c 언어로 파일 크기를 가져와 파일이 존재하는지 판단합니다

#import <sys/stat.h>

//         
bool file_exists(const char *filename){
    return access(filename, 0) == 0;
}

//        1
long file_size(const char *file){
    long length = -1;
    FILE *fp = fopen(file, "rb+");
    if (fp == NULL) {
        return length;
    }
    fseek(fp, 0, SEEK_END);
    length = ftell(fp);
    fclose(fp);
    return length;
}

//        2
long get_file_size(const char *file){
    long length = -1;
    struct stat statbuff;
    if(stat(file, &statbuff) < 0){
        return length;
    }else{
        length = statbuff.st_size;
    }
    return length;
}

//     
char *str_cat(char *str, char *str2){
	long len = strlen(str) + strlen(str2);
	char *s = (char *)malloc(sizeof(char) * len);
	strcpy(s, str);
	strcat(s, str2);
	return s;
}

//    

char *file_get_contents(const char *filename){
	FILE *fp;
	size_t size = 1024, n = 0, count = 0, sz = sizeof(char);

	char *data = (char *)malloc(sizeof(char) * size);
	if(file_exists(filename)){
		fp = fopen(filename, "r+");
		if(fp){
			do{
				if(count > 0){
					data = realloc(data, (size + count) * sz);
				}
				n = fread(data + count, sz, size, fp);
				if(n < 0){
					free(data);
					data = NULL;
				}
				count += n;
			}while(n > 0);

			fclose(fp);

			if(data){
				if (0 == (count + sz) % 512){//       
					data = realloc(data, count + sz);
				}
				data[count] = '\0';
			}
			return data;
		}
	}

	return NULL;
}