SEMGET(2-SVR4)      RISC/os Reference Manual       SEMGET(2-SVR4)



NAME
     semget - get set of semaphores

SYNOPSIS
     #include <sys/types.h>
     #include <sys/ipc.h>
     #include <sys/sem.h>

     int semget(keyt key, int nsems, int semflg);

DESCRIPTION
     semget returns the semaphore identifier associated with key.

     A semaphore identifier and associated data structure and set
     containing nsems semaphores [see intro(2)] are created for
     key if one of the following is true:

          key is equal to IPC_PRIVATE.

          key does not already have a semaphore identifier asso-
          ciated with it, and (semflg&IPC_CREAT) is true.

     On creation, the data structure associated with the new
     semaphore identifier is initialized as follows:

          sem_perm.cuid, sem_perm.uid, sem_perm.cgid, and
          sem_perm.gid are set equal to the effective user ID and
          effective group ID, respectively, of the calling pro-
          cess.

          The access permission bits of sem_perm.mode are set
          equal to the access permission bits of semflg.

          sem_nsems is set equal to the value of nsems.

          sem_otime is set equal to 0 and sem_ctime is set equal
          to the current time.

     semget fails if one or more of the following are true:

     EINVAL         nsems is either less than or equal to zero or
                    greater than the system-imposed limit.

     EACCES         A semaphore identifier exists for key, but
                    operation permission [see intro(2)] as speci-
                    fied by the low-order 9 bits of semflg would
                    not be granted.

     EINVAL         A semaphore identifier exists for key, but
                    the number of semaphores in the set associ-
                    ated with it is less than nsems, and nsems is
                    not equal to zero.



                        Printed 11/19/92                   Page 1

SEMGET(2-SVR4)      RISC/os Reference Manual       SEMGET(2-SVR4)



     ENOENT         A semaphore identifier does not exist for key
                    and (semflg&IPC_CREAT) is false.

     ENOSPC         A semaphore identifier is to be created but
                    the system-imposed limit on the maximum
                    number of allowed semaphore identifiers sys-
                    tem wide would be exceeded.

     ENOSPC         A semaphore identifier is to be created but
                    the system-imposed limit on the maximum
                    number of allowed semaphores system wide
                    would be exceeded.

     EEXIST         A semaphore identifier exists for key but
                    both (semflg&IPC_CREAT) and (semflg&IPC_EXCL)
                    are both true.

SEE ALSO
     intro(2), semctl(2), semop(2), stdipc(3C).

DIAGNOSTICS
     Upon successful completion, a non-negative integer, namely a
     semaphore identifier, is returned.  Otherwise, a value of -1
     is returned and errno is set to indicate the error.































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