How to set environemt variable without rebooting Ubuntu?

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http://askubuntu.com – Problem: During Android development, in order to add ADB path to environment variable; I did following things in short- gedit /etc/environment - Added my desired path in the file such as :/media/Software/00.AndroidLinux/ADT/sdk/platform-tools But, What I noticed that, adding path to the file has no effect to $PATH until I reboot my Ubuntu. My question is, How can I add path to /etc/environment variable, and without restarting Ubuntu?, So that I can work with my modified $PATH. Please Note: I'm new to Ubuntu and learning each day. (HowTos)