Deletes all instances of the environment variable name from the
    environment list.

    Format

      #include  <stdlib.h>

      void unsetenv  (const char *name);

1  –  Argument

 name

    The environment variable to delete from the environment list.

2  –  Description

    The unsetenv function deletes all instances of the variable name
    pointed to by the name argument from the environment list.