$ touch foo bar
$ cat <<EOF >hash-filename
#!/bin/sh
sha1sum | awk '{ print \$1 }'
EOF
$ chmod +x hash-filename
$ ls foo bar | mmv -i ./hash-filename
$ ls
e242ed3bffccdf271b7fbaf34ed72d089537b42f hash-filename
f1d2d2f924e986ac86fdf7b36c94bcdf32beec15