These are a few of my favorite commands ...

I'm imagining Julie Andrews singing this :)

tail -f [filename]
The tail command shows the last few lines of a file. When you run with the
flag, tail keeps running and updates when the file is updated. This is commonly used when you want to monitor the progress of a background task. Press
to stop output.
cat [filename] | awk '{print $2 " " $3 " " $4}'
This will print the 2nd, 3rd, and 4th columns of a file. Columns are delimited by whitespace. Different delimiters can be given with the
find . | grep [regex]
This finds all files in this directory and subdirectories that matches the regular expression.
Have you ever started a linux command that takes 5 hours and then 4 hours in your terminal closes and the command stops? I have, and I swore at my computer. If you run screen, you can run the command and then detach from the screen and log out of the terminal without the command stopping. Amaze Balls! To do this, run: screen; [command]; Ctrl-a d. To resume screen: screen -r. To see the open screen sessions: screen -ls. To exit a screen session: exit.
sed -i s/string_to_replace/replacement_string/g [filename]
This replaces all occurences of 'string_to_replace' with 'replacement_string' in the file. You can do the replacement in multiple files like your entire codebase if [filename] = src/*.cpp.
watch -n [seconds] [command]