I've been archiving a bunch of diskettes and wanted to be able to check the CRCK.COM checksums on the Linux box they're received on. I found a copy of `crck.c` in the UNIX C User's Group archives and cleaned it up for using on modern systems:

https://github.com/glitchwrks/crck

There's patches against the original source in the `orig` subdirectory. I added a Makefile and reformatted the manpage too. `make` builds it, `make install` as root will install the binary and the manpage. There's a Slackbuild for it too:

https://github.com/glitchwrks/crck-slackbuild

It's not submitted to slackbuilds.org yet since they're down for maintenance for the upcoming Slackware 15.0 release!