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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 36] 36.6 Miscellaneous sort Hints </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="1998-08-04T21:48:42Z"><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="ch36_01.htm"TITLE="36. Sorting"><LINKREL="prev"HREF="ch36_05.htm"TITLE="36.5 Alphabetic and Numeric Sorting "><LINKREL="next"HREF="ch36_07.htm"TITLE="36.7 Sorting Multiline Entries "></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="ch36_05.htm"TITLE="36.5 Alphabetic and Numeric Sorting "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 36.5 Alphabetic and Numeric Sorting "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 36<BR>Sorting</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch36_07.htm"TITLE="36.7 Sorting Multiline Entries "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 36.7 Sorting Multiline Entries "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-2921">36.6 Miscellaneous sort Hints </A></H2><PCLASS="para">Here is a grab bag of useful, if not exactly interesting, <EMCLASS="emphasis">sort</EM>features.The utility will actually do quite a bit, if you let it.<ACLASS="indexterm"NAME="AUTOID-41702"></A></P><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="UPT-ART-2921-SECT-1.1">36.6.1 Dealing with Repeated Lines </A></H3><PCLASS="para"><EMCLASS="emphasis">sort -u</EM> sorts the file and eliminates duplicate lines.It'smore powerful than<SPANCLASS="link"><EMCLASS="emphasis">uniq</EM> (<ACLASS="linkend"HREF="ch35_20.htm"TITLE="Quick Reference: uniq ">35.20</A>)</SPAN>because:</P><ULCLASS="itemizedlist"><LICLASS="listitem"><PCLASS="para">It sorts the file for you; <EMCLASS="emphasis">uniq</EM> assumes that the file is alreadysorted, and won't do you any good if it isn't.</P></LI><LICLASS="listitem"><PCLASS="para">It is much more flexible.<EMCLASS="emphasis">sort -u</EM> considers lines "unique" ifthe<SPANCLASS="link">sort fields (<ACLASS="linkend"HREF="ch36_02.htm"TITLE="Sort Fields: How sort Sorts ">36.2</A>)</SPAN>you've selected match.So the lines don't even haveto be (strictly speaking) unique; differences outside of the sortfields are ignored.<ACLASS="indexterm"NAME="AUTOID-41718"></A></P></LI></UL><PCLASS="para">In return, there are a few things that <EMCLASS="emphasis">uniq</EM> does that <EMCLASS="emphasis">sort</EM>won't do - like print only those lines that aren't repeated, or countthe number of times each line is repeated.But on the whole, I find<EMCLASS="emphasis">sort -u</EM> more useful.</P><PCLASS="para">Here's one idea for using <EMCLASS="emphasis">sort -u</EM>.When I was writing a manual, Ioften needed to make tables of error messages.The easiest way to dothis was to <EMCLASS="emphasis">grep</EM> the source code for <EMCLASS="emphasis">printf</EM> statements;write some<SPANCLASS="link">Emacs (<ACLASS="linkend"HREF="ch32_01.htm#UPT-ART-5540"TITLE="Emacs: The Other Editor ">32.1</A>)</SPAN>macros to eliminate junk that I didn't careabout; use <EMCLASS="emphasis">sort -u</EM> to put the messages in order and get rid ofduplicates; and write some more Emacs macros to format the errormessages into a table.All I had to do was write the descriptions.<ACLASS="indexterm"NAME="AUTOID-41731"></A></P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="UPT-ART-2921-SECT-1.2">36.6.2 Ignoring Blanks </A></H3><PCLASS="para">One important option (that I've mentioned a number of times) is<EMCLASS="emphasis">-b</EM>; this tells <EMCLASS="emphasis">sort</EM> to ignore extra white space at thebeginning of each field.This is absolutely essential; otherwise,your sorts will have rather strange results.In my opinion, <EMCLASS="emphasis">-b</EM>should be the default.But they didn't ask me.</P><PCLASS="para">Another thing to remember about <EMCLASS="emphasis">-b</EM>: it only works if youexplicitly specify which fields you want to sort.By itself, <EMCLASS="emphasis">sort-b</EM> is the same as <EMCLASS="emphasis">sort</EM>: white space characters are counted.I call this a bug, don't you?<ACLASS="indexterm"NAME="AUTOID-41744"></A></P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="UPT-ART-2921-SECT-1.3">36.6.3 Case-Insensitive Sorts </A></H3><PCLASS="para">If you don't care about the difference between uppercase andlowercase letters, invoke <EMCLASS="emphasis">sort</EM> with the <EMCLASS="emphasis">-f</EM> (case-fold)option.This folds lowercase letters into uppercase.In other words, it treats all letters as uppercase.<ACLASS="indexterm"NAME="AUTOID-41752"></A></P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="UPT-ART-2921-SECT-1.4">36.6.4 Dictionary Order </A></H3><PCLASS="para">The <EMCLASS="emphasis">-d</EM> option tells <EMCLASS="emphasis">sort</EM> to ignore all characters exceptfor letters, digits, and white space.In particular, <EMCLASS="emphasis">sort -d</EM>ignores punctuation.<ACLASS="indexterm"NAME="AUTOID-41761"></A></P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="UPT-ART-2921-SECT-1.5">36.6.5 Month Order </A></H3><PCLASS="para">The <EMCLASS="emphasis">-M</EM> option tells <EMCLASS="emphasis">sort</EM> to treat the first threenon-blank characters of a field as a three-letter month abbreviation,and to sort accordingly.That is, JAN comes before FEB, which comesbefore MAR.This option isn't available on all versions of UNIX.<ACLASS="indexterm"NAME="AUTOID-41769"></A></P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="UPT-ART-2921-SECT-1.6">36.6.6 Reverse Sort </A></H3><PCLASS="para">The <EMCLASS="emphasis">-r</EM> option tells <EMCLASS="emphasis">sort</EM> to "reverse" the order of thesort; i.e., Z comes before A, 9 comes before 1, and so on.You'll find that this option is really useful.For example, imagineyou have a program running in the background that records the numberof free blocks in the filesystem at midnight each night.Your logfile might look like this:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">Jan 1 1992: 108 free blocksJan 2 1992: 308 free blocksJan 3 1992: 1232 free blocksJan 4 1992: 76 free blocks...</PRE></BLOCKQUOTE></P><PCLASS="para">The script below finds the smallest and largest number of free blocksin your log file:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"> <ACLASS="co"HREF="ch25_20.htm"TITLE="25.20 Printing the Top of a File ">head</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">#!/bin/shecho "Minimum free blocks"sort -t: +1nb logfile | head -1echo "Maximum free blocks"sort -t: +1nbr logfile | head -1</PRE></TD></TR></TABLE></P><PCLASS="para">It's not profound, but it's an example of what you can do.</P></DIV><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">ML</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="ch36_05.htm"TITLE="36.5 Alphabetic and Numeric Sorting "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 36.5 Alphabetic and Numeric Sorting "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="ch36_07.htm"TITLE="36.7 Sorting Multiline Entries "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 36.7 Sorting Multiline Entries "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">36.5 Alphabetic and Numeric Sorting </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">36.7 Sorting Multiline Entries </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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