# include <sys/types.h> # include <sys/ipc.h> # include <sys/msg.h> # include <sys/sem.h> # include <sys/shm.h>
0400 Read by user. 0200 Write by user.Bits 0100, 0010, and 0001 (the execute bits) are unused by the system. Furthermore, "write" effectively means "alter" for a semaphore set. The same system header file also defines the following symbolic constants:0040 Read by group. 0020 Write by group.0004 Read by others. 0002 Write by others.