Any comand in "Preprocessor commad" and "Line-matching preprocessor commad" ends with error message "Preprocessing possibly failed. Check this command...".
Exactly:
Ubuntu 9.10 (gnome environment)
kdiff3 0.9.95 (KDE 4.3.2)
Preprocessor commad: egrep -e '^ *[^ #]'
Line-matching preprocessor commad: sed 's/#/\/\//'
I tried it also in Opensuse 11.1 (KDE 3.5.10), kdiff3 0.9.92 and it works OK there.
Compared error massage (with intentionaly wrong command) - error message in kdiff3 0.9.95 does not contain pipeline from source file to /tmp.
The single quotation marks won't work with QProcess it seems.
Use the double quotation makrs: sed "s/#/\/\//"
Sorry for the inconvenience. I'll have to update the docs.
Joachim