کد زیر چیست ؟ لطفا این کد را برای من تحلیل کنید

Question

#include < stdio.h >
#include 
#include 
#include 
#include 
#include 
#include 
int get_block (int fd, int logical_block)
{
int ret;
ret = ioctl (fd, FIBMAP, &logical_block);
if (ret < 0) {
perror ("ioctl");
return −1;
}
return logical_block;
}
int get_nr_blocks (int fd)
{
struct stat buf;
int ret;
ret = fstat (fd, &buf);
if (ret < 0) {
perror ("fstat");
return −1;
}
return buf.st_blocks;
}
void print_blocks (int fd)
{
int nr_blocks, i;
nr_blocks = get_nr_blocks (fd);
if (nr_blocks < 0) {
fprintf (stderr, "get_nr_blocks failed!\n");
return;
}
if (nr_blocks == 0) {
printf ("no allocated blocks\n");
return;
} else if (nr_blocks == 1)
printf ("1 block\n\n");
else
printf ("%d blocks\n\n", nr_blocks);
for (i = 0; i < nr_blocks; i++) {
int phys_block;
phys_block = get_block (fd, i);
if (phys_block < 0) {
fprintf (stderr, "get_block failed!\n");
return;
}
if (!phys_block)
continue;
printf ("(%u, %u) ", i, phys_block);
}
putchar ('\n');
}
int main (int argc, char *argv[])
{
int fd;
if (argc < 2) {
fprintf (stderr, "usage: %s \n", argv[0]);
return 1;
}
fd = open (argv[1], O_RDONLY);
if (fd < 0) {
perror ("open");
return 1;
}
print_blocks (fd);
return 0;
}