This command is used to show who is logged in currently on the system. It comes from “coreutils-x.x” package. This will give useful information about the currently logged in users and their login related details like time stamps etc. Every system administrator or Linux enthusiast should know about this command and its optional switches.
Examples:
1. To see who is logged in
| $ who |
2. To see all the details provided by this command in one switch, use “-a”,
| $ who -a |
3. To see when was the last time of system booted, use this switch i.e. “-b”
| $ who -b |
4. To see the dead processes
| $ who -d |
5. To see the column headings in the output of “who” command, so we get to know what information is mentioned in that particular column.
| $ who -H |
6. To print system login processes
| $ who -l |
7. To print active processes spawned by init
| $ who -p |
8. To get the names of who all are logged into the system and get the count the all logins use “-q” switch option.
| $ who -q |
9. This command also give information about the systems current runlevel, with the “-r” switch, as below
| $ who -r |
10. To print system last clock change
| $ who -t |
