I've always used this to load an image from a tar
```sh
docker load < image.tar
```
is same as:
```sh
docker load --input image.tar
```

Useful when I had to run something like:
```
cat docker-cache/docker-tags.txt | xargs -t -I % docker load < docker-cache/images/%
```

That fails because loading the file into stdin gets evaluated first before the value from xargs.

```
cat docker-cache/docker-tags.txt | xargs -t -I % docker load --input docker-cache/images/%
```