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-<td width="80%" align="center" valign="bottom">Chapter 11 Process Control</td>
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-<div class="SECT1">
-<h1 class="SECT1"><a id="PROCESS-CONTROL-PS" name="PROCESS-CONTROL-PS">11.3 <tt
-class="COMMAND">ps</tt></a></h1>
-
-<p>So now you know how to switch back and forth between several processes that you've
-started from the command line. And you also know that there are lots of processes running
-all the time. So how do you list all of these programs? Well, you make use of the <tt
-class="COMMAND">ps</tt>(1) command. This command has a lot of options, so we'll only
-cover the most important ones here. For a complete listing, see the man page for ps. Man
-pages are covered in-depth in <a href="help.html#HELP-SYSTEM-MAN">Section 2.1.1</a>.</p>
-
-<p>Simply typing <tt class="COMMAND">ps</tt> will get you a listing of the programs
-running on your terminal. This incudes the foreground processes (which include whatever
-shell you are using, and of course, <tt class="COMMAND">ps</tt> itself). Also listed are
-backgrounded processes you may have running. Many times, that will be a very short
-listing:</p>
-
-<div class="FIGURE"><a id="FIG-PROCESS-CONTROL-PS-SHORT"
-name="FIG-PROCESS-CONTROL-PS-SHORT"></a>
-<p><b>Figure 11-1. Basic <tt class="COMMAND">ps</tt> output</b></p>
-
-<table border="0" bgcolor="#E0E0E0" width="100%">
-<tr>
-<td>
-<pre class="SCREEN">
-<samp class="PROMPT">%</samp> <kbd class="USERINPUT">ps</kbd>
- PID TTY TIME CMD
- 7923 ttyp0 00:00:00 bash
- 8059 ttyp0 00:00:00 ps
-</pre>
-</td>
-</tr>
-</table>
-</div>
-
-<p>Even though this is not a lot of processes, the information is very typical. You'll
-get the same columns using regular ps no matter how many processes are running. So what
-does it all mean?</p>
-
-<p>Well, the <var class="LITERAL">PID</var> is the <span class="emphasis"><i
-class="EMPHASIS">process ID</i></span>. All running processes are given a unique
-identifier which ranges between 1 and 32767. Each process is assigned the next free PID.
-When a process quits (or is killed, as you will see in the next section), it gives up its
-PID. When the max PID is reached, the next free one will wrap back around to the lowest
-free one.</p>
-
-<p>The <var class="LITERAL">TTY</var> column indicates which terminal the process is
-running on. Doing a plain <tt class="COMMAND">ps</tt> will only list all the programs
-running on the current terminal, so all the processes give the same information in the
-TTY column. As you can see, both processes listed are running on <tt
-class="FILENAME">ttyp0</tt>. This indicates that they are either running remotely or from
-an X terminal of some variety.</p>
-
-<p>The <var class="LITERAL">TIME</var> column indicated how much CPU time the process has
-been running. This is different from the actual amount of time that a process runs.
-Remember that Linux is a multitasking operating system. There are many processes running
-all the time, and these processes each get a small portion of the processor's time. So,
-the TIME column should show much less time for each process than it actually takes to
-run. If you see more than several minutes in the TIME column, it could mean that
-something is wrong.</p>
-
-<p>Finally, the <var class="LITERAL">CMD</var> column shows what the program actually is.
-It only lists the base name of the program, not any command line options or similar
-information. To get that information, you'll need to use one of the many options to <tt
-class="COMMAND">ps</tt>. We'll discuss that shortly.</p>
-
-<p>You can get a complete listing of the processes running on your system using the right
-combination of options. This will probably result in a long listing of processes
-(fifty-five on my laptop as I write this sentence), so I'll abbreviate the output:</p>
-
-<table border="0" bgcolor="#E0E0E0" width="100%">
-<tr>
-<td>
-<pre class="SCREEN">
-<samp class="PROMPT">%</samp> <kbd class="USERINPUT">ps -ax</kbd>
- PID TTY STAT TIME COMMAND
- 1 ? S 0:03 init [3]
- 2 ? SW 0:13 [kflushd]
- 3 ? SW 0:14 [kupdate]
- 4 ? SW 0:00 [kpiod]
- 5 ? SW 0:17 [kswapd]
- 11 ? S 0:00 /sbin/kerneld
- 30 ? SW 0:01 [cardmgr]
- 50 ? S 0:00 /sbin/rpc.portmap
- 54 ? S 0:00 /usr/sbin/syslogd
- 57 ? S 0:00 /usr/sbin/klogd -c 3
- 59 ? S 0:00 /usr/sbin/inetd
- 61 ? S 0:04 /usr/local/sbin/sshd
- 63 ? S 0:00 /usr/sbin/rpc.mountd
- 65 ? S 0:00 /usr/sbin/rpc.nfsd
- 67 ? S 0:00 /usr/sbin/crond -l10
- 69 ? S 0:00 /usr/sbin/atd -b 15 -l 1
- 77 ? S 0:00 /usr/sbin/apmd
- 79 ? S 0:01 gpm -m /dev/mouse -t ps2
- 94 ? S 0:00 /usr/sbin/automount /auto file /etc/auto.misc
- 106 tty1 S 0:08 -bash
- 108 tty3 SW 0:00 [agetty]
- 109 tty4 SW 0:00 [agetty]
- 110 tty5 SW 0:00 [agetty]
- 111 tty6 SW 0:00 [agetty]
- [output cut]
-</pre>
-</td>
-</tr>
-</table>
-
-<p>Most of these processes are started at boot time on most systems. I've made a few
-modifications to my system, so your mileage will most likely vary. However, you will see
-most of these processes on your system too. As you can see, these options display command
-line options to the running processes. Recently, a kernel vulnerability in <tt
-class="COMMAND">ptrace</tt> facilitated a fix which no longer shows command line options
-for many running processes. These are now listed in brackets like PIDs 108 through 110.
-It also brings up a few more columns and some other interesting output.</p>
-
-<p>First, you'll notice that most of these processes are listed as running on tty
-&#8220;?&#8221;. Those are not attached to any particular terminal. This is most common
-with daemons, which are processes which run without attaching to any particular terminal.
-Common daemons are sendmail, BIND, apache, and NFS. They typically listen for some
-request from a client, and return information to it upon request.</p>
-
-<p>Second, there is a new column: <var class="LITERAL">STAT</var>. It shows the status of
-the process. <var class="LITERAL">S</var> stands for sleeping: the process is waiting for
-something to happen. <var class="LITERAL">Z</var> stands for a zombied process. A zombied
-processes is one whose parent has died, leaving the child processes behind. This is not a
-good thing. <var class="LITERAL">D</var> stands for a process that has entered an
-uninterruptible sleep. Often, these processes refuse to die even when passed a SIGKILL.
-You can read more about SIGKILL later in the next section on <tt
-class="COMMAND">kill</tt> . W stands for paging. A dead process is marked with an <var
-class="LITERAL">X</var>. A process marked <var class="LITERAL">T</var> is traced, or
-stopped. <var class="LITERAL">R</var> means that the process is runable.</p>
-
-<p>If you want to see even more information about the running processes, try this
-out:</p>
-
-<table border="0" bgcolor="#E0E0E0" width="100%">
-<tr>
-<td>
-<pre class="SCREEN">
-<samp class="PROMPT">%</samp> <kbd class="USERINPUT">ps -aux</kbd>
- USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
- root 1 0.0 0.0 344 80 ? S Mar02 0:03 init [3]
- root 2 0.0 0.0 0 0 ? SW Mar02 0:13 [kflushd]
- root 3 0.0 0.0 0 0 ? SW Mar02 0:14 [kupdate]
- root 4 0.0 0.0 0 0 ? SW Mar02 0:00 [kpiod]
- root 5 0.0 0.0 0 0 ? SW Mar02 0:17 [kswapd]
- root 11 0.0 0.0 1044 44 ? S Mar02 0:00 /sbin/kerneld
- root 30 0.0 0.0 1160 0 ? SW Mar02 0:01 [cardmgr]
- bin 50 0.0 0.0 1076 120 ? S Mar02 0:00 /sbin/rpc.port
- root 54 0.0 0.1 1360 192 ? S Mar02 0:00 /usr/sbin/sysl
- root 57 0.0 0.1 1276 152 ? S Mar02 0:00 /usr/sbin/klog
- root 59 0.0 0.0 1332 60 ? S Mar02 0:00 /usr/sbin/inet
- root 61 0.0 0.2 1540 312 ? S Mar02 0:04 /usr/local/sbi
- root 63 0.0 0.0 1796 72 ? S Mar02 0:00 /usr/sbin/rpc.
- root 65 0.0 0.0 1812 68 ? S Mar02 0:00 /usr/sbin/rpc.
- root 67 0.0 0.2 1172 260 ? S Mar02 0:00 /usr/sbin/cron
- root 77 0.0 0.2 1048 316 ? S Mar02 0:00 /usr/sbin/apmd
- root 79 0.0 0.1 1100 152 ? S Mar02 0:01 gpm
- root 94 0.0 0.2 1396 280 ? S Mar02 0:00 /usr/sbin/auto
- chris 106 0.0 0.5 1820 680 tty1 S Mar02 0:08 -bash
- root 108 0.0 0.0 1048 0 tty3 SW Mar02 0:00 [agetty]
- root 109 0.0 0.0 1048 0 tty4 SW Mar02 0:00 [agetty]
- root 110 0.0 0.0 1048 0 tty5 SW Mar02 0:00 [agetty]
- root 111 0.0 0.0 1048 0 tty6 SW Mar02 0:00 [agetty]
- [output cut]
-</pre>
-</td>
-</tr>
-</table>
-
-<p>That's a whole lot of information. Basically, it adds information including what user
-started the process, how much of the system resources the process is using (the %CPU,
-%MEM, VSZ, and RSS columns), and on what date the process was started. Obviously, that's
-a lot of information that could come in handy for a system administrator. It also brings
-up another point: the information now goes off the edge of the screen so that you cannot
-see it all. The <var class="OPTION">-w</var> option will force <tt
-class="COMMAND">ps</tt> to wrap long lines.</p>
-
-<p>It's not terribly pretty, but it does the job. You've now got the complete listings
-for each process. There's even more information that you can display about each process.
-Check out the very in-depth man page for <tt class="COMMAND">ps</tt>. However, the
-options shown above are the most popular ones and will be the ones you need to use the
-most often.</p>
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