This appendix describes how Emacs uses environment variables. An environment variable is a string passed from the operating system to Emacs, and the collection of environment variables is known as the environment. Environment variable names are case sensitive and it is conventional to use upper case letters only.
Because environment variables come from the operating system there is no
general way to set them; it depends on the operating system and
especially the shell that you are using. For example, here's how to set
the environment variable
ORGANIZATION to `not very much'
export ORGANIZATION="not very much"
and here's how to do it in csh or tcsh:
setenv ORGANIZATION "not very much"
When Emacs is set-up to use the X windowing system, it inherits the use of a large number of environment variables from the X library. See the X documentation for more information.