Friday, May 25, 2007

Checking out all the running process in Linux system

Everybody know that "ps" command can be used to find out the running processes in a Linux OS. But "top" is not so well-known as "ps". Sometimes it's a much better way to view all the processes, because it displays the information DYNAMICALLY!
I happened to find the article today: Show all running processes in Linux .

Here's the content:
ps command gives a snapshot of the current processes. If you want a repetitive update of this status, use top command.

Task: Use ps commandType the following ps command to display all running process
# ps aux less

-A: select all processes
a: select all processes on a terminal, including those of other users
x: select processes without controlling ttys

Task: see every process on the system
# ps -A
# ps -e

Task: See every process except those running as root
# ps -U root -u root -N
Task: See process run by user vivek
# ps -u vivek

Task: Use top command
The top program provides a dynamic real-time view of a running system. Type the top at command prompt:
# top
To quite press q for help press h.

Task: display a tree of processespstree shows running processes as a tree.
The tree is rooted at either pid or init if pid is omitted. If a user name is specified, all process trees rooted at processes owned by that user are shown.

Task: Lookup process
Use pgrep command. pgrep looks through the currently running processes and lists the process IDs which matches the selection criteria to screen.
For example display firefox process id:
$ pgrep firefox
Following command will list the process called sshd which is owned by root user.
$ pgrep -u root sshd

Say hello to htop
htop is interactive process viewer just like top, but allows to scroll the list vertically and horizontally to see all processes and their full command lines. Tasks related to processes (killing, renicing) can be done without entering their PIDs.
To install htop type command:
# apt-get install htopor
# yum install htop
Now type htop to run the command:
# htop

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