Content-type: text/html Man page of sem_timedwait

sem_timedwait

Section: Realtime Library Functions (3RT)
Updated: 30 Jan 2004
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NAME

sem_timedwait, sem_reltimedwait_np - lock a semaphore  

SYNOPSIS

cc [ flag... ] file... -lrt [ library... ]
#include <semaphore.h>
#include <time.h>

int sem_timedwait(sem_t *restrict sem, const struct timespec *restrict abs_timeout);

int sem_reltimedwait_np(sem_t *restrict sem, const struct timespec *restrict rel_timeout);  

DESCRIPTION

The sem_timedwait() function locks the semaphore referenced by sem as in the sem_wait(3RT) function. However, if the semaphore cannot be locked without waiting for another process or thread to unlock the semaphore by performing a sem_post(3RT) function, this wait is terminated when the specified timeout expires.

The sem_reltimedwait_np() function is identical to the sem_timedwait() function, except that the timeout is specified as a relative time interval.

For sem_timedwait(), the timeout expires when the absolute time specified by abs_timeout passes, as measured by the CLOCK_REALTIME clock (that is, when the value of that clock equals or exceeds abs_timeout), or if the absolute time specified by abs_timeout has already been passed at the time of the call.

For sem_reltimedwait_np(), the timeout expires when the time interval specified by rel_timeout passes, as measured by the CLOCK_REALTIME clock, or if the time interval specified by rel_timeout is negative at the time of the call.

The resolution of the timeout is the resolution of the CLOCK_REALTIME clock. The timespec data type is defined as a structure in the <time.h> header.

Under no circumstance does the function fail with a timeout if the semaphore can be locked immediately. The validity of the abs_timeout need not be checked if the semaphore can be locked immediately.  

RETURN VALUES

The sem_timedwait() and sem_reltimedwait_np() functions return 0 if the calling process successfully performed the semaphore lock operation on the semaphore designated by sem. If the call was unsuccessful, the state of the semaphore is be unchanged and the function returns -1 and sets errno to indicate the error.  

ERRORS

The sem_timedwait() and sem_reltimedwait_np() functions will fail if:

EINVAL The sem argument does not refer to a valid semaphore.

EINVAL The process or thread would have blocked, and the timeout parameter specified a nanoseconds field value less than zero or greater than or equal to 1,000 million.

ETIMEDOUT The semaphore could not be locked before the specified timeout expired.

The sem_timedwait() and sem_reltimedwait_np() functions may fail if:

EDEADLK A deadlock condition was detected.

EINTR A signal interrupted this function.

 

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPEATTRIBUTE VALUE
Interface StabilitySee below.
MT-LevelMT-Safe

The sem_timedwait() is function Standard. The sem_reltimedwait_np() function is Stable.  

SEE ALSO

semctl(2), semget(2), semop(2), time(2), sem_post(3RT), sem_trywait(3RT)sem_wait(3RT), attributes(5), standards(5)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUES
ERRORS
ATTRIBUTES
SEE ALSO

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Time: 02:39:04 GMT, October 02, 2010