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

SYNOPSIS
  #include <signal.h>

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

LIBRARY
  Realtime Library (librt.so, librt.a)

PARAMETERS
  pid Specifies the ID of the target process.

  signo
      Specifies the signal to be queued. 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 is queued to the specified process.
  If the process has the SA_SIGINFO option enabled for the queued signal, the
  specified value is 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
  (zero). 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.

SEE ALSO
  Headers: siginfo(5)

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

  Guide to Realtime Programming

Index for Section 3

Alphabetical listing for S

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