preinst is in ivtools-bin 1.2.11a1-11.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 | #!/bin/sh
set -e
case $1 in
install|upgrade)
dpkg-divert --package ivtools-bin --divert /usr/bin/dclock.dclock \
--rename /usr/bin/dclock
dpkg-divert --package ivtools-bin --divert /usr/share/man/man1/dclock.dclock.1.gz \
--rename /usr/share/man/man1/dclock.1.gz
;;
esac
|