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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 44] 44.14 Putting awk, sed, etc., Inside Shell Scripts </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="1998-08-04T21:53:50Z"><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="ch44_01.htm"TITLE="44. Shell Programming for the Uninitiated"><LINKREL="prev"HREF="ch44_13.htm"TITLE="44.13 read: Reading from the Keyboard "><LINKREL="next"HREF="ch44_15.htm"TITLE="44.15 Handling Command-Line Arguments in Shell Scripts "></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="ch44_13.htm"TITLE="44.13 read: Reading from the Keyboard "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 44.13 read: Reading from the Keyboard "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 44<BR>Shell Programming for the Uninitiated</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch44_15.htm"TITLE="44.15 Handling Command-Line Arguments in Shell Scripts "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 44.15 Handling Command-Line Arguments in Shell Scripts "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0029">44.14 Putting awk, sed, etc., Inside Shell Scripts </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-51196"></A><ACLASS="indexterm"NAME="AUTOID-51199"></A><ACLASS="indexterm"NAME="AUTOID-51201"></A>In <EMCLASS="emphasis">SunExpert</EM> magazine, in his article on <EMCLASS="emphasis">awk</EM> (January, 1991),Peter Collinson suggests a stylization similar to this for <EMCLASS="emphasis">awk</EM> programs in<SPANCLASS="link">shell scripts (<ACLASS="linkend"HREF="ch44_01.htm#UPT-ART-0065"TITLE="Everyone Should Learn Some Shell Programming ">44.1</A>)</SPAN>:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">#!/bin/shawkprog='/foo/{print $3}/bar/{print $4}'awk "$awkprog" $*</PRE></BLOCKQUOTE></P><PCLASS="para">He argues that this is more intelligible in long pipelines because itseparates the program from the command. For example:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">grep foo $input | sed .... | awk "$awkprog" - | ...</PRE></BLOCKQUOTE></P><PCLASS="para">Not everyone is thrilled by the "advantages" of writing <EMCLASS="emphasis">awk</EM> this way,but it's true that there are disadvantages to writing <EMCLASS="emphasis">awk</EM> in the standard way.</P><PCLASS="para">Here's an even more complex variation:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"> <ACLASS="co"HREF="ch08_18.htm"TITLE="8.18 Here Documents "><<\</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">#!/bin/shtemp=/tmp/awk.prog.$$cat > $temp <CODECLASS="literal"><<\</CODE>END/foo/{print $3}/bar/{print $4}ENDawk -f $temp $1rm -f $temp</PRE></TD></TR></TABLE></P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-51222"></A><ACLASS="indexterm"NAME="AUTOID-51225"></A>This version makes it a bit easier to create complex programsdynamically. The final <EMCLASS="emphasis">awk</EM> command becomes the equivalent of ashell<SPANCLASS="link"><EMCLASS="emphasis">eval</EM> (<ACLASS="linkend"HREF="ch08_10.htm"TITLE="eval: When You Need Another Chance ">8.10</A>)</SPAN>;it executes something that has been built up atruntime. The first strategy (program in shell variable) could alsobe massaged to work this way.</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-51232"></A><ACLASS="indexterm"NAME="AUTOID-51235"></A><ACLASS="indexterm"NAME="AUTOID-51238"></A><ACLASS="indexterm"NAME="AUTOID-51241"></A>As another example a program that I used oncewas really just one long pipeline, about 200 lines long.Huge <EMCLASS="emphasis">awk</EM> scripts and <EMCLASS="emphasis">sed</EM> scripts intervenedin the middle. As a result, it was almost completely unintelligible.But if you start each program with a comment block and end it with a pipe,the result can be fairly easy to read.It's more direct than using big shell variables or temporary files,especially if there are several scripts.</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">## READ THE FILE AND DO XXX WITH awk:#awk ' ...<EMCLASS="emphasis">the indented awk program</EM>... ... ...' <CODECLASS="userinput"><B>|</B></CODE>## SORT BY THE FIRST FIELD, THEN BY XXX:#sort +0n -1 +3r <CODECLASS="userinput"><B>|</B></CODE>## MASSAGE THE LINES WITH sed AND XXX:#sed ' ...</PRE></BLOCKQUOTE></P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-51252"></A>Multiline pipes like that one are uglier in the C shell because<SPANCLASS="link">each line has to end with a backslash (<CODECLASS="literal">\</CODE>) (<ACLASS="linkend"HREF="ch08_15.htm"TITLE="Differences Between Bourne and C Shell Quoting ">8.15</A>)</SPAN>.Articles<ACLASS="xref"HREF="ch08_14.htm"TITLE="Bourne Shell Quoting ">8.14</A>and<ACLASS="xref"HREF="ch08_15.htm"TITLE="Differences Between Bourne and C Shell Quoting ">8.15</A>have more about quoting.</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">ML</SPAN>, <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="ch44_13.htm"TITLE="44.13 read: Reading from the Keyboard "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 44.13 read: Reading from the Keyboard "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="ch44_15.htm"TITLE="44.15 Handling Command-Line Arguments in Shell Scripts "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 44.15 Handling Command-Line Arguments in Shell Scripts "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">44.13 read: Reading from the Keyboard </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">44.15 Handling Command-Line Arguments in Shell Scripts </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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