100 Useful Command-Line Utilities

by Oliver; 2014

53. alias, unalias

As mentioned in An Introduction to the Command-Line (on Unix-like systems) - Aliases, Functions, aliasing is a way of mapping one word to another. It can reduce your typing burden by making a shorter expression stand for a longer one: This means every time you type a c the terminal is going to read it as cat, so instead of writing:

$ cat file.txt

you just write:

$ c file.txt

Another use of alias is to weld particular flags onto a command, so every time the command is called, the flags go with it automatically, as in: or Recall the former allows you to copy directories as well as files, and the later allows you to make nested directories. Perhaps you always want to use these options, but this is a tradeoff between convenience and freedom. In general, I prefer to use new words for aliases and not overwrite preexisting bash commands. Here are some aliases I use in my setup file:

# coreutils
alias c="cat"
alias e="clear"
alias s="less -S"
alias l="ls -hl"
alias lt="ls -hlt"
alias ll="ls -al"
alias rr="rm -r"
alias r="readlink -m"
alias ct="column -t"
alias ch="chmod -R 755"
alias chh="chmod -R 644"
alias grep="grep --color"
alias yy="rsync -azv --progress"
# remove empty lines with white space
alias noempty="perl -ne '{print if not m/^(\s*)$/}'"

# awk 
alias awkf="awk -F'\t'"
alias length="awk '{print length}'"
# notesappend, my favorite alias
alias n="history | tail -2 | head -1 | tr -s ' ' | cut -d' ' -f3- | awk '{print \"# \"\$0}' >> notes"

# HTML-related
alias htmlsed="sed 's|\&|\&amp\;|g; s|>|\&gt\;|g; s|<|\&lt\;|g;'"

# git
alias ga="git add" 
alias gc="git commit -m"
alias gac="git commit -a -m"
alias gp="git pull"
alias gpush="git push"
alias gs="git status"
alias gl="git log"
alias gg="git log --oneline --decorate --graph --all"
# alias gg="git log --pretty=format:'%h %s %an' --graph"
alias gb="git branch"
alias gch="git checkout"
alias gls="git ls-files"
alias gd="git diff"

To display all of your current aliases:

$ alias

To get rid of an alias, use unalias, as in:

$ unalias myalias

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