Ubuntu – Difference between $LOGNAME and logname

The 1st one sets the value to the variable. For instance you can do

echo $MAVEN_OPTS

and have it return the value but if you would issue that outside your shell you will have an empty string returned.

In comes export.

Export is an instruction to the shell. It tells the shell to make this environment variable available to other programs. Without the export, they are only available within the shell itself.

If you want the variable to be permanently available ssh reads ~/.ssh/environment,ssh2 reads /etc/environment and ~/.ssh2/environment, and adds lines of the format VARNAME=value to the environment. From the ssh man page.

~/.bashrc is usually read for secondary interactive shells after you log in. If you want to initialise your parameters on login the use ~/.profile instead. To apply you parameters system-wide use /etc/profile. It's the first file read by bash.

To make things clearer I think I'd explain a bit more.

• When you login, your login shell reads first the global /etc/profile, then ~/.profile and parameters/variables mentioned there are initialised. However you don't see this shell as terminal because the X-window system GUI is running.
• After login when you open a secondary terminal/terminal-emulator e.g. gnome-terminal ~/.bashrc is read and and the parameters/variables declared in it are available to the secondary terminal only. Note that this secondary terminal is a child process of your login shell.
• When you launch an application from menu, it's executed as a child process of your login shell and it inherits the parameters from it's ancestor process. But .bashrc was not available for the main login shell; so it's not available for applications too. So anything in .bashrc won't be available for those applications if run from menu. But when you open a gnome-terminal and executes command from there, applications are launched as children of gnome-terminal and inherits .bashrc's parameters from it.