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26 .\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
27 .\" Portable Operating System Interface (POSIX), The Open Group Base
28 .\" Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of
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41 .Nd "lock a semaphore"
48 .Fn sem_timedwait "sem_t * restrict sem" "const struct timespec * restrict abs_timeout"
50 .Fn sem_clockwait_np "sem_t * restrict sem" "clockid_t clock_id" "int flags" "const struct timespec * rqtp" "struct timespec * rmtp"
54 function locks the semaphore referenced by
59 However, if the semaphore cannot be locked without waiting for
60 another process or thread to unlock the semaphore by performing
63 function, this wait will be terminated when the specified timeout expires.
65 The timeout will expire when the absolute time specified by
67 passes, as measured by the clock on which timeouts are based (that is,
68 when the value of that clock equals or exceeds
71 absolute time specified by
73 has already been passed at the time of the call.
75 Note that the timeout is based on the
81 is not checked if the semaphore can be locked immediately.
85 function is a more flexible variant of
89 parameter specifies the reference clock.
94 then the requested timeout
96 is an absolute timeout; otherwise,
97 the timeout is relative.
98 If this function fails with
100 and the timeout is relative,
103 will be updated to contain the amount of time remaining in the interval
105 the requested time minus the time actually slept
107 An absolute timeout has no effect on
109 A single structure can be used for both
115 functions return zero if the calling process successfully performed the
116 semaphore lock operation on the semaphore designated by
118 If the call was unsuccessful, the state of the semaphore is unchanged,
119 and the function returns a value of \-1 and sets the global variable
121 to indicate the error.
123 These functions will fail if:
128 argument does not refer to a valid semaphore, or the process or thread would
129 have blocked, and the
131 parameter specified a nanoseconds field value less than zero or greater than
132 or equal to 1000 million.
134 The semaphore could not be locked before the specified timeout expired.
136 A signal interrupted this function.
149 function is not specified by any standard;
152 at the time of this writing.
156 function first appeared in
160 function first appeared in