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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 45] 45.17 Making a for Loop with Multiple Variables </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="1998-08-04T21:54:41Z"><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_16.htm"TITLE="45.16 Standard Input to a for Loop "><LINKREL="next"HREF="ch45_18.htm"TITLE="45.18 Using basename and dirname "></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_16.htm"TITLE="45.16 Standard Input to a for Loop "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 45.16 Standard Input to a for Loop "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_18.htm"TITLE="45.18 Using basename and dirname "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 45.18 Using basename and dirname "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0216">45.17 Making a for Loop with Multiple Variables </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-53345"></A><ACLASS="indexterm"NAME="AUTOID-53348"></A><ACLASS="indexterm"NAME="AUTOID-53351"></A>The normal Bourne shell<SPANCLASS="link"><EMCLASS="emphasis">for</EM> loop (<ACLASS="linkend"HREF="ch44_16.htm"TITLE="Handling Command-Line Arguments with a for Loop ">44.16</A>)</SPAN>lets you take a list of items, storethe items one by one in a shell variable, and loop through a set of commandsonce for each item: </P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">for file in prog1 prog2 prog3do <ICLASS="lineannotation">...process $file</I>done</PRE></BLOCKQUOTE></P><PCLASS="para">I wanted a <EMCLASS="emphasis">for</EM> loop that stores several different shell variablesand makes one pass through the loop for each <EMCLASS="emphasis">set</EM> of variables (insteadof one pass for each <EMCLASS="emphasis">item</EM>, as a regular <EMCLASS="emphasis">for</EM> loop does).This loop does the job:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"> <ACLASS="co"HREF="ch44_19.htm"TITLE="44.19 The Bourne Shell set Command ">set</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">for bunch in "ellie file16" "donna file23" "steve file34"do # PUT FIRST WORD (USER) IN $1, SECOND (FILE) IN $2...<ACLASS="indexterm"NAME="AUTOID-53366"></A> set $bunch mail $1 < $2done</PRE></TD></TR></TABLE></P><PCLASS="para">If you have any command-line arguments and still need them, store them inanother variable before you do that.Or, you can make the loop this way:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">for bunch in "u=ellie f=file16 s='your files'" \ "u=donna f=file23 s='a memo'" "u=steve f=file34 s=report"do # SET $u (USER), $f (FILENAME), $s (SUBJECT): eval $bunch mail -s "$s" $u < $fdone</PRE></BLOCKQUOTE></P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-53374"></A>This script uses the shell's<SPANCLASS="link"><EMCLASS="emphasis">eval</EM> (<ACLASS="linkend"HREF="ch08_10.htm"TITLE="eval: When You Need Another Chance ">8.10</A>)</SPAN>command to re-scan the contents of the<EMCLASS="emphasis">bunch</EM> variable and store it in separate variables.Notice the single quotes like <CODECLASS="literal">s='your files'</CODE>; this groups thewords for <EMCLASS="emphasis">eval</EM>.The shell removes those single quotes before it stores the value intothe <EMCLASS="emphasis">s</EM> variable.</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">JP</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_16.htm"TITLE="45.16 Standard Input to a for Loop "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 45.16 Standard Input to a for Loop "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_18.htm"TITLE="45.18 Using basename and dirname "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 45.18 Using basename and dirname "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">45.16 Standard Input to a for Loop </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">45.18 Using basename and dirname </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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