find.c

FIND.C

#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
#include "kernel/fs.h"
#define PATH_MAX 512

char *path_append(char *dest, char *src) {
  char *ptr =
      dest +
      strlen(dest); // ptr 需要是一个指针
                    // 这样获得了dest最后元素也就是结束符'\0'的位置
                    // 如果使用数组访问dest[strlen(dest)]获得的是结束符元素
  while (*src != '\0') {
    //"\0"是一个 字符串常量   后跟一个隐式的结束符 \0
    // 而'\0'是字符常量 是 C 字符串的结束标志
    *(ptr++) = *(src++);
    /*
    *ptr =*src
    src++;
    ptr++;
    */
  }
  *ptr = '\0'; //增加结束符
  return dest;
}
void find_file(char *path, char *filename_) {
  int fd;
  char buf[PATH_MAX];
  struct dirent de;
  struct stat st;

  // open file by only read mode and get fd
  if ((fd = open(path, 0)) < 0) {
    fprintf(2, "dir_name=%s Wrong\n", path);
    exit(1);
  }

  if (fstat(fd, &st) < 0) {
    fprintf(2, "dir_name=%s Wrong\n", path);
    close(fd); // get fd before
    exit(1);
  }

  while ((read(fd, &de, sizeof(de)) == sizeof(de))) {
    if (de.inum == 0) {
      // empty dir
      continue;
    }
    if (strcmp(de.name, ".") == 0 || strcmp(de.name, "..") == 0) {
      // skip the dir now and father of dir now
      continue;
    }
    if (strlen(de.name) + strlen(path) + 2 > PATH_MAX) {
      //拼接之后的是path/de.name+"\0" 一共len1+len2=2
      fprintf(2, "Path too long\n");
      continue;
    }
    strcpy(buf, path);
    if (path[strlen(path) - 1] != '/') {
      path_append(buf, "/");
    }
    path_append(buf, de.name);

    // check new path
    if (stat(buf, &st) < 0) {
      fprintf(2, "Path not available\n");
      continue;
    }

    // begin to match filename_
    if (st.type == T_FILE) {
      if (strcmp(de.name, filename_) == 0) {
        printf("%s\n", buf);
      }
    } else if (st.type == T_DIR) {
      find_file(buf, filename_);
    }
  }
}
int main(int argc, char *argv[]) {
  if (argc != 3) {
    fprintf(2, "Usage: find <path> <filename>\n");
    exit(1);
  }
  find_file(argv[1], argv[2]);
  exit(0);
}