semaphore.h — semaphores
#include <semaphore.h>
The <semaphore.h> header shall define the sem_t type, used in performing semaphore operations. The semaphore may be implemented using a file descriptor, in which case applications are able to open up at least a total of {OPEN_MAX} files and semaphores.
The <semaphore.h> header shall define the timespec structure as described in <time.h>.
The <semaphore.h> header shall define the symbolic constant SEM_FAILED which shall have type sem_t *.
The <semaphore.h> header shall define O_CREAT and O_EXCL as described in <fcntl.h>.
The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.
int sem_clockwait(sem_t *restrict, clockid_t, const struct timespec *restrict); int sem_close(sem_t *); int sem_destroy(sem_t *); int sem_getvalue(sem_t *restrict, int *restrict); int sem_init(sem_t *, int, unsigned); sem_t *sem_open(const char *, int, ...); int sem_post(sem_t *); int sem_timedwait(sem_t *restrict, const struct timespec *restrict); int sem_trywait(sem_t *); int sem_unlink(const char *); int sem_wait(sem_t *);Inclusion of the <semaphore.h> header may make visible symbols defined in the <fcntl.h> and <time.h> headers.
None.
None.
None.
<fcntl.h> , <sys/types.h> , <time.h>
XSH sem_clockwait , sem_close , sem_destroy , sem_getvalue , sem_init , sem_open , sem_post , sem_trywait , sem_unlink
First released in Issue 5. Included for alignment with the POSIX Realtime Extension.
The <semaphore.h> header is marked as part of the Semaphores option.
The Open Group Corrigendum U021/3 is applied, adding a description of SEM_FAILED.
The sem_timedwait() function is added for alignment with IEEE Std 1003.1d-1999.
The restrict keyword is added to the prototypes for sem_getvalue() and sem_timedwait().
SD5-XBD-ERN-57 is applied, allowing the header to make visible symbols from the <time.h> header.
The <semaphore.h> header is moved from the Semaphores option to the Base.
This reference page is clarified with respect to macros and symbolic constants.
Austin Group Defect 592 is applied, requiring <semaphore.h> to define the timespec structure.
Austin Group Defect 593 is applied, adding O_CREAT and O_EXCL.
Austin Group Defect 1216 is applied, adding sem_clockwait().
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