If You Did Not Know ...: Environment variables in Ubuntu

Hi guys,

I have been using the .bashrc file for long time but it was today that I understood clearly the syntax of export in .bashrc file.
Before, going into that let's get to know about the environment variables little bit more.
When we open a terminal session and type in a command like ls it is searched in the directories that are marked by the PATH variable.
PATH is an environment variable.
An environment variable is a variable that persists for the life of a terminal session. The applications running in that session can access these variables. A listing of all the environment variables can be obtained by

PATH environment variable has a special format. Use echo command to have a look at the variable:

PATH variable is a : separated set of directories. All these directories will be searched when you execute a command in the terminal.
Let's give the PATH variable a different set of values

export PATH=/usr/bin:/usr/sbin
now, if we execute the ls command once again it will give an error because it no longer has /bin in the PATH variable.

Instead of changing or replacing the current set of directories in the PATH variable what you should do is to append it.

These changes, however, will be only valid to the current session. In order to making the changes permanent we can use a specific file called .bashrc file.

In Ubuntu (UNIX), files beginning with . are configuration files and are usually hidden.
To view these files use ls -a

if you wish to have certain directories automatically added to PATH variable simply place those commands at the end of this file

p.s.

If you are interested in knowing the full path of a binary like ls you can use the command which to find that out

e.g. abc@def:~$ which ls will give you the result -> /bin/ls
so, the executable ls is located in /bin directory

credit should go to the original contributor at http://www.cs.purdue.edu/homes/cs348/unix_path.html

If You Did Not Know ...