#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <dirent.h>

char* txtOpen(char* txtName){
    FILE* txt = fopen(txtName, "r");
    if (txt == NULL){
        printf("ERROR\n");
    return NULL;
    }
    fseek(txt,0,SEEK_END);
    int txtSize = ftell(txt);
    fseek(txt,0,SEEK_SET);
    if(txtSize == 0){
    fclose(txt);
        return NULL;
    }
    char* txtStr = (char*)malloc(sizeof(char)*10000);
    fgets(txtStr, txtSize*sizeof(char),txt);
    fclose(txt);
    return txtStr;
}

void list_dir(const char* dirName, char** strsTxt, int* len){
    char current_path[10000];
    strcpy(current_path, dirName);
    DIR *current_dir = opendir(current_path);
    if (current_dir == NULL) return;
    struct dirent* current_dir_file =readdir(current_dir);
    while(current_dir_file){
        int path_len = strlen(current_path);
    strcat(current_path, "/");
    strcat(current_path, current_dir_file->d_name);
        if(current_dir_file->d_type == DT_REG && strstr(current_dir_file->d_name, ".txt") != NULL){
        if((strsTxt[*len] = (char*)txtOpen(current_path)) != NULL)
        (*len)++;
    }
    if (current_dir_file->d_type == DT_DIR && strcmp(".", current_dir_file->d_name) != 0 && strcmp("..",current_dir_file->d_name) != 0) list_dir(current_path,strsTxt,len);
    current_path[path_len] = '\0';
    current_dir_file = readdir(current_dir);
    }
    closedir(current_dir);
}

int compare(const void* a, const void* b){
    int a_value = atoi(*(char**)a);
    int b_value = atoi(*(char**)b);
    if (a_value > b_value)
        return 1;
    if (a_value < b_value)
        return -1;
    return 0;
}

int main(){
    char** strs = (char**)malloc(sizeof(char*)*1000);
    int len = 0;
    int i=0;
    char str[1000];
    FILE* fo;
    fo=fopen("fo","w");
    list_dir(".",strs,&len);
    qsort(strs, len, sizeof(char*), compare);
    for (i=0;i<len;i++) fprintf(fo,"%s\n", strs[i]);
    fclose(fo); //закрываем
    fo=fopen("fo","r");
    while (fgets(str, 1000, fo))
      printf("%s", str);
    fclose(fo);
    for (i=0;i<len;i++) free(strs[i]);
    free(strs);
    return 0;
}