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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 22] 22.18 Clear Your Terminal for Security, to Stop Burn-in </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="1998-08-04T21:40:40Z"><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="ch22_01.htm"TITLE="22. File Security, Ownership, and Sharing"><LINKREL="prev"HREF="ch22_17.htm"TITLE="22.17 Ways of Improving the Security of crypt "><LINKREL="next"HREF="ch22_19.htm"TITLE="22.19 Shell Scripts Must be Readable and (Usually) Executable"></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="ch22_17.htm"TITLE="22.17 Ways of Improving the Security of crypt "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 22.17 Ways of Improving the Security of crypt "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 22<BR>File Security, Ownership, and Sharing</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch22_19.htm"TITLE="22.19 Shell Scripts Must be Readable and (Usually) Executable"><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 22.19 Shell Scripts Must be Readable and (Usually) Executable"BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-3050">22.18 Clear Your Terminal for Security, to Stop Burn-in </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-24790"></A><ACLASS="indexterm"NAME="AUTOID-24792"></A>The <EMCLASS="emphasis">clear</EM> command reads your<SPANCLASS="link"><EMCLASS="emphasis">termcap</EM> or <EMCLASS="emphasis">terminfo</EM> (<ACLASS="linkend"HREF="ch05_02.htm"TITLE="The Idea of a Terminal Database ">5.2</A>)</SPAN>entry to find out how to erase your screen, then it sends that command.If you're typing something confidential that other people shouldn'tread, just type <CODECLASS="literal">clear</CODE> at a shell prompt when you can.Many UNIX programs let you do a<SPANCLASS="link">shell escape (<ACLASS="linkend"HREF="ch30_26.htm"TITLE="Shell Escapes: Running One UNIX Command While Using Another">30.26</A>)</SPAN>to run a single UNIX command - you can clear your screen that way, bytyping something like <CODECLASS="literal">!clear</CODE> from inside the program.</P><BLOCKQUOTECLASS="note"><PCLASS="para"><STRONG>NOTE:</STRONG> <ACLASS="indexterm"NAME="AUTOID-24804"></A><ACLASS="indexterm"NAME="AUTOID-24807"></A>Some terminals and window systems have memories - scrolling buffers thatsave previous screens or the current one.The <EMCLASS="emphasis">clear</EM> command probably won't clear those.Check your manual to find out how - or, if you're desperate, log off UNIX,then turn off your screen's power for a minute.</P></BLOCKQUOTE><PCLASS="para">If you leave your desk for a long meeting or for the day, then remember thatyou didn't erase your screen, you can probably clear your screen from anotheruser's terminal.(If your system has the<SPANCLASS="link"><EMCLASS="emphasis">tty</EM>-group-write protection (<ACLASS="linkend"HREF="ch22_13.htm"TITLE="Groups and Group Ownership ">22.13</A>)</SPAN>,then you'll have to log in or<SPANCLASS="link"><EMCLASS="emphasis">su</EM> (<ACLASS="linkend"HREF="ch22_22.htm"TITLE="The su Command Isn't Just for the Superuser ">22.22</A>)</SPAN>to your account from the other terminal first.)If the other terminal has the same terminal type, use the command:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"><ACLASS="co"HREF="ch51_04.htm"TITLE="51.4 Who's On? ">who</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">% who<CODECLASS="userinput"><B> | grep </B></CODE><CODECLASS="replaceable"><I>yourname</I></CODE><CODECLASS="replaceable"><I>yourname</I></CODE> ttyp3 Jun 24 10:44% <CODECLASS="userinput"><B>clear > /dev/ttyp3</B></CODE></PRE></TD></TR></TABLE></P><PCLASS="para">If you're on a different type of terminal, you'll need to set the <EMCLASS="emphasis">TERM</EM>environment variable<SPANCLASS="link">temporarily (<ACLASS="linkend"HREF="ch06_10.htm"TITLE="Running a Command with a Temporarily Different Environment ">6.10</A>)</SPAN>before you use that command.</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="ch22_17.htm"TITLE="22.17 Ways of Improving the Security of crypt "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 22.17 Ways of Improving the Security of crypt "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="ch22_19.htm"TITLE="22.19 Shell Scripts Must be Readable and (Usually) Executable"><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 22.19 Shell Scripts Must be Readable and (Usually) Executable"BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">22.17 Ways of Improving the Security of crypt </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">22.19 Shell Scripts Must be Readable and (Usually) Executable</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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