Detecting child exit with pipe

childexit-pipe.c

#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <assert.h>
#include <sys/select.h>
#include <stdbool.h>



int main(void) {
    int fds[2];
    assert(pipe(fds) == 0);
    fcntl(fds[0], F_SETFD, O_CLOEXEC);
    if (fork()) {
        close(fds[1]);
        fd_set fdset;
        FD_ZERO(&fdset);
        FD_SET(fds[0], &fdset);
        int ret;
        do {
            ret = select(fds[0] + 1, &fdset, NULL, NULL, NULL);
            printf("%d\n", ret);
        } while (ret == 0);
        if (ret < 0)
            perror("select err");
        puts("Child exits!\n");
        return 0;
        // parent
        
    } else {
        // child
        sleep(1);
        printf("exits");
        return 1;
    }
    assert(false && "should not reach");
    return 0;
}