A nice chunk of useful tips for unix:

Bash

• In bash, ctrl-r searches your command history as you type.
• Input from the commandline as if it were a file by replacing command < file.in with command <<< "some input text":
• ^ is a sed-like operator to replace chars from last command:
  ls docs; ^docs^web^ is equal to ls web.
  The second argument can be empty.
• !!:n selects the nth argument of the last command, and !$ the last arg: ls file1 file2 file3; cat !!:1-2 shows all files and cats only 1 and 2.
• nohup ./long_script & to leave stuff in background even if you logout.
• cd - to change to the previous directory you were working on.
• Ctrl-x Ctrl-e opens an editor to work with long or complex command lines.
• Add set editing-mode vi in your ~/.inputrc to use the vi keybindings for bash and all readline-enabled applications (python, mysql, etc).

Pseudo aliases for commonly used long commands

• function lt() { ls -ltrsa "$@" | tail; }
• function psgrep() { ps axuf | grep -v grep | grep "$@" -i --color=auto; }
• function fname() { find . -iname "*$@*"; }

Tools

• htop instead of top.
• ranger is a nice console file manager for vi fans.
• Use apt-file to see which package provides that file you`re missing.
• dict is a commandline dictionary.
• trash-cli sends files to the trash instead of deleting them forever.
• sort | uniq to check for duplicate lines.
• echo start_backup.sh | at midnight starts a command at the specified time.
• Pipe any command over column -t to nicely align the columns.
• diff --side-by-side fileA.txt fileB.txt | pager to see a nice diff.
• learn to use pushd to save time navigating folders.
• run jobs in parallel easily: ls \*.png | parallel -j4 convert {} {.}.jpg.

Networking

• python -m SimpleHTTPServer 8080 shares all the files in the current folder over HTTP, port 8080.
• ssh -R 12345:localhost:22 server.com "sleep 1000; exit" forwards server.com's port 12345 to your local ssh port, even if you machine is not externally visible on the net. Now you can ssh localhost -p 12345 from server.com and you will log into your machine. sleep avoids getting kicked out from server.com for inactivity.
• socat TCP4-LISTEN:1234,fork TCP4:192.168.1.1:22 forwards your port 1234 to another machine`s port 22. Very useful for quick NAT redirection.
• lsof -i monitors network connections in real time.
• iftop shows bandwith usage per connection.
• nethogs shows the bandwith usage per process.
• Pipe a compressed file over ssh to avoid creating large temporary .tgz files:
  tar cz folder/ | ssh server "tar xz" or even better, use rsync.
• ssmtp can use a Gmail account as SMTP and send emails from the command line:
  echo "Hello, User!" | mail user@domain.com
  Configure your /etc/ssmtp/ssmtp.conf:

root=<email>
mailhub=smtp.gmail.com:587
rewriteDomain=
hostname=smtp.gmail.com:587
UseSTARTTLS=YES
UseTLS=YES
AuthUser=<email>
AuthPass=<password>
AuthMethod=LOGIN
FromLineOverride=YES

-~- (CC) by-nc, Carles Fenollosa carles.fenollosa@bsc.es
Retrieved from http://mmb.pcb.ub.es/~carlesfe/unix/tricks.txt
Last modified: lun 11 mar 2013 05:13:37 CET
Taken from http://mmb.pcb.ub.es/~carlesfe/unix/tricks.txt