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 semget(2)							   semget(2)




 NAME
      semget - get set of semaphores

 SYNOPSIS
      #include <&lt&lt&lt;sys/sem.h>&gt&gt&gt;

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

 DESCRIPTION
      semget() returns the semaphore identifier associated with key.

      A semaphore identifier and associated data structure and set
      containing nsems semaphores are created for key if one of the
      following is true:

	   key is equal to IPC_PRIVATE.	 This call creates a new identifier,
	   subject to available resources.  The identifier is never returned
	   by another call to semget() until it has been released by a call
	   to semctl().	 The identifier should be used among the calling
	   process and its descendents; however, it is not a requirement.
	   The resource can be accessed by any process having the proper
	   permissions.

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

      Specific behavior can be requested by ORing the following masks into
      semflg.

	   IPC_CREAT: Create a semaphore identifier if one does not already
	   exist for key.

	   IPC_EXCL: If IPC_CREAT is specified and key already has a
	   semaphore identifier associated with it, return an error.

      The low-order 9 bits of semflg are the semaphore operation permissions
      which are defined in glossary(9).

      Upon creation, the data structure associated with the new semaphore
      identifier is initialized as follows:

	   In the operation-permission structure, sem_perm.cuid and
	   sem_perm.uid are set equal to the effective-user-ID of the
	   calling process, while sem_perm.cgid and sem_perm.gid are set to
	   the effective-group-ID 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.




 Hewlett-Packard Company	    - 1 -   HP-UX Release 11i: November 2000






 semget(2)							   semget(2)




	   sem_otime is set equal to 0 and sem_ctime is set equal to the
	   current time.

 EXAMPLES
      The following call to semget() returns a semid associated with the key
      returned by ftok("myfile", 'A').	If a semid associated with the key
      does not exist, a new semid, set of 4 semaphores, and associated data
      structure will be created.  If a semid for the key already exists, the
      semid is simply returned.

	   int semid;

	   mysemid = semget (ftok("myfile",'A'), 4, IPC_CREAT | 0600);

 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.

 ERRORS
      semget() fails if one or more of the following is true:

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

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

	   [EINVAL]	  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
			  zero.

	   [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 semaphore identifiers system wide would be
			  exceeded.

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

 SEE ALSO
      ipcrm(1), ipcs(1), semctl(2), semop(2), stdipc(3C).

 STANDARDS CONFORMANCE
      semget(): SVID2, SVID3, XPG2, XPG3, XPG4



 Hewlett-Packard Company	    - 2 -   HP-UX Release 11i: November 2000