how TOP command gets USER information

[dileepkantamneni]

Hi all ,
when i type command top I got the message as follws

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 15 0 2100 720 624 S 0.0 0.1 0:01.06 init
2 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
3 root 34 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/0
4 root 10 -5 0 0 0 S 0.0 0.0 0:00.04 events/0
5 root 18 -5 0 0 0 S 0.0 0.0 0:00.00 khelper
6 root 11 -5 0 0 0 S 0.0 0.0 0:00.00 kthread
9 root 10 -5 0 0 0 S 0.0 0.0 0:00.00 kblockd/0

I want to know how this top command getting USER information exactly.

[dally]

The top program provides a dynamic real-time view of a running system.
It can display system summary information as well as a list of tasks
currently being managed by the Linux kernel. The types of system sum-
mary information shown and the types, order and size of information
displayed for tasks are all user configurable and that configuration
can be made persistent across restarts.

[Lakshmipathi]

how this top command getting USER information exactly.

If i'm not wrong,all process related informations are obtain from /proc directory.Here you will have a directory for each and every running process will have thier information here.Check man proc.

You can also explore source code top,to exactly track down how it ges the info.