On unix, you generally find the PATH being declared in a file called /etc/PATH, readonly by root that's read by the shell upon login. You can see if that's in your distro of linux or you can do what the others have already stated, that being editing (go vi!) your .profile or .bash_profile or you could export a new
path with the following:
$ echo $PATH
<path here>
$ export PATH=$PATH:<add in path extension here>
$ echo $PATH
<path with additions here>
This will add those extensions to your path ONLY for the duration of that shell. Once you exit, everything's cleaned up and those changes won't be permanent. This is a good thing though because you'll learn that with shell scripts, you'll want to 'jail' a shell script so that it's limited to what can be done, in the event it gets taken over by a "malicious" (Geez, hasn't the media overused that word) user.
$ echo $PATH
<path listed here with all kinds of directories>
$ cat foo
#!/bin/sh
PATH=/bin:/usr/bin
echo $PATH
$ ./foo
<path with only /bin and /usr/bin listed here>
It's a security thing mainly but it is useful. If you 'export' a path in a shell script, your remaining shell session will have said path in
the PATH variable...not really recommended.
Hope this helps.
