use gcc clean.c then ./a.out /home/somewhere/.minetest/worlds/world/

gistfile1.txt

/*
 * Application to delete empty player files from a minetest world.
 * Usage: ./clean /path/to/minetest/world
 *
 * Criteria for removal of a player file and auth line:
 * The player must have nothing in his inventory and mut not have interact.
 * This obviously won't work well for servers where interact is granted by
 * default, but all you have to do is remove the
 * " || strstr(player->privs, "interact")" part for those servers.
 */


#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <stdlib.h>
#include <time.h>
#include <stdbool.h>


#define MAX_EMPTY 47
#define NAME_LEN 20
#define HASH_LEN 29
#define PRIVS_LEN 256
#define PF_LINE_LEN 256


typedef struct {
	char name[NAME_LEN];
	char hash[HASH_LEN];
	char privs[PRIVS_LEN];
	bool cleared;
} Auth;


int main(int argc, char *argv[]);
Auth *read_auth(char worldpath[], Auth *auth_list);
void read_auth_line(FILE *authf, Auth *auth);
bool check_playerfile(char worldpath[], Auth *player);
void write_auth(char worldpath[], Auth *auth_list);
void cleanup(Auth *auth_list);


int main(int argc, char *argv[]) {
	Auth *auth_list;
	int i, num_removed = 0;
	clock_t start = clock();

	if (argc != 2) {
		printf("Usage:\n"
			"  %s <WorldPath>\n",
			argv[0]);
		exit(1);
	}

	auth_list = read_auth(argv[1], auth_list);

	for (i = 0; auth_list[i].name[0] != '\0'; i++) {
		if (check_playerfile(argv[1], &auth_list[i])) {
			num_removed++;
		}
	}

	write_auth(argv[1], auth_list);

	cleanup(auth_list);

	printf("%d player entries deleted in %f seconds\n", num_removed, (float)(clock() - start) / CLOCKS_PER_SEC);
	return 0;
}


Auth *read_auth(char worldpath[], Auth *auth_list) {
	char filename[FILENAME_MAX];
	FILE *authf;
	int ch, i, auth_len = 0;

	strcpy(filename, worldpath);
	strcat(filename, "/auth.txt");

	authf = fopen(filename, "r");

	if (!authf) {
		printf("Error opening %s for reading\n", filename);
		exit(1);
	}

	/* Get the number of lines in the auth file */
	while ((ch = getc(authf)) != EOF) {
		if (ch == '\n') {
			auth_len++;
		}
	}

	printf("%d lines found\n", auth_len);

	/* We need to increment the length in case the file doesn't end with
	 * a newline */
	auth_len++;

	/* Then get back to the top of the file */
	rewind(authf);

	/* Allocate our array of structs */
	auth_list = (Auth *) calloc(auth_len + 1, sizeof(Auth));

	/* Load the auth data into our array */
	for (i = 0; !feof(authf); i++) {
		if (ferror(authf)) {
			perror("Error reading auth file: ");
			exit(1);
		}
		read_auth_line(authf, &auth_list[i]);
	}

	/* Null out the last item */
	auth_list[i].name[0] = '\0';

	fclose(authf);

	return auth_list;
}


void read_auth_line(FILE *authf, Auth *auth) {
	int ch, i = 0;

	while ((ch = fgetc(authf)) != ':') {
		if (ch == EOF) break;
		auth->name[i] = ch;
		i++;
	}
	auth->name[i] = '\0';

	i = 0;
	while ((ch = fgetc(authf)) != ':') {
		if (ch == EOF) break;
		auth->hash[i] = ch;
		i++;
	}
	auth->hash[i] = '\0';

	i = 0;
	while ((ch = fgetc(authf)) != '\n') {
		if (ch == EOF) break;
		auth->privs[i] = ch;
		i++;
	}
	auth->privs[i] = '\0';

	auth->cleared = false;

	return;
}


/* Checks if a player file has deviated from the
 * default and deletes it if it hasn't.
 */
bool check_playerfile(char worldpath[], Auth *player) {
	char filename[FILENAME_MAX];
	FILE *playerfile;
	char line[PF_LINE_LEN];
	int i = 0;

	/* Check for null entries and players with interact. Includes basic_privs */
	if (player->name[0] == '\0' || strstr(player->privs, "interact")) {
		return false;
	}

       	strcpy(filename, worldpath);
       	strcat(filename, "/players/");
	strcat(filename, player->name);

	playerfile = fopen(filename, "r");

	if (!playerfile) {
		return false;
	}

	/* Count the number of empty inventory slots */
	while (fscanf(playerfile, " %s", line) != EOF) {
		if (strcmp(line, "Empty") == 0) {
			i++;
		}
	}

	fclose(playerfile);

	if (i >= MAX_EMPTY) {
		remove(filename);
		player->cleared = true;
		return true;
	}
	return false;
}


void write_auth(char worldpath[], Auth *auth_list) {
	char filename[FILENAME_MAX];
	FILE *authf;
	int i;

       	strcpy(filename, worldpath);
	strcat(filename, "/auth.txt");

	authf = fopen(filename, "w");

	if (!authf) {
		printf("Unable to save auth data\n");
		exit(1);
	}

	for (i = 0; auth_list[i].name[0] != '\0'; i++) {
		if (auth_list[i].cleared) {
			continue;
		}
		fprintf(authf, "%s:%s:%s\n",
			auth_list[i].name,
			auth_list[i].hash,
			auth_list[i].privs);
	}

	fclose(authf);
	return;
}


void cleanup(Auth *auth_list) {
	free(auth_list);
	return;
}