The bug itself wasn't very interesting, just a brainfart. But it wasn't doing what it should, so I added debugging output - one line per pixel. (I was generatin

The bug itself wasn't very interesting, just a brainfart. But it wasn't doing what it should, so I added debugging output - one line per pixel. (I was generating a png from a custom image format.) Because there was so much output, I did a `| head` to keep it manageable. Saw what I was doing wrong, fixed it, reran the command, it seemed fine - but the output image looked exactly the same as it had before. It took me about an hour to realise that once head had exited, the pipeline sent a signal to my program, killing it. The image wasn't getting written until after all the pixels had been processed, so it never got to that stage.