6_5.cpp

// 同时输出数据到终端和文件的程序
#include<assert.h>
#include<stdio.h>
#include<unistd.h>
#include<errno.h>
#include<string.h>
#include<fcntl.h>

int main(int argc, char* argv[]){
    if(argc !=2){
        printf("usage: %s <file>\n", argv[0]);
        return 1;
    }

    int filefd = open(argv[1], O_CREAT | O_WRONLY | O_TRUNC, 0666);
    assert(filefd > 0);

    int pipefd_stdout[2];
    int ret = pipe(pipefd_stdout);
    assert(ret != -1);

    int pipefd_file[2];
    ret = pipe(pipefd_file);
    assert(ret != -1);

    // 将标准输入内容输入管道pipefd_stdout
    ret = splice(STDIN_FILENO, NULL, pipefd_stdout[1], NULL, 32768, SPLICE_F_MORE | SPLICE_F_MOVE);
    assert(ret != -1);

    // 将管道pipefd_stdout的输出复制到管道pipefd_file的输入端
    ret = tee(pipefd_stdout[0], pipefd_file[1], 32768, SPLICE_F_NONBLOCK);
    assert(ret != -1);

    // 将管道pipefd_file的输出定向到文件描述符filefd上，从而将标准输入的内容写入文件
    ret = splice(pipefd_file[0], NULL, filefd, NULL, 32768, SPLICE_F_MORE | SPLICE_F_MOVE);
    assert(ret != -1);

    // 将管道pipefd_stdout的输出定向到标准输出，其内容和写入文件的内容完全一致
    ret = splice(pipefd_stdout[0], NULL, STDOUT_FILENO, NULL, 32768, SPLICE_F_MORE | SPLICE_F_MOVE);
    assert(ret != -1);

    close(filefd);
    close(pipefd_stdout[0]);
    close(pipefd_stdout[1]);
    close(pipefd_file[0]);
    close(pipefd_file[1]);

    return 0;
}