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35 .Nd "queue a signal to a process (REALTIME)"
41 .Fn sigqueue "pid_t pid" "int signo" "const union sigval value"
45 system call causes the signal specified by
47 to be sent with the value specified by
49 to the process specified by
53 is zero (the null signal), error checking is performed but
54 no signal is actually sent.
55 The null signal can be used to check the
58 The conditions required for a process to have permission to queue a
59 signal to another process are the same as for the
64 system call queues a signal to a single process specified by the
70 system call returns immediately.
72 available to queue the signal, the signal will be queued and sent to
73 the receiving process.
79 to be generated for the sending process, and if
81 is not blocked for the calling thread and if no other thread has
83 unblocked or is waiting in a
89 or at least the pending, unblocked signal will be delivered to the
93 Should any multiple pending signals in the range
97 be selected for delivery, it is the lowest numbered
99 The selection order between realtime and non-realtime signals, or
100 between multiple pending non-realtime signals, is unspecified.
110 No resources are available to queue the signal.
111 The process has already
114 signals that are still pending at the receiver(s),
115 or a system-wide resource limit has been exceeded.
119 argument is an invalid or unsupported signal number.
121 The process does not have the appropriate privilege to send the signal
122 to the receiving process.
137 .Xr pthread_sigmask 3 ,
142 system call conforms to
147 realtime signal queue first appeared in
152 to send signals to a process which might have a different ABI
153 (for instance, one is 32-bit and the other 64-bit),
158 can be delivered reliably, but the
160 may be truncated in endian dependent ways and must not be relied on.
161 Further, many pointer integrity schemes disallow sending pointers to other
162 processes, and this technique should not be used in programs intended to