PS – it's just like Top but shows more information

ps – Displays The Processes

ps command will report a snapshot of the current processes. To select all processes use the -A or -e option:
# ps -A
Sample Outputs:

ps -A
PID TTY TIME CMD
1 ttyp0 00:00:22 init
89 ? 00:00:00 init-logger
142 ? 00:00:00 udevd
634 ? 00:00:00 syslog-ng
635 ? 00:20:39 syslog-ng
718 ? 00:00:00 zabbix_agentd
720 ? 00:04:02 zabbix_agentd
736 ? 00:00:00 xinetd
754 ? 00:00:00 mysqld_safe
784 ? 21:08:05 mysqld
788 pts/2 00:00:00 zsh
820 ? 00:00:01 logger
826 ? 00:00:00 httpd
827 ? 00:00:34 httpd
1154 ? 00:00:00 gam_server
1633 ? 00:05:30 httpd
1642 ? 00:00:05 pure-ftpd
....
32656 ? 00:00:00 exim
32659 ? 00:00:02 php5
32660 ? 00:00:00 php5
32691 ? 00:00:00 gam_server
32698 ? 00:00:01 php5
32700 ? 00:00:00 php5
32704 ? 00:00:00 exim
32705 ? 00:00:00 cpsrvd-ssl
32707 pts/0 00:00:00 ps

Now for some switches that will allow you to do a lot more with this command:

Show Long Format Output

# ps -Al

To turn on extra full mode (it will show command line arguments passed to process):

# ps -AlF

To See Threads ( LWP and NLWP)

# ps -AlFH

To See Threads After Processes

# ps -AlLm

Print All Process On The Server

# ps ax
# ps axu

Print A Process Tree

# ps -ejH
# ps axjf
# pstree

Print Security Information

# ps -eo euser,ruser,suser,fuser,f,comm,label
# ps axZ
# ps -eM

See Every Process Running As User Vivek

# ps -U vivek -u vivek u

Set Output In a User-Defined Format

# ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm
# ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm
# ps -eopid,tt,user,fname,tmout,f,wchan

Display Only The Process IDs of httpd (apache)

# ps -C httpd -o pid=
OR
# pgrep httpd
OR
# pgrep -u vivek php-cgi

Display The Name of PID 58721

# ps -p 58721 -o comm=

Find Out The Top 10 Memory Consuming Process

# ps -auxf | sort -nr -k 4 | head -10

Find Out top 10 CPU Consuming Process

# ps -auxf | sort -nr -k 3 | head -10

Finally – when in doubt – consult the man page…

Mix it up a little and do some testing – I promise this will become a best friend in your arsenal.