_CP_clearfile is equivalent to the clearfile BASIC statement.
int _CP_clearfile(int expression)
The expression should be an integer file descriptor returned by the _CP_open call. This function returns -1 if an error occurs. The error code is contained in _CP_errno.
CPSTR * s = _CP_mkstr("myfile");
int f;
_CP_open(&f,_CP_str_null,s);
_CP_clearfile(f);