Rocksmith save game transfer tool

rsmith_save.c

// Author: pcsmith
// Modifications: danielkza (danielkza2@gmail.com)
// License: GPLv3 https://www.gnu.org/licenses/gpl.html
// More info: http://rsmods.oakey-dev.eu/index.php?title=Savegame_Transfer
//

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <stdint.h>
#include <inttypes.h>

uint32_t get_id(FILE* handle)
{
    uint32_t id = 0;
    if(fseek(handle, 8, SEEK_SET) != 0)
        return 0;

    if(fread(&id, sizeof(id), 1, handle) != 1 || ferror(handle))
        return 0;

    return id;
}

int main(int argc, char* argv[])
{
    FILE* handle;
    uint32_t id;

    if(argc<2)
    {
        printf("Rocksmith Profiles ID Changer v0.2.1 by pcsmith\n");
        printf("------------------------------------------------\n");
        printf("Rocksmith only loads profiles with certain IDs.\n");
        printf("This tool can show and modify them.\n\n");
        printf("syntax: get profile ID: rsprofiles file\n");
        printf("        set profile ID: rsprofiles profileID file_1 [file_2] ... [file_n]\n");
        printf("More info:\n");
        printf("        http://rsmods.oakey-dev.eu/index.php?title=Savegame_Transfer\n\n");

        return 1;
    }

    if(argc == 2) // read mode
    {
        handle = fopen(argv[1], "rb");
        if(handle == NULL) {
            fprintf(stderr, "ERROR: Can't open file %s:", argv[1]);
            perror(NULL);
            return 1;
        }

        id =  get_id(handle);
        if(id == 0) {
            fprintf(stderr, "ERROR: failed to retrieve ID\n");
            return 1;
        }
        
        fclose(handle);
        printf("%" PRIx32, id);

        return 0;
    }
    else // write mode
    {
        int i;

         // scan the new id
        if(strlen(argv[1]) != 8 || sscanf(argv[1], "%" SCNx32, &id) != 1) {
            fprintf(stderr, "ERROR: input id must be a 4 byte hex number in the form 'abcdef01'!\n");
            return 1;
        }

        // write it to all files
        for(i = 2; i < argc; i++)
        {
            uint32_t old_id;
            handle = fopen(argv[i], "r+b");
            if(handle == NULL) {
                fprintf(stderr, "WARNING: Can't open file %s, skipping:", argv[i]);
                perror(NULL);
                continue;
            }

            old_id = get_id(handle);
            if(fseek(handle, 8, SEEK_SET) != 0 || fwrite(&id, sizeof(uint32_t), 1, handle) != 1) {
                fprintf(stderr, "ERROR: failed to write ID to file %s", argv[i]);
            } else {
                fprintf(stderr, "OK: Changed profile ID from %" PRIx32 " to %" PRIx32 " (file %s)\n", old_id, id, argv[i]);
            }

            fclose(handle);
        }

        return 0;
    }

    return 0;
}