Wonderful though Clearcase is, its support tools leave a lot to be desired. Take the file comparison application that comes bundled. It only flags lines which have changed, so you often have to spend a couple of moments scanning the line to spot the changes. There are loads of file comparers out there to choose from. So here is how to integrate it with Clearcase. The simplest way is to find a file comparer with Clearcase integration capabilities like KDiff3. The integration is simple:

1. Download KDiff3 and install.
2. Run it up.
3. From the menu select Settings->Configure KDiff3.
4. Go into the Operation tab.
5. Click Integrate with Clearcase.
6. Click Ok.

Simple, but what if your file comparison tool doesn’t have an integrate with Clearcase button? Changing the Clearcase hooks is quite straight forward. The mapping file exists in:

<installation-root>\ClearCase\lib\mgrs\map

The file is keyed in extension (or class) and action, so replace the following lines in the map file.

_rftdef            xcompare  C:\Program Files\KDiff3\kdiff3.exe
_rftmap            xcompare  C:\Program Files\KDiff3\kdiff3.exe
_rftvp             xcompare  C:\Program Files\KDiff3\kdiff3.exe
_xml               xcompare  C:\Program Files\KDiff3\kdiff3.exe
_xml               xmerge    C:\Program Files\KDiff3\kdiff3.exe
_xml2              xcompare  C:\Program Files\KDiff3\kdiff3.exe
_xml2              xmerge    C:\Program Files\KDiff3\kdiff3.exe
_xtools            xcompare  C:\Program Files\KDiff3\kdiff3.exe
text_file_delta    xcompare  C:\Program Files\KDiff3\kdiff3.exe
text_file_delta    xmerge    C:\Program Files\KDiff3\kdiff3.exe
whole_copy         xcompare  C:\Program Files\KDiff3\kdiff3.exe
whole_copy         xmerge    C:\Program Files\KDiff3\kdiff3.exe
z_text_file_delta  xcompare  C:\Program Files\KDiff3\kdiff3.exe
z_text_file_delta  xmerge    C:\Program Files\KDiff3\kdiff3.exe
z_whole_copy       xcompare  C:\Program Files\KDiff3\kdiff3.exe
z_whole_copy       xmerge    C:\Program Files\KDiff3\kdiff3.exe