Inserts or resets the environment variable name in the current
    environment list.

    Format

      #include  <stdlib.h>

      int setenv  (const char *name, const char *value, int

                  overwrite);

1 - Arguments

 name

    A variable name in the environment variable list.

 value

    The value for the environment variable.

 overwrite

    A value of 0 or 1 indicating whether to reset the environment
    variable, if it exists.

2 - Description

    This function inserts or resets the environment variable name
    in the current environment list. If the variable name does not
    exist in the list, it is inserted with the value argument. If the
    variable does exist, the overwrite argument is tested. When the
    overwrite argument value is:

    o  0 (zero) - then the variable is not reset.

    o  1 - then the variable is reset to value.

3 - Return Values

    0                  Indicates success.
    -1                 Indicates an error. errno is set to ENOMEM-
                       Not enough memory available to expand the
                       environment list.