This is signals/t_sigqueue.c (Listing 22-2, page 459), an example from the book, The Linux Programming Interface.

The source code file is copyright 2022, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

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Function list (Bold in this list means a function is not static)

#define _POSIX_C_SOURCE 199309
#include <signal.h>
#include "tlpi_hdr.h"
main(int argc, char *argv[])
    int sig, numSigs, j, sigData;
    union sigval sv;

    if (argc < 4 || strcmp(argv[1], "--help") == 0)
        usageErr("%s pid sig-num data [num-sigs]\n", argv[0]);

    /* Display our PID and UID, so that they can be compared with the
       corresponding fields of the siginfo_t argument supplied to the
       handler in the receiving process */

    printf("%s: PID is %ld, UID is %ld\n", argv[0],
            (long) getpid(), (long) getuid());

    sig = getInt(argv[2], 0, "sig-num");
    sigData = getInt(argv[3], GN_ANY_BASE, "data");
    numSigs = (argc > 4) ? getInt(argv[4], GN_GT_0, "num-sigs") : 1;

    for (j = 0; j < numSigs; j++) {
        sv.sival_int = sigData + j;
        if (sigqueue(getLong(argv[1], 0, "pid"), sig, sv) == -1)
            errExit("sigqueue %d", j);



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