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USER related commands in UNIX


whoami
The command lets you know the user name of the current shell you are at.

Example:
root@Microknoppix:/home/knoppix# whoami
root
root@Microknoppix:/home/knoppix# su knoppix
knoppix@Microknoppix:~$ whoami
knoppix

su
The su command is used to become another user during a login session. Invoked without a username, su defaults to becoming the superuser. The optional argument - may be used to provide an environment similar to what the user would expect had the user logged in directly.

Example :
root@Microknoppix:/home/knoppix# su knoppix
password:
knoppix@Microknoppix:~$

knoppix@Microknoppix:/root$ su -
password:
root@Microknoppix:~#

knoppix@Microknoppix:/root$ su
password:
root@Microknoppix:~#

finger
The finger displays information about the system users.
Example:
root@Microknoppix:~# finger knoppix
Login: knoppix Name: Knoppix User
Directory: /home/knoppix Shell: /bin/bash
On since Sun Jun 30 01:43 (UTC) on console from :0
2 hours 8 minutes idle
(messages off)
On since Sun Jun 30 01:43 (UTC) on :0 (messages off)
On since Sun Jun 30 03:31 (UTC) on pts/0 from :0
No mail.
No Plan.

root@Microknoppix:~# finger root
Login: root Name: root
Directory: /root Shell: /bin/bash
Never logged in.
No mail.
No Plan.




who
Print information about users who are currently logged in.

who -a, who --all
knoppix@Microknoppix:/root$ who -a
2013-06-30 01:43 1858 id=si term=0 exit=0
system boot 2013-06-30 01:43
run-level 5 2013-06-30 01:43 last=S
2013-06-30 01:43 2482 id=1
2013-06-30 01:43 2486 id=x1
2013-06-30 01:43 2485 id=4
2013-06-30 01:43 2484 id=3
2013-06-30 01:43 2483 id=2
knoppix - console 2013-06-30 01:43 old 2486 (:0)
knoppix ? :0 2013-06-30 01:43 ? 2486
knoppix + pts/0 2013-06-30 03:31 . 12227 (:0)

who -d, who --dead
To print dead processes
knoppix@Microknoppix:/root$ who -d
2013-06-30 01:43 1858 id=si term=0 exit=0
who -p, who --process
To print active processes spawned by init.

knoppix@Microknoppix:/root$ who -p
2013-06-30 01:43 2482 id=1
2013-06-30 01:43 2486 id=x1
2013-06-30 01:43 2485 id=4
2013-06-30 01:43 2484 id=3
2013-06-30 01:43 2483 id=2

who -q, who--count
To list all login names and number of users logged on
knoppix@Microknoppix:/root$ who -q
knoppix susilaarya susil
# users=3


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