linux pipe read

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main() {
    int pipefd[2];
    pid_t cpid;
    char buf;

    if (pipe(pipefd) == -1) {
        perror("pipe");
        exit(EXIT_FAILURE);
    }

    cpid = fork();
    if (cpid == -1) {
        perror("fork");
        exit(EXIT_FAILURE);
    }

    if (cpid == 0) {    // 子进程
        close(pipefd[1]);  // 关闭子进程的写端
        while (read(pipefd[0], &buf, 1) > 0)
            write(STDOUT_FILENO, &buf, 1);
        write(STDOUT_FILENO, "\n", 1);
        close(pipefd[0]);
        _exit(EXIT_SUCCESS);
    } else {            // 父进程
        close(pipefd[0]);  // 关闭父进程的读端
        write(pipefd[1], "Hello, world!\n", 14);
        close(pipefd[1]);  // 关闭写端以通知子进程数据已经发送完毕
        wait(NULL);        // 等待子进程结束
        exit(EXIT_SUCCESS);
    }
}