如何在C中删除文件中的最后7个字节？

FILE* file = fopen("file.txt", "rb+");

fseek(file, -7, SEEK_END);

size_t file_size;
fseek(file, 0, SEEK_END);
file_size = ftell(file);

fseek(file, -7, SEEK_END);
size_t remaining_bytes = file_size - ftell(file);
char* buffer = (char*)malloc(remaining_bytes);
fread(buffer, sizeof(char), remaining_bytes, file);

fseek(file, -7, SEEK_END);
fwrite(buffer, sizeof(char), remaining_bytes, file);

fseek(file, -7, SEEK_END);
ftruncate(fileno(file), ftell(file));

fclose(file);
free(buffer);

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

int main() {
    FILE* file = fopen("file.txt", "rb+");
    if (file == NULL) {
        printf("Failed to open file.");
        return 1;
    }

    fseek(file, -7, SEEK_END);

    size_t file_size;
    fseek(file, 0, SEEK_END);
    file_size = ftell(file);

    fseek(file, -7, SEEK_END);
    size_t remaining_bytes = file_size - ftell(file);
    char* buffer = (char*)malloc(remaining_bytes);
    fread(buffer, sizeof(char), remaining_bytes, file);

    fseek(file, -7, SEEK_END);
    fwrite(buffer, sizeof(char), remaining_bytes, file);

    fseek(file, -7, SEEK_END);
    ftruncate(fileno(file), ftell(file));

    fclose(file);
    free(buffer);

    return 0;
}