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Show process tree
Show process tree

pstree is similiar enough to ps, except it displays the processes in a graphical manner, using ascii characters to build up a tree to give a visualisation of how the processes link into one another and what runs what. This can be useful if you need to kill the starter of a process to prevent it from restarting the process you wish to stop. It also visually merges lines of repetition so that if a process is running 8 or 9 times it is only displayed once by pstree but its name is prefixed by the number or occurances of the process and a * to indicated the number of times that the process is currently running.

$ pstree 

init-+-6*[WindowMaker]
     |-WindowMaker---xterm---bash---mozilla-bin---mozilla-bin---4*[mozilla-bin]
     |-7*[Xvnc]
     |-apache---12*[apache]
     |-apache-ssl-+-15*[apache-ssl]
     |            `-gcache
     |-bdflush
     |-bnc
     |-cron
     |-5*[fetchmail]
     |-6*[getty]
     |-inetd-+-2*[imapd]
     |       `-2*[stunnel]
     |-java---java---9*[java]
     |-keventd
     |-khubd
     |-7*[kjournald]
     |-klogd
     |-ksoftirqd_CPU0
     |-ksoftirqd_CPU1
     |-kswapd
     |-kupdated
     |-log2mail
     |-oidentd
     |-postmaster---postmaster---postmaster
     |-safe_mysqld---mysqld---mysqld---21*[mysqld]
     |-safe_mysqld---mysqld---mysqld---2*[mysqld]
     |-2*[screen---bash---ncftp]
     |-4*[screen---bash]
     |-screen-+-bash
     |        `-mutt
     |-2*[screen---irssi]
     |-5*[screen---BitchX]
     |-2*[screen---bitchx]
     |-screen---2*[bash]
     |-2*[screen---ncftp]
     |-snmpd
     |-snmptrapd
     |-snort
     |-sshd-+-sshd---sshd---bash---irssi
     |      |-7*[sshd---sshd---bash]
     |      |-sshd---sshd---bash-+-2*[talk]
     |      |                    `-2*[vim]
     |      |-sshd---sshd---bash---mutt
     |      |-sshd---sshd---bash-+-pstree
     |      |                    `-talk
     |      `-sshd---sshd---bash---talk
     |-syslog-ng
     |-walter
     `-xfs

As you can see its a little hard to work out who's running what, but it does give a clear indication of just how the various processes are interconnected. This will probably be the most common way that pstree is used but again man pstree will give a full list of all the options and you can even use pstree to just give the graphical representation of the processes being run by a single user.