postinst is in libtxc-dxtn-s2tc 1.0+git20151227-2.
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 | #!/bin/sh
set -e
update-alternatives --install \
/usr/lib/x86_64-linux-gnu/libtxc_dxtn.so libtxc-dxtn-x86_64-linux-gnu /usr/lib/x86_64-linux-gnu/s2tc/libtxc_dxtn.so 10
|