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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!-- but may not be published or retransmitted without explicit permission.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 21:47:47 2005 by faqproc version 2.7 --><!-- from source file osdepfile.sgml dated Sat Jun 26 20:52:13 2004 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/osdep/insdelrec.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:59:02 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 19.14</title><link href="ftruncate.html" rev=precedes><link href="fdfilename.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="ftruncate.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="fdfilename.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 19.14</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>How can I insert or delete a line(or record)in the middle of a file?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>In general, there is no way todo this.<a href="nonseq.html" rel=subdocument>[footnote]</a>The usual solution is simply to rewrite the file.</p><p>When you find yourself needing to insert datainto an existing file,here are a few alternatives you can try:</p><UL><li>Rearrange the data file so that you can append the new information at the end.<li>Put the information in a second file.<li>Leave some blank space(e.g. a line of 80 spaces,or a field like <TT>0000000000</TT>)in the file when it is first written,and overwrite itlaterwith the finalinformation(see also question <a href="../stdio/fupdate.html">12.30</a>).(This technique is most portable in binary mode;on some systems,overwriting a text file may truncate it.)<li>Use a databaseinstead of a flat file.</UL><p>Instead of actually deleting records,you might considerjust marking them as deleted,and having the code which reads the file ignore them.(You could run a separatecoalescionprogram once in a whileto rewrite the file,finallydiscardingthe deleted records.Or,if the records are all the same length,you could take the last recordand use it to overwrite the record to be deleted,then truncate the file.)</p><p>See also questions<a href="../stdio/fupdate.html">12.30</a>and<a href="ftruncate.html">19.13</a>.</p><p>Additional links:<a href="insertf.20000216.html">further reading</a></p><!-- aend --><p><hr><a href="ftruncate.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="fdfilename.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/osdep/insdelrec.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:59:02 GMT --></html>⌨️ 快捷键说明
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