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semget(2)                        System Calls                        semget(2)



NAME
       semget - get set of semaphores

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

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

DESCRIPTION
       The  semget() function 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 fol-
       lowing is true:

         o  key is equal to IPC_PRIVATE.

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


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

         o  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, respec-
            tively, of the calling process.

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

         o  sem_nsems is set equal to the value of nsems.

         o  sem_otime is set equal to 0 and sem_ctime is set equal to the cur-
            rent time.


RETURN VALUES
       Upon successful completion, a non-negative integer representing a sema-
       phore  identifier  is  returned. Otherwise, -1 is returned and errno is
       set to indicate the error.

ERRORS
       The semget() function will fail if:

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



       EEXIST          A semaphore identifier exists for key  but  both  (sem-
                       flg&&amp;IPC_CREAT) and (semflg&&amp;IPC_EXCL) are both true.



       EINVAL          The nsems argument is either less than or equal to 0 or
                       greater than the system-imposed limit. See NOTES.

                       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.



       ENOENT          A semaphore identifier does not exist for key and (sem-
                       flg&&amp;IPC_CREAT) is false.



       ENOSPC          A semaphore identifier is to be created but the system-
                       imposed limit on the maximum number  of  allowed  sema-
                       phores  or  semaphore  identifiers system-wide would be
                       exceeded. See NOTES.



ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:


       tab()    allbox;    cw(2.750000i)|     cw(2.750000i)     lw(2.750000i)|
       lw(2.750000i).   ATTRIBUTE TYPEATTRIBUTE VALUE Interface StabilityStan-
       dard


SEE ALSO
       ipcrm(1),  ipcs(1),   rctladm(1M),   intro(2),   semctl(2),   semop(2),
       setrctl(2), ftok(3C), attributes(5), standards(5)

NOTES
       The  system-imposed  limit  on  the  value of the nsems argument is the
       maintained on  a  per-process  basis  using  the  process.max-sem-nsems
       resource control.

       The  system-imposed  limit  on  the  number of semaphore identifiers is
       maintained  on  a  per-project  basis  using  the   project.max-sem-ids
       resource control.

        See  rctladm(1M)  and  setrctl(2) for information about using resource
       controls.



SunOS 5.10                        11 Feb 2003                        semget(2)