B.4.1 Values of environment variables

Values for environment variables are obtained by the following means, which are arranged in order of decreasing precedence:

1. Command-line options. See Invocation.
2. The environment configuration file—more on this below.
3. Actual environment variables (defined in the shell or other parent process).

The environment configuration file is located through application of the usual algorithm for configuration files (see File locations), except that its contents do not affect the search path used to find environment itself. Use of environment is discouraged on systems that allow an arbitrarily large environment; it is supported for use on systems like MS-DOS that limit environment size.

environment is composed of lines having the form key=value, where key and the equals sign (=) are required, and value is optional. If value is given, variable key is given that value; if value is absent, variable key is undefined (deleted). Variables may not be defined with a null value.

Environment substitutions are performed on each line in the file (see Environment substitutions).

See Configuration files, for more details on formatting of the environment configuration file.

Please note: Support for environment is not yet implemented.