Manual Pages for UNIX Operating System command usage for man semget

System Calls                                            semget(2)



NAME
     semget - get set of semaphores

SYNOPSIS
     #include 
     #include 
     #include 

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


DESCRIPTION
     The semget() function returns the semaphore identifier asso-
     ciated 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:

         o    key is equal to IPC_PRIVATE.

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


     On creation, the data  structure  associated  with  the  new
     semaphore identifier 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, respectively, of  the  cal-
              ling 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 current time.

RETURN VALUES
     Upon   successful   completion,   a   non-negative   integer
     representing  a semaphore 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  opera-
               tion permission (see Intro(2)) as specified by the



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System Calls                                            semget(2)



               low-order 9 bits of semflg would not be granted.


     EEXIST    A semaphore identifier exists  for  key  but  both
               (semflg&IPC_CREAT)  and (semflg&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
               (semflg&IPC_CREAT) is false.


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


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



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | Standard                    | See standards(5).           |
    |_____________________________|_____________________________|


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.





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System Calls                                            semget(2)



     The system-imposed limit on the number of semaphore identif-
     iers   is  maintained  on  a  per-project  basis  using  the
     project.max-sem-ids resource control. The   zone.max-sem-ids
     resource  control  limis the total number of semaphore iden-
     tifiers that can be allocated by a zone.


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














































SunOS 5.11          Last change: 14 Aug 2006                    3