#!/bin/bash
#
# Author:   ModestUser
# Version:   0.1
# License:   GPLv2
#
# Simple management tool for setting packages on hold, unhold them or install/hold them
# Install: own as root, make executable, copy to /usr/local/bin
#
# For usage: hold -h

function usage () {
   cat <<EOF
USAGE:   ${my_name} [ -i | -u | -h ] [ -n ] package1 package2 ...

   Without any arguments all packages that are set to HOLD are displayed.
   Without any option the packages are set to HOLD.

OPTIONS:
   -i   installs packages and sets them to HOLD
   -u   unhold packages, i.e. set to install (no dist-upgrade)
   -n   use numbers instead of package names to reference packages
   -h   display this help
EOF
}

function print_error () {
   echo >&2 "${*}"
   exit 1
}
   
function numbers_to_packages () {
   [[ -f ${hold_list} ]] || print_error "Error: hold list has not been generated! Run 'hold' without arguments first!"
   numbers="${packages}"
   packages=
   for num in ${numbers}; do
      packages="${packages} $(sed -n "${num}p" ${hold_list})"   
   done
}

function write_hold_list () {
   dpkg --get-selections | awk '/hold$/ { print $1 }' > "${hold_list}"
}

function display_hold_list () {
   echo "Packages on hold:"
   cat -n "${hold_list}"
}

function set_hold () {
   for package in ${packages}; do
      echo "Setting package ${package} to hold..."
      echo "${package} hold" | dpkg --set-selections
   done
}

function hold_install () {
   apt-get update && apt-get -V install ${packages}
   set_hold
}

function unhold () {
   for package in ${packages}; do
      echo "Setting package ${package} to install..."
      echo "${package} install" | dpkg --set-selections
   done
}

(($UID)) && print_error "You must be root to run this script!"

my_name="$(basename $0)"
hold_list="${TMPDIR:=/tmp}/${my_name}.list"
action="set_hold"
use_numbers=0


if ((${#} == 0)); then
   write_hold_list && display_hold_list
   exit 0
fi

while getopts "hinu" opt; do
   case $opt in
      i)   [[ "${action}" == "unhold" ]] && print_error "Error: Options -i and -u are not compatible!"
         action="hold_install" ;;
      u)    [[ "${action}" == "hold_install" ]] && print_error "Error: Options -i and -u are not compatible!"
         action="unhold" ;;
      n)   use_numbers=1 ;;
      h)   usage; exit 0 ;;
   esac
done

shift $((${OPTIND} - 1))
packages="${@}"
((${use_numbers})) && numbers_to_packages
${action}
write_hold_list && display_hold_list
exit 0