Many of us, customize our shells under Unix (for the difference between Unix and UNIX - see the Art of Unix Programming). We usually add to our PATH environment variable. Usually what we do is
PATH=$PATH:[paths to add]
Lets assume this file is called .profile and is read by the shell on start-up. This approach is good, but if the user were to change our .profile and run
Then on seeing the PATH variable, it would have repeated path names.
If the change to PATH was
The on running . $HOME/.profile for the first time the user would see PATH as
[original]:[user's home directory]/bin:.:[user's home directory]/bin:.
One easy way to work around this problem is to use the following approach in your .profile
and then customize PATH as the user did previously, repeated running of
. $HOME/.profile shall now not cause the PATH environment variable to grow uncontrollably