postinst is in unrar-free 1:0.0.1+cvs20071127-2.
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 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | #!/bin/sh
set -e
case "$1" in
    configure|abort-upgrade)
        update-alternatives --install /usr/bin/unrar unrar \
        /usr/bin/unrar-free 30 \
        --slave /usr/share/man/man1/unrar.1.gz unrar.1.gz \
        /usr/share/man/man1/unrar-free.1.gz
    ;;
    
    abort-remove|abort-deconfigure)
    ;;
    
    *)
      echo "postinst called with unknown argument \$1'" >&2
      exit 0
    ;;
esac
exit 0
 |