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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN"><!-- This collection of hypertext pages is Copyright 1995-2005 by Steve Summit. --><!-- Content from the book "C Programming FAQs: Frequently Asked Questions" --><!-- (Addison-Wesley, 1995, ISBN 0-201-84519-9) is made available here by --><!-- permission of the author and the publisher as a service to the community. --><!-- It is intended to complement the use of the published text --><!-- and is protected by international copyright laws. --><!-- The on-line content may be accessed freely for personal use --><!-- but may not be published or retransmitted without explicit permission. --><!-- --><!-- this page built Sat Dec 24 21:47:46 2005 by faqproc version 2.7 --><!-- from source file lib1.sgml dated Sat Feb 7 18:46:53 2004 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/lib/strtok.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:58 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 13.6</title><link href="toupper.html" rev=precedes><link href="regex.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="toupper.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="regex.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../index-2.html"><img src="../images/buttontop.gif" alt="top/contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><hr><p><!-- qbegin --><h1>comp.lang.c FAQ list<font color=blue>·</font><!-- qtag -->Question 13.6</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>How can I split up astringintowhitespace-separated fields?<br>How can I duplicate the processby which <TT>main()</TT>is handed <TT>argc</TT> and <TT>argv</TT>?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>The only Standard functionavailableforthis kind of``tokenizing''is<TT>strtok</TT>,although it can be tricky to use<a href="strtokstate.html" rel=subdocument>[footnote]</a>and it may not do everything you want it to.(For instance, it does not handle quoting.)Here is a usage example,which simply prints each field as it's extracted:<pre>#include <stdio.h>#include <string.h>char string[] = "this is a test"; /* not char *; see Q <a href="../strangeprob/strlitnomod.html">16.6</a> */char *p;for(p = strtok(string, " \t\n"); p != NULL; p = strtok(NULL, " \t\n")) printf("\"%s\"\n", p);</pre></p><p>As an alternative,here is a routine I usefor building an <TT>argv</TT> all at once:<pre>#include <ctype.h>int makeargv(char *string, char *argv[], int argvsize){ char *p = string; int i; int argc = 0; for(i = 0; i < argvsize; i++) { /* skip leading whitespace */ while(isspace(*p)) p++; if(*p != '\0') argv[argc++] = p; else { argv[argc] = 0; break; } /* scan over arg */ while(*p != '\0' && !isspace(*p)) p++; /* terminate arg: */ if(*p != '\0' && i < argvsize-1) *p++ = '\0'; } return argc;}</pre></p><p>Calling <TT>makeargv</TT> is straightforward:<pre> char *av[10]; int i, ac = makeargv(string, av, 10); for(i = 0; i < ac; i++) printf("\"%s\"\n", av[i]);</pre></p><p>If you want each separator character to be significant,for instance if you want two tabs in a row to indicate an omitted field,it's probablymore straightforwardto use <TT>strchr</TT>:<pre>#include <stdio.h>#include <string.h>char string[] = "this\thas\t\tmissing\tfield";char *p = string;while(1) { /* break in middle */ char *p2 = strchr(p, '\t'); if(p2 != NULL) *p2 = '\0'; printf("\"%s\"\n", p); if(p2 == NULL) break; p = p2 + 1;}</pre></p><p>All thecode fragmentspresented heremodify theinput string,by inserting<TT>\0</TT>'sto terminate each field(meaning that the string must be writable;see question <a href="../decl/strlitinit.html">1.32</a>).If you'll need the original string later,make a copy before breaking it up.</p><p>References:K&R2 Sec. B3 p. 250<br>ISO Sec. 7.11.5.8<br>H&S Sec. 13.7 pp. 333-4<br>PCS p. 178<br></p><!-- aend --><p><hr><a href="toupper.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="regex.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../questions.html"><img src="../images/buttontop.gif" alt="contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><br><!-- lastfooter --><a href="../about.html">about this FAQ list</a> <a href="../eskimo.html">about eskimo</a> <a href="../search.html">search</a> <a href="../feedback.html">feedback</a> <a href="copyright.html">copyright</a><p>Hosted by<a href="http://www.eskimo.com/"><img src="../../www.eskimo.com/img/link/eskitiny.gif" alt="Eskimo North"></a></body><!-- Mirrored from c-faq.com/lib/strtok.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:58 GMT --></html>⌨️ 快捷键说明
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