You must install a command line version of RCS. An easy way to get a lot of Unix commands, is by installing the Cygwin package.
First check if you have RCS available:
If no ci binary is available, you don't have RCS. For Unix systems get the source from a GNU mirror in /pub/gnu/rcs, and install it in the normal fashion with "tar xvzf ...; cd rcs...; ./configure; make; make install".
- With Gentoo just use 'emerge rcs'. -- Jogi
- I installed JSPWiki under Gentoo Linux 2004.4. I emerged rcs, but the RCSFileProvider does not work. The FileSystemProvider and the VersioningFileProvider are working fine. -- Jogi
Notably Solaris 8 ship without RCS (_AND_ it ships without a C compiler).