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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 35] 35.19 Joining Lines with join </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="1998-08-04T21:48:25Z"><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="ch35_01.htm"TITLE="35. You Can't Quite Call This Editing"><LINKREL="prev"HREF="ch35_18.htm"TITLE="35.18 Pasting Things in Columns "><LINKREL="next"HREF="ch35_20.htm"TITLE="35.20 Quick Reference: uniq "></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="ch35_18.htm"TITLE="35.18 Pasting Things in Columns "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 35.18 Pasting Things in Columns "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 35<BR>You Can't Quite Call This Editing</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch35_20.htm"TITLE="35.20 Quick Reference: uniq "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 35.20 Quick Reference: uniq "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0297">35.19 Joining Lines with join </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-41168"></A><ACLASS="indexterm"NAME="AUTOID-41170"></A>If you've worked with databases, you'll probably know what to do withthe UNIX <EMCLASS="emphasis">join</EM> command; see your online manual page.If you don't have a database (as far as you know!), you'll stillprobably have a use for <EMCLASS="emphasis">join</EM>: combining or "joining" twocolumn-format files.<EMCLASS="emphasis">join</EM> searches certain columns in the files; when it finds columnsthat match one another, it "glues the lines together" at that column.This is easiest to show with an example.</P><PCLASS="para">I needed to summarize the information in thousands of email messagesunder the MH mail system.MH made that easy: it has one command (<EMCLASS="emphasis">scan</EM>) that gave mealmost all the information I wanted about each message in the format I wanted.But I also had to use<SPANCLASS="link"><EMCLASS="emphasis">wc -l</EM> (<ACLASS="linkend"HREF="ch29_06.htm"TITLE="Counting Lines, Words, and Characters: wc ">29.6</A>)</SPAN>to count the number of lines in eachmessage.I ended up with two files, one with <EMCLASS="emphasis">scan</EM> output and the other with<EMCLASS="emphasis">wc</EM> output.One field in both lines was the message number; I used<SPANCLASS="link"><EMCLASS="emphasis">sort</EM> (<ACLASS="linkend"HREF="ch36_01.htm#UPT-ART-7640"TITLE="Putting Things in Order ">36.1</A>)</SPAN>tosort the files on that field.I used <CODECLASS="literal">awk '{print $1 "," $2}'</CODE> to massage <EMCLASS="emphasis">wc</EM> outputinto comma-separated fields.Then I used <EMCLASS="emphasis">join</EM> to "glue" the two lines together on themessage-number field.(Next I fed the file to a PC running <EMCLASS="emphasis">dBASE</EM>, but that's another story.)</P><PCLASS="para">Here's the file that I told <EMCLASS="emphasis">scan</EM> to output.The columns (message number, email address, comment, name, and datesent) are separated with commas (<CODECLASS="literal">,</CODE>):</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">0001,andrewe@isc.uci.edu,,Andy Ernbaum,199012190002,bc3170x@cornell.bitnet,,Zoe Doan,199101040003,zcode!postman@uunet.uu.net,,Head Honcho,19910105 ...</PRE></BLOCKQUOTE></P><PCLASS="para">Here's the file from <EMCLASS="emphasis">wc</EM> and <EMCLASS="emphasis">awk</EM> with the message number andnumber of lines:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">0001,110002,50003,187 ...</PRE></BLOCKQUOTE></P><PCLASS="para">Then, this <EMCLASS="emphasis">join</EM> command joined the two files at their firstcolumns (<CODECLASS="literal">-t,</CODE> tells <EMCLASS="emphasis">join</EM> that the fields are comma-separated):</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>join -t, scanfile wcfile</B></CODE></PRE></BLOCKQUOTE></P><PCLASS="para">The output file looked like:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">0001,andrewe@isc.uci.edu,,Andy Ernbaum,19901219,110002,bc3170x@cornell.bitnet,,Zoe Doan,19910104,50003,zcode!postman@uunet.uu.net,,Head Honcho,19910105,187 ...</PRE></BLOCKQUOTE></P><PCLASS="para">Of course, <EMCLASS="emphasis">join</EM> can do a lot more than this simple example shows.See your online manual page.</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="ch35_18.htm"TITLE="35.18 Pasting Things in Columns "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 35.18 Pasting Things in Columns "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="ch35_20.htm"TITLE="35.20 Quick Reference: uniq "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 35.20 Quick Reference: uniq "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">35.18 Pasting Things in Columns </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">35.20 Quick Reference: uniq </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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