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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 49] 49.3 Gotchas in Base Conversion </TITLE><METANAME="DC.title"CONTENT="UNIX Power Tools"><METANAME="DC.creator"CONTENT="Jerry Peek, Tim O'Reilly & Mike Loukides"><METANAME="DC.publisher"CONTENT="O'Reilly & Associates, Inc."><METANAME="DC.date"CONTENT="1998-08-04T21:56:40Z"><METANAME="DC.type"CONTENT="Text.Monograph"><METANAME="DC.format"CONTENT="text/html"SCHEME="MIME"><METANAME="DC.source"CONTENT="1-56592-260-3"SCHEME="ISBN"><METANAME="DC.language"CONTENT="en-US"><METANAME="generator"CONTENT="Jade 1.1/O'Reilly DocBook 3.0 to HTML 4.0"><LINKREV="made"HREF="mailto:online-books@oreilly.com"TITLE="Online Books Comments"><LINKREL="up"HREF="ch49_01.htm"TITLE="49. Working with Numbers"><LINKREL="prev"HREF="ch49_02.htm"TITLE="49.2 bc: Hexadecimal or Binary Conversion "><LINKREL="next"HREF="ch49_04.htm"TITLE="49.4 bc's Sine and Cosine Are in Radians "></HEAD><BODYBGCOLOR="#FFFFFF"TEXT="#000000"><DIVCLASS="htmlnav"><H1><IMGSRC="gifs/smbanner.gif"ALT="UNIX Power Tools"USEMAP="#srchmap"BORDER="0"></H1><MAPNAME="srchmap"><AREASHAPE="RECT"COORDS="0,0,466,58"HREF="index.htm"ALT="UNIX Power Tools"><AREASHAPE="RECT"COORDS="467,0,514,18"HREF="jobjects/fsearch.htm"ALT="Search this book"></MAP><TABLEWIDTH="515"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch49_02.htm"TITLE="49.2 bc: Hexadecimal or Binary Conversion "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 49.2 bc: Hexadecimal or Binary Conversion "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 49<BR>Working with Numbers</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch49_04.htm"TITLE="49.4 bc's Sine and Cosine Are in Radians "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 49.4 bc's Sine and Cosine Are in Radians "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-3923">49.3 Gotchas in Base Conversion </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-58564"></A>Say you want to convert between octal and hex, and you type:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>bcibase=8obase=1617</B></CODE>11</PRE></BLOCKQUOTE></P><PCLASS="para">It looks like something's gone haywire.17 octal ought to be F hexadecimal, not 11.What's wrong?</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-58572"></A><ACLASS="indexterm"NAME="AUTOID-58573"></A>In fact, since you set <EMCLASS="emphasis">ibase</EM> to octal before you set <EMCLASS="emphasis">obase</EM>, what youreally asked for was <EMCLASS="emphasis">obase</EM> equal to 16 octal (14 decimal)!</P><PCLASS="para">In short, always set <EMCLASS="emphasis">obase</EM> before <EMCLASS="emphasis">ibase</EM>, or you're in for asurprise.</P><PCLASS="para">Similarly, suppose you'd set <EMCLASS="emphasis">ibase</EM> to 16, and want to set itback to 10. You need to type:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">ibase=A</PRE></BLOCKQUOTE></P><PCLASS="para">not:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">ibase=10</PRE></BLOCKQUOTE></P><PCLASS="para">Another thing to look out for is typing a hex digit when <EMCLASS="emphasis">ibase</EM>is set to something other than 16. <EMCLASS="emphasis">bc</EM> isn't smart enough toreject the input, and gives you back garbage.</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">TOR</SPAN></P></DIV></DIV><DIVCLASS="htmlnav"><P></P><HRALIGN="LEFT"WIDTH="515"TITLE="footer"><TABLEWIDTH="515"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch49_02.htm"TITLE="49.2 bc: Hexadecimal or Binary Conversion "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 49.2 bc: Hexadecimal or Binary Conversion "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><ACLASS="book"HREF="index.htm"TITLE="UNIX Power Tools"><IMGSRC="gifs/txthome.gif"SRC="gifs/txthome.gif"ALT="UNIX Power Tools"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch49_04.htm"TITLE="49.4 bc's Sine and Cosine Are in Radians "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 49.4 bc's Sine and Cosine Are in Radians "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">49.2 bc: Hexadecimal or Binary Conversion </TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><ACLASS="index"HREF="index/idx_0.htm"TITLE="Book Index"><IMGSRC="gifs/index.gif"SRC="gifs/index.gif"ALT="Book Index"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172">49.4 bc's Sine and Cosine Are in Radians </TD></TR></TABLE><HRALIGN="LEFT"WIDTH="515"TITLE="footer"><IMGSRC="gifs/smnavbar.gif"SRC="gifs/smnavbar.gif"USEMAP="#map"BORDER="0"ALT="The UNIX CD Bookshelf Navigation"><MAPNAME="map"><AREASHAPE="RECT"COORDS="0,0,73,21"HREF="../index.htm"ALT="The UNIX CD Bookshelf"><AREASHAPE="RECT"COORDS="74,0,163,21"HREF="index.htm"ALT="UNIX Power Tools"><AREASHAPE="RECT"COORDS="164,0,257,21"HREF="../unixnut/index.htm"ALT="UNIX in a Nutshell"><AREASHAPE="RECT"COORDS="258,0,321,21"HREF="../vi/index.htm"ALT="Learning the vi Editor"><AREASHAPE="RECT"COORDS="322,0,378,21"HREF="../sedawk/index.htm"ALT="sed & awk"><AREASHAPE="RECT"COORDS="379,0,438,21"HREF="../ksh/index.htm"ALT="Learning the Korn Shell"><AREASHAPE="RECT"COORDS="439,0,514,21"HREF="../lrnunix/index.htm"ALT="Learning the UNIX Operating System"></MAP></DIV></BODY></HTML>⌨️ 快捷键说明
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