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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 2] 2.15 Unclutter Logins: Show Login Messages Just Once </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="1998-08-04T21:32:20Z"><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="ch02_01.htm"TITLE="2. Logging In"><LINKREL="prev"HREF="ch02_14.htm"TITLE="2.14 motd.diff: Show New Lines in Login Messages"><LINKREL="next"HREF="ch02_16.htm"TITLE="2.16 Approved Shells: Using Unapproved Login Shell "></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="ch02_14.htm"TITLE="2.14 motd.diff: Show New Lines in Login Messages"><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 2.14 motd.diff: Show New Lines in Login Messages"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 2<BR>Logging In</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch02_16.htm"TITLE="2.16 Approved Shells: Using Unapproved Login Shell "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 2.16 Approved Shells: Using Unapproved Login Shell "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-6440">2.15 Unclutter Logins: Show Login Messages Just Once </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-3747"></A><ACLASS="indexterm"NAME="AUTOID-3749"></A>Ignoring your system login messages because they're so long?You might miss something important some day.Here's a way to see the message, from the file <EMCLASS="emphasis">/etc/motd</EM>,only if it's changed since the last time you read it.The <EMCLASS="emphasis">ls</EM> option<SPANCLASS="link"><EMCLASS="emphasis">-t</EM> (<ACLASS="linkend"HREF="ch16_02.htm"TITLE="Finding Oldest or Newest Files with ls -t and ls -u ">16.2</A>)</SPAN>sorts a list of files with the most recently modified file first.The following lines use a<SPANCLASS="link"><EMCLASS="emphasis">csh</EM> array (<ACLASS="linkend"HREF="ch47_05.htm"TITLE="Using C Shell Arrays ">47.5</A>)</SPAN>to store the output of <EMCLASS="emphasis">ls -t</EM> comparing two files' modification times.If the <EMCLASS="emphasis">/etc/motd</EM> file is newer than the <EMCLASS="emphasis">~/.hushlogin</EM> file,two commands are run.I use these lines in my<SPANCLASS="link"><EMCLASS="emphasis">.login</EM> file (<ACLASS="linkend"HREF="ch02_02.htm"TITLE="Shell Setup Files-Which, Where, and Why ">2.2</A>)</SPAN>,though they will work anywhere in the C shell:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen"> set files=(`ls -t /etc/motd ~/.hushlogin`)if ( $files[1] == /etc/motd ) then cat /etc/motd touch ~/.hushloginendifunset files</PRE></BLOCKQUOTE></P><BLOCKQUOTECLASS="note"><PCLASS="para"><STRONG>NOTE:</STRONG> <ACLASS="indexterm"NAME="AUTOID-3769"></A>If you have <EMCLASS="emphasis">ls</EM><SPANCLASS="link">aliased (<ACLASS="linkend"HREF="ch10_02.htm"TITLE="Aliases for Common Commands ">10.2</A>)</SPAN>to output anything but filenames (forinstance, to print the sizes of files with <EMCLASS="emphasis">-s</EM>) you'll need touse the system version with<CODECLASS="literal">/bin/ls</CODE> instead of just <CODECLASS="literal">ls</CODE>.</P></BLOCKQUOTE><PCLASS="para">This method uses the <EMCLASS="emphasis">.hushlogin</EM> files on many UNIXes:if that file exists, the login process is quiet.We make <EMCLASS="emphasis">.hushlogin</EM> do double duty by<SPANCLASS="link">storing the current timestamp with <EMCLASS="emphasis">touch</EM> (<ACLASS="linkend"HREF="ch21_07.htm"TITLE="Setting File Modification Time with touch ">21.7</A>)</SPAN>.<ACLASS="indexterm"NAME="AUTOID-3781"></A><ACLASS="indexterm"NAME="AUTOID-3784"></A></P><PCLASS="para">(This <EMCLASS="emphasis">ls -t</EM> file-comparison technique will work on all UNIXesand it's useful any time you need to compare two files.You can use the same technique to mark the time that something has happenedto any file - orto compare any two files or directories.Use the<SPANCLASS="link"><EMCLASS="emphasis">ls -d</EM> option (<ACLASS="linkend"HREF="ch16_08.htm"TITLE="The ls -d Option ">16.8</A>)</SPAN>for directories.)</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="ch02_14.htm"TITLE="2.14 motd.diff: Show New Lines in Login Messages"><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 2.14 motd.diff: Show New Lines in Login Messages"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="ch02_16.htm"TITLE="2.16 Approved Shells: Using Unapproved Login Shell "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 2.16 Approved Shells: Using Unapproved Login Shell "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">2.14 motd.diff: Show New Lines in Login Messages</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">2.16 Approved Shells: Using Unapproved Login Shell </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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