#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <time.h>
#include <errno.h>
#include <pwd.h>
#define len 32

int main(int argc, char const *argv[]) {

    if(argc != 2) {
        printf("Usage: %s [OPTION]\n", argv[0]);
        goto err;
    }
    time_t t;
    time(&t);
    char uid_n[10];
    char gid[10];
    uid_t uid;
    char level[9];
    struct passwd *pwd;
    unsigned char symbol;
    int total = 0;
    DIR *file = NULL;
    struct dirent *dir = NULL;
    struct stat st;
    file = opendir(argv[1]);
    if(file == NULL) {
        printf("Line %d occurs %d error\n", __LINE__,errno);
        goto err;
    }
    /*this step is needed,it'll fail on function stat as its path is not clear*/
    if(-1 == chdir(argv[1])) {
        printf("Line %d occurs %d error\n", __LINE__,errno);
        goto err;
    }
    while ((dir = readdir(file)) != NULL) {

        if(-1 == (stat(dir->d_name, &st))) {
            printf("Line %d occurs %d error\n", __LINE__,errno);
            goto err;
        }
        #if 0 /*another way to check the file type*/
        if(S_ISDIR(st.st_mode))
            printf("d");
        else if(S_ISREG(st.st_mode))
            printf("-");
        else if(S_ISCHR(st.st_mode))
            printf("c");
        else if(S_ISBLK(st.st_mode))
            printf("b");
        else if(S_ISFIFO(st.st_mode))
            printf("p");
        else if(S_ISLNK(st.st_mode))
            printf("l");
        else if(S_ISSOCK(st.st_mode))
            printf("s");
        else
            printf("?");
        /*also can be written like this*/

         switch(st.st_mode & S_IFMT)
        {
            case S_IFDIR:
                printf("d");
                break;
            case S_IFREG:
                printf("-");
                break;
            case S_IFCHR:
                printf("c");
                break;
            case S_IFBLK:
                printf("b");
                break;
            case S_IFIFO:
                printf("p");
                break;
            case S_IFLNK:
                printf("l");
                break;
            case S_IFSOCK:
                printf("s");
                break;
            default:
                printf("?");
                break;
        #endif
        total += st.st_blocks;
        switch (dir->d_type) {
            case DT_DIR:     symbol = 'd'; break;
            case DT_REG:     symbol = '-'; break;
            case DT_BLK:     symbol = 'b'; break;
            case DT_LNK:     symbol = 'l'; break;
            case DT_FIFO:    symbol = 'p'; break;
            case DT_SOCK:    symbol = 's'; break;
            case DT_UNKNOWN: symbol = '?'; break;
            default: printf("error happens\n");break;
        }

        uid = getuid();

        pwd = getpwuid(uid);
        if( NULL == pwd ) {
            printf("Line %d:%d\n",__LINE__,errno);
            goto err;
        }
        if(st.st_uid == getuid() || st.st_gid == getgid()) {
            strcpy(uid_n,pwd->pw_name);
            strcpy(gid,uid_n);
        }
        else{
            strcpy(uid_n,"root");
            strcpy(gid,uid_n);
        }

         /*文件所有者权限*/
        if(st.st_mode & S_IRUSR)
            level[0] = 'r';
        else
            level[0] = '-';
         if(st.st_mode & S_IWUSR)
            level[1] = 'w';
        else
            level[1] = '-';
         if(st.st_mode & S_IXUSR)
            level[2] = 'x';
        else
            level[2] = '-';
        /*用户组权限*/
         if(st.st_mode & S_IRGRP)
            level[3] = 'r';
        else
            level[3] = '-';
         if(st.st_mode & S_IWGRP)
            level[4] = 'w';
        else
            level[4] = '-';
         if(st.st_mode & S_IXGRP)
            level[5] = 'x';
        else
            level[5] = '-';
        /*其他用户权限*/
         if(st.st_mode & S_IROTH)
            level[6] = 'r';
        else
            level[6] = '-';
         if(st.st_mode & S_IWOTH)
            level[7] = 'w';
        else
            level[7] = '-';
         if(st.st_mode & S_IXOTH)
            level[8] = 'x';
        else
            level[8] = '-';

    
        printf("%c",symbol);
        printf("%s",level);
        printf("%4u\t",st.st_nlink); /*在ac上运行需要用%u*/
        printf("%s",uid_n);
        printf("\t");
        printf("%s",gid);
        printf("%8lld\t",st.st_size); /*在ac上运行需要用%lld*/
        printf("%24.24s ",ctime(&st.st_mtime));
        printf("%s",dir->d_name);
        printf("\t");

        //printf("\n");
        printf("\n");

        if(NULL == dir && errno == 0)
            break;
        if(NULL == dir && errno != 0) {
            printf("Line %d occurs %d error\n", __LINE__,errno);
           goto err;
        }
    }

printf("total %d\n",total/2); //getconf PAGESIZE可以查看块的大小

closedir(file);

err:
  exit(1);

return 0;
}