Here are a few tips:
Tip: stty -echo
Description: Anything that is typed after this command does not appear on the screen (like when you type passwords on the terminal). This command can be undone by the stty echo command.
Tip: touch filename.date +%d
Description: Creates a file with the name filename.23 if the date on that day is the 23rd. You can add %m to also have the month in the name. Helps to have a track of when you made a particular file. (date +%d must be within backticks. pls fix this if someone can.)
Tip: !.
Description: Short command for ./a.out.
Tip: top -H -d <time> -p <PID>
Description: The top command gives information about the currently running processes on the OS. -H flag is used to display threaad level information. -d specifies the refresh rate of the command. -p is used to specify the process ID of the process about which you want top to display information about.
Tip: sudo !!
Description: The !! command gets the last command. For example, when you forget to add sudo in front of the command apt-get install <name> running sudo !! lets you update without having to type the whole command again.
Tip: last
Description: The “last” command show the history of last logged in users. This command searches through the file “/var/log/wtmp” and shows a list of logged-in and logged-out users along with tty’s.(tty is one of those funky Unix commands that prints the name of the terminal connected to standard input.)
Tip: curl ifconfig.me
Description: This command outputs your external IP address right into your terminal.