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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!-- but may not be published or retransmitted without explicit permission.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 stdio.sgml dated Wed Dec 21 13:07:57 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/stdio/commaprint.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:57 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 12.11</title><link href="printfvwid.html" rev=precedes><link href="scanf1.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="printfvwid.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="scanf1.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 12.11</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>How can I print numbers with commas separating the thousands?<br>What about currency formatted numbers?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>The functions in <TT><locale.h></TT>begin to provide some supportfor these operations,butthereis no standard C functionfor doing eithertask.(In Standard C, the only thing <TT>printf</TT> doesin response to a custom locale settingis to change itsdecimal-point character.)</p><p>POSIX specifies a <TT>strfmon</TT> function for formatting monetary quantitiesin a locale-appropriate way,and that the apostrophe flag in a numeric <TT>printf</TT> format specifier(e.g. <TT>%'d</TT>, <TT>%'f</TT>)requests comma-separated digits.</p><p>Here is a little routine for formatting comma-separated numbers,using the locale's thousands separator, if available:<pre>#include <locale.h>char *commaprint(unsigned long n){ static int comma = '\0'; static char retbuf[30]; char *p = &retbuf[sizeof(retbuf)-1]; int i = 0; if(comma == '\0') { struct lconv *lcp = localeconv(); if(lcp != NULL) { if(lcp->thousands_sep != NULL && *lcp->thousands_sep != '\0') comma = *lcp->thousands_sep; else comma = ','; } } *p = '\0'; do { if(i%3 == 0 && i != 0) *--p = comma; *--p = '0' + n % 10; n /= 10; i++; } while(n != 0); return p;}</pre>(A better implementation would usethe <TT>grouping</TT> field ofthe <TT>lconv</TT> structure,rather than assuming groups of three digits.A safer size for <TT>retbuf</TT> might be<TT>4*(sizeof(long)*CHAR_BIT+2)/3/3+1</TT>;see question <a href="sprintfsize.html">12.21</a>.)</p><p>References:ISO Sec. 7.4<br>H&S Sec. 11.6 pp. 301-4<br></p><!-- aend --><p><hr><a href="printfvwid.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="scanf1.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/stdio/commaprint.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:57 GMT --></html>⌨️ 快捷键说明
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