This utility is a wrapper for the md5(3), sha1(3), rmd160(3), and
tiger hash routines.  It is remarkably similar to the digest package,
except that it can recursively checksum directory trees.

While a simple checksum on a tar file is usually satisfactory, once
said archive has been extracted, it is virtually impossible to
repackage the extracted tree in a form that can yield a repeatable
checksum.  To be specific, changes in timestamps and ownership, and
changes in file ordering within directories can affect the checksum of
the archive, while not really impacting the actual code at all.

The algorithm used to checksum a directory in this implementation
is considers only the files' pathnames, the files' types (ie,
directory vs.  file vs. symbolic link), and their contents (for
the latter two).  It is described in greater detail in the man
page.

Homepage:
https://www.NetBSD.org/docs/software/packages.html
