Thursday, April 30, 2015

w Command

Hello everyone,

Yesterday, I came across a very useful command that I thought it's very helpful/useful to share with everybody if you don't know it already. The command is called "w". Yes, just w.

                                                                            Figure 1 

w shows who is logged on the server or machine and  what they are doing. Referring to Figure 1, I just ran w command and it shows me that currently two persons logged in to server. Under USER column, the second user is me "ktaraghi" that ran w command and you can see it under WHAT column.

Let me explain in more details:
The first row, as you see in Figure 1, shows useful information about machine, users and processes. So, the first item in the first row shows the current time and the second item shows how long the system has been running. The third item shows how many users are currently logged on and the last item shows the system load averages for the past 1, 5, and 15 minutes.

The second row, shows column headers which are (from left to right): Usernames currently logged in, the tty name or terminal name, the login time, idle time, JCPU and PCPU. According to man page, the JCPU time is the time used by all processes attached to the tty and it doesn't include past background jobs, but does include currently running background jobs.
The PCPU time is the time used by the current process, named in the "WHAT" column.

There are some switches that is used with this command.
w -h :Don't print the headers

                                                                             Figure 2

w -s :Short format. Don't print the login name, JCPU, and PCPU.

                                                                              Figure 3

w -f :Adds another column "FROM" which shows remote hostname or IP

                                                                               Figure 4

and finally, -V which shows the version of w command.
Hopefully you enjoyed,
Khosro Taraghi

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