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28.\" $FreeBSD: src/lib/libc_r/man/pthread_cond_timedwait.3,v 1.8.2.6 2001/08/17 15:42:51 ru Exp $
29.\"
30.Dd July 28, 1998
31.Dt PTHREAD_COND_TIMEDWAIT 3
32.Os
33.Sh NAME
34.Nm pthread_cond_timedwait
35.Nd "wait on a condition variable for a specific amount of time"
36.Sh SYNOPSIS
37.Fd #include <pthread.h>
38.Ft int
39.Fo pthread_cond_timedwait
40.Fa "pthread_cond_t *restrict cond"
41.Fa "pthread_mutex_t *restrict mutex"
42.Fa "const struct timespec *restrict abstime"
43.Fc
44.Sh DESCRIPTION
45The
46.Fn pthread_cond_timedwait
47function atomically blocks the current thread waiting on the condition
48variable specified by
49.Fa cond
50and unblocks the mutex specified by
51.Fa mutex .
52The waiting thread unblocks only after another thread calls
53.Xr pthread_cond_signal 3 ,
54or
55.Xr pthread_cond_broadcast 3
56with the same condition variable, or if the system time reaches the
57time specified in
58.Fa abstime ,
59and the current thread reacquires the lock on
60.Fa mutex .
61.Pp
62Values for struct timespec can be obtained by adding the required
63time interval to the the current time obtained using
64.Xr gettimeofday 2 .
65.Pp
66.Fa Note
67that struct timeval and struct timespec use different units to specify
68the time. Hence, the user should always take care to perform the time unit
69conversions accordingly.
70.Sh EXAMPLE
71.Pp
72 struct timeval tv;
73 struct timespec ts;
74 gettimeofday(&tv, NULL);
75 ts.tv_sec = tv.tv_sec + 0;
76 ts.tv_nsec = 0;
77.Pp
78.Sh RETURN VALUES
79If successful, the
80.Fn pthread_cond_timedwait
81function will return zero.
82Otherwise, an error number will be returned to
83indicate the error.
84.Sh ERRORS
85.Fn pthread_cond_timedwait
86will fail if:
87.Bl -tag -width Er
88.It Bq Er EINVAL
89The value specified by
90.Fa cond ,
91.Fa mutex
92or
93.Fa abstime
94is invalid.
95.It Bq Er ETIMEDOUT
96The system time has reached or exceeded the time specified in
97.Fa abstime .
98.El
99.Sh SEE ALSO
100.Xr pthread_cond_broadcast 3 ,
101.Xr pthread_cond_destroy 3 ,
102.Xr pthread_cond_init 3 ,
103.Xr pthread_cond_signal 3 ,
104.Xr pthread_cond_wait 3 ,
105.Xr gettimeofday 2
106.Sh STANDARDS
107.Fn pthread_cond_timedwait
108conforms to
109.St -p1003.1-96 .