1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2<HTML> 3<HEAD> 4 <TITLE>Class Template basic_grep_filter</TITLE> 5 <LINK REL="stylesheet" HREF="../../../../boost.css"> 6 <LINK REL="stylesheet" HREF="../theme/iostreams.css"> 7</HEAD> 8<BODY> 9 10<!-- Begin Banner --> 11 12 <H1 CLASS="title">Class Template <CODE>basic_grep_filter</CODE></H1> 13 <HR CLASS="banner"> 14 15<!-- End Banner --> 16 17<DL class="page-index"> 18 <DT><A href="#description">Description</A></DT> 19 <DT><A href="#headers">Headers</A></DT> 20 <DT><A href="#installation">Installation</A></DT> 21 <DT><A href="#reference">Reference</A></DT> 22</DL> 23 24<HR> 25 26<A NAME="description"></A> 27<H2>Description</H2> 28 29<P> 30 The class template <CODE>basic_grep_filter</CODE> filters a character sequence line by line using a regular expression provided at construction, in a manner similar to the command-line utility <i>grep</i> (<A CLASS="bib_ref" HREF="../bibliography.html#grep">[IEEE]</A>). The filter uses regular expressions from the <A HREF="http://www.boost.org/libs/regex" TARGET="_top">Boost Regular Expression Library</A> (<A CLASS="bib_ref" HREF="../bibliography.html#maddock">[Maddock]</A>). 31</P> 32<P> 33 By default, the filtered character sequence consists of those lines of the unfiltered sequence that contain a subsequence matching the regular expression. By specifying appropriate options at construction, <CODE>basic_grep_filter</CODE> can be made to pass through only those lines which exactly match the regular expression (as if the option <i>-x</i> had been passed to the command-line utility) or only those lines that <i>do not</i> contain a match (as if the option <i>-v</i> had been passed to the command-line utility). 34</P> 35<P> 36 A running count of the lines in the filtered character sequence is available via the member function <code><a href="#count">count</a></code>. 37</P> 38 39<A NAME="headers"></A> 40<H2>Headers</H2> 41 42<DL class="page-index"> 43 <DT><A CLASS="header" HREF="../../../../boost/iostreams/filter/grep.hpp"><CODE><boost/iostreams/filter/grep.hpp></CODE></A></DT> 44</DL> 45 46<A NAME="installation"></A> 47<H2>Installation</H2> 48 49<P> 50 The template <CODE>basic_grep_filter</CODE> uses the <A HREF="http://www.boost.org/libs/regex" TARGET="_top">Boost Regular Expression Library</A>, which must be built separately. See <A HREF="http://www.boost.org/libs/regex/doc/html/boost_regex/install.html" TARGET="_top">here</A> for details. 51</P> 52 53<A NAME="reference"></A> 54<H2>Reference</H2> 55 56<H4>Synopsis</H4> 57 58<PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams { 59 60<SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/function.hpp" TARGET="_top"><SPAN CLASS="literal"><boost/function.hpp></SPAN></A> 61<SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/regex.hpp" TARGET="_top"><SPAN CLASS="literal"><boost/regex.hpp></SPAN></A> 62 63<SPAN CLASS="keyword">namespace</SPAN> grep { 64 65<SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> invert; 66<SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> whole_line; 67 68} 69 70<SPAN CLASS="keyword">template</SPAN>< <SPAN CLASS="keyword">typename</SPAN> <A HREF="#template_params" CLASS="documented">Ch</A>, 71 <SPAN CLASS="keyword">typename</SPAN> <A HREF="#template_params" CLASS="documented">Tr</A> = regex_traits<Ch>, 72 <SPAN CLASS="keyword">typename</SPAN> <A HREF="#template_params" CLASS="documented">Alloc</A> = std::allocator<Ch> > 73<SPAN CLASS="keyword">class</SPAN> <A HREF="#template_params" CLASS="documented">basic_grep_filter</A> { 74<SPAN CLASS="keyword">public:</SPAN> 75 <A CLASS="documented" HREF="#constructor">basic_grep_filter</A>( <SPAN CLASS="keyword">const</SPAN> basic_regex<Ch, Tr, Alloc>& pattern, 76 regex_constants::match_flag_type flags = 77 regex_constants::match_default, 78 <SPAN CLASS="keyword">int</SPAN> options = <SPAN CLASS="numeric_literal">0</SPAN> ); 79 <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#count">count</A>() <SPAN CLASS="keyword">const</SPAN>; 80}; 81 82<SPAN CLASS="keyword">typedef</SPAN> basic_grep_filter<<SPAN CLASS="keyword">char</SPAN>> <SPAN CLASS="defined">grep_filter</SPAN>; 83<SPAN CLASS="keyword">typedef</SPAN> basic_grep_filter<<SPAN CLASS="keyword">wchar_t</SPAN>> <SPAN CLASS="defined">wgrep_filter</SPAN>; 84 85} } // End namespace boost::io</PRE> 86 87<A NAME="template_params"></A> 88<H4>Template parameters</H4> 89 90<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2> 91<TR> 92 <TR> 93 <TD VALIGN="top"><I>Ch</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> 94 <TD>The character type</TD> 95 </TR> 96 <TR> 97 <TD VALIGN="top"><I>Tr</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> 98 <TD>The <A HREF="http://www.boost.org/libs/regex/doc/html/boost_regex/ref/regex_traits.html" TARGET="_top">regular expression traits</A> type</TD> 99 </TR> 100 <TR> 101 <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> 102 <TD>A standard library allocator type (<A CLASS="bib_ref" HREF="../bibliography.html#iso">[ISO]</A>, 20.1.5), used to allocate character buffers</TD> 103 </TR> 104</TABLE> 105 106<A NAME="constructor"></A> 107<H4><CODE>basic_grep_filter::basic_grep_filter</CODE></H4> 108 109<PRE CLASS="broken_ie"> <B>basic_grep_filter</B>( <SPAN CLASS="keyword">const</SPAN> basic_regex<Ch, Tr, Alloc>& pattern, 110 regex_constants::match_flag_type flags = 111 regex_constants::match_default, 112 <SPAN CLASS="keyword">int</SPAN> options = <SPAN CLASS="numeric_literal">0</SPAN> );</PRE> 113 114<P>Constructs a <CODE>basic_grep_filter</CODE> from the given regular expression, match flags, and grep options. The parameters have the following interpretations:</P> 115 116<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2> 117<TR> 118 <TR> 119 <TD VALIGN="top"><I>pattern</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> 120 <TD>The regular expression to be matched against the stream of unfiltered data</TD> 121 </TR> 122 <TR> 123 <TD VALIGN="top"><I>flags</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> 124 <TD>The flags passed to <A HREF="http://www.boost.org/libs/regex/doc/html/boost_regex/ref/regex_search.html" TARGET="_top">regex_search</A> or <A HREF="http://www.boost.org/libs/regex/doc/html/boost_regex/ref/regex_match.html" TARGET="_top">regex_match</A> to specify regular expression matching behavior</TD> 125 </TR> 126 <TR> 127 <TD VALIGN="top"><I>options</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> 128 <TD>A bitwise OR of zero or more constants from the namespace <CODE>boost::iostreams::grep</CODE>. Currently two constants are recongnized: <CODE>grep::whole_line</CODE> causes the filter to pass through only those lines which exactly match the regular expression, and <CODE>grep::invert</CODE> causes the filter to pass through only those lines that <i>do not</i> contain a match.</TD> 129 </TR> 130</TABLE> 131 132</P> 133 134<A NAME="count"></A> 135<H4><CODE>basic_grep_filter::count</CODE></H4> 136 137<A NAME="second_constructor"></A> 138 139<PRE CLASS="broken_ie"> <SPAN CLASS="keyword">int</SPAN> count() <SPAN CLASS="keyword">const</SPAN>;</PRE> 140 141<P>Returns a running count of the lines passed through from the unfiltered character sequence to the filtered character sequence. The count is reset to zero automatically when the filter begins processing a new character sequence.</P> 142 143<!-- Begin Footer --> 144 145<HR> 146 147<P CLASS="copyright">© Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a></P> 148<P CLASS="copyright"> 149 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">http://www.boost.org/LICENSE_1_0.txt</A>) 150</P> 151 152<!-- End Footer --> 153 154</BODY> 155