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<?xml version="1.0" encoding="UTF-8"?>
<!--
* Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
* Copyright (C) INRIA
*
* This file must be used under the terms of the CeCILL.
* This source file is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at
* http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
*
-->
<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:svg="http://www.w3.org/2000/svg" xmlns:ns5="http://www.w3.org/1999/xhtml" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:db="http://docbook.org/ns/docbook" xmlns:scilab="http://www.scilab.org" xml:id="grep" xml:lang="en">
<refnamediv>
<refname>grep</refname>
<refpurpose>find matches of a string in a vector of strings</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Calling Sequence</title>
<synopsis>row = grep(haystack, needle )
[row, which] = grep(haystack, needle )
row = grep(haystack, needle, [flag])
[row, which] = grep(haystack, needle, [flag])
</synopsis>
</refsynopsisdiv>
<refsection>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term>haystack</term>
<listitem>
<para>a row vector of character strings.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>needle</term>
<listitem>
<para>
a character string or a row vector of character strings. The
string(s) to search in <varname>haystack</varname>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>row</term>
<listitem>
<para>
a vector of indices: row where a match has been found or an
empty matrix if no match found.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>which</term>
<listitem>
<para>
a vector of indices: index of <varname>needle</varname> string found
or an empty matrix if no match found.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>flag</term>
<listitem>
<para>
a character (<literal>"r"</literal> for regular expression).
</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Description</title>
<para>
For each entry of <varname>haystack</varname>, <function>grep</function>
searches if at least a string in <varname>needle</varname> which matches a
substring. The <varname>haystack</varname> entries index where at least a
match has been found are returned in the <varname>row</varname> output
argument. The optional <varname>which</varname> output argument gives the
index of first string of <varname>needle</varname> found.
</para>
<para>
When using the third parameter <varname>flag</varname><literal>="r"</literal>, the
<varname>needle</varname> is expected to be a regular expression string.
In this case, <function>grep</function> uses the
<varname>needle</varname> as a regular expression and compares it
against <varname>haystack</varname> according to the regular expressions
rules. See the <link linkend="regexp">regexp</link> function for details about
regular expressions.
</para>
</refsection>
<refsection>
<title>Example #1</title>
<para>
In the following example, we search one or two strings in a text,
which is stored in the <varname>txt</varname> variable.
</para>
<programlisting role="example"><![CDATA[
txt=['find matches of a string in a vector of strings'
'search position of a character string in an other string'
'Compare Strings'];
grep(txt,'strings')
grep(txt,['strings' 'Strings'])
[r,w]=grep(txt,['strings' 'Strings'])
]]></programlisting>
</refsection>
<refsection>
<title>Example #2</title>
<para>In the following example, we perform regexp searches.</para>
<programlisting role="example"><![CDATA[
str = ["hat";"cat";"hhat";"chat";"hcat";"ccchat";"at";"dog"]
grep(str,'/[hc]+at/','r')
grep(str,'/[hc]?at/','r')
grep(str,'/cat|dog/','r')
]]></programlisting>
</refsection>
<refsection role="see also">
<title>See Also</title>
<simplelist type="inline">
<member>
<link linkend="strindex">strindex</link>
</member>
<member>
<link linkend="regexp">regexp</link>
</member>
</simplelist>
</refsection>
</refentry>
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