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semget(2) [osx man page]

SEMGET(2)						      BSD System Calls Manual							 SEMGET(2)

semget -- obtain a semaphore id SYNOPSIS
#include <sys/sem.h> int semget(key_t key, int nsems, int semflg); DESCRIPTION
Based on the values of key and semflg, semget() returns the identifier of a newly created or previously existing set of semaphores. The key is analogous to a filename: it provides a handle that names an IPC object. There are three ways to specify a key: o IPC_PRIVATE may be specified, in which case a new IPC object will be created. o An integer constant may be specified. If no IPC object corresponding to key is specified and the IPC_CREAT bit is set in semflg, a new one will be created. o The ftok(3) function may be used to generate a key from a pathname. The mode of a newly created IPC object is determined by OR'ing the following constants into the semflg argument: SEM_R Read access for user. SEM_A Alter access for user. (SEM_R>>3) Read access for group. (SEM_A>>3) Alter access for group. (SEM_R>>6) Read access for other. (SEM_A>>6) Alter access for other. If a new set of semaphores is being created, nsems is used to indicate the number of semaphores the set should contain. Otherwise, nsems may be specified as 0. RETURN VALUES
The semget() system call returns the id of a semaphore set if successful; otherwise, -1 is returned and errno is set to indicate the error. ERRORS
The semget() system call will fail if: [EACCES] Access permission failure. [EEXIST] IPC_CREAT and IPC_EXCL were specified, and a semaphore set corresponding to key already exists. [EINVAL] The number of semaphores requested is either less than 1 or greater than the system imposed maximum per set. [EINVAL] A semaphore identifier exists for the argument key, but the number of semaphores in the set associated with it is less than nsems, and nsems is non-zero. [ENOENT] No semaphore set was found corresponding to key, and IPC_CREAT was not specified. [ENOSPC] Insufficiently many semaphores are available. [ENOSPC] The kernel could not allocate a struct semid_ds. LEGACY SYNOPSIS
#include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> The include files <sys/types.h> and <sys/ipc.h> are necessary. SEE ALSO
semctl(2), semop(2), ftok(3), compat(5) BSD
September 12, 1995 BSD

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semget(2)							   System Calls 							 semget(2)

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 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 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 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 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 (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 attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ 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. The zone.max-sem-ids resource control limis the total number of semaphore identifiers that can be allocated by a zone. See rctladm(1M) and setrctl(2) for information about using resource controls. SunOS 5.11 14 Aug 2006 semget(2)
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