alternatives-helper

#!/usr/bin/env bash

#### Configure as "The default administration directory" in alternatives man page:
alternatives_admindir='/var/lib/alternatives'

#### When running the command, you might grep for these terms:
# "could provide" "missing" "exists" "not recommended" "is recommended"

#### Correcting the alternatives can probably be accomplished with one of these commands:
# alternatives --auto foo
# alternatives --config foo


####################################################################################################
# Validate the alternatives_admindir
####################################################################################################
[[ ! -d "${alternatives_admindir}" ]] && echo "${alternatives_admindir} is not a directory" && exit 1

alts=( "${alts[@]}" $(find "${alternatives_admindir}" -maxdepth 1 -type f) )
[[ "${#alts[@]}" -lt 1 ]] && echo "${alternatives_admindir} is empty" && exit 1

####################################################################################################
# Check for missing or non-priority symlinks
####################################################################################################
for i in "${alts[@]}"; do
    is_symlink=0
    command=$(head -2 "${i}" | tail -1)
    test -L "${command}" && is_symlink=1

    if [[ "${is_symlink}" -eq 0 ]];
       then
           if test -x "${command}"; then
                                        echo "alternative $(basename ${i}) could provide ${command} but an executable already exists"
           else
              test ! -f "${command}" || echo "alternative $(basename ${i}) could provide ${command} which appears to be broken"
              test   -f "${command}" || echo "alternative $(basename ${i}) could provide ${command} which appears to be missing"
           fi
    else
       priority=$(grep '^[0-9]' "${i}" | sort -nk 1 | tail -1)
       symlink_config=$(grep -B1 "${priority}" "${i}" | head -1)
       symlink_actual=$(readlink -f "${command}")
       if [[ "${symlink_actual}" != "${symlink_config}" ]] &&
          [[ "$(readlink -f "${symlink_config}")" != "${symlink_actual}" ]]; then
          echo "alternative $(basename ${i}) = ${command} = ${symlink_actual} but not recommended"
       else
          echo "alternative $(basename ${i}) = ${command} = ${symlink_actual} and is recommended"
       fi
    fi
done