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<P>Suppose you enter <TT><B>ps -f</B></TT> and see the following response:</P>
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UID PID PPID C STIME TTY TIME COMMAND
chris 65 1 0 11:40:11 tty01 0:06 -bash
chris 71 65 61 11:42:01 tty01 0:14 total_updt inventory
chris 231 65 80 11:46:02 tty01 0:00 ps -f
chris 187 53 60 15:32:01 tty02 123:45 crunch stats
chris 53 1 0 15:31:34 tty02 1:06 -bash
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<P>To kill process 187, normally you would enter <TT>kill 187</TT>. If you then enter <TT>ps -f</TT> again and see that the process is still there, you know the process is set up to ignore the <TT>kill</TT> command. To kill it unconditionally, enter <TT><B>kill -9 187</B></TT>. When you enter <TT>ps -f</TT> again, you see that the process is no longer around.</P>
<BLOCKQUOTE>
<P><FONT SIZE="-1"><HR><B>CAUTION: </B><BR>A disadvantage to using this unconditional version of the <TT>kill</TT> command is that <TT>kill -9</TT> doesn’t allow a process to finish what it’s doing before it terminates the process. If you use <TT>kill -9</TT> with a program that’s updating a file, you could lose the updated material or the entire file.
<P>Use the powerful <TT>kill -9</TT> command responsibly. In most cases, you don’t need the -9 option; the <TT>kill</TT> command, issued without arguments, stops most processes.<HR></FONT>
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<P><FONT SIZE="+1"><B>Termination of All Background Processes</B></FONT></P>
<P>To kill all background jobs, enter <TT><B>kill 0</B></TT>. Commands that run in the background sometimes initiate more than one process; tracking down all the PID numbers associated with the process you want to kill can be tedious. Because <TT>kill 0</TT> terminates all processes started by the current shell, it’s a faster and less tedious way to terminate processes. Enter the <TT>jobs</TT> command to see what commands are running in the background for the current shell.</P>
<H3><A NAME="Heading19"></A><FONT COLOR="#000077">From Here…</FONT></H3>
<P>This chapter presented the commands you need to manage multiple processes. You saw that you run multiple processes whenever you put jobs in the background with the ampersand (&) or when you use pipes. You can schedule jobs at a specific time with the <TT>at</TT> command, at a time the system feels is appropriate with the <TT>batch</TT> command, and at regularly scheduled times with <TT>cron</TT> and <TT>crontab</TT>. For more information, see the following:</P>
<DL>
<DD><B>•</B> The chapters in Part III, “Managing the File System,” discuss how to monitor and maintain your Linux system. System administration isn’t an easy topic to learn and, in fact, requires a hands-on learning approach. This part of the book provides you with a basic understanding of the concepts and the tasks required of a systems administrator (often called a <I>sys admin</I>).
<DD><B>•</B> Chapter 18, “Understanding Linux Shells,” provides the shell-specific information to program scripts to start, stop, and monitor processes on your Linux system.
</DL>
<P>In addition, check out the man pages for the various commands discussed in this chapter.
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