2001-09-30 10:30:14 +00:00
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2000-09-26 11:48:28 +00:00
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2001-09-30 10:30:14 +00:00
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content="text/html; charset=iso-8859-1">
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<meta name="Template"
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content="C:\PROGRAM FILES\MICROSOFT OFFICE\OFFICE\html.dot">
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<meta name="GENERATOR" content="Microsoft FrontPage Express 2.0">
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<title>Regex++, Format String Reference</title>
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<body bgcolor="#FFFFFF" link="#0000FF" vlink="#800080">
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<p> </p>
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<table border="0" cellpadding="7" cellspacing="0" width="100%">
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<tr>
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<td valign="top"><h3><img src="../../c++boost.gif"
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alt="C++ Boost" width="276" height="86"></h3>
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</td>
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<td valign="top"><h3 align="center">Regex++, Format
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String Reference.</h3>
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<p align="left"><i>Copyright (c) 1998-2001 </i></p>
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<p align="left"><i>Dr John Maddock</i></p>
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<p align="left"><i>Permission to use, copy, modify,
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distribute and sell this software and its documentation
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for any purpose is hereby granted without fee, provided
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that the above copyright notice appear in all copies and
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that both that copyright notice and this permission
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notice appear in supporting documentation. Dr John
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Maddock makes no representations about the suitability of
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this software for any purpose. It is provided "as is"
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without express or implied warranty.</i></p>
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</td>
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</tr>
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</table>
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<hr>
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<h3><a name="format_string"></a>Format String Syntax</h3>
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<p>Format strings are used by the algorithms <a
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href="template_class_ref.htm#reg_format">regex_format</a> and <a
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href="template_class_ref.htm#reg_merge">regex_merge</a>, and are
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used to transform one string into another. </p>
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<p>There are three kind of format string: sed, perl and extended,
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the extended syntax is the default so this is covered first. </p>
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<p><b><i>Extended format syntax</i></b> </p>
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<p>In format strings, all characters are treated as literals
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except: ()$\?: </p>
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<p>To use any of these as literals you must prefix them with the
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escape character \ </p>
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<p>The following special sequences are recognized: <br>
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<br>
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</p>
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<p><i>Grouping:</i> </p>
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<p>Use the parenthesis characters ( and ) to group sub-expressions
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within the format string, use \( and \) to represent literal '('
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and ')'. <br>
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<br>
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</p>
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<p><i>Sub-expression expansions:</i> </p>
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<p>The following perl like expressions expand to a particular
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matched sub-expression: <br>
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</p>
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<table border="0" cellpadding="7" cellspacing="0" width="100%">
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">$`</td>
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<td valign="top" width="43%">Expands to all the text from
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the end of the previous match to the start of the current
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match, if there was no previous match in the current
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operation, then everything from the start of the input
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string to the start of the match.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">$'</td>
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<td valign="top" width="43%">Expands to all the text from
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the end of the match to the end of the input string.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">$&</td>
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<td valign="top" width="43%">Expands to all of the
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current match.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">$0</td>
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<td valign="top" width="43%">Expands to all of the
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current match.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">$N</td>
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<td valign="top" width="43%">Expands to the text that
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matched sub-expression <i>N</i>.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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</table>
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<p><br>
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</p>
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<p><i>Conditional expressions:</i> </p>
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<p>Conditional expressions allow two different format strings to
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be selected dependent upon whether a sub-expression participated
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in the match or not: </p>
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<p>?Ntrue_expression:false_expression </p>
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<p>Executes true_expression if sub-expression <i>N</i>
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participated in the match, otherwise executes false_expression. </p>
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<p>Example: suppose we search for "(while)|(for)" then
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the format string "?1WHILE:FOR" would output what
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matched, but in upper case. <br>
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<br>
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</p>
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<p><i>Escape sequences:</i> </p>
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<p>The following escape sequences are also allowed: <br>
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</p>
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<table border="0" cellpadding="7" cellspacing="0" width="100%">
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\a</td>
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<td valign="top" width="43%">The bell character.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\f</td>
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<td valign="top" width="43%">The form feed character.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\n</td>
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<td valign="top" width="43%">The newline character.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\r</td>
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<td valign="top" width="43%">The carriage return
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character.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\t</td>
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<td valign="top" width="43%">The tab character.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\v</td>
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<td valign="top" width="43%">A vertical tab character.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\x</td>
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<td valign="top" width="43%">A hexadecimal character -
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for example \x0D.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\x{}</td>
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<td valign="top" width="43%">A possible unicode
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hexadecimal character - for example \x{1A0}</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\cx</td>
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<td valign="top" width="43%">The ASCII escape character
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x, for example \c@ is equivalent to escape-@.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\e</td>
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<td valign="top" width="43%">The ASCII escape character.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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<tr>
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<td valign="top" width="8%"> </td>
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<td valign="top" width="40%">\dd</td>
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<td valign="top" width="43%">An octal character constant,
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for example \10.</td>
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<td valign="top" width="9%"> </td>
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</tr>
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</table>
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<p><br>
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</p>
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<p><b><i>Perl format strings</i></b> </p>
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<p>Perl format strings are the same as the default syntax except
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that the characters ()?: have no special meaning. </p>
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<p><b><i>Sed format strings</i></b> </p>
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<p>Sed format strings use only the characters \ and & as
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special characters. </p>
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<p>\n where n is a digit, is expanded to the nth sub-expression. </p>
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<p>& is expanded to the whole of the match (equivalent to \0).
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</p>
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<p>Other escape sequences are expanded as per the default syntax.
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<br>
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</p>
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<hr>
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<p><i>Copyright </i><a href="mailto:John_Maddock@compuserve.com"><i>Dr
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John Maddock</i></a><i> 1998-2000 all rights reserved.</i> </p>
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</body>
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</html>
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