Gets a set of semaphores.

    This function is OpenVMS Alpha and Integrity servers only.

    Format

      #include  <sem.h>

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

1  –  Argument

 key

    The key for which the associated semaphore identifier is
    returned.

 nsems

    Value used to initialize the sem_nsems member of the semid_ds
    data structure. See the description.

 semflg

    Flag used to initialize the low-order 9 bits of the sem_perm.mode
    member of the semid_ds data structure associated with the new
    semaphore. See the description.

 value

    The initial value to be given to the semaphore. This argument is
    used only when the semaphore is being created.

2  –  Description

    The semget function returns the semaphore identifier associated
    with key.

    A semaphore identifier with its associated semid_ds data
    structure and its associated set of nsems semaphores (see
    the <sys/sem.h> header file) is created for key if one of the
    following is true:

    o  The key argument is equal to IPC_PRIVATE.

    o  The key argument does not already have a semaphore identifier
       associated with it and (semflg &IPC_CREAT) is nonzero.

    When it is created, the semid_ds data structure associated with
    the new semaphore identifier is initialized as follows:

    o  In the operation permissions structure 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.

    o  The low-order 9 bits of sem_perm.mode are set equal to the
       low-order 9 bits of the semflg argument.

    o  The variable sem_nsems is set equal to the value of the nsems
       argument.

    o  The variable sem_otime is set equal to 0 and the variable sem_
       ctime is set equal to the current time.

    o  The data structure associated with each semaphore in the
       set does not need to be initialized. You can use the semctl
       function with the command SETVAL or SETALL to initialize each
       semaphore.

3  –  Return Values

    n                  Successful completion. The function returns a
                       non-negative integer semaphore identifier.
    -1                 Indicates an error. The function sets errno to
                       one of the following values:

                       o  EACCES - A semaphore identifier exists for
                          key, but operation permission as specified
                          by the low-order 9 bits of semflg was not
                          granted.

                       o  EEXIST - A semaphore identifier exists
                          for key but ((semflg &IPC_CREAT) &&(semflg
                          &IPC_EXCL)) is nonzero.

                       o  EFAULT - The arguments passed to the
                          function are not accessible.

                       o  EINVAL - The value of nsems is either
                          less than or equal to 0 or greater than
                          the system-imposed limit, or a semaphore
                          identifier exists for key, but the number
                          of semaphores in the set associated with it
                          is less than nsems and nsems is not equal
                          to 0.

                       o  ENOENT - A semaphore identifier does not
                          exist for key and (semflg &IPC_CREAT) is
                          equal to 0.

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

                       o  EVMSERR - OpenVMS specific nontranslatable
                          error code.