osx man page for sem_wait

Query: sem_wait

OS: osx

Section: 2

Format: Original Unix Latex Style Formatted with HTML and a Horizontal Scroll Bar

SEM_WAIT(2)						      BSD System Calls Manual						       SEM_WAIT(2)

NAME
sem_trywait, sem_wait -- lock a semaphore
SYNOPSIS
#include <semaphore.h> int sem_trywait(sem_t *sem); int sem_wait(sem_t *sem);
DESCRIPTION
The semaphore referenced by sem is locked. When calling sem_wait(), if the semaphore's value is zero, the calling thread will block until the lock is acquired or until the call is interrupted by a signal. Alternatively, the sem_trywait() function will fail if the semaphore is already locked, rather than blocking on the semaphore. If successful (the lock was acquired), sem_wait() and sem_trywait() will return 0. Otherwise, -1 is returned and errno is set, and the state of the semaphore is unchanged.
ERRORS
sem_wait() and sem_trywait() succeed unless: [EAGAIN] The semaphore is already locked. [EDEADLK] A deadlock was detected. [EINTR] The call was interrupted by a signal. [EINVAL] sem is not a valid semaphore descriptor.
NOTES
Applications may encounter a priority inversion while using semaphores. When a thread is waiting on a semaphore which is about to be posted by a lower-priority thread and the lower-priority thread is preempted by another thread (of medium priority), a priority inversion has occured, and the higher-priority thread will be blocked for an unlimited time period. Programmers using the realtime functionality of the system should take care to avoid priority inversions.
SEE ALSO
sem_open(2), sem_post(2), semctl(2), semget(2), semop(2)
HISTORY
sem_wait() and sem_trywait() are specified in the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995). Darwin June 8, 2000 Darwin
Related Man Pages
sem_wait(2) - mojave
sem_trywait(3p) - centos
sem_trywait(2) - hpux
sem_wait(3) - osf1
sem_wait(3rt) - sunos
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semaphores
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Error