extern "C" CMDAPIIMPORT APIRET CMDUnsetEnv ( const char * name ) ;
This function unsets the value of the environment variable named by the string pointed to by the name parameter. It returns zero on success and a non-zero system error code on failure. The non-existence of an environment variable by the given name is treated as failure.
If the environment variable name contains an equals ('=') character, the behaviour is undefined.