When upgrading software (e.g. with slackpkg) you usually have customized the config files to your personal need. Now the config files of the new software version also differ from the original version. What you want is an easy way to get your own modifications into the new config files.

The solution is exemplified with just 1 configuration file called conf:

• conf.org is the original config file of old version of the software. Eighter you have created that file by copying before you made any modifications to conf or you can get it again by downloading the old version of the software.
• conf is your version of conf.org. You have customized to your needs.
• conf.new is the brandnew pristine version coming from the upgrade.

The following commands merges both the differences between conf.org and conf and the differences between conf.org and conf.new back into conf:

patch conf conf.org conf.new

An alternative to the merge command is diff3, it should produce the same result:

diff3 -m conf conf.org conf.new > conf.out
mv conf.out conf

Sometimes you have to create a config file which did not exist before (e.g. myConfigFile). In order not to forget such files during update, it is advisable to create an empty counterpart file myConfFile.org.

A manual check after the patch is applied is advisable, for there are situations imaginable where the tools do not produce the expected results:

conf.org:      conf:       conf.new:     desired:    result:

[mitwitz]      [mitwitz]   [coburg]      [coburg]    [coburg]
Otto=5         Otto=5      Otto=5        Otto=5      Otto=5
Guenter=6      Guenter=6   Guenter=6     Guenter=6   Guenter=6
Harry=7        Harry=7     Harry=7       Harry=7     Harry=7
Franz=8        Franz=-999  Franz=8       Franz=8     Franz=-999
Helga=9        Helga=9     Helga=9       Helga=9     Helga=9
Egon=10        Egon=10     Egon=10       Egon=10     Egon=10
Anton=11       Anton=11    Anton=11      Anton=11    Anton=11
                           [mitwitz]     [mitwitz]   [mitwitz]
                           Otto=5        Otto=5      Otto=5
                           Guenter=6     Guenter=6   Guenter=6
                           Harry=7       Harry=7     Harry=7
                           Franz=8       Franz=-999  Franz=8
                           Helga=9       Helga=9     Helga=9