*) how to use nanosleep

#define TEN_MILLIS_IN_NANOS 10000000

struct timespec t;
int seed=0;

t.tv_sec = 0;
t.tv_nsec = rand_r(&seed)%(TEN_MILLIS_IN_NANOS+1);
nanosleep(&t, NULL);

*) how to read/write a char and offset from/to a file

if (!(file_in = fopen(infile, "r"))) {
     error("could not open input file for reading");
 }

...

result.offset = ftell(file_in);     /* get position of byte in file */
result.byte = fgetc(file_in);       /* read byte from file */

...

fclose(infile)

--------------------------------------------------------

if (!(file_out = fopen(outfile, "w"))) {
    error("could not open output file for writing");
}
...

if (fseek(file_out, d.offset, SEEK_SET) == -1) {
    fprintf(stderr, "error setting output file position to %u\n",
            (unsigned int) d.offset);
    exit(-1);
}
if (fputc(d.byte, file_out) == EOF) {
    fprintf(stderr, "error writing byte %d to output file\n", d.byte);
    exit(-1);
}
...
fclose(infile)


*) When does the program finish?