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| <div class="section" lang="en"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_regex.syntax.basic_extended"></a><a class="link" href="basic_extended.html" title="POSIX Extended Regular Expression Syntax"> POSIX Extended Regular |
| Expression Syntax</a> |
| </h3></div></div></div> |
| <a name="boost_regex.syntax.basic_extended.synopsis"></a><h4> |
| <a name="id915916"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.synopsis">Synopsis</a> |
| </h4> |
| <p> |
| The POSIX-Extended regular expression syntax is supported by the POSIX C |
| regular expression API's, and variations are used by the utilities <code class="computeroutput"><span class="identifier">egrep</span></code> and <code class="computeroutput"><span class="identifier">awk</span></code>. |
| You can construct POSIX extended regular expressions in Boost.Regex by passing |
| the flag <code class="computeroutput"><span class="identifier">extended</span></code> to the |
| regex constructor, for example: |
| </p> |
| <pre class="programlisting"><span class="comment">// e1 is a case sensitive POSIX-Extended expression: |
| </span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="identifier">e1</span><span class="special">(</span><span class="identifier">my_expression</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">extended</span><span class="special">);</span> |
| <span class="comment">// e2 a case insensitive POSIX-Extended expression: |
| </span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="identifier">e2</span><span class="special">(</span><span class="identifier">my_expression</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">extended</span><span class="special">|</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">icase</span><span class="special">);</span> |
| </pre> |
| <a name="boost_regex.posix_extended_syntax"></a><p> |
| </p> |
| <a name="boost_regex.syntax.basic_extended.posix_extended_syntax"></a><h4> |
| <a name="id916095"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.posix_extended_syntax">POSIX |
| Extended Syntax</a> |
| </h4> |
| <p> |
| In POSIX-Extended regular expressions, all characters match themselves except |
| for the following special characters: |
| </p> |
| <pre class="programlisting">.[{}()\*+?|^$</pre> |
| <a name="boost_regex.syntax.basic_extended.wildcard_"></a><h5> |
| <a name="id916116"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.wildcard_">Wildcard:</a> |
| </h5> |
| <p> |
| The single character '.' when used outside of a character set will match |
| any single character except: |
| </p> |
| <div class="itemizedlist"><ul type="disc"> |
| <li> |
| The NULL character when the flag <code class="computeroutput"><span class="identifier">match_no_dot_null</span></code> |
| is passed to the matching algorithms. |
| </li> |
| <li> |
| The newline character when the flag <code class="computeroutput"><span class="identifier">match_not_dot_newline</span></code> |
| is passed to the matching algorithms. |
| </li> |
| </ul></div> |
| <a name="boost_regex.syntax.basic_extended.anchors_"></a><h5> |
| <a name="id916168"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.anchors_">Anchors:</a> |
| </h5> |
| <p> |
| A '^' character shall match the start of a line when used as the first character |
| of an expression, or the first character of a sub-expression. |
| </p> |
| <p> |
| A '$' character shall match the end of a line when used as the last character |
| of an expression, or the last character of a sub-expression. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.marked_sub_expressions_"></a><h5> |
| <a name="id916191"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.marked_sub_expressions_">Marked |
| sub-expressions:</a> |
| </h5> |
| <p> |
| A section beginning <code class="computeroutput"><span class="special">(</span></code> and ending |
| <code class="computeroutput"><span class="special">)</span></code> acts as a marked sub-expression. |
| Whatever matched the sub-expression is split out in a separate field by the |
| matching algorithms. Marked sub-expressions can also repeated, or referred |
| to by a back-reference. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.repeats_"></a><h5> |
| <a name="id916224"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.repeats_">Repeats:</a> |
| </h5> |
| <p> |
| Any atom (a single character, a marked sub-expression, or a character class) |
| can be repeated with the <code class="computeroutput"><span class="special">*</span></code>, |
| <code class="computeroutput"><span class="special">+</span></code>, <code class="computeroutput"><span class="special">?</span></code>, |
| and <code class="computeroutput"><span class="special">{}</span></code> operators. |
| </p> |
| <p> |
| The <code class="computeroutput"><span class="special">*</span></code> operator will match the |
| preceding atom <span class="emphasis"><em>zero or more times</em></span>, for example the expression |
| <code class="computeroutput"><span class="identifier">a</span><span class="special">*</span><span class="identifier">b</span></code> will match any of the following: |
| </p> |
| <pre class="programlisting">b |
| ab |
| aaaaaaaab |
| </pre> |
| <p> |
| The <code class="computeroutput"><span class="special">+</span></code> operator will match the |
| preceding atom <span class="emphasis"><em>one or more times</em></span>, for example the expression |
| a+b will match any of the following: |
| </p> |
| <pre class="programlisting">ab |
| aaaaaaaab |
| </pre> |
| <p> |
| But will not match: |
| </p> |
| <pre class="programlisting">b |
| </pre> |
| <p> |
| The <code class="computeroutput"><span class="special">?</span></code> operator will match the |
| preceding atom <span class="emphasis"><em>zero or one times</em></span>, for example the expression |
| <code class="computeroutput"><span class="identifier">ca</span><span class="special">?</span><span class="identifier">b</span></code> will match any of the following: |
| </p> |
| <pre class="programlisting">cb |
| cab |
| </pre> |
| <p> |
| But will not match: |
| </p> |
| <pre class="programlisting">caab |
| </pre> |
| <p> |
| An atom can also be repeated with a bounded repeat: |
| </p> |
| <p> |
| <code class="computeroutput"><span class="identifier">a</span><span class="special">{</span><span class="identifier">n</span><span class="special">}</span></code> Matches |
| 'a' repeated <span class="emphasis"><em>exactly n times</em></span>. |
| </p> |
| <p> |
| <code class="computeroutput"><span class="identifier">a</span><span class="special">{</span><span class="identifier">n</span><span class="special">,}</span></code> Matches |
| 'a' repeated <span class="emphasis"><em>n or more times</em></span>. |
| </p> |
| <p> |
| <code class="computeroutput"><span class="identifier">a</span><span class="special">{</span><span class="identifier">n</span><span class="special">,</span> <span class="identifier">m</span><span class="special">}</span></code> Matches 'a' repeated <span class="emphasis"><em>between n |
| and m times inclusive</em></span>. |
| </p> |
| <p> |
| For example: |
| </p> |
| <pre class="programlisting">^a{2,3}$</pre> |
| <p> |
| Will match either of: |
| </p> |
| <pre class="programlisting"><span class="identifier">aa</span> |
| <span class="identifier">aaa</span> |
| </pre> |
| <p> |
| But neither of: |
| </p> |
| <pre class="programlisting"><span class="identifier">a</span> |
| <span class="identifier">aaaa</span> |
| </pre> |
| <p> |
| It is an error to use a repeat operator, if the preceding construct can not |
| be repeated, for example: |
| </p> |
| <pre class="programlisting"><span class="identifier">a</span><span class="special">(*)</span> |
| </pre> |
| <p> |
| Will raise an error, as there is nothing for the <code class="computeroutput"><span class="special">*</span></code> |
| operator to be applied to. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.back_references_"></a><h5> |
| <a name="id916530"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.back_references_">Back references:</a> |
| </h5> |
| <p> |
| An escape character followed by a digit <span class="emphasis"><em>n</em></span>, where <span class="emphasis"><em>n</em></span> |
| is in the range 1-9, matches the same string that was matched by sub-expression |
| <span class="emphasis"><em>n</em></span>. For example the expression: |
| </p> |
| <pre class="programlisting">^(a*).*\1$</pre> |
| <p> |
| Will match the string: |
| </p> |
| <pre class="programlisting"><span class="identifier">aaabbaaa</span> |
| </pre> |
| <p> |
| But not the string: |
| </p> |
| <pre class="programlisting"><span class="identifier">aaabba</span> |
| </pre> |
| <div class="caution"><table border="0" summary="Caution"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../../../doc/src/images/caution.png"></td> |
| <th align="left">Caution</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| The POSIX standard does not support back-references for "extended" |
| regular expressions, this is a compatible extension to that standard. |
| </p></td></tr> |
| </table></div> |
| <a name="boost_regex.syntax.basic_extended.alternation"></a><h5> |
| <a name="id916594"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.alternation">Alternation</a> |
| </h5> |
| <p> |
| The <code class="computeroutput"><span class="special">|</span></code> operator will match either |
| of its arguments, so for example: <code class="computeroutput"><span class="identifier">abc</span><span class="special">|</span><span class="identifier">def</span></code> will |
| match either "abc" or "def". |
| </p> |
| <p> |
| Parenthesis can be used to group alternations, for example: <code class="computeroutput"><span class="identifier">ab</span><span class="special">(</span><span class="identifier">d</span><span class="special">|</span><span class="identifier">ef</span><span class="special">)</span></code> |
| will match either of "abd" or "abef". |
| </p> |
| <a name="boost_regex.syntax.basic_extended.character_sets_"></a><h5> |
| <a name="id916661"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.character_sets_">Character |
| sets:</a> |
| </h5> |
| <p> |
| A character set is a bracket-expression starting with [ and ending with ], |
| it defines a set of characters, and matches any single character that is |
| a member of that set. |
| </p> |
| <p> |
| A bracket expression may contain any combination of the following: |
| </p> |
| <a name="boost_regex.syntax.basic_extended.single_characters_"></a><h6> |
| <a name="id916682"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.single_characters_">Single |
| characters:</a> |
| </h6> |
| <p> |
| For example <code class="computeroutput"><span class="special">[</span><span class="identifier">abc</span><span class="special">]</span></code>, will match any of the characters 'a', 'b', |
| or 'c'. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.character_ranges_"></a><h6> |
| <a name="id916713"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.character_ranges_">Character |
| ranges:</a> |
| </h6> |
| <p> |
| For example <code class="computeroutput"><span class="special">[</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">c</span><span class="special">]</span></code> |
| will match any single character in the range 'a' to 'c'. By default, for |
| POSIX-Extended regular expressions, a character <span class="emphasis"><em>x</em></span> is |
| within the range <span class="emphasis"><em>y</em></span> to <span class="emphasis"><em>z</em></span>, if it |
| collates within that range; this results in locale specific behavior . This |
| behavior can be turned off by unsetting the <code class="computeroutput"><span class="identifier">collate</span></code> |
| <a class="link" href="../ref/syntax_option_type.html" title="syntax_option_type">option flag</a> - in |
| which case whether a character appears within a range is determined by comparing |
| the code points of the characters only. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.negation_"></a><h6> |
| <a name="id916774"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.negation_">Negation:</a> |
| </h6> |
| <p> |
| If the bracket-expression begins with the ^ character, then it matches the |
| complement of the characters it contains, for example <code class="computeroutput"><span class="special">[^</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">c</span><span class="special">]</span></code> matches any character that is not in the |
| range <code class="computeroutput"><span class="identifier">a</span><span class="special">-</span><span class="identifier">c</span></code>. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.character_classes_"></a><h6> |
| <a name="id916828"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.character_classes_">Character |
| classes:</a> |
| </h6> |
| <p> |
| An expression of the form <code class="computeroutput"><span class="special">[[:</span><span class="identifier">name</span><span class="special">:]]</span></code> |
| matches the named character class "name", for example <code class="computeroutput"><span class="special">[[:</span><span class="identifier">lower</span><span class="special">:]]</span></code> matches any lower case character. See |
| <a class="link" href="character_classes.html" title="Character Class Names">character class names</a>. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.collating_elements_"></a><h6> |
| <a name="id916880"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.collating_elements_">Collating |
| Elements:</a> |
| </h6> |
| <p> |
| An expression of the form <code class="computeroutput"><span class="special">[[.</span><span class="identifier">col</span><span class="special">.]</span></code> matches |
| the collating element <span class="emphasis"><em>col</em></span>. A collating element is any |
| single character, or any sequence of characters that collates as a single |
| unit. Collating elements may also be used as the end point of a range, for |
| example: <code class="computeroutput"><span class="special">[[.</span><span class="identifier">ae</span><span class="special">.]-</span><span class="identifier">c</span><span class="special">]</span></code> |
| matches the character sequence "ae", plus any single character |
| in the range "ae"-c, assuming that "ae" is treated as |
| a single collating element in the current locale. |
| </p> |
| <p> |
| Collating elements may be used in place of escapes (which are not normally |
| allowed inside character sets), for example <code class="computeroutput"><span class="special">[[.^.]</span><span class="identifier">abc</span><span class="special">]</span></code> would |
| match either one of the characters 'abc^'. |
| </p> |
| <p> |
| As an extension, a collating element may also be specified via its <a class="link" href="collating_names.html" title="Collating Names">symbolic name</a>, for example: |
| </p> |
| <pre class="programlisting"><span class="special">[[.</span><span class="identifier">NUL</span><span class="special">.]]</span> |
| </pre> |
| <p> |
| matches a NUL character. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.equivalence_classes_"></a><h6> |
| <a name="id917665"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.equivalence_classes_">Equivalence |
| classes:</a> |
| </h6> |
| <p> |
| An expression of the form <code class="computeroutput"><span class="special">[[=</span><span class="identifier">col</span><span class="special">=]]</span></code>, |
| matches any character or collating element whose primary sort key is the |
| same as that for collating element <span class="emphasis"><em>col</em></span>, as with colating |
| elements the name <span class="emphasis"><em>col</em></span> may be a <a class="link" href="collating_names.html" title="Collating Names">symbolic |
| name</a>. A primary sort key is one that ignores case, accentation, or |
| locale-specific tailorings; so for example <code class="computeroutput"><span class="special">[[=</span><span class="identifier">a</span><span class="special">=]]</span></code> matches |
| any of the characters: a, À, Á, Â, Ã, Ä, Å, A, à, á, â, ã, ä and å. Unfortunately implementation |
| of this is reliant on the platform's collation and localisation support; |
| this feature can not be relied upon to work portably across all platforms, |
| or even all locales on one platform. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.combinations_"></a><h6> |
| <a name="id917722"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.combinations_">Combinations:</a> |
| </h6> |
| <p> |
| All of the above can be combined in one character set declaration, for example: |
| <code class="computeroutput"><span class="special">[[:</span><span class="identifier">digit</span><span class="special">:]</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">c</span><span class="special">[.</span><span class="identifier">NUL</span><span class="special">.]]</span></code>. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.escapes"></a><h5> |
| <a name="id917775"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.escapes">Escapes</a> |
| </h5> |
| <p> |
| The POSIX standard defines no escape sequences for POSIX-Extended regular |
| expressions, except that: |
| </p> |
| <div class="itemizedlist"><ul type="disc"> |
| <li> |
| Any special character preceded by an escape shall match itself. |
| </li> |
| <li> |
| The effect of any ordinary character being preceded by an escape is undefined. |
| </li> |
| <li> |
| An escape inside a character class declaration shall match itself: in |
| other words the escape character is not "special" inside a |
| character class declaration; so <code class="computeroutput"><span class="special">[\^]</span></code> |
| will match either a literal '\' or a '^'. |
| </li> |
| </ul></div> |
| <p> |
| However, that's rather restrictive, so the following standard-compatible |
| extensions are also supported by Boost.Regex: |
| </p> |
| <a name="boost_regex.syntax.basic_extended.escapes_matching_a_specific_character"></a><h6> |
| <a name="id917828"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.escapes_matching_a_specific_character">Escapes |
| matching a specific character</a> |
| </h6> |
| <p> |
| The following escape sequences are all synonyms for single characters: |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Escape |
| </p> |
| </th> |
| <th> |
| <p> |
| Character |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| \a |
| </p> |
| </td> |
| <td> |
| <p> |
| '\a' |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \e |
| </p> |
| </td> |
| <td> |
| <p> |
| 0x1B |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \f |
| </p> |
| </td> |
| <td> |
| <p> |
| \f |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \n |
| </p> |
| </td> |
| <td> |
| <p> |
| \n |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \r |
| </p> |
| </td> |
| <td> |
| <p> |
| \r |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \t |
| </p> |
| </td> |
| <td> |
| <p> |
| \t |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \v |
| </p> |
| </td> |
| <td> |
| <p> |
| \v |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \b |
| </p> |
| </td> |
| <td> |
| <p> |
| \b (but only inside a character class declaration). |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \cX |
| </p> |
| </td> |
| <td> |
| <p> |
| An ASCII escape sequence - the character whose code point is X |
| % 32 |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \xdd |
| </p> |
| </td> |
| <td> |
| <p> |
| A hexadecimal escape sequence - matches the single character whose |
| code point is 0xdd. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \x{dddd} |
| </p> |
| </td> |
| <td> |
| <p> |
| A hexadecimal escape sequence - matches the single character whose |
| code point is 0xdddd. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \0ddd |
| </p> |
| </td> |
| <td> |
| <p> |
| An octal escape sequence - matches the single character whose code |
| point is 0ddd. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \N{Name} |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches the single character which has the symbolic name name. |
| For example <code class="computeroutput"><span class="special">\\</span><span class="identifier">N</span><span class="special">{</span><span class="identifier">newline</span><span class="special">}</span></code> matches the single character \n. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="boost_regex.syntax.basic_extended._quot_single_character_quot__character_classes_"></a><h6> |
| <a name="id918135"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended._quot_single_character_quot__character_classes_">"Single |
| character" character classes:</a> |
| </h6> |
| <p> |
| Any escaped character <span class="emphasis"><em>x</em></span>, if <span class="emphasis"><em>x</em></span> is |
| the name of a character class shall match any character that is a member |
| of that class, and any escaped character <span class="emphasis"><em>X</em></span>, if <span class="emphasis"><em>x</em></span> |
| is the name of a character class, shall match any character not in that class. |
| </p> |
| <p> |
| The following are supported by default: |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Escape sequence |
| </p> |
| </th> |
| <th> |
| <p> |
| Equivalent to |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">d</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[[:</span><span class="identifier">digit</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">l</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[[:</span><span class="identifier">lower</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">s</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[[:</span><span class="identifier">space</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">u</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[[:</span><span class="identifier">upper</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">w</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[[:</span><span class="identifier">word</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">D</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[^[:</span><span class="identifier">digit</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">L</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[^[:</span><span class="identifier">lower</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">S</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[^[:</span><span class="identifier">space</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">U</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[^[:</span><span class="identifier">upper</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">W</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[^[:</span><span class="identifier">word</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="boost_regex.syntax.basic_extended.character_properties"></a><h6> |
| <a name="id918637"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.character_properties">Character |
| Properties</a> |
| </h6> |
| <p> |
| The character property names in the following table are all equivalent to |
| the names used in character classes. |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Form |
| </p> |
| </th> |
| <th> |
| <p> |
| Description |
| </p> |
| </th> |
| <th> |
| <p> |
| Equivalent character set form |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">pX</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches any character that has the property X. |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[[:</span><span class="identifier">X</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">p</span><span class="special">{</span><span class="identifier">Name</span><span class="special">}</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches any character that has the property Name. |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[[:</span><span class="identifier">Name</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">PX</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches any character that does not have the property X. |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[^[:</span><span class="identifier">X</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">P</span><span class="special">{</span><span class="identifier">Name</span><span class="special">}</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches any character that does not have the property Name. |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">[^[:</span><span class="identifier">Name</span><span class="special">:]]</span></code> |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <p> |
| For example <code class="computeroutput"><span class="special">\</span><span class="identifier">pd</span></code> |
| matches any "digit" character, as does <code class="computeroutput"><span class="special">\</span><span class="identifier">p</span><span class="special">{</span><span class="identifier">digit</span><span class="special">}</span></code>. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.word_boundaries"></a><h6> |
| <a name="id918955"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.word_boundaries">Word Boundaries</a> |
| </h6> |
| <p> |
| The following escape sequences match the boundaries of words: |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Escape |
| </p> |
| </th> |
| <th> |
| <p> |
| Meaning |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\<</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches the start of a word. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\></span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches the end of a word. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">b</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches a word boundary (the start or end of a word). |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">B</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches only when not at a word boundary. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="boost_regex.syntax.basic_extended.buffer_boundaries"></a><h6> |
| <a name="id919116"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.buffer_boundaries">Buffer |
| boundaries</a> |
| </h6> |
| <p> |
| The following match only at buffer boundaries: a "buffer" in this |
| context is the whole of the input text that is being matched against (note |
| that ^ and $ may match embedded newlines within the text). |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Escape |
| </p> |
| </th> |
| <th> |
| <p> |
| Meaning |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| \` |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches at the start of a buffer only. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| \' |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches at the end of a buffer only. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">A</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches at the start of a buffer only (the same as \`). |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">z</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches at the end of a buffer only (the same as \'). |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">Z</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches an optional sequence of newlines at the end of a buffer: |
| equivalent to the regular expression <code class="computeroutput"><span class="special">\</span><span class="identifier">n</span><span class="special">*\</span><span class="identifier">z</span></code> |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="boost_regex.syntax.basic_extended.continuation_escape"></a><h6> |
| <a name="id919308"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.continuation_escape">Continuation |
| Escape</a> |
| </h6> |
| <p> |
| The sequence <code class="computeroutput"><span class="special">\</span><span class="identifier">G</span></code> |
| matches only at the end of the last match found, or at the start of the text |
| being matched if no previous match was found. This escape useful if you're |
| iterating over the matches contained within a text, and you want each subsequence |
| match to start where the last one ended. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.quoting_escape"></a><h6> |
| <a name="id919335"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.quoting_escape">Quoting |
| escape</a> |
| </h6> |
| <p> |
| The escape sequence <code class="computeroutput"><span class="special">\</span><span class="identifier">Q</span></code> |
| begins a "quoted sequence": all the subsequent characters are treated |
| as literals, until either the end of the regular expression or <code class="computeroutput"><span class="special">\</span><span class="identifier">E</span></code> is found. |
| For example the expression: <code class="computeroutput"><span class="special">\</span><span class="identifier">Q</span><span class="special">\*+\</span><span class="identifier">Ea</span><span class="special">+</span></code> would match either of: |
| </p> |
| <pre class="programlisting"><span class="special">\*+</span><span class="identifier">a</span> |
| <span class="special">\*+</span><span class="identifier">aaa</span> |
| </pre> |
| <a name="boost_regex.syntax.basic_extended.unicode_escapes"></a><h6> |
| <a name="id919416"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.unicode_escapes">Unicode |
| escapes</a> |
| </h6> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Escape |
| </p> |
| </th> |
| <th> |
| <p> |
| Meaning |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">C</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches a single code point: in Boost regex this has exactly the |
| same effect as a "." operator. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="special">\</span><span class="identifier">X</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Matches a combining character sequence: that is any non-combining |
| character followed by a sequence of zero or more combining characters. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="boost_regex.syntax.basic_extended.any_other_escape"></a><h6> |
| <a name="id919521"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.any_other_escape">Any other |
| escape</a> |
| </h6> |
| <p> |
| Any other escape sequence matches the character that is escaped, for example |
| \@ matches a literal '@'. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.operator_precedence"></a><h5> |
| <a name="id919538"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.operator_precedence">Operator |
| precedence</a> |
| </h5> |
| <p> |
| The order of precedence for of operators is as follows: |
| </p> |
| <div class="orderedlist"><ol type="1"> |
| <li> |
| Collation-related bracket symbols <code class="computeroutput"><span class="special">[==]</span> |
| <span class="special">[::]</span> <span class="special">[..]</span></code> |
| </li> |
| <li> |
| Escaped characters <code class="computeroutput"><span class="special">\</span></code> |
| </li> |
| <li> |
| Character set (bracket expression) <code class="computeroutput"><span class="special">[]</span></code> |
| </li> |
| <li> |
| Grouping <code class="computeroutput"><span class="special">()</span></code> |
| </li> |
| <li> |
| Single-character-ERE duplication <code class="computeroutput"><span class="special">*</span> |
| <span class="special">+</span> <span class="special">?</span> |
| <span class="special">{</span><span class="identifier">m</span><span class="special">,</span><span class="identifier">n</span><span class="special">}</span></code> |
| </li> |
| <li> |
| Concatenation |
| </li> |
| <li> |
| Anchoring ^$ |
| </li> |
| <li> |
| Alternation <code class="computeroutput"><span class="special">|</span></code> |
| </li> |
| </ol></div> |
| <a name="boost_regex.syntax.basic_extended.what_gets_matched"></a><h5> |
| <a name="id919700"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.what_gets_matched">What |
| Gets Matched</a> |
| </h5> |
| <p> |
| When there is more that one way to match a regular expression, the "best" |
| possible match is obtained using the <a class="link" href="leftmost_longest_rule.html" title="The Leftmost Longest Rule">leftmost-longest |
| rule</a>. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.variations"></a><h4> |
| <a name="id919722"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.variations">Variations</a> |
| </h4> |
| <a name="boost_regex.syntax.basic_extended.egrep"></a><h5> |
| <a name="id919735"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.egrep">Egrep</a> |
| </h5> |
| <p> |
| When an expression is compiled with the <a class="link" href="../ref/syntax_option_type.html" title="syntax_option_type">flag |
| <code class="computeroutput"><span class="identifier">egrep</span></code></a> set, then the |
| expression is treated as a newline separated list of <a class="link" href="basic_extended.html#boost_regex.posix_extended_syntax">POSIX-Extended |
| expressions</a>, a match is found if any of the expressions in the list |
| match, for example: |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="identifier">e</span><span class="special">(</span><span class="string">"abc\ndef"</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">egrep</span><span class="special">);</span> |
| </pre> |
| <p> |
| will match either of the POSIX-Basic expressions "abc" or "def". |
| </p> |
| <p> |
| As its name suggests, this behavior is consistent with the Unix utility |
| <code class="computeroutput"><span class="identifier">egrep</span></code>, and with grep when |
| used with the -E option. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.awk"></a><h5> |
| <a name="id919974"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.awk">awk</a> |
| </h5> |
| <p> |
| In addition to the <a class="link" href="basic_extended.html#boost_regex.posix_extended_syntax">POSIX-Extended |
| features</a> the escape character is special inside a character class |
| declaration. |
| </p> |
| <p> |
| In addition, some escape sequences that are not defined as part of POSIX-Extended |
| specification are required to be supported - however Boost.Regex supports |
| these by default anyway. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.options"></a><h4> |
| <a name="id919999"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.options">Options</a> |
| </h4> |
| <p> |
| There are a <a class="link" href="../ref/syntax_option_type/syntax_option_type_extended.html" title="Options for POSIX Extended Regular Expressions">variety |
| of flags</a> that may be combined with the <code class="computeroutput"><span class="identifier">extended</span></code> |
| and <code class="computeroutput"><span class="identifier">egrep</span></code> options when constructing |
| the regular expression, in particular note that the <a class="link" href="../ref/syntax_option_type/syntax_option_type_extended.html" title="Options for POSIX Extended Regular Expressions"><code class="computeroutput"><span class="identifier">newline_alt</span></code></a> option alters the syntax, |
| while the <a class="link" href="../ref/syntax_option_type/syntax_option_type_extended.html" title="Options for POSIX Extended Regular Expressions"><code class="computeroutput"><span class="identifier">collate</span></code>, <code class="computeroutput"><span class="identifier">nosubs</span></code> |
| and <code class="computeroutput"><span class="identifier">icase</span></code> options</a> |
| modify how the case and locale sensitivity are to be applied. |
| </p> |
| <a name="boost_regex.syntax.basic_extended.references"></a><h4> |
| <a name="id920077"></a> |
| <a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.references">References</a> |
| </h4> |
| <p> |
| <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap09.html" target="_top">IEEE |
| Std 1003.1-2001, Portable Operating System Interface (POSIX ), Base Definitions |
| and Headers, Section 9, Regular Expressions.</a> |
| </p> |
| <p> |
| <a href="http://www.opengroup.org/onlinepubs/000095399/utilities/grep.html" target="_top">IEEE |
| Std 1003.1-2001, Portable Operating System Interface (POSIX ), Shells and |
| Utilities, Section 4, Utilities, egrep.</a> |
| </p> |
| <p> |
| <a href="http://www.opengroup.org/onlinepubs/000095399/utilities/awk.html" target="_top">IEEE |
| Std 1003.1-2001, Portable Operating System Interface (POSIX ), Shells and |
| Utilities, Section 4, Utilities, awk.</a> |
| </p> |
| </div> |
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| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 1998 -2010 John Maddock<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
| </p> |
| </div></td> |
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