In this post, the concept of .bashrc is introduced.

.bashrc

When a user first runs bash, it is designed to execute a specific set of files. These files can vary and be executed depending on the context. However for now, we will only consider the .bashrc file located in the home directory. By customizing the .bashrc file, we can modify our shell’s start-up configuration.

$PATH

In order to add locations to $PATH, you can do as follows. Click here to know more about PATH.

• open .bashrc file

    vi ~/.bashrc
  

  Notice that ‘~’ means the home directory.

• add PATH

    export PATH = "$PATH:/your/new/path"
  

  “$PATH:” means you append your new directory to existing $PATH data. If you do not write it, it will overwrite.

• source .bashrc

    source ~/.bashrc
  

alias

There are several ways to make alias. You can find out current aliases applied by typing ‘alias’.

temporary way

Easily, you can use the alias/unalias command to make alias as below. However, this alias will not exist when you exit and rerun the shell in the future.

update .bashrc

You can make permanent alias by configuring the .bashrc file. You can do so by as below.

• open .bashrc file

    vim ~/.bashrc
  

• add alias

    alias t='cd ~/environment/hello_linux; cat test'
  

  Notice that there should be no black or tabs between “=” after alias name and “ ‘ “.

• source .bashrc

    source ~/.bashrc
  

make .bash_aliases

You can make .bash_aliases file under home directory that defines your aliases and apply it to .bashrc file. The name .bash_aliases is a convention, you can use different name. Your .bash_aliases file may look like this.

alias t='cd ~/environment/hello_linux; cat test'
alias c='clear'
alias l='ls'
function test{
    if [ -f $1 ] ; then
        COMMAND
    else
        COMMAND
    fi
}

You can also define functions in it, but more details later. Now, you have add certain lines to your .bashrc file to use .bash_aliases.

if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases
fi

The grammar of if statement is as below. We check the existence of file with certain names with -f.

if [condition]; then
    code to execute
fi