Linux / Unix Command: sigqueue

Command Library

NAME

sigqueue - queue a signal and data to a process  

SYNOPSIS

#include <signal.h>

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

DESCRIPTION

sigqueue() sends the signal specified in sig to the process whose PID is given in pid. The permissions required to send a signal are the same as for kill(2). As with kill(2), the null signal (0) can be used to check if a process with a given PID exists.

The value argument is used to specify an accompanying item of data (either an integer or a pointer value) to be sent with the signal, and has the following type:

union sigval {
    int   sival_int;
    void *sival_ptr;
};

If the receiving process has installed a handler for this signal using the SA_SIGINFO flag to sigaction(2), then it can obtain this data via the si_value field of the siginfo_t structure passed as the second argument to the handler. Furthermore, the si_code field of that structure will be set to SI_QUEUE.  

RETURN VALUE

On success, sigqueue() returns 0, indicating that the signal was successfully queued to the receiving proces. Otherwise -1 is returned and errno is set to indicate the error.  

ERRORS

EAGAIN

The limit of signals which may be queued has been reached. (See signal(7) for further information.)

EINVAL

sig was invalid.

ESRCH

No process has a PID matching pid.

EPERM

The process does not have permission to send the signal to the receiving process. (See kill(2) for further information.)

 

SEE ALSO

kill(2), sigaction(2), signal(2), sigwait(3), signal(7)

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