{replacement} is inserted
|
|
|
1213 exactly as it is, the only alterations being case changes as needed.
|
|
|
1214 If it is @code{nil} (the default), then the character @samp{\} is treated
|
|
|
1215 specially. If a @samp{\} appears in @var{replacement}, then it must be
|
|
|
1216 part of one of the following sequences:
|
|
|
1217
|
|
|
1218 @table @asis
|
|
|
1219 @item @samp{\&}
|
|
|
1220 @cindex @samp{&} in replacement
|
|
|
1221 @samp{\&} stands for the entire text being replaced.
|
|
|
1222
|
|
|
1223 @item @samp{\@var{n}}
|
|
|
1224 @cindex @samp{\@var{n}} in replacement
|
|
|
1225 @samp{\@var{n}}, where @var{n} is a digit, stands for the text that
|
|
|
1226 matched the @var{n}th subexpression in the original regexp.
|
|
|
1227 Subexpressions are those expressions grouped inside @samp{\(@dots{}\)}.
|
|
|
1228
|
|
|
1229 @item @samp{\\}
|
|
|
1230 @cindex @samp{\} in replacement
|
|
|
1231 @samp{\\} stands for a single @samp{\} in the replacement text.
|
|
|
1232 @end table
|
|
|
1233 @end defun
|
|
|
1234
|
|
|
1235 @node Entire Match Data
|
|
|
1236 @subsection Accessing the Entire Match Data
|
|
|
1237
|
|
|
1238 The functions @code{match-data} and @code{set-match-data} read or
|
|
|
1239 write the entire match data, all at once.
|
|
|
1240
|
|
|
1241 @defun match-data
|
|
|
1242 This function returns a newly constructed list containing all the
|
|
|
1243 information on what text the last search matched. Element zero is the
|
|
|
1244 position of the beginning of the match for the whole expression; element
|
|
|
1245 one is the position of the end of the match for the expression. The
|
|
|
1246 next two elements are the positions of the beginning and end of the
|
|
|
1247 match for the first subexpression, and so on. In general, element
|
|
|
1248 @ifinfo
|
|
|
1249 number 2@var{n}
|
|
|
1250 @end ifinfo
|
|
|
1251 @tex
|
|
|
1252 number {\mathsurround=0pt $2n$}
|
|
|
1253 @end tex
|
|
|
1254 corresponds to @code{(match-beginning @var{n})}; and
|
|
|
1255 element
|
|
|
1256 @ifinfo
|
|
|
1257 number 2@var{n} + 1
|
|
|
1258 @end ifinfo
|
|
|
1259 @tex
|
|
|
1260 number {\mathsurround=0pt $2n+1$}
|
|
|
1261 @end tex
|
|
|
1262 corresponds to @code{(match-end @var{n})}.
|
|
|
1263
|
|
|
1264 All the elements are markers or @code{nil} if matching was done on a
|
|
|
1265 buffer, and all are integers or @code{nil} if matching was done on a
|
|
|
1266 string with @code{string-match}. (In Emacs 18 and earlier versions,
|
|
|
1267 markers were used even for matching on a string, except in the case
|
|
|
1268 of the integer 0.)
|
|
|
1269
|
|
|
1270 As always, there must be no possibility of intervening searches between
|
|
|
1271 the call to a search function and the call to @code{match-data} that is
|
|
|
1272 intended to access the match data for that search.
|
|
|
1273
|
|
|
1274 @example
|
|
|
1275 @group
|
|
|
1276 (match-data)
|
|
|
1277 @result{} (#<marker at 9 in foo>
|
|
|
1278 #<marker at 17 in foo>
|
|
|
1279 #<marker at 13 in foo>
|
|
|
1280 #<marker at 17 in foo>)
|
|
|
1281 @end group
|
|
|
1282 @end example
|
|
|
1283 @end defun
|
|
|
1284
|
|
|
1285 @defun set-match-data match-list
|
|
|
1286 This function sets the match data from the elements of @var{match-list},
|
|
|
1287 which should be a list that was the value of a previous call to
|
|
|
1288 @code{match-data}.
|
|
|
1289
|
|
|
1290 If @var{match-list} refers to a buffer that doesn't exist, you don't get
|
|
|
1291 an error; that sets the match data in a meaningless but harmless way.
|
|
|
1292
|
|
|
1293 @findex store-match-data
|
|
|
1294 @code{store-match-data} is an alias for @code{set-match-data}.
|
|
|
1295 @end defun
|
|
|
1296
|
|
|
1297 @node Saving Match Data
|
|
|
1298 @subsection Saving and Restoring the Match Data
|
|
|
1299
|
|
|
1300 When you call a function that may do a search, you may need to save
|
|
|
1301 and restore the match data around that call, if you want to preserve the
|
|
|
1302 match data from an earlier search for later use. Here is an example
|
|
|
1303 that shows the problem that arises if you fail to save the match data:
|
|
|
1304
|
|
|
1305 @example
|
|
|
1306 @group
|
|
|
1307 (re-search-forward "The \\(cat \\)")
|
|
|
1308 @result{} 48
|
|
|
1309 (foo) ; @r{Perhaps @code{foo} does}
|
|
|
1310 ; @r{more searching.}
|
|
|
1311 (match-end 0)
|
|
|
1312 @result{} 61 ; @r{Unexpected result---not 48!}
|
|
|
1313 @end group
|
|
|
1314 @end example
|
|
|
1315
|
|
|
1316 You can save and restore the match data with @code{save-match-data}:
|
|
|
1317
|
|
|
1318 @defmac save-match-data body@dots{}
|
|
|
1319 This special form executes @var{body}, saving and restoring the match
|
|
|
1320 data around it.
|
|
|
1321 @end defmac
|
|
|
1322
|
|
|
1323 You can use @code{set-match-data} together with @code{match-data} to
|
|
|
1324 imitate the effect of the special form @code{save-match-data}. This is
|
|
|
1325 useful for writing code that can run in Emacs 18. Here is how:
|
|
|
1326
|
|
|
1327 @example
|
|
|
1328 @group
|
|
|
1329 (let ((data (match-data)))
|
|
|
1330 (unwind-protect
|
|
|
1331 @dots{} ; @r{May change the original match data.}
|
|
|
1332 (set-match-data data)))
|
|
|
1333 @end group
|
|
|
1334 @end example
|
|
|
1335
|
|
|
1336 Emacs automatically saves and restores the match data when it runs
|
|
|
1337 process filter functions (@pxref{Filter Functions}) and process
|
|
|
1338 sentinels (@pxref{Sentinels}).
|
|
|
1339
|
|
|
1340 @ignore
|
|
|
1341 Here is a function which restores the match data provided the buffer
|
|
|
1342 associated with it still exists.
|
|
|
1343
|
|
|
1344 @smallexample
|
|
|
1345 @group
|
|
|
1346 (defun restore-match-data (data)
|
|
|
1347 @c It is incorrect to split the first line of a doc string.
|
|
|
1348 @c If there's a problem here, it should be solved in some other way.
|
|
|
1349 "Restore the match data DATA unless the buffer is missing."
|
|
|
1350 (catch 'foo
|
|
|
1351 (let ((d data))
|
|
|
1352 @end group
|
|
|
1353 (while d
|
|
|
1354 (and (car d)
|
|
|
1355 (null (marker-buffer (car d)))
|
|
|
1356 @group
|
|
|
1357 ;; @file{match-data} @r{buffer is deleted.}
|
|
|
1358 (throw 'foo nil))
|
|
|
1359 (setq d (cdr d)))
|
|
|
1360 (set-match-data data))))
|
|
|
1361 @end group
|
|
|
1362 @end smallexample
|
|
|
1363 @end ignore
|
|
|
1364
|
|
|
1365 @node Searching and Case
|
|
|
1366 @section Searching and Case
|
|
|
1367 @cindex searching and case
|
|
|
1368
|
|
|
1369 By default, searches in Emacs ignore the case of the text they are
|
|
|
1370 searching through; if you specify searching for @samp{FOO}, then
|
|
|
1371 @samp{Foo} or @samp{foo} is also considered a match. Regexps, and in
|
|
|
1372 particular character sets, are included: thus, @samp{[aB]} would match
|
|
|
1373 @samp{a} or @samp{A} or @samp{b} or @samp{B}.
|
|
|
1374
|
|
|
1375 If you do not want this feature, set the variable
|
|
|
1376 @code{case-fold-search} to @code{nil}. Then all letters must match
|
|
|
1377 exactly, including case. This is a buffer-local variable; altering the
|
|
|
1378 variable affects only the current buffer. (@xref{Intro to
|
|
|
1379 Buffer-Local}.) Alternatively, you may change the value of
|
|
|
1380 @code{default-case-fold-search}, which is the default value of
|
|
|
1381 @code{case-fold-search} for buffers that do not override it.
|
|
|
1382
|
|
|
1383 Note that the user-level incremental search feature handles case
|
|
|
1384 distinctions differently. When given a lower case letter, it looks for
|
|
|
1385 a match of either case, but when given an upper case letter, it looks
|
|
|
1386 for an upper case letter only. But this has nothing to do with the
|
|
|
1387 searching functions Lisp functions use.
|
|
|
1388
|
|
|
1389 @defopt case-replace
|
|
|
1390 This variable determines whether the replacement functions should
|
|
|
1391 preserve case. If the variable is @code{nil}, that means to use the
|
|
|
1392 replacement text verbatim. A non-@code{nil} value means to convert the
|
|
|
1393 case of the replacement text according to the text being replaced.
|
|
|
1394
|
|
|
1395 The function @code{replace-match} is where this variable actually has
|
|
|
1396 its effect. @xref{Replacing Match}.
|
|
|
1397 @end defopt
|
|
|
1398
|
|
|
1399 @defopt case-fold-search
|
|
|
1400 This buffer-local variable determines whether searches should ignore
|
|
|
1401 case. If the variable is @code{nil} they do not ignore case; otherwise
|
|
|
1402 they do ignore case.
|
|
|
1403 @end defopt
|
|
|
1404
|
|
|
1405 @defvar default-case-fold-search
|
|
|
1406 The value of this variable is the default value for
|
|
|
1407 @code{case-fold-search} in buffers that do not override it. This is the
|
|
|
1408 same as @code{(default-value 'case-fold-search)}.
|
|
|
1409 @end defvar
|
|
|
1410
|
|
|
1411 @node Standard Regexps
|
|
|
1412 @section Standard Regular Expressions Used in Editing
|
|
|
1413 @cindex regexps used standardly in editing
|
|
|
1414 @cindex standard regexps used in editing
|
|
|
1415
|
|
|
1416 This section describes some variables that hold regular expressions
|
|
|
1417 used for certain purposes in editing:
|
|
|
1418
|
|
|
1419 @defvar page-delimiter
|
|
|
1420 This is the regexp describing line-beginnings that separate pages. The
|
|
|
1421 default value is @code{"^\014"} (i.e., @code{"^^L"} or @code{"^\C-l"});
|
|
|
1422 this matches a line that starts with a formfeed character.
|
|
|
1423 @end defvar
|
|
|
1424
|
|
|
1425 The following two regular expressions should @emph{not} assume the
|
|
|
1426 match always starts at the beginning of a line; they should not use
|
|
|
1427 @samp{^} to anchor the match. Most often, the paragraph commands do
|
|
|
1428 check for a match only at the beginning of a line, which means that
|
|
|
1429 @samp{^} would be superfluous. When there is a nonzero left margin,
|
|
|
1430 they accept matches that start after the left margin. In that case, a
|
|
|
1431 @samp{^} would be incorrect. However, a @samp{^} is harmless in modes
|
|
|
1432 where a left margin is never used.
|
|
|
1433
|
|
|
1434 @defvar paragraph-separate
|
|
|
1435 This is the regular expression for recognizing the beginning of a line
|
|
|
1436 that separates paragraphs. (If you change this, you may have to
|
|
|
1437 change @code{paragraph-start} also.) The default value is
|
|
|
1438 @w{@code{"[@ \t\f]*$"}}, which matches a line that consists entirely of
|
|
|
1439 spaces, tabs, and form feeds (after its left margin).
|
|
|
1440 @end defvar
|
|
|
1441
|
|
|
1442 @defvar paragraph-start
|
|
|
1443 This is the regular expression for recognizing the beginning of a line
|
|
|
1444 that starts @emph{or} separates paragraphs. The default value is
|
|
|
1445 @w{@code{"[@ \t\n\f]"}}, which matches a line starting with a space, tab,
|
|
|
1446 newline, or form feed (after its left margin).
|
|
|
1447 @end defvar
|
|
|
1448
|
|
|
1449 @defvar sentence-end
|
|
|
1450 This is the regular expression describing the end of a sentence. (All
|
|
|
1451 paragraph boundaries also end sentences, regardless.) The default value
|
|
|
1452 is:
|
|
|
1453
|
|
|
1454 @example
|
|
|
1455 "[.?!][]\"')@}]*\\($\\| $\\|\t\\| \\)[ \t\n]*"
|
|
|
1456 @end example
|
|
|
1457
|
|
|
1458 This means a period, question mark or exclamation mark, followed
|
|
|
1459 optionally by a closing parenthetical character, followed by tabs,
|
|
|
1460 spaces or new lines.
|
|
|
1461
|
|
|
1462 For a detailed explanation of this regular expression, see @ref{Regexp
|
|
|
1463 Example}.
|
|
|
1464 @end defvar
|
