Bash Aliases¶
Intro¶
Read the bash docs on aliases. Basically, we do something like this:
alias ls='ls --classify --color=auto'
alias tt='tree -CFa'
Then, when we run the “command” ls, it will actually run
ls --classify --color=auto and when we run tt it will actually
run tree -CFa
How To Unalias‽¶
We aliased ls to ls. It is not uncommon to do this for some
commands. But what if we want to run the “original” ls, not its
aliased version? What if we don’t want --classify or
--color=auto in a given situation? Then we can make prevent the
shell from treating the word as an alias to be expanded.
The bash man page on the Aliases section states that:
“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.”
-- Bash man page on the Aliases section
According to the man page, if we quote the word, bash won’t try to treat it as an alias to be expanded.
How do we do this quoting thing‽ We can use either single or double quotation marks or escape it with a basckslash.
The screenshot shows how to see what an alias expands to (alias
ls) and then proceeds to first run the aliased ls, which shows
classification indication (“/” at the end of directories, “*” at the
end of executable files, etc. and different colors for different types
of files as well, like bluish for directories and greenish for
executables). Then, the remaining three commands show the ways to
quote a word.
Note
In bash, in certain contexts the basckslash is not an escape, but a quoting mechanism.
Manually Expanding Aliases¶
When the word at the cursor is an alias, we can expand it. For
example, type lsEscTab. Esc can also be triggered
with Ctrl-[.
$ alias ls='ls --classify --color=always'
$ ls<Esc><Tab>
The line gets replaced with:
$ ls --classify --color=always
Tricky aliases 😮¶
One could be evil and create an alias with this:
alias '\ls'='ls ...'
Then one would try to prevent the ls alias with \ls but that
would be itself an alias… Thankfully, as of 2021 (at least), Bash
doesn’t allow aliases name like that.
Another example:
$ 'he'
-bash: he: command not found
$ alias w00t='echo w00t'
$ w00t
w00t
$ \w00t
-bash: w00t: command not found
$ 'w00t'
-bash: w00t: command not found