Random things

I have yet to figure out where to put this information, which is why they are here, in the random chapter. These will be moved to different chapters in the future.

w command

The w command shows all the users, logged in to the computer. If you pass the -f flag, it toggles information about where each user is logged in from.

$ w 17:22:41 up 24 days, 11:37, 2 users, load average: 0.56, 0.50, 0.59 USER TTY LOGIN@ IDLE JCPU PCPU WHAT kdas tty2 31May17 22days 3:07m 3:16 i3 -a –restart /run/user/1000/i3/restart-state.28641

How long is the system running?

We have the uptime command which gives us information about how long the system is running. You can figure out the last time the system turned off or rebooted at a glance. For my laptop, it was 24 days ago.

$ uptime 17:31:30 up 24 days, 11:46, 2 users, load average: 0.76, 0.98, 0.81

Finding CPU time of a command

The time command will help you to find the CPU time spent for any command. The following example will tell us how much time `du -sh took to calculate the disk usage.

$ time du -sh
5.5G        .

real        0m1.026s
user        0m0.235s
sys 0m0.783s

dmesg command

The dmesg command prints out messages from the kernel buffer. Using this tool we can learn about the messages and information from the kernel drivers during and after the boot up process. This can be very handy when troubleshooting; for e.g. when the machine fails to boot or a certain piece of hardware does not function correctly.

Whats next?

After you are familiar with the commands in this book, we would suggest you to learn shell scripting.

Start from https://www.shellscript.sh and then you can read the beginners bash guide.