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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.fseek" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>fseek</refname>
<refpurpose>Seeks on a file pointer</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>int</type><methodname>fseek</methodname>
<methodparam><type>resource</type><parameter>stream</parameter></methodparam>
<methodparam><type>int</type><parameter>offset</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>whence</parameter><initializer><constant>SEEK_SET</constant></initializer></methodparam>
</methodsynopsis>
<para>
Sets the file position indicator for the file referenced by
<parameter>stream</parameter>. The new position, measured in bytes
from the beginning of the file, is obtained by adding
<parameter>offset</parameter> to the position specified by
<parameter>whence</parameter>.
</para>
<para>
In general, it is allowed to seek past the end-of-file; if data is then
written, reads in any unwritten region between the end-of-file and the
sought position will yield bytes with value 0. However, certain streams
may not support this behavior, especially when they have an underlying
fixed size storage.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>stream</parameter></term>
<listitem>
&fs.file.pointer;
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>offset</parameter></term>
<listitem>
<para>
The offset.
</para>
<para>
To move to a position before the end-of-file, you need to pass
a negative value in <parameter>offset</parameter> and
set <parameter>whence</parameter>
to <constant>SEEK_END</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>whence</parameter></term>
<listitem>
<para>
<parameter>whence</parameter> values are:
<simplelist>
<member><constant>SEEK_SET</constant> - Set position equal to <parameter>offset</parameter> bytes.</member>
<member><constant>SEEK_CUR</constant> - Set position to current location plus <parameter>offset</parameter>.</member>
<member><constant>SEEK_END</constant> - Set position to end-of-file plus <parameter>offset</parameter>.</member>
</simplelist>
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Upon success, returns 0; otherwise, returns -1.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>fseek</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
$fp = fopen('somefile.txt', 'r');
// read some data
$data = fgets($fp, 4096);
// move back to the beginning of the file
// same as rewind($fp);
fseek($fp, 0);
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="notes">
&reftitle.notes;
<note>
<para>
If you have opened the file in append (<literal>a</literal> or
<literal>a+</literal>) mode, any data you write to the file will always be
appended, regardless of the file position, and the result of calling
<function>fseek</function> will be undefined.
</para>
</note>
<note>
<para>
Not all streams support seeking. For those that do not support seeking,
forward seeking from the current position is accomplished by reading
and discarding data; other forms of seeking will fail.
</para>
</note>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>ftell</function></member>
<member><function>rewind</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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