alias (define command shortcuts)
The alias shell builtin creates a command shortcut. It comes in handy if you often use a command with particular options and want to save yourself some typing. Try entering the following in your shell:
alias ll=`ls -l'
From now on, whenever you type ll, the command ls -l will be executed. You have essentially created a new command out of an existing command – an alias. To display the aliases that are in effect, call alias without arguments. If you want to remove an alias that you created, use the command unalias.
The shell will “forget” about your aliases once you log out, unless you save them in one of your Bash configuration files, such as ~/.bashrc. Many people keep the following aliases there to avoid deleting files by mistake:
alias cp=`cp -i'
alias mv=`mv -i'
alias rm=`rm -i'
The option -i (“interactive”) makes the above commands ask for your permission before overwriting or deleting files. You should put these aliases in your ~/.bashrc if you haven't already.