Pm Wiki uses the external program diff to store previous versions of pages. While these programs are commonly available on most Unix systems, they are generally not available under Windows.

Win Diff (http://www.pmichaud.com/pub/windiff/windiff.zip) is a special package containing Windows versions of the diff and patch programs from the Gnuwin32 project. To use this package, simply create a windiff/ subdirectory in the directory that holds your pmwiki.php script and copy the files from the zip archive into that directory. Then, add the following lines to your local/config.php file:

    $SysDiffCmd = 'windiff\\diff';
    $SysPatchCmd = 'windiff\\patch --silent';

That should be all there is to it! Questions and comments can be sent to pmwiki-users@pmichaud.com.

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Those with MSys already installed may find the following config lines helpful:

    $SysDiffCmd = 'C:/msys/1.0/bin/diff.exe';
    $SysPatchCmd = 'C:/msys/1.0/bin/patch.exe';

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Thx! I also make my copy of Tavi on Win32 works with Diff now! (i.e. Tavi works with the Diff from PmWiki's but not from GNU utilities for Win32 nor Gnuwin32 project) -- Aaron Law? , 2004-06-26 10:50

--- this solution WILL NOT work on the windows 2003 servers that will not allow foreign programs to work under IIS 6. you have to use php (sript versions) of difff and patch please find it here: http://www.pmwiki.org/wiki/Cookbook/PHPDiffEngine

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Failure to install a valid diff and patch application can cause a DOS window to open with the message "The system could not find the specified path." which may also appear in your error logs. The reason is that the php engine is looking for diff and patch in /usr/bin which does not exist. This is true, even if the "recent changes" function continues to work.
-- Mark Goldey