environ/3¶

environ(? EnvVar,+ EnvValue)*

Unify environment variable EnvVar with its value EnvValue, if there is one. This predicate is backtrackable in Unix systems, but not currently in Win32 configurations.

 ?- environ( 'HOME' ,V).

 V = 'C:\\cygwin\\home\\administrator' ?

EnvVar may be bound to an atom, or just be unbound. In the latter case environ//22 will enumerate over all environment variables.