How to recursively create a hash file (sha512sum) inside each folder of a tree?

Question

For a given tree, say /var/ftpd, how do I create a hash file in each folder of that tree with the contents of that folder within a given tree? sha1sum and sha512sum does not have recursion options.

Answer 1

FWIW the solution is:

user@host bin]$ cat mkshaindir 
#!/bin/dash
cd $1
sha512sum * >.sha512sum

[user@host bin]$ find /var/ftpd -type d -print0 | xargs -0 -i  mkshaindir  {}

Note that mkshaindir, for my purposes, is a separate component because there may be a need for me to make a hash of files in a new folder, or of one that was recently changed.

The rest is left as an exercise for the reader.

Note: sha512sum will complain to STDERR about non file input (e.g. directories, block files, etc).

Answer 2

The script should avoid to include the hashfile itself into the calculation, as saving the hashfile invalidates the hash.
Moreover, I suggest to use find -exec to save resources:

find /var/ftpd -type d -print0 ! -name .sha512sum -exec mkshaindir {} \;