Environment Variables
Unix & MS-DOS provide a number of variables for passing information about
the state of the user's environment, the state in which their shell
is currently configured.
Under Unix, there may
be environment variables (usually named in allcaps) storing the user's:
- home directory path
(HOME)
- default printer (PRINTER)
- terminal type (TERM)
- current directory
path (PWD)
- ...and lots besides.
From within a C program, environment variables may be read by calling
char* getenv(char*)
a function whose prototype appears within stdlib.h
From the Unix shell,
environment variables may be read using printenv and set using setenv.
Refer to the Unix man
pages for further details.