Today we will look at an interesting topic of alias or aliases in Redhat or Centos Linux.
1. List current aliases. alias and “alias -p” commands are synonym to each other.
[root@nglinux ~]# alias
alias cp='cp -i'
alias l.='ls -d .* --color=auto'
alias ll='ls -l --color=auto'
alias ls='ls --color=auto'
alias mv='mv -i'
alias rm='rm -i'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'
[root@nglinux ~]#
OR,
[root@nglinux ~]# alias -p
alias cp='cp -i'
alias l.='ls -d .* --color=auto'
alias ll='ls -l --color=auto'
alias ls='ls --color=auto'
alias mv='mv -i'
alias rm='rm -i'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'
[root@nglinux ~]#
2. Creating new alias.
[root@nglinux ~]# alias msg="echo 'Welcome to NGELinux.com'"
[root@nglinux ~]# msg
Welcome to NGELinux.com
[root@nglinux ~]# alias
alias cp='cp -i'
alias l.='ls -d .* --color=auto'
alias ll='ls -l --color=auto'
alias ls='ls --color=auto'
alias msg='echo '\''Welcome to NGELinux.com'\'''
alias mv='mv -i'
alias rm='rm -i'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'
[root@nglinux ~]#
3. Removing alias: Use of unalias command.
[root@nglinux ~]# unalias msg
[root@nglinux ~]# alias
alias cp='cp -i'
alias l.='ls -d .* --color=auto'
alias ll='ls -l --color=auto'
alias ls='ls --color=auto'
alias mv='mv -i'
alias rm='rm -i'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'
[root@nglinux ~]# msg
-bash: msg: command not found
[root@nglinux ~]#
4. Making alias permanent.
There is no option with alias command to make it permanent.
Every time we reboot out system, the aliases gets removed.
To make it permanent, we need to add the alias command in our bashrc file (/etc/bashrc for system-wide seetings, and .bashrc for user-wide settings).
Let us take an example:
[root@nglinux ~]# cat /etc/profile | grep -i alias
# Functions and aliases go in /etc/bashrc
[root@nglinux ~]# cat /etc/bashrc | grep -i alias
# System wide functions and aliases
[root@nglinux ~]# cat .bash_profile | grep -i alias
# Get the aliases and functions
[root@nglinux ~]# cat .bashrc | grep -i alias
# User specific aliases and functions
alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'
5. Tip: How to run a command’s unaliased version.
[root@nglinux ~]# cd /
[root@nglinux /]# ls
bin boot cgroup dev etc home lib lost+found media mnt newpart opt proc root sbin selinux srv sys tmp usr var
[root@nglinux /]# \ls
bin boot cgroup dev etc home lib lost+found media mnt newpart opt proc root sbin selinux srv sys tmp usr var
[root@nglinux /]# alias ls
alias ls='ls --color=auto'
[root@nglinux /]#
To understand this, lets have a look at below screenshot.
We can see the color was there earlier, since the alias has “–color” parameter with it.
And when we ran its unaliased version we can see the list without color.
