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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 28] 28.14 Even More Uses for make </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="1998-08-04T21:44:53Z"><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="ch28_01.htm"TITLE="28. Comparing Files"><LINKREL="prev"HREF="ch28_13.htm"TITLE="28.13 make Isn't Just for Programmers! "><LINKREL="next"HREF="ch28_15.htm"TITLE="28.15 Show Changes in a troff File with diffmk "></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="ch28_13.htm"TITLE="28.13 make Isn't Just for Programmers! "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 28.13 make Isn't Just for Programmers! "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 28<BR>Comparing Files</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch28_15.htm"TITLE="28.15 Show Changes in a troff File with diffmk "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 28.15 Show Changes in a troff File with diffmk "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-5381">28.14 Even More Uses for make </A></H2><PCLASS="para">Thinking about <EMCLASS="emphasis">make</EM> will pay off in many ways. One way to getideas about how to use it is to look at other <EMCLASS="emphasis">makefiles</EM>.</P><PCLASS="para">One of my favorites is the <EMCLASS="emphasis">makefile</EM> for<SPANCLASS="link">NIS (<ACLASS="linkend"HREF="ch01_33.htm"TITLE="UNIX Networking and Communications ">1.33</A>)</SPAN>(formerly called yp,or "Yellow Pages"). I like this <EMCLASS="emphasis">makefile</EM> because itdoes something that you'd never think of doing, even though it suits <EMCLASS="emphasis">make</EM> perfectly: updating a distributed database.</P><PCLASS="para">The <EMCLASS="emphasis">makefile</EM> is fairly complicated, so I don't want to get intoa line-by-line explication of the <EMCLASS="emphasis">makefile</EM>; but I will give youa sketch of how it works. Here's the problem. A system administratorupdates one or more files (we'll say the <EMCLASS="emphasis">passwd</EM> file), and wantsto get his changes into the <EMCLASS="emphasis">yp</EM> database. So you need to checkwhether or not the new password file is more recent than thedatabase. Unfortunately, the database isn't represented by a singlefile, so there's nothing to "check" against. The NIS <EMCLASS="emphasis">makefile</EM> handlesthis situation by creating empty files that serve as timestamps. There's a separate <EMCLASS="emphasis">.time</EM> file for every databasethat NIS serves.When you type <EMCLASS="emphasis">make</EM>, <EMCLASS="emphasis">make</EM> checks everymaster file against the corresponding timestamp. If a master fileis newer than the timestamp, <EMCLASS="emphasis">make</EM> knows that it has to rebuildpart of the database. After rebuilding the database, the <EMCLASS="emphasis">makefile</EM>"touches" the timestamp, so that it reflects the time at which thedatabase was built.</P><PCLASS="para">The <EMCLASS="emphasis">makefile</EM> looks something like this:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"> <ACLASS="co"HREF="ch21_07.htm"TITLE="21.7 Setting File Modification Time with touch ">touch</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">passwd: passwd.timepasswd.time: /etc/master/passwd @ <EMCLASS="emphasis">lots of commands that rebuild the database</EM> @ touch passwd.time @ <EMCLASS="emphasis">more commands to distribute the new database</EM>hosts: hosts.timehosts.time: <EMCLASS="emphasis">similar stuff</EM></PRE></TD></TR></TABLE></P><PCLASS="para">You may never need to write a <EMCLASS="emphasis">makefile</EM> this complicated; butyou should look for situations in which you can use <EMCLASS="emphasis">make</EM> profitably.It isn't just for programming.</P><ACLASS="indexterm"NAME="AUTOID-31708"></A><ACLASS="indexterm"NAME="AUTOID-31709"></A><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="ch28_13.htm"TITLE="28.13 make Isn't Just for Programmers! 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