DragonOS/user/apps/test_eventfd/main.c

#include <err.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/eventfd.h>
#include <sys/types.h>
#include <unistd.h>

int
main(int argc, char *argv[])
{
    int       efd;
    uint64_t  u;
    ssize_t   s;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s <num>...\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    efd = eventfd(0, 0);
    if (efd == -1)
        err(EXIT_FAILURE, "eventfd");

    switch (fork()) {
        case 0:
            for (size_t j = 1; j < argc; j++) {
                printf("Child writing %s to efd\n", argv[j]);
                u = strtoull(argv[j], NULL, 0);
                /* strtoull() allows various bases */
                s = write(efd, &u, sizeof(uint64_t));
                if (s != sizeof(uint64_t))
                    err(EXIT_FAILURE, "write");
            }
            printf("Child completed write loop\n");

            exit(EXIT_SUCCESS);

        default:
            sleep(2);

            printf("Parent about to read\n");
            s = read(efd, &u, sizeof(uint64_t));
            if (s != sizeof(uint64_t))
                err(EXIT_FAILURE, "read");
            printf("Parent read %"PRIu64" (%#"PRIx64") from efd\n", u, u);
            exit(EXIT_SUCCESS);

        case -1:
            err(EXIT_FAILURE, "fork");
    }
}