sha256 treehash used for amazon glacier
To compile:
gcc treehash.c -lcrypto -o treehash
There will be some warnings (at least on os x) but that's just because sha256 isn't considered
secure, but you are probably using this for amazon glacier and not cryptographic purposes.
To run:
cat file1 file2 | ./treehash
If you want to install, put the treehash file somewhere in your $PATH, perhaps /usr/local/bin.