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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 45] 45.14 Finding the Last Command-Line Argument </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="1998-08-04T21:54:37Z"><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="ch45_01.htm"TITLE="45. Shell Programming for the Initiated"><LINKREL="prev"HREF="ch45_13.htm"TITLE="45.13 Save Disk Space and Programming: Multiple Names for a Program"><LINKREL="next"HREF="ch45_15.htm"TITLE="45.15 How to Unset all Command-Line Parameters "></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="ch45_13.htm"TITLE="45.13 Save Disk Space and Programming: Multiple Names for a Program"><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 45.13 Save Disk Space and Programming: Multiple Names for a Program"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 45<BR>Shell Programming for the Initiated</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch45_15.htm"TITLE="45.15 How to Unset all Command-Line Parameters "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 45.15 How to Unset all Command-Line Parameters "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0236">45.14 Finding the Last Command-Line Argument </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-53235"></A>Do you need to pick up the last parameter <CODECLASS="literal">$1</CODE>, <CODECLASS="literal">$2</CODE> <CODECLASS="literal">...</CODE>from the parameter list [the "command line"-<EMCLASS="emphasis">JP</EM> ]?It looks like <CODECLASS="literal">eval \$$#</CODE> would do it:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"> <ACLASS="co"HREF="ch08_10.htm"TITLE="8.10 eval: When You Need Another Chance ">eval</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">$ <CODECLASS="userinput"><B>set foo bar baz</B></CODE>$ <CODECLASS="userinput"><B>eval echo \$$#</B></CODE><ACLASS="indexterm"NAME="AUTOID-53248"></A>baz</PRE></TD></TR></TABLE></P><PCLASS="para"> except for a small problem with <EMCLASS="emphasis">sh</EM> argument syntax:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">$ <CODECLASS="userinput"><B>set m n o p q r s t u v w x</B></CODE>$ <CODECLASS="userinput"><B>echo $11</B></CODE>m1</PRE></BLOCKQUOTE></P><PCLASS="para"><CODECLASS="literal">$11</CODE> means <CODECLASS="literal">${1}1</CODE>, and not <CODECLASS="literal">${11}</CODE>.Trying <CODECLASS="literal">${11}</CODE> directly gives <CODECLASS="literal">bad substitution</CODE>.</P><PCLASS="para">The only reliable way to get at the last parameter is to use something like</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">for i do last="$i"; done</PRE></BLOCKQUOTE></P><PCLASS="para">[That <EMCLASS="emphasis">for</EM> loop assigns each parameter to the shell variable named<EMCLASS="emphasis">last</EM>;after the loop ends, <CODECLASS="literal">$last</CODE> will have the last parameter.Also, note that you won't need this trick on all <EMCLASS="emphasis">sh</EM>-like shells.The Korn shell and <EMCLASS="emphasis">bash</EM> understand <CODECLASS="literal">${11}</CODE>. <EMCLASS="emphasis">-JP</EM> ]</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">CT</SPAN> <SPANCLASS="bibliomisc">in <ACLASS="systemitem.newsgroup"HREF="news:comp.unix.questions">comp.unix.questions</A> on Usenet, 15 January 1990</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="ch45_13.htm"TITLE="45.13 Save Disk Space and Programming: Multiple Names for a Program"><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 45.13 Save Disk Space and Programming: Multiple Names for a Program"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="ch45_15.htm"TITLE="45.15 How to Unset all Command-Line Parameters "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 45.15 How to Unset all Command-Line Parameters "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">45.13 Save Disk Space and Programming: Multiple Names for a Program</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">45.15 How to Unset all Command-Line Parameters </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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