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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 38] 38.6 The Controlling Terminal </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="1998-08-04T21:49:40Z"><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="ch38_01.htm"TITLE="38. Starting, Stopping, and Killing Processes"><LINKREL="prev"HREF="ch38_05.htm"TITLE="38.5 The ps Command "><LINKREL="next"HREF="ch38_07.htm"TITLE="38.7 Why ps Prints Some Commands in Parentheses "></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="ch38_05.htm"TITLE="38.5 The ps Command "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 38.5 The ps Command "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 38<BR>Starting, Stopping, and Killing Processes</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch38_07.htm"TITLE="38.7 Why ps Prints Some Commands in Parentheses "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 38.7 Why ps Prints Some Commands in Parentheses "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-8007">38.6 The Controlling Terminal </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-42729"></A>In article<ACLASS="xref"HREF="ch38_05.htm"TITLE="The ps Command ">38.5</A>,we pointed out that the <EMCLASS="emphasis">ps</EM> command needs special options(<EMCLASS="emphasis">-x</EM> for BSD and <EMCLASS="emphasis">-e</EM> for System V) to list processeswithout a controlling terminal.</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-42736"></A><ACLASS="indexterm"NAME="AUTOID-42739"></A><ACLASS="indexterm"NAME="AUTOID-42741"></A>But just what is a controlling terminal? Just what it sounds like:the terminal from which the process was started. In the <EMCLASS="emphasis">ps</EM>listing, this is usually given as a <EMCLASS="emphasis">tty</EM>, or terminal id.That <EMCLASS="emphasis">ps</EM> entryusually corresponds to a serial port, or a<SPANCLASS="link"><EMCLASS="emphasis">pty</EM> (<ACLASS="linkend"HREF="ch41_08.htm"TITLE="ptys and Window Systems ">41.8</A>)</SPAN>.A <EMCLASS="emphasis">pty</EM> or "pseudo-terminal" is a construct that makes a window or<SPANCLASS="link">network login (<ACLASS="linkend"HREF="ch01_33.htm"TITLE="UNIX Networking and Communications ">1.33</A>)</SPAN>look to the operating system just like a terminal.</P><PCLASS="para">In the <EMCLASS="emphasis">ps</EM> listing, a tty might appear as <CODECLASS="literal">t1</CODE> for<EMCLASS="emphasis">/dev/tty1</EM>, <CODECLASS="literal">p3</CODE> for <EMCLASS="emphasis">/dev/ttyp3</EM>, or as some otherdesignation, such as <CODECLASS="literal">co</CODE> for <EMCLASS="emphasis">/dev/console</EM>, the full screendisplay of a workstation before any window system is started.Processes without a controlling terminal show a question mark (<CODECLASS="literal">?</CODE>).</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-42760"></A>How does a process "lose" its controlling terminal? Easy. Someprocesses, such as system<SPANCLASS="link">"daemons" (<ACLASS="linkend"HREF="ch01_14.htm"TITLE="The Kernel and Daemons ">1.14</A>)</SPAN>never had one - they were startedby system scripts that weren't started from any terminal,or they disconnected themselves from their controlling terminals.But it'salso possible that you started a process running in the background,logged out, and logged back later or on anotherterminal to find it still running without a controlling terminal.</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-42765"></A>The <EMCLASS="emphasis">tty</EM> command can be used to report which "terminal" you'recurrently connected to.For example:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>tty</B></CODE>/dev/ttyp2</PRE></BLOCKQUOTE></P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-42772"></A>Running <EMCLASS="emphasis">tty</EM> without a controlling terminal gives themessage <CODECLASS="literal">not</CODE> <CODECLASS="literal">a</CODE> <CODECLASS="literal">tty</CODE>.</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">TOR</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="ch38_05.htm"TITLE="38.5 The ps Command "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 38.5 The ps Command "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="ch38_07.htm"TITLE="38.7 Why ps Prints Some Commands in Parentheses "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 38.7 Why ps Prints Some Commands in Parentheses "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">38.5 The ps Command </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">38.7 Why ps Prints Some Commands in Parentheses </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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