roks

#!/usr/bin/env bash
#cito M:755 O:0 G:0 T:/usr/local/bin/roks
#------------------------------------------------------------------------------
# Project Name      - ShellProjects/source/roks
# Started On        - Sun 17 Sep 23:32:47 BST 2017
# Last Change       - Fri 11 Aug 13:08:38 BST 2023
# Author E-Mail     - terminalforlife@yahoo.com
# Author GitHub     - https://github.com/terminalforlife
#------------------------------------------------------------------------------
# Written as an improvement over the now-deprecated script called
# 'purge-old-kernels' found in the 'byobu' package. This small program will
# clear out your system of old kernel versions on an Ubuntu- or Debian-based
# system.
#
# By way of example, assume the following:
#
#   6.2.11
#   6.3.0       <-- Currently Loaded
#   6.3.1
#   6.3.2
#   6.3.3
#   6.3.4
#
# ROKs will ignore anything newer than 6.3.0, opting to keep 6.3.0, because it
# is currently loaded, and 6.2.11 will by default be kept as well, because it's
# the fallback. If no fallback is selected (keep 1), 6.2.11 will be selected
# for removal or purging.
#
# NOTE:
#
#   Noticed on 2023-08-11, that linux-version(1) was actually incorrectly
#   sorting the kernel version strings, which of course is a huge problem. To
#   handle this issue, sort(1) was used, with its `-V` flag to sort version
#   strings, which it appears to do correctly with at least regular MAJ.MIN.REV
#   version strings.
#
# Features:
#
# N/A
#
# Bugs:
#
# N/A
#
# Dependencies:
#
#   apt (>= 1.6.12)
#   bash (>= 4.1)
#   coreutils (>= 8.25-2)
#   linux-base (>= 4.5)
#------------------------------------------------------------------------------

CurVer='2023-08-11'
Progrm='roks'
ProgrmFancy='ROKs'

Usage() {
	read -d '' <<-EOF
		Usage: $Progrm [OPTS]

		  -h, --help               - Display this help information.
		  -v, --version            - Output the version datestamp.
		  -k, --keep INT           - Keep INT number of kernels, instead of 1.
		  -p, --purge              - Don't just remove, but purge the kernels.
		  -t, --type TYPE          - Work with TYPE kernels. Any by default.

		  Remember to check before saying yes to APT, in-case gathered packages
		  aren't as expected. By default, two kernel will be held back, which
		  includes the one currently loaded. Kernels newer than your currently
		  loaded kernel will be ignored. $ProgrmFancy may not be suitable for all Linux
		  systems or kernel types.

		  Unrecognised flags will be passed to apt-get(8).
	EOF

	printf '%s' "$REPLY"
}

Err() {
	printf 'Err: %s\n' "$2" 1>&2
	(( $1 > 0 )) && exit $1
}

KernKeep=2

Args=()
while [[ -n $1 ]]; do
	case $1 in
		-[^-]*)
			Str=${1#-}
			Len=${#Str}
			for (( Index = 0; Index < Len; Index++ )); {
				Args+=(-"${Str:Index:1}")
			} ;;
		*)
			Args+=("$1") ;;
	esac
	shift
done

set -- "${Args[@]}"

NoRoot='False'

while [[ -n $1 ]]; do
	case $1 in
		--help|-h)
			Usage; exit 0 ;;
		--version|-v)
			printf '%s\n' "$CurVer"
			exit 0 ;;
		--keep|-k)
			if [[ $2 == +([0-9]) ]]; then
				if (( $2 == 0 )); then
					Err 1 "Unable to remove currently-loaded kernel."
				else
					KernKeep=$2
					shift
				fi
			else
				Err 1 "Option '$1' given non-numeric argument."
			fi ;;
		--type|-t)
			shift; KernType="-$1" ;;
		--purge|-p)
			DoPurge='--purge' ;;
		-*)
			AptGetOpts+=" $1" ;;
		*)
			Err 1 "Incorrect argument(s) provided." ;;
	esac
	shift
done

DepCount=0
for CurDep in apt-get linux-version sort; {
	if ! type -P "$CurDep" &> /dev/null; then
		Err 0 "Dependency '$CurDep' not met."
		(( DepCount++ ))
	fi
}

(( DepCount > 0 )) && exit 1

(( UID == 0 )) || NoRoot='True'

ProcVerFile='/proc/version'
if type -P uname &> /dev/null; then
	Current=`uname -r`
elif [[ -f $ProcVerFile && -r $ProcVerFile ]]; then
	read _ _ Current _ < /proc/version
else
	Err 1 'Unable to determine current kernel version.'
fi

readarray -t <<< "$(linux-version list | sort -V)"

Kerns=()
for Line in "${MAPFILE[@]}"; {
	[[ $Line == $Current ]] && break

	Kerns+=("$Line")
}

KernsAvail=${#Kerns[@]}
Kerns=("${Kerns[@]:0:${#Kerns[@]} - KernKeep + 1}")

if [[ $NoRoot == True ]]; then
	printf "Found %d kernel installation(s):\n\n" ${#MAPFILE[@]}
	for Kern in "${MAPFILE[@]}"; {
		if [[ $Kern == $Current ]]; then
			printf '  %s <-- Active\n' "$Kern"
		else
			printf '  %s\n' "$Kern"
		fi
	}

	printf '\nUp to %d kernel(s) available for uninstallation.\n' $KernsAvail

	if (( KernsAvail > 0 )); then
		printf "Launch %s with 'root' privileges to take action.\n" "$ProgrmFancy"
	fi
else
	if (( ${#Kerns[@]} == 0 )); then
		Err 1 'No suitable kernels found.'
	fi

	Packages=()
	for Kern in "${Kerns[@]}"; {
		Packages+=(linux-{image,headers}-"$Kern")
	}

	apt-get $AptGetOpts -o Dpkg::Progress=true\
		-o Dpkg::Progress-Fancy=true remove $DoPurge "${Packages[@]}"

	Exit=$?
	if (( Exit > 0 )); then
		Err 1 "Exit $Exit detected from apt-get(8)."
	fi
fi