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

long int filesize (FILE * fp) {
    long int save_pos, size_of_file;

    save_pos = ftell(fp);
    fseek(fp, 0L, SEEK_END);
    size_of_file = ftell(fp);
    fseek(fp, save_pos, SEEK_SET);

    return(size_of_file);
}

int main (int argc, char * argv[]) {
    FILE * fin;
    FILE * fout;

    fout = fopen("output.txt", "w");

    if (argv[1] == NULL) {
        fprintf(fout, "Usage: stat filename\n");
        fclose(fout);
        exit(1);
    } else {
        fin = fopen(argv[1], "r");

        if (fin == NULL) {
            fprintf(fout, "Can't open file %s", argv[1]);
            fclose(fout);
            exit(2);
        } else {
            fprintf(fout, "%ld", filesize(fin));
            fclose(fout);
            fclose(fin);
            exit(0);
        }
    }

    return 0;
}