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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta name="generator" content="HTML Tidy, see www.w3.org" /><title>Processes</title><meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.7" /><link rel="HOME" title="FreeBSD Handbook" href="index.html" /><link rel="UP" title="UNIX Basics" href="basics.html" /><link rel="PREVIOUS" title="Mounting and Unmounting File Systems"href="mount-unmount.html" /><link rel="NEXT" title="Daemons, Signals, and Killing Processes"href="basics-daemons.html" /><link rel="STYLESHEET" type="text/css" href="docbook.css" /></head><body class="SECT1" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#840084"alink="#0000FF"><div class="NAVHEADER"><table summary="Header navigation table" width="100%" border="0" cellpadding="0"cellspacing="0"><tr><th colspan="3" align="center">FreeBSD Handbook</th></tr><tr><td width="10%" align="left" valign="bottom"><a href="mount-unmount.html"accesskey="P">Prev</a></td><td width="80%" align="center" valign="bottom">Chapter 3 UNIX Basics</td><td width="10%" align="right" valign="bottom"><a href="basics-daemons.html"accesskey="N">Next</a></td></tr></table><hr align="LEFT" width="100%" /></div><div class="SECT1"><h1 class="SECT1"><a id="BASICS-PROCESSES" name="BASICS-PROCESSES">3.7 Processes</a></h1><p>FreeBSD is a multi-tasking operating system. This means that it seems as though morethan one program is running at once. Each program running at any one time is called a <iclass="FIRSTTERM">process</i>. Every command you run will start at least one new process,and there are a number of system processes that run all the time, keeping the systemfunctional.</p><p>Each process is uniquely identified by a number called a <i class="FIRSTTERM">processID</i>, or <i class="FIRSTTERM">PID</i>, and, like files, each process also has one ownerand group. The owner and group information is used to determine what files and devicesthe process can open, using the file permissions discussed earlier. Most processes alsohave a parent process. The parent process is the process that started them. For example,if you are typing commands to the shell then the shell is a process, and any commands yourun are also processes. Each process you run in this way will have your shell as itsparent process. The exception to this is a special process called <ahref="http://www.FreeBSD.org/cgi/man.cgi?query=init&sektion=8"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">init</span>(8)</span></a>. <ttclass="COMMAND">init</tt> is always the first process, so its PID is always 1. <ttclass="COMMAND">init</tt> is started automatically by the kernel when FreeBSD starts.</p><p>Two commands are particularly useful to see the processes on the system, <ahref="http://www.FreeBSD.org/cgi/man.cgi?query=ps&sektion=1"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">ps</span>(1)</span></a> and <ahref="http://www.FreeBSD.org/cgi/man.cgi?query=top&sektion=1"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">top</span>(1)</span></a>. The <ttclass="COMMAND">ps</tt> command is used to show a static list of the currently runningprocesses, and can show their PID, how much memory they are using, the command line theywere started with, and so on. The <tt class="COMMAND">top</tt> command displays all therunning processes, and updates the display every few seconds, so that you caninteractively see what your computer is doing.</p><p>By default, <tt class="COMMAND">ps</tt> only shows you the commands that are runningand are owned by you. For example:</p><pre class="SCREEN"><samp class="PROMPT">%</samp> <kbd class="USERINPUT">ps</kbd> PID TT STAT TIME COMMAND 298 p0 Ss 0:01.10 tcsh 7078 p0 S 2:40.88 xemacs mdoc.xsl (xemacs-21.1.14)37393 p0 I 0:03.11 xemacs freebsd.dsl (xemacs-21.1.14)48630 p0 S 2:50.89 /usr/local/lib/netscape-linux/navigator-linux-4.77.bi48730 p0 IW 0:00.00 (dns helper) (navigator-linux-)72210 p0 R+ 0:00.00 ps 390 p1 Is 0:01.14 tcsh 7059 p2 Is+ 1:36.18 /usr/local/bin/mutt -y 6688 p3 IWs 0:00.00 tcsh10735 p4 IWs 0:00.00 tcsh20256 p5 IWs 0:00.00 tcsh 262 v0 IWs 0:00.00 -tcsh (tcsh) 270 v0 IW+ 0:00.00 /bin/sh /usr/X11R6/bin/startx -- -bpp 16 280 v0 IW+ 0:00.00 xinit /home/nik/.xinitrc -- -bpp 16 284 v0 IW 0:00.00 /bin/sh /home/nik/.xinitrc 285 v0 S 0:38.45 /usr/X11R6/bin/sawfish</pre><p>As you can see in this example, the output from <ahref="http://www.FreeBSD.org/cgi/man.cgi?query=ps&sektion=1"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">ps</span>(1)</span></a> is organizedinto a number of columns. <var class="LITERAL">PID</var> is the process ID discussedearlier. PIDs are assigned starting from 1, go up to 99999, and wrap around back to thebeginning when you run out. The <var class="LITERAL">TT</var> column shows the tty theprogram is running on, and can safely be ignored for the moment. <varclass="LITERAL">STAT</var> shows the program's state, and again, can be safely ignored.<var class="LITERAL">TIME</var> is the amount of time the program has been running on theCPU--this is usually not the elapsed time since you started the program, as most programsspend a lot of time waiting for things to happen before they need to spend time on theCPU. Finally, <var class="LITERAL">COMMAND</var> is the command line that was used to runthe program.</p><p><a href="http://www.FreeBSD.org/cgi/man.cgi?query=ps&sektion=1"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">ps</span>(1)</span></a> supports anumber of different options to change the information that is displayed. One of the mostuseful sets is <var class="LITERAL">auxww</var>. <var class="OPTION">a</var> displaysinformation about all the running processes, not just your own. <varclass="OPTION">u</var> displays the username of the process' owner, as well as memoryusage. <var class="OPTION">x</var> displays information about daemon processes, and <varclass="OPTION">ww</var> causes <ahref="http://www.FreeBSD.org/cgi/man.cgi?query=ps&sektion=1"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">ps</span>(1)</span></a> to display thefull command line, rather than truncating it once it gets too long to fit on thescreen.</p><p>The output from <a href="http://www.FreeBSD.org/cgi/man.cgi?query=top&sektion=1"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">top</span>(1)</span></a> is similar. Asample session looks like this:</p><pre class="SCREEN"><samp class="PROMPT">%</samp> <kbd class="USERINPUT">top</kbd>last pid: 72257; load averages: 0.13, 0.09, 0.03 up 0+13:38:33 22:39:1047 processes: 1 running, 46 sleepingCPU states: 12.6% user, 0.0% nice, 7.8% system, 0.0% interrupt, 79.7% idleMem: 36M Active, 5256K Inact, 13M Wired, 6312K Cache, 15M Buf, 408K FreeSwap: 256M Total, 38M Used, 217M Free, 15% Inuse PID USERNAME PRI NICE SIZE RES STATE TIME WCPU CPU COMMAND72257 nik 28 0 1960K 1044K RUN 0:00 14.86% 1.42% top 7078 nik 2 0 15280K 10960K select 2:54 0.88% 0.88% xemacs-21.1.14 281 nik 2 0 18636K 7112K select 5:36 0.73% 0.73% XF86_SVGA 296 nik 2 0 3240K 1644K select 0:12 0.05% 0.05% xterm48630 nik 2 0 29816K 9148K select 3:18 0.00% 0.00% navigator-linu 175 root 2 0 924K 252K select 1:41 0.00% 0.00% syslogd 7059 nik 2 0 7260K 4644K poll 1:38 0.00% 0.00% mutt...</pre><p>The output is split into two sections. The header (the first five lines) shows the PIDof the last process to run, the system load averages (which are a measure of how busy thesystem is), the system uptime (time since the last reboot) and the current time. Theother figures in the header relate to how many processes are running (47 in this case),how much memory and swap space has been taken up, and how much time the system isspending in different CPU states.</p><p>Below that are a series of columns containing similar information to the output from<a href="http://www.FreeBSD.org/cgi/man.cgi?query=ps&sektion=1"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">ps</span>(1)</span></a>. As before youcan see the PID, the username, the amount of CPU time taken, and the command that wasrun. <a href="http://www.FreeBSD.org/cgi/man.cgi?query=top&sektion=1"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">top</span>(1)</span></a> also defaultsto showing you the amount of memory space taken by the process. This is split into twocolumns, one for total size, and one for resident size--total size is how much memory theapplication has needed, and the resident size is how much it is actually using at themoment. In this example you can see that <b class="APPLICATION"><spanclass="TRADEMARK">Netscape</span>®</b> has required almost 30 MB of RAM, but iscurrently only using 9 MB.</p><p><a href="http://www.FreeBSD.org/cgi/man.cgi?query=top&sektion=1"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">top</span>(1)</span></a> automaticallyupdates this display every two seconds; this can be changed with the <varclass="OPTION">s</var> option.</p></div><div class="NAVFOOTER"><hr align="LEFT" width="100%" /><table summary="Footer navigation table" width="100%" border="0" cellpadding="0"cellspacing="0"><tr><td width="33%" align="left" valign="top"><a href="mount-unmount.html"accesskey="P">Prev</a></td><td width="34%" align="center" valign="top"><a href="index.html"accesskey="H">Home</a></td><td width="33%" align="right" valign="top"><a href="basics-daemons.html"accesskey="N">Next</a></td></tr><tr><td width="33%" align="left" valign="top">Mounting and Unmounting File Systems</td><td width="34%" align="center" valign="top"><a href="basics.html"accesskey="U">Up</a></td><td width="33%" align="right" valign="top">Daemons, Signals, and Killing Processes</td></tr></table></div><p align="center"><small>This, and other documents, can be downloaded from <ahref="ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/">ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/</a>.</small></p><p align="center"><small>For questions about FreeBSD, read the <ahref="http://www.FreeBSD.org/docs.html">documentation</a> before contacting <<ahref="mailto:questions@FreeBSD.org">questions@FreeBSD.org</a>>.<br />For questions about this documentation, e-mail <<ahref="mailto:doc@FreeBSD.org">doc@FreeBSD.org</a>>.</small></p></body></html>⌨️ 快捷键说明
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