output_flags = std_flags .|. o_CREAT
read_flags = std_flags .|. o_RDONLY
write_flags = output_flags .|. o_WRONLY
rw_flags = output_flags .|. o_RDWR
append_flags = write_flags .|. o_APPEND
output_flags = std_flags .|. o_CREAT
read_flags = std_flags .|. o_RDONLY
write_flags = output_flags .|. o_WRONLY
rw_flags = output_flags .|. o_RDWR
append_flags = write_flags .|. o_APPEND