用文件IO操作实现ls命令

#include <stdio.h>
#include <time.h>
#include <string.h>
#include <fcntl.h>
#include <pwd.h>
#include <grp.h>
#include <dirent.h>
#include <sys/stat.h>
#include <sys/types.h>

#define N 256

void DisplayFile(struct stat buf, char fname[])
{
 int n;
 struct tm *tp;

 switch (buf.st_mode & S_IFMT)
 {
 case S_IFREG:
  printf("-");
  break;
 case S_IFDIR:
  printf("d");
  break;
 case S_IFSOCK:
  printf("s");
  break;
 case S_IFLNK:
  printf("l");
  break;
 case S_IFBLK:
  printf("b");
  break;
 case S_IFCHR:
  printf("c");
  break;
 case S_IFIFO:
  printf("p");
  break;
 }

 for (n=8; n>=0; n--)
 {
  if (buf.st_mode & (1<<n))
  {
   switch (n % 3)
   {
   case 2 :
    printf("r");
    break;
   case 1 :
    printf("w");
    break;
   case 0:
    printf("x");
    break;
   }
  }
  else
  {
   printf("-");
  }
 }

 printf(" %u ", buf.st_nlink);
 printf("%s ", getpwuid(buf.st_uid)->pw_name);
 printf("%s ", getgrgid(buf.st_gid)->gr_name);
 printf("%ld", buf.st_size);
 tp = localtime(&buf.st_mtime);
 printf("  %d-%d-%d %d:%d ", tp->tm_year+1900, tp->tm_mon+1,
                             tp->tm_mday, tp->tm_hour, tp->tm_min); 

 printf("%s\n", fname);

 return ;
}

void DisplayDir(char fname[])
{
 DIR *mydir;
 struct dirent *myitem;
 char dirname[N];
 struct stat buf;

 if ((mydir = opendir(fname)) == NULL)
 {
  perror("fail to opendir");
  return;
 }
 while ((myitem = readdir(mydir)) != NULL)
 {
  if (myitem->d_name[0] == '.') continue;
  strcpy(dirname, fname);
  strcat(dirname, "/");
  strcat(dirname, myitem->d_name);
  //printf("%s\n", dirname);
  stat(dirname, &buf);
  DisplayFile(buf, myitem->d_name);
 }
 closedir(mydir);
}

int main(int argc, char *argv[])
{
 struct stat buf;
 char fname[N];

 if (argc < 2)
 {
  printf("Usage : %s <file>\n", argv[0]);
  return -1;
 }

 if (stat(argv[1], &buf) < 0)
 {
  perror("fail to stat");
  return -1;
 }

 strcpy(fname, argv[1]);
 if ( S_ISDIR(buf.st_mode) )
 {
    DisplayDir(fname); 
 }
 else
 {
  DisplayFile(buf, fname);
 }

 return 0;
}