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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!-- but may not be published or retransmitted without explicit permission.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/substr.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 13.3</title><link href="strncpy.html" rev=precedes><link href="strupper.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="strncpy.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="strupper.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 13.3</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>Does C have anything like the ``substr''(extract substring)routine present in other languages?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>Not as such.(Onereason it doesn'tis that,as mentioned inquestion <a href="../malloc/malloc2.html">7.2</a>andsection <a href="../charstring/index.html">8</a>,C has no managed string type.)</p><p>To extract a substring of length <TT>LEN</TT>starting at index <TT>POS</TT> in a source string,use something like<pre> char dest[LEN+1]; strncpy(dest, &source[POS], LEN); dest[LEN] = '\0'; /* ensure \0 termination */</pre>or,using the trick fromquestion <a href="strncpy.html">13.2</a>,<pre> char dest[LEN+1] = ""; strncat(dest, &source[POS], LEN);</pre>or,making use of pointer instead of array notation,<pre> strncat(dest, source + POS, LEN);</pre>(The expression <TT>source + POS</TT> is,by definition,identical to <TT>&source[POS]</TT>--seealsosection <a href="../aryptr/index.html">6</a>.)</p><!-- aend --><p><hr><a href="strncpy.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="strupper.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/substr.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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