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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) 2001-2004 IEEE and The Open Group, All Rights Reserved --><title>strtok</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="strtok"></a> <a name="tag_03_742"></a><!-- strtok --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2004 Edition<br>Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_742_01"></a>NAME</h4><blockquote>strtok, strtok_r - split string into tokens</blockquote><h4><a name="tag_03_742_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/string.h.html">string.h</a>><br><br> char *strtok(char *restrict</tt> <i>s1</i><tt>, const char *restrict</tt> <i>s2</i><tt>);<br></tt></code></p><div class="box"><code><tt><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> char *strtok_r(char *restrict</tt> <i>s</i><tt>, const char *restrict</tt> <i>sep</i><tt>,<br> char **restrict</tt> <i>lasts</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_742_03"></a>DESCRIPTION</h4><blockquote><p>For <i>strtok</i>(): <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. Anyconflict between the requirements described here and the ISO C standard is unintentional. This volume ofIEEE Std 1003.1-2001 defers to the ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><p>A sequence of calls to <i>strtok</i>() breaks the string pointed to by <i>s1</i> into a sequence of tokens, each of which isdelimited by a byte from the string pointed to by <i>s2</i>. The first call in the sequence has <i>s1</i> as its first argument,and is followed by calls with a null pointer as their first argument. The separator string pointed to by <i>s2</i> may be differentfrom call to call.</p><p>The first call in the sequence searches the string pointed to by <i>s1</i> for the first byte that is <i>not</i> contained inthe current separator string pointed to by <i>s2</i>. If no such byte is found, then there are no tokens in the string pointed toby <i>s1</i> and <i>strtok</i>() shall return a null pointer. If such a byte is found, it is the start of the first token.</p><p>The <i>strtok</i>() function then searches from there for a byte that <i>is</i> contained in the current separator string. If nosuch byte is found, the current token extends to the end of the string pointed to by <i>s1</i>, and subsequent searches for a tokenshall return a null pointer. If such a byte is found, it is overwritten by a null byte, which terminates the current token. The<i>strtok</i>() function saves a pointer to the following byte, from which the next search for a token shall start.</p><p>Each subsequent call, with a null pointer as the value of the first argument, starts searching from the saved pointer andbehaves as described above.</p><p>The implementation shall behave as if no function defined in this volume of IEEE Std 1003.1-2001 calls<i>strtok</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>strtok</i>() function need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.<img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The <i>strtok_r</i>() function considers the null-terminated string <i>s</i> as a sequence of zero or more text tokens separated byspans of one or more characters from the separator string <i>sep</i>. The argument <i>lasts</i> points to a user-provided pointerwhich points to stored information necessary for <i>strtok_r</i>() to continue scanning the same string.</p><p>In the first call to <i>strtok_r</i>(), <i>s</i> points to a null-terminated string, <i>sep</i> to a null-terminated string ofseparator characters, and the value pointed to by <i>lasts</i> is ignored. The <i>strtok_r</i>() function shall return a pointer tothe first character of the first token, write a null character into <i>s</i> immediately following the returned token, and updatethe pointer to which <i>lasts</i> points.</p><p>In subsequent calls, <i>s</i> is a NULL pointer and <i>lasts</i> shall be unchanged from the previous call so that subsequentcalls shall move through the string <i>s</i>, returning successive tokens until no tokens remain. The separator string <i>sep</i>may be different from call to call. When no token remains in <i>s</i>, a NULL pointer shall be returned. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_742_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>strtok</i>() shall return a pointer to the first byte of a token. Otherwise, if there is notoken, <i>strtok</i>() shall return a null pointer.</p><p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The <i>strtok_r</i>() function shall return a pointer to the token found, or a NULL pointer when no token is found. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_742_05"></a>ERRORS</h4><blockquote><p>No errors are defined.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_742_06"></a>EXAMPLES</h4><blockquote><h5><a name="tag_03_742_06_01"></a>Searching for Word Separators</h5><p>The following example searches for tokens separated by <space>s.</p><pre><tt>#include <string.h>...char *token;char *line = "LINE TO BE SEPARATED";char *search = " ";<br>/* Token will point to "LINE". */token = strtok(line, search);<br>/* Token will point to "TO". */token = strtok(NULL, search);</tt></pre><h5><a name="tag_03_742_06_02"></a>Breaking a Line</h5><p>The following example uses <i>strtok</i>() to break a line into two character strings separated by any combination of<space>s, <tab>s, or <newline>s.</p><pre><tt>#include <string.h>...struct element { char *key; char *data;};...char line[LINE_MAX];char *key, *data;...key = strtok(line, " \n");data = strtok(NULL, " \n");...</tt></pre></blockquote><h4><a name="tag_03_742_07"></a>APPLICATION USAGE</h4><blockquote><p>The <i>strtok_r</i>() function is thread-safe and stores its state in a user-supplied buffer instead of possibly using a staticdata area that may be overwritten by an unrelated call from another thread.</p></blockquote><h4><a name="tag_03_742_08"></a>RATIONALE</h4><blockquote><p>The <i>strtok</i>() function searches for a separator string within a larger string. It returns a pointer to the last substringbetween separator strings. This function uses static storage to keep track of the current string position between calls. The newfunction, <i>strtok_r</i>(), takes an additional argument, <i>lasts</i>, to keep track of the current position in the string.</p></blockquote><h4><a name="tag_03_742_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_742_10"></a>SEE ALSO</h4><blockquote><p>The Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/string.h.html"><i><string.h></i></a></p></blockquote><h4><a name="tag_03_742_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_742_12"></a>Issue 5</h4><blockquote><p>The <i>strtok_r</i>() function is included for alignment with the POSIX Threads Extension.</p><p>A note indicating that the <i>strtok</i>() function need not be reentrant is added to the DESCRIPTION.</p></blockquote><h4><a name="tag_03_742_13"></a>Issue 6</h4><blockquote><p>Extensions beyond the ISO C standard are marked.</p><p>The <i>strtok_r</i>() function is marked as part of the Thread-Safe Functions option.</p><p>In the DESCRIPTION, the note about reentrancy is expanded to cover thread-safety.</p><p>The APPLICATION USAGE section is updated to include a note on the thread-safe function and its avoidance of possibly using astatic data area.</p><p>The <b>restrict</b> keyword is added to the <i>strtok</i>() and <i>strtok_r</i>() prototypes for alignment with theISO/IEC 9899:1999 standard.</p></blockquote><div class="box"><em>End of informative text.</em></div><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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