Environment Variables

Every process has an environment block that contains a set of environment variables and their values. The command processor provides the set command to display its environment block or to create new environment variables. Programs started by the command processor inherit the command processor's environment variables.

By default, a child process inherits the environment variables of its parent process. However, you can specify a different environment for the child process by creating a new environment block and passing a pointer to it as a parameter to the CreateProcess function.

The GetEnvironmentStrings function returns a pointer to the environment block of the calling process. This should be treated as a read-only block; do not modify it directly. Instead, use the SetEnvironmentVariable function to change an environment variable. When you are finished with the environment block obtained from GetEnvironmentStrings, call the FreeEnvironmentStrings function to free the block.

The GetEnvironmentVariable function determines whether a specified variable is defined in the environment of the calling process, and, if so, what its value is.

For more information, see the examples in Changing Environment Variables.