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SEM_WAIT (3) | C library functions | Unix Manual Pages | :man▋

NAME

sem_wait, sem_trywait - decrement (lock) a semaphore

CONTENTS

Library
Synopsis
Description
Return Values
Errors
See Also
Standards

LIBRARY


.Lb libc

SYNOPSIS


.In semaphore.h int sem_wait "sem_t *sem" int sem_trywait "sem_t *sem"

DESCRIPTION

The sem_wait function decrements (locks) the semaphore pointed to by sem, but blocks if the value of sem is zero, until the value is non-zero and the value can be decremented.

The sem_trywait function decrements (locks) the semaphore pointed to by sem only if the value is non-zero. Otherwise, the semaphore is not decremented and an error is returned.

RETURN VALUES


.Rv -std

ERRORS

The sem_wait and sem_trywait functions will fail if:
[EINVAL]
The sem argument points to an invalid semaphore.

Additionally, sem_trywait will fail if:

[EAGAIN]
The semaphore value was zero, and thus could not be decremented.

SEE ALSO

sem_getvalue(3), sem_post(3), sem(4)

STANDARDS

 
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