swapfile

#!/bin/bash

# SPDX-FileCopyrightText: 2023 - 2024 sudorook <daemon@nullcodon.com>
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
# This program is free software: you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
# for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program. If not, see <https://www.gnu.org/licenses/>.

set -euo pipefail

ROOT="$(dirname "${0}")"

source "${ROOT}"/globals

! check_command blkid grep mkswap swapoff swapon && exit 3

function set_swap_on {
  # First, make sure that SWAPFILE is defined.
  if ! [ -v SWAPFILE ] || [ -z "${SWAPFILE}" ]; then
    show_error "ERROR: SWAPFILE is not defined. Exiting."
    exit 3
  fi

  # Create destination dir for swap file if it doesn't exist."
  local swapdir
  swapdir="$(dirname "${SWAPFILE}")"
  if [ "${swapdir}" != '/' ] && ! [ -d "${swapdir}" ]; then
    mkdir -p "${swapdir}"
  fi

  # Create swapfile if it doesn't exist.
  if ! [ -f "${SWAPFILE}" ]; then
    show_info "Creating ${SWAPFILE@Q}"
    dd if=/dev/zero of="${SWAPFILE}" bs=1M count="${SWAPSIZE}" status=progress
    sync
  fi

  # Set permissions.
  if [[ "$(stat -c "%a" "${SWAPFILE}")" != 600 ]]; then
    show_info "Setting ${SWAPFILE@Q} permissions"
    chmod 0600 "${SWAPFILE}"
  fi

  # Create UUID.
  if ! blkid -o value "${SWAPFILE}" | grep -q "^swap$"; then
    show_info "Setting ${SWAPFILE@Q} UUID"
    mkswap -U clear "${SWAPFILE}"
  fi

  # Check if swap partition active. If not run
  if ! swapon --show | grep -q "^${SWAPFILE}\s"; then
    show_info "Activating ${SWAPFILE@Q}"
    swapon "${SWAPFILE}"
  fi
}

function set_swap_off {
  # First, make sure that SWAPFILE is defined.
  if ! [ -v SWAPFILE ] || [ -z "${SWAPFILE}" ]; then
    show_error "ERROR: SWAPFILE is not defined. Exiting."
    exit 3
  fi

  # Disable swap partition if it is active.
  if swapon --show | grep -q "^${SWAPFILE}\s"; then
    show_info "Flushing cache"
    sync
    [ -e /proc/sys/vm/drop_caches ] && echo 3 > /proc/sys/vm/drop_caches
    sync
    show_info "Deactivating ${SWAPFILE@Q}"
    swapoff "${SWAPFILE}"
  fi

  # Delete swap file if it exists.
  if [ -f "${SWAPFILE}" ]; then
    show_info "Deleting ${SWAPFILE@Q}"
    rm "${SWAPFILE}"
  fi
}

function print_usage {
  show_header "Usage: swapfile <on|off> ..."
  show_listitem "\
    -f|--file  path for swap file (default: /swapfile)
    -s|--size  size of swap file in Mb (default: 8192)
    -h|--help  print (this) help message"
}


OPTIONS=f:hs:
LONGOPTIONS=file:,help,size:
PARSED=$(getopt -o "${OPTIONS}" --long "${LONGOPTIONS}" -n "${0}" -- "${@}")
eval set -- "${PARSED}"

while [ ${#} -ge 1 ]; do
  case "${1}" in
    -f | --file)
      SWAPFILE="${2}"
      shift 2
      ;;
    -h | --help)
      print_usage
      exit
      ;;
    -s | --size)
      SWAPSIZE="${2}"
      shift 2
      ;;
    --)
      shift
      break
      ;;
    *)
      show_error "ERROR: invalid option."
      exit 3
      ;;
  esac
done

if ! [ "${#}" -eq 1 ]; then
  show_error "ERROR: Incorrect # of parameters. Exiting."
  exit 3
fi

SWAPFILE="${SWAPFILE:-/swapfile}"
SWAPSIZE="${SWAPSIZE:-8192}"

case "${1}" in
  on)
    if [ ${EUID} -eq 0 ]; then
      set_swap_on
    else
      sudo bash -c "SWAPSIZE=${SWAPSIZE}; SWAPFILE=${SWAPFILE}; source ${ROOT}/globals; $(declare -f set_swap_on); set_swap_on"
    fi
    ;;
  off)
    if [ ${EUID} -eq 0 ]; then
      set_swap_off
    else
      sudo bash -c "SWAPSIZE=${SWAPSIZE}; SWAPFILE=${SWAPFILE}; source ${ROOT}/globals; $(declare -f set_swap_off); set_swap_off"
    fi
    ;;
  help)
    print_usage
    exit
    ;;
  *)
    show_error "ERROR: ${1@Q} not understood. Exiting."
    print_usage
    exit 3
    ;;
esac