深入理解计算机系统_3e 第十章家庭作业 CS:APP3e chapter 10 homework

**10.6**

1.若成功打开“foo.txt”：

-->1.1若成功打开“baz.txt”：输出“4\n”

-->1.2若未能成功打开“baz.txt”：输出“-1\n”

2.若未能成功打开“foo.txt”：

-->2.1若成功打开“baz.txt”：输出“3\n”

-->2.2若未能成功打开“baz.txt”：输出“-1\n”

10.7

#include "csapp.h"

int main(int argc, char **argv)

{

    int n;

    rio_t rio;

    char buf[MAXBUF];

    Rio_readinitb(&rio, STDIN_FILENO);

    while((n = Rio_readnb(&rio, buf, MAXBUF)) != 0)

	    Rio_writen(STDOUT_FILENO, buf, n);

    exit(0);

}

10.8

#include "csapp.h"

#include "csapp.c"

#include <string.h>

#include <stdio.h>

int main (int argc, char **argv)

{

    struct stat stat;

    char *type, *readok;

    char buf[MAXBUF];

    char filename[MAXBUF];

    memset(buf, 0, MAXBUF);

    memset(filename, 0, MAXBUF);

    if (argc != 2)  {

    fprintf(stderr, "usage: %s <descriptor number>\n", argv[0]);

    exit(0);

    }

    sprintf(buf+sprintf(buf, "/proc/self/fd/"), argv[1]);

    if(readlink(buf, filename, sizeof(filename)) == -1)

    {

        fprintf(stderr, "bad file descriptor\n");

        exit(EXIT_FAILURE);

    }

    Stat(filename, &stat);

    if (S_ISREG(stat.st_mode))     /* Determine file type */

    type = "regular";

    else if (S_ISDIR(stat.st_mode))

    type = "directory";

    else

    type = "other";

    if ((stat.st_mode & S_IRUSR)) /* Check read access */

    readok = "yes";

    else

    readok = "no";

    printf("type: %s, read: %s\n", type, readok);

    exit(0);

}

参考：Getting Filename from file descriptor in C

10.9

这里只是模拟一下基本的操作，就是将文价描述符argv[1]（3）指向“foo.txt”（STDIN_FILENO），shell实际实现肯定有许多没写到的。

if (Fork() == 0){ /* child */

  dup2(STDIN_FILENO, atoi(argv[1]));

  Execve("fstatcheck", argv, envp);

}

10.10

如果有infile参数的话，将STDIN_FILENO指向该文件。

#include "csapp.h"

int main(int argc, char **argv)

{

    int n;

    rio_t rio;

    char buf[MAXLINE];

    if (argc == 2) /* infile */

    {

        int fd = open(argv[1], O_RDONLY|O_CREAT);

        dup2(fd, STDIN_FILENO);

        close(fd);

    }

    Rio_readinitb(&rio, STDIN_FILENO);

    while((n = Rio_readlineb(&rio, buf, MAXLINE)) != 0)

	    Rio_writen(STDOUT_FILENO, buf, n);

    exit(0);

}

巴特西

深入理解计算机系统_3e 第十章家庭作业 CS:APP3e chapter 10 homework

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