alias

Create an alias, aliases allow a string to be substituted for a word when it is used as the first word of a simple command.

Syntax
      alias [-p] [name[=value] ...]

      unalias [-a] [name ... ]

Key
   -p   Print the current values

   -a   Remove All aliases

If arguments are supplied, an alias is defined for each name whose value is given.

If no value is given, alias will print the current value of the alias.

Without arguments or with the -p option, alias prints the list of aliases on the standard output in a form that allows them to be reused as input.

The value cannot contain any positional parameters ($1 etc), if you need to do that use a shell function instead.

The name may not be 'alias' or 'unalias'.

unalias may be used to remove each name from the list of defined aliases.

Make an alias permanent

Use your favorite text editor to create a file called ~/.bash_aliases, and type the alias commands into the file.
.bash_aliases will run at login (or you can just execute it with ..bash_aliases )

Expand Multiple aliases

If the last character of the alias value is a space or tab character, then the next command word following the alias is also checked for alias expansion.

Examples:

Create an alias 'c' that will clear the screen:
$ alias c='clear'

Create an alias 'ls' that will change the default action of ls:
$ alias ls='ls --classify'
$ ls
$ unalias ls

More aliases for ls:
$ alias la='ls -lAXh --color=always'   #Show all, sort by extension
$ alias ls-al='ls -al'   #fix typo missing space
$ alias l="ls -l"
$ alias la="ls -la"

Use alias to cd into to sub-sub directories:
$ alias ..='cd ..'
$ alias ...='cd ../..'
$ alias ....='cd ../../..'

Use alias to fix missing space typos:
$ alias cd..='cd ..'

Display the working directory
$ alias .='echo $PWD'

Prevent accidental deletions by making rm interactive:
$ alias rm='rm -i'

Shorten apt-get installation commands:
$ alias canhaz='sudo apt-get install'

Run firefox and open a specific website:
$ alias fftr='/home/simon/firefox/firefox http://ss64.com'

Details

The first word of each simple command, if unquoted, is checked to see if it has an alias. If so, that word is replaced by the text of the alias. The alias name and the replacement text may contain any valid shell input, including shell metacharacters, with the exception that the alias name may not contain `='.

The first word of the replacement text is tested for aliases, but a word that is identical to an alias being expanded is not expanded a second time. This means that one may alias ls to "ls -F", for instance, and Bash does not try to recursively expand the replacement text.

Aliases are not expanded when the shell is not interactive, unless the expand_aliases shell option is set using shopt .

The rules concerning the definition and use of aliases are somewhat confusing. Bash always reads at least one complete line of input before executing any of the commands on that line. Aliases are expanded when a command is read, not when it is executed. Therefore, an alias definition appearing on the same line as another command does not take effect until the next line of input is read. The commands following the alias definition on that line are not affected by the new alias. This behavior is also an issue when functions are executed. Aliases are expanded when a function definition is read, not when the function is executed, because a function definition is itself a compound command. As a consequence, aliases defined in a function are not available until after that function is executed. To be safe, always put alias definitions on a separate line, and do not use alias in compound commands.

`alias' and `unalias' are BASH built-ins. For almost every purpose, shell functions are preferred over aliases.

“There are many reasons why novelists write, but they all have one thing in common - a need to create an alternative world” ~ John Fowles

Related:

export - Set an environment variable
env - Display, set, or remove environment variables
echo - Display message on screen
readonly - Mark variables/functions as readonly
shift - Shift positional parameters
alias.sh - Manage all of your aliases online
Equivalent Windows command: SET - Display, set, or remove Windows environment variables.


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