socketpair usage

socketpair.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>

void child(int sock) {
    char buf[1024];
    while (1) {
        ssize_t n = read(sock, buf, sizeof(buf));
        if (n <= 0) {
            perror("read");
            exit(1);
        }
        write(STDOUT_FILENO, buf, n);
    }
}

void parent(int sock) {
    char buf[1024];
    while (1) {
        ssize_t n = read(STDIN_FILENO, buf, sizeof(buf));
        if (n <= 0) {
            perror("read");
            exit(1);
        }
        write(sock, buf, n);
    }
}

int main(void) {
    int sv[2];
    if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv) == -1) {
        perror("socketpair");
        exit(1);
    }

    pid_t pid = fork();
    if (pid == -1) {
        perror("fork");
        exit(1);
    } else if (pid == 0) {
        close(sv[0]);
        child(sv[1]);
    } else {
        close(sv[1]);
        parent(sv[0]);
    }

    return 0;
}