linux - Useful Commandline Commands on Unix

As there is a windows version of this question, I decided to open a community wiki for the same question under unix, linux, and the like.

I'll be updating this list with the answers:

• bash: exec 3<> /dev/tcp/localhost/80 # Redirect to port 80 of localhost


• find: search for files in a directory hierarchy



• htop: interactive process viewer, similar to top


• xargs: build and execute command lines from standard input


• tmux: detachable, re-attachable command line sessions


• apropo: find relevant man pages


• vmstat: See the state of your system

Websites:

• commandlinefu.com


• serverfault.com

Keyboard shortcuts:
- Ctrl T (BSD specific): send SIGINFO to a running program
- Magic SesRq key (Linux specific): en.wikipedia.org/wiki/Magic_SysRq_key