read_subs.c

#include <stdio.h>

int main(int argc, char** argv)
{
    FILE *fp;
    unsigned int len = 0;
    unsigned char buffer[256];

    if ( argc < 3 ){
        fprintf(stderr, "USAGE: %s <FILENAME> <OFFSET>\n", argv[0]);
        exit(0);
    }
    fp = fopen(argv[1], "rb");
    if ( ! fp ){
        fprintf(stderr, "Can't open file %s\n", argv[1]);
        exit(0);
    }
    fseek(fp, atoi(argv[2]), 0);
    do{
        len = fgetc(fp);
        if ( !len ) break;
        if ( ! fread(buffer, 1, len, fp) ){
            fprintf(stderr, "Tried to read an invalid block. File ends before whole block could be read.\n");
            exit(0);
        }
        fwrite(buffer, 1, len, stdout);
    } while( ! feof(fp) );
    fclose(fp);
    exit(1);
}