5 ms·

You missed a nuance in the GP's problem set: > dd if=random-linux-image.img of=/dev/mmcblk0 bs=512 count=62499 seek=1 skip=1 is not the same as: > sudo dd if

You missed a nuance in the GP's problem set: > dd if=random-linux-image.img of=/dev/mmcblk0 bs=512 count=62499 seek=1 skip=1 is not the same as: > sudo dd if=/dev/sda of=/tmp/boot.1 bs=512 count=1 You are missing the "seek" and "skip" arguments which the GP challenges you to make `head` do.

fbn79 4y ago
You right. To skip you can pipe tail. sudo head -c 1024 /dev/sda | tail -zc 512 > /tmp/boot.2 Read 1024, keep last 512
- jstimpfle 4y ago
  What if the position is not at 512 but at 512G?
  - fbn79 4y ago
    Not tested, by I think the performance will be in the same order. Would be nice to do a benchmark test.
    - jstimpfle 4y ago
      No, it is O(n) vs O(1). Why would you read 512G + 512 bytes if you only need to read 512 bytes at offset 512G?
      - fbn79 4y ago
        I think you can just invert and do tail first sudo tail -zc +513 /dev/sda | head -c 512 > /tmp/boot.2
        jstimpfle 4y ago
        Well now you're seeking to the offset (tail is).