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sigqueue(3)
NAME
  sigqueue -  Queue a signal and data to a running process.

SYNOPSIS
  #include <signal.h>

  int sigqueue (
  pid_t pid,
  int signo,
  const union sigval value);

PARAMETERS
  pid	  Specifies the process.

  signo	  Specifies the signal. If the signo parameter is 0 (the null
	  signal), error checking is performed but no signal is sent. This
	  can be used to check the validity of the pid parameter.

  value	  Specifies the application-defined value to be queued to the
	  receiving process.

DESCRIPTION
  The sigqueue function causes the signal specified by signo to be sent with
  the value specified by value to the process specified by pid.

  The conditions required for a process to have permission to queue a signal
  to another process are the same as for the kill function.

  If the call is successful, the signal will be queued to the specified
  process. If the process has the SA_SIGINFO flag enabled for the queued
  signal, the specified value will be delivered to its signal handler as the
  si_value field of the siginfo parameter. Nonprivileged callers are
  restricted in the number of signals they can have actively queued. This
  per-process quota value can be returned with sysconf(_SC_SIGQUEUE_MAX).

RETURN VALUES
  Upon successful completion, the sigqueue function returns a value of 0.
  Otherwise, a value of -1 is returned and errno is set to indicate the
  error.

ERRORS
  If sigqueue fails, no signal is sent, and errno is set to one of the
  following values:

  [EAGAIN]	 No resources are available to queue the signal. The process
		 has already queued {SIGQUEUE_MAX} signals that are still
		 pending at the receiver(s), or a system wide resource limit
		 has been exceeded.

  [EINVAL]	 The signo parameter is not a valid signal number.

  [EINVAL]	 The signo parameter is SIGKILL, SIGSTOP, SIGTSTP, or
		 SIGCONT, and the pid parameter is 1 (process 1 -- init).

  [ESRCH]	 No process can be found corresponding to that specified by
		 the pid parameter.

  [EPERM]	 The real or saved user ID does not match the real or
		 effective user ID of the receiving process, the calling
		 process does not have appropriate privilege, or the process
		 is not sending a SIGCONT signal to one of its session's
		 processes.

RELATED INFORMATION
  Headers: siginfo(5)

  Functions: kill(2), sigaction(2), sysconf(3)

Index for Section 3

Alphabetical listing for S

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