#include <stdio.h>
#include <dirent.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/types.h>
//#include <assert.h>
//#include <ctype.h>
//#include <errno.h>


/*int scandir(const char* dirname, dirent*** name_list,
            int (*filter)(const dirent*),
            int (*comparator)(const dirent**, const dirent**))*/
 

extern int alphasort(const struct dirent** a, const struct dirent** b);
int isDir(char *filename)
{
    struct stat stat;
    lstat(filename, &stat);
    printf("%s size is : %d\n",filename,stat.st_size);
    if (S_ISDIR(stat.st_mode))
    {
        return 1;
    }

    //stat(filename,&info);
 

    //if(S_ISDIR(info.st_mode))
    //    return 1;
    return 0;
}

static int filter_dot(const struct dirent *d)
{
    return (strcmp(d->d_name, "..") && strcmp(d->d_name, "."));
}

int myscandir(char *dir)
{
    int entries = 0;
    struct dentry *dentries;
    struct dirent **namelist = NULL;
    int
 
 ret = -1;

    if (dir)
    {
        entries = scandir(dir, &namelist, filter_dot, (void*)alphasort);
    }
    if(entries == -1)
    {
        printf("arg is a file or not exit: %s, please set a dir \n",dir);
    }

    for(int i=0;i<entries;i++)
    {
        int len = strlen(dir) + 1 + strlen(namelist[i]->d_name) + 1;
        char *path = malloc(len * sizeof(char));
        if(path)
        {
            strcpy(path,dir);
            strcat(path,"/");
            strcat(path,namelist[i]->d_name);
        }
        else
        {
            printf("malloc fail in myscandir\n");
            return -1;
        }
        #ifndef DT_DIR
        #define DT_DIR 4
        #endif
        //or isDir(path)
        if(namelist[i]->d_type == DT_DIR)
        {
            free(namelist[i]);
            printf(" dir : %s\n",path);
            ret = myscandir(path);
            free(path);
        }
        else
        {
            free(namelist[i]);
            ret = 0;
            printf("file : %s\n",path);
            free(path);
        }
    }
    return ret;
}

char* getdir(int argc,char **argv)
{
    char *optstring = "d:";
    char op;
    char *dir = NULL;

    extern char* optarg;

    while((op=getopt(argc,argv,optstring)) != -1)
    {
        switch (op)
        {
            case 'd':
            if(!optarg)
                return NULL;
            dir = malloc(strlen(optarg)+1);
            if(!dir)
            {
                printf("malloc fail in getdir \n");
                return NULL;
            }
            strcpy(dir,optarg);
            break;
            case '?':
            default:
            printf("option is invalid or need arg\n");
            printf("Usage: -d dir or -d file or no option indicate current dir\n");
            break;
        }
    }

    if(!dir)
    {
        dir = getcwd(NULL,0);
        if(!dir)
        {
            printf("malloc fail in getdir \n");
            return NULL;
        }
    }

    return dir;
}

int main(int argc,char *argv[])
{
    char *dir = NULL;

    dir = getdir(argc,argv);
    if(dir)
    {
        myscandir(dir);
        free(dir);
        return 0;
    }

    printf("error find \n");
    return -1;
}

在ubuntu 12.04 LTS 終端執行：
$gcc -o main main.c -std=c99 # 生成main 可執行程式

$main -d dir # 顯示dir 目錄下所有目錄和檔案

$main # 顯示當前目錄下所有檔案和目錄