DouKaku?

#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>

int main (int argc, char *argv[]){

    if( argc < 2 ){
        return 1;
    }

    struct stat sb;
    if( 0 != stat(argv[1], &sb) ){
        perror(NULL);
        return 1;
    }

    printf("File size: %d\n", sb.st_size);
    return 0;
}