semget(PCI)                    6 January 1993                    semget(PCI)


 Name

    semget - get set of semaphores

 Syntax


    #include <pcilib.h>


    #include <memmdl.h>


    #include <ipc.h>

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


 Description

    semget returns the semaphore identifier associated with key.  The
    operations are performed on the current host (as specified in the most
    recent dflthost call).

    A semaphore identifier and associated data structure and set containing
    nsems semaphores (see Intro(PCI)) are created for key if one of the fol-
    lowing is true:

    +  key is equal to IPCPRIVATE.

    +  key does not already have a semaphore identifier associated with it,
       and (semflg & IPCCREAT) is "true."

    On creation, the data structure associated with the new semaphore iden-
    tifier is initialized as follows:

    +  semperm.cuid, semperm.uid, semperm.cgid, and semperm.gid are set
       to the effective user ID and effective group IDs, respectively, of the
       calling process.

    +  The low-order nine bits of semperm.mode are set equal to the low-
       order nine bits of semflg.

    +  semnsems is set to the value of nsems.

    +  semotime is set to zero, and semctime is set to the current UNIX op-
       erating system 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
              UNIX operating system-imposed limit.

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

    [EINVAL]  A semaphore identifier exists for key, but the number of sema-
              phores in the set associated with it is less than nsems and
              nsems is not equal to zero.

    [ENOENT]  A semaphore identifier does not exist for key, and (semflg &
              IPCCREAT) is "false."

    [ENOSPC]  A semaphore identifier is to be created, but the number of
              semaphore identifiers would exceed the system maximum allowed
              for that host.

    [EEXIST]  A semaphore identifier exists for key, but (semflg & IPCCREAT)
              & (semflg & IPCEXCL) is "true."


 Return value

    On successful completion, a semaphore identifier returns.  Otherwise, a
    value of -1 returns and errno is set to indicate the error.

 See also

    dflthost(PCI), Intro(PCI), semctl(PCI), semop(PCI)