Initialisation files are a special kind of file that is read
when a program is started.
When a user logs in, the operating system
starts some default scripts, which set up the standard path, the user,
the home directory and the system's default environment. Each user can
have a special file usually called .profile in their home
directory, which is run for them at login. In addition the shells also
have special scripts that set up aliases and the like for users. For
bash the initialisation file is called .bashrc, for
csh it is .cshrc. If some alias or path change should be made
permanent it should be entered into the shell's initialisation file.
If a change is made to the shell's initialisation file it has to be
reread by the shell. Simply executing the script will not have any
effect as the shell will not inherit the child's (or script's)
environment. We have to use the special source
command:
$source ~/.bashrc $