SEMGET(S)                XENIX System V                 SEMGET(S)



     Name
          semget - Gets set of semaphores.

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

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

     Description
          semget returns the semaphore identifier associated with key.

          A semaphore identifier, and an associated data structure and
          set containing nsems semaphores (see intro(S)) are created
          for key if one of the following are true:

               key is equal to IPC_PRIVATE.

               key does not already have a semaphore identifier
               associated with it, and (semflg & IPC_CREAT) is
               ``true''.

          Upon 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
               process.

               The low-order 9 bits of sem_perm.mode are set equal to
               the low-order 9 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 will fail if one or more of the following are true:

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

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

               A semaphore identifier exists for key, but the number
               of semaphores in the set associated with it is less



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     SEMGET(S)                XENIX System V                 SEMGET(S)



               than nsems and nsems is not equal to zero.  [EINVAL]

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

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

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

               A semaphore identifier exists for key but ( (semflg &
               IPC_CREAT ") and (" semflg & IPC_EXCL) ) is ``true''.
               [EEXIST]

     Return Value
          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.

     See Also
          intro(S), semctl(S), semop(S)

     Notes
          Programmers using this function must be compiled with the -
          Me compiler option.


























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