my backup system

libmbu.sh

# library

# sanitizes paths and interprets them as relative to / (adds / at the beginning, removes it at the end, deduplicates multiple /, removes .. and .)
SED_DIRSANIT='s`(^|$)`/`g;s`/+`/`g;:b;s`/\./`/`;tb;:a;s`(^|/[^/]*?)/\.\./`/`g;ta;s`^(.+)/$`\1`g'

# escapes strings for use in a sed command
SED_ESCAPE='s/[]\/$*.^[]/\\&/g'

die() { # vararg errmsg
  (tput bold
  tput setaf 1
  echo "$@"
  tput sgr0)>&2
  exit 1
}

warn() { # vararg msg
  (tput bold
  tput setaf 11
  echo "$@"
  tput sgr0)>&2
}

sed_escape() {
  sed -e "$SED_ESCAPE"
}

is_dir_mbu() { # dir
  test -f "$1/mbu.conf"
}

cfbd() { # dir
  if ! is_dir_mbu "$1"; then
    die "'$1' is not a mbu backup directory."
  fi
}

create_bd() { # dir, srcdir
  test -d "$2" || die "Source directory '$2' does not exist"
  mkdir -p "$1" || die "Couldn't create backup directory '$1'."
  touch "$1/mbu.conf"
  setsrcdir "$1" "$2"
  cfg_write "$1/mbu.conf" 'bdirformat' 'backup-%Y%m%d-%H%M%S'
  touch "$1/excludes.conf"
}

setsrcdir() { # dir, srcdir
  cfbd "$1"
  test -d "$2" || die "Source directory '$2' does not exist"
  cfg_write "$1/mbu.conf" 'srcdir' "$(cd "$2"; pwd)"
}

setdirformat() { # dir, dirformat
  cfbd "$1"
  date "+$2" > /dev/null 2> /dev/null || die "Invalid format. Look at \`man date\` for more info."
  printf 'Preview: %s\n' "$(date "+$2")"
  cfg_write "$1/mbu.conf" 'bdirformat' "$2"
}

get_new_backup_dir() { # dir
  cfbd "$1"
  cfg_haskey "$1/mbu.conf" 'bdirformat' || cfg_write "$1/mbu.conf" 'bdirformat' 'backup-%Y%m%d-%H%M%S'
  local format="$(cfg_read "$1/mbu.conf" 'bdirformat')"
  date "+$format"
}

execbackup() { # dir
  cfbd "$1"
  local backupdir="$(get_new_backup_dir "$1")"
  local bdpath="$1/$backupdir"
  printf "Creating backup '%s'\n" "$backupdir"
  mkdir -p "$bdpath/files" || die "Could not create backup directory."
  touch "$bdpath/backup.conf"
  local prevb_args=""
  if cfg_haskey "$1/mbu.conf" 'latest'; then
    local prevbackup="$(cfg_read "$1/mbu.conf" 'latest')"
    if [ -d "$1/$prevbackup/files" ]; then
      cfg_write "$bdpath/backup.conf" 'prev' "$prevbackup"
      prevb_args="--link-dest=../../$prevbackup/files "
    else
      warn "Nonexistent previous backup: '$prevbackup'"
    fi
  fi

  local sourcedir="$(cfg_read "$1/mbu.conf" 'srcdir')/"
  test -d "$sourcedir" || die "Source directory '$sourcedir' does not exist."
  local excludesfile="$1/excludes.conf"

  # local excludesfile="/tmp/excludes_$RANDOM.tmp"

  # do the thing
  rsync -aAXSh --info=progress2 --delete --exclude-from="$excludesfile" ${prevb_args} "$sourcedir" "$bdpath/files/" || die "Error while backing up files."

  # rm "$excludesfile"

  cfg_write "$1/mbu.conf" 'latest' "$backupdir"
  echo 'Backup finished!'
}

exclude_add() { # dir, excludedir
  cfbd "$1"
  test "x$2" = "x" && die "Empty exclude directory"
  echo "$2" >> "$1/excludes.conf"
  exclude_cleanup "$1"
}

exclude_remove() { # dir, excludedir
  cfbd "$1"
  sed -i "/^$(echo $2 | sed_escape)$/d" "$1/excludes.conf"
  exclude_cleanup "$1"
}

exclude_list() { # dir
  cfbd "$1"
  cat "$1/excludes.conf" | sed "s|^|($(cfg_read "$1/mbu.conf" srcdir))|g"
}

exclude_cleanup() { # dir
  cfbd "$1"
  local tmpfile=/tmp/.excludes.$RANDOM.conf
  cp "$1/excludes.conf" "$tmpfile"
  sed -Ei "$SED_DIRSANIT" "$tmpfile" 
  sort -uo "$tmpfile" "$tmpfile"
  mv "$tmpfile" "$1/excludes.conf"
}

purge() { # dir, keep_no
  cfbd "$1"
  die stub
}

getprev() { # path, backup_instance
  cfbd "$1"
  test -f "$1/$2/backup.conf" || die "'$2' is not a valid backup"
  cfg_haskey "$1/$2/backup.conf" 'prev' && cfg_read "$1/$2/backup.conf" 'prev'
}

cfg_write() { # path, key, value
  cfg_delete "$1" "$2"
  echo "$2=$3" >> "$1"
}

cfg_read() { # path, key -> value
  test -f "$1" && grep "^$(echo "$2" | sed_escape)=" "$1" | sed "s/^$(echo "$2" | sed_escape)=//" | tail -1
}

cfg_delete() { # path, key
  test -f "$1" && sed -i "/^$(echo $2 | sed_escape).*$/d" "$1"
}

cfg_haskey() { # path, key
  test -f "$1" && grep "^$(echo "$2" | sed_escape)=" "$1" > /dev/null
}

mbu.sh

#!/bin/bash

source $(dirname "$(readlink -f "$0")")/lib/libmbu.sh || exit 5

print_help() {
  cat <<EOF
usage: mbu <backup dir> <operation> [...]
operations:
  mbu <backup dir> create <source dir>
  mbu <backup dir> backup
  mbu <backup dir> excla <subdir>
  mbu <backup dir> exclr <subdir>
  mbu <backup dir> excll
  mbu <backup dir> setbf <format>
  mbu <backup dir> setsrc <source dir>
  mbu <backup dir> purge

create: Creates a new backup directory.
backup: Creates a new incremental backup.
excla:  Adds a new excluded file/directory.
exclr:  Removes a file/directory from the excludes list.
excll:  Lists the currently excluded files/directories.
setbf:  Sets the format for the backup folders.
        See \`man date\` for more information about the format.
setsrc: Changes the source directory.
purge:  Purges everything but the last 4 backups.
EOF
exit 2
}

case "$2" in
  create)
    create_bd "$1" "$3"
    ;;
  backup)
    execbackup "$1"
    ;;
  excla)
    exclude_add "$1" "$3"
    ;;
  exclr)
    exclude_remove "$1" "$3"
    ;;
  excll)
    exclude_list "$1"
    ;;
  setbf)
    setdirformat "$1" "$3"
    ;;
  setsrc)
    setsrcdir "$1" "$3"
    ;;
  purge)
    purge "$1" 4
    ;;
  *)
    print_help
    ;;
esac