20165334 实现mypwd

学习pwd命令

研究pwd实现需要的系统调用(man -k; grep),写出伪代码

man -k pwd

man -k current directory | grep 2

man getcwd

伪代码

void get_file_name(*filepath){
  获取当前i-Node;
  通过i-Node获取当前路径名称filepath(%s)；

   cd ..;
  获取当前i-Node;
  通过i-Node获取当前路径名filepath称(%s)；
   get_file_name(*filepath);
  if(..i-Node == . i-Node){
  return;
  }
   printf('/'+filename);
  return;
}

实现mypwd

编写mypwd

 #include <stdio.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <dirent.h>
 #include <pwd.h>
  ino_t get_inode(char *);
  void printpathto(ino_t);
  void inum_to_name(ino_t, char *, int);

  int main() {
 printpathto(get_inode(".")); /* print path to here */
 putchar('\n'); /* then add newline */
 return 0;
}

/*
 *        prints path leading down to an object with this inode
 * kind of recursive
*/
void printpathto(ino_t this_inode) {
ino_t my_inode;
char its_name[BUFSIZ];
if (get_inode("..") != this_inode) {
    chdir(".."); /* up one dir */
    inum_to_name(this_inode, its_name, BUFSIZ);/* get its name*/
    my_inode = get_inode("."); /* print head */
    printpathto(my_inode); /* recursively */
    printf("/%s", its_name); /* now print name of this */
  }
}
void inum_to_name(ino_t inode_to_find, char *namebuf, int buflen) {
DIR *dir; 
struct dirent *direntp; 
dir = opendir(".");

 while ((direntp = readdir(dir)) != NULL)
    if (direntp->d_ino == inode_to_find) {
        strncpy(namebuf, direntp->d_name, buflen);
        namebuf[buflen - 1] = '\0'; 
        closedir(dir);
        return;
    }

  exit(1);

}


 ino_t get_inode(char *filename) {   //返回文件的i-Node值
struct stat file;

if (stat(filename, &info) == -1) {
    perror(fname);
    return 1;
}
return file.st_ino;
}

测试mypwd