Linux shell tips and tricks

I’m using Linux shell (Bash) on a daily basis, but I often forgot some useful command or shell tip. Yes, I can remember commands, but I can’t say that if I used it just once for a specific task. Then I started to write Linux shell tips in a text file on my Dropbox account and now I decided to share that. This list will be updated over time. Also, keep in mind that for some tips you will need to install additional software on your Linux distribution.