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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>ftell</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="ftell"></a> <a name="tag_03_196"></a><!-- ftell --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_196_01"></a>NAME</h4><blockquote>ftell, ftello - return a file offset in a stream</blockquote><h4><a name="tag_03_196_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/stdio.h.html">stdio.h</a>><br><br> long ftell(FILE *</tt><i>stream</i><tt>);<br></tt></code></p><div class="box"><code><tt><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> off_t ftello(FILE *</tt><i>stream</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]"border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_196_03"></a>DESCRIPTION</h4><blockquote><div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between therequirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers tothe ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div><p>The <i>ftell</i>() function shall obtain the current value of the file-position indicator for the stream pointed to by<i>stream</i>.</p><p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> The<i>ftello</i>() function shall be equivalent to <i>ftell</i>(), except that the return value is of type <b>off_t</b>. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_196_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>ftell</i>() <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> and <i>ftello</i>() <img src="../images/opt-end.gif" alt="[Option End]" border="0"> shall return the current value of the file-position indicator for the stream measured in bytesfrom the beginning of the file.</p><p>Otherwise, <i>ftell</i>() <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> and <i>ftello</i>() <img src="../images/opt-end.gif" alt="[Option End]" border="0"> shall return-1, cast to <b>long</b> and <b>off_t</b> respectively, and set <i>errno</i> to indicate the error.</p></blockquote><h4><a name="tag_03_196_05"></a>ERRORS</h4><blockquote><p>The <i>ftell</i>() <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> and <i>ftello</i>() <img src="../images/opt-end.gif" alt="[Option End]" border="0"> functionsshall fail if:</p><dl compact><dt>[EBADF]</dt><dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The file descriptor underlying <i>stream</i> is not an open file descriptor. <img src="../images/opt-end.gif" alt="[Option End]"border="0"></dd><dt>[EOVERFLOW]</dt><dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">For <i>ftell</i>(), the current file offset cannot be represented correctly in an object of type <b>long</b>. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd><dt>[EOVERFLOW]</dt><dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">For <i>ftello</i>(), the current file offset cannot be represented correctly in an object of type <b>off_t</b>. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd><dt>[ESPIPE]</dt><dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The file descriptor underlying <i>stream</i> is associated with a pipe or FIFO. <img src="../images/opt-end.gif" alt="[Option End]"border="0"></dd></dl><p>The <i>ftell</i>() function may fail if:</p><dl compact><dt>[ESPIPE]</dt><dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The file descriptor underlying <i>stream</i> is associated with a socket. <img src="../images/opt-end.gif" alt="[Option End]"border="0"></dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_196_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_196_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_196_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_196_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_196_10"></a>SEE ALSO</h4><blockquote><p><a href="fgetpos.html"><i>fgetpos</i>()</a> , <a href="fopen.html"><i>fopen</i>()</a> , <a href="fseek.html"><i>fseek</i>()</a>, <a href="lseek.html"><i>lseek</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/stdio.h.html"><i><stdio.h></i></a></p></blockquote><h4><a name="tag_03_196_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</p></blockquote><h4><a name="tag_03_196_12"></a>Issue 5</h4><blockquote><p>Large File Summit extensions are added.</p></blockquote><h4><a name="tag_03_196_13"></a>Issue 6</h4><blockquote><p>Extensions beyond the ISO C standard are marked.</p><p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p><ul><li><p>The <i>ftello</i>() function is added.</p></li><li><p>The [EOVERFLOW] error conditions are added.</p></li></ul><p>An additional [ESPIPE] error condition is added for sockets.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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