Aliases not available when using sudo

I was playing around with aliases today and I noticed that aliases don't seem to be available whilst using sudo:

danny@kaon:~$ alias
alias egrep='egrep --color=auto'
alias fgrep='fgrep --color=auto'
alias grep='grep --color=auto'
alias l='ls -CF'
alias la='ls -A'
alias ll='ls -alF'
alias ls='ls --color=auto'

danny@kaon:~$ ll -d /
drwxr-xr-x 23 root root 4096 2011-01-06 20:29 //

danny@kaon:~$ sudo -i
root@kaon:~# ll -d /
drwxr-xr-x 23 root root 4096 2011-01-06 20:29 //
root@kaon:~# exit
logout

danny@kaon:~$ sudo ll -d /
sudo: ll: command not found

Is there any reason why you cannot use aliases whilst using sudo?

Solution 1:

Add the following line to your ~/.bashrc:

alias sudo='sudo '

From the bash manual:

Aliases allow a string to be substituted for a word when it is used as the first word of a simple command. The shell maintains a list of aliases that may be set and unset with the alias and unalias builtin commands.

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 characters ‘/’, ‘$’, ‘`’, ‘=’ and any of the shell metacharacters or quoting characters listed above may not appear in an alias name. The replacement text may contain any valid shell input, including shell metacharacters. 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. 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.

^{(Emphasis mine).}
Bash only checks the first word of a command for an alias, any words after that are not checked. That means in a command like sudo ll, only the first word (sudo) is checked by bash for an alias, ll is ignored. We can tell bash to check the next word after the alias (i.e sudo) by adding a space to the end of the alias value.

Solution 2:

I wrote a Bash function for it that shadows sudo.

It checks whether I have an alias for the given command and runs the aliased command instead of the literal one with sudo in that case.

Here is my function as one-liner:

sudo() { if alias "$1" &> /dev/null ; then $(type "$1" | sed -E 's/^.*`(.*).$/\1/') "${@:2}" ; else command sudo $@ ; fi }

Or nicely formatted:

sudo() { 
    if alias "$1" &> /dev/null ; then 
        $(type "$1" | sed -E 's/^.*`(.*).$/\1/') "${@:2}"
    else 
        command sudo "$@"
    fi 
}

You can append it to your .bashrc file, don't forget to source it or restart your terminal session afterwards to apply the changes though.

Solution 3:

The aliases are user specific - you need to define them in /root/.bashrc

Solution 4:

@Alvins answer is the shortest one. No doubt! :-)

However I thought of a command line solution to execute an aliased command in sudo where there is no need to redefine sudo with an alias command.

Here is my proposal for those to whom it may interest:

Solution

type -a <YOUR COMMAND HERE> | grep -o -P "(?<=\`).*(?=')" | xargs sudo

Example

In the case of the ll command

type -a ll | grep -o -P "(?<=\`).*(?=')" | xargs sudo

Explanation

when you have an alias (such as: ll) the command type -a returns the aliased expression:

$type -a ll
ll is aliased to `ls -l'

with grep you select the text between the accent ` and apostrophe ' in that case ls -l

And xargs executes the selected text ls -l as parameter of sudo.

Yes, a bit longer but completely clean ;-) No need to redefine sudo as alias.