rename the config for it to be coherent with the script itself, add the license text and some comment fixes

backup.cfg

@@ -1,11 +0,0 @@
-protocol=ssh # ftp, sftp, ftps, ssh or local
-remote_host=hostname.tld
-backup_dir=relative_or_full_path
-#snap_file=/var/backup/snapshot.list
-#exclude_list=/usr/local/etc/backup/excludes.list
-compress_format=xz # gz, bz2, xz or empty for non-compressed
-remote_user=username
-remote_pass=PassWd
-source_dirs=( '/home/user/source1:/var/backup/snapshot.list' )
-
-# vim: ft=zsh

backup.zsh

@@ -1,71 +1,111 @@
 #!/usr/bin/env zsh
-self_name=$0
-default_cfg='/usr/local/etc/backup.cfg'
-default_postfix=$(date +%F-%H%M)
+#
+# The MIT License (MIT)
+#
+# Copyright (c) 2014 Von Random
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+#
 
+self_name=$0
+
+# some hardcoded defaults
+default_cfg='/etc/backup.zsh.cfg'
+default_postfix=$(date +%F-%H%M)
+default_ftp_port='21'
+default_ssh_port='22'
+
+# echo to stderr
 function err
 {
-	[[ -n $1 ]] && echo $1 >&2
+	[[ -n $1 ]] && printf "%s\n" $1 >&2
 }
 
+# standard configuration error message to stderr
 function cfg_err
 {
-	[[ -n $1 ]] && echo "$1 is not set in configuration, but is required by $0 to work." >&2
+	[[ -n $1 ]] && printf "%s is not set in configuration, but is required by %s to work.\n" $1 $self_name >&2
 }
 
+# print help
 function usage
 {
-	echo "usage: $self_name [--help|--config]
-	--help    -h - show this message
-	--config  -c - use config from the specified path
-
-	Default config path /usr/local/etc/backup.cfg will be used if invoked without options"
+	printf "usage: %s [--help|--conf /path/to/config]\n" $self_name
+	printf "       --help  -h   show this message\n"
+	printf "       --conf  -c   use config from the specified path\n\n"
+	printf "Default config path %s will be used if invoked without options\n" $default_cfg
 }
 
-# function to read the configuration file and spit out some exceptions if stuff is missing
+# read the configuration file and spit out some exceptions if stuff is missing
 function apply_config
 {
-	source $cfg || err 15 'Config file does not exist'
-	[[ -z $source_dirs ]] && { cfg_err 'Backup source'; exit 5 }
-	[[ -z $remote_host ]] && { cfg_err 'Remote host'; exit 5 }
-	[[ -z $protocol ]] && { cfg_err 'Backup protocol'; exit 5 }
-	[[ -z $backup_dir && $protocol != 'ssh' ]] && { cfg_err 'Target directory'; exit 5 }
-	if [[ -z $local_host ]]; then
-		local_host=$HOST
-	fi
-	# date postfix
-	if [[ -z $outfile_postfix ]]; then
-		postfix=$default_postfix
-	else
-		postfix=$outfile_postfix
-	fi
-	if [[ -z $remote_port ]]; then
-		case $protocol in
-			('ftp'|'ftps') remote_port='21';;
-			('sftp'|'ssh') remote_port='22';;
-			('local') unset remote_port;;
-			(*) err 1 "$protocol is not a valid value for the protocol option.";;
-		esac
+	# testing remote settings only needed for non-local backups
+	function test_remote_settings
+	{
+		if [[ -z $remote_host ]]; then
+			cfg_err 'remote_host'
+			return 5
+		fi
+		if [[ -z $remote_user ]]; then
+			cfg_err 'remote_user'
+			return 5
+		fi
+		if [[ -z $remote_pass ]]; then
+			cfg_err 'remote_pass'
+			return 5
+		fi
+		if ! (( port )); then
+			err 'remote_port is not a numeric value.'
+			return 5
+		fi
+	}
+	# import contents of the config (including functions if present)
+	source $cfg || { err "Config file $cfg is unreadable or does not exist"; return 15 }
+	hostname=${local_host:-$HOST}
+	postfix=${outfile_postfix:-$default_postfix}
+	# do the tests
+	if [[ -z $source_dirs ]]; then
+		cfg_err 'source_dirs'
+		return 5
 	fi
+	# set defaults and / or fail to run if something is missing
+	local exit_code
+	case $protocol in
+		('ftp'|'ftps') port=${remote_port:-$default_ftp_port}; test_remote_settings; exit_code=$?; (( exit_code )) && return $exit_code;;
+		('sftp'|'ssh') port=${remote_port:-$default_ssh_port}; test_remote_settings; exit_code=$?; (( exit_code )) && return $exit_code;;
+		('local') unset remote_port;;
+		(*) cfg_err 'protocol'; return 5;;
+	esac
+	unset exit_code
+	# set variables for tar command
 	case $compress_format in
 		('xz') compress_flag='J' ;;
 		('bz2') compress_flag='j' ;;
 		('gz') compress_flag='z' ;;
-		('') unset compress_flag; unset compress_format ;;
-		(*) err 1 "$compress_format is not a valid value for the compression format option.";;
+		('') unset compress_flag ;;
+		(*) err "$compress_format is not a valid value for the compression format option."; return 5;;
 	esac
 	if [[ -n $exclude_list ]]; then
 		if [[ -r $exclude_list ]]; then
 			exclude_option='-X'
 		else
-			err 1 "Exclusion list $exclude_list is either unreadable or does not exist."
-		fi
-	fi
-	if [[ -n $snap_file ]]; then
-		if printf '' >> $snap_file; then
-			snapshot_option='-g'
-		else
-			err 1 "Snapshot file $snap_file cannot be written."
+			err "Exclusion list $exclude_list is either unreadable or does not exist. Proceeding without it."
 		fi
 	fi
 }
@@ -75,59 +115,91 @@ function generate_fullpath
 {
 	local backup_type
 	# increment or full backup
-	if [[ -s $snap_file ]]; then
+	if [[ -s $snapshot_file ]]; then
 		backup_type='incr'
 	else
 		backup_type='full'
 	fi
 	if [[ -z $backup_filename ]]; then
-		outfile="$backup_dir/${local_host}-${src_basename}_${postfix}_${backup_type}.t${compress_format:-'ar'}"
+		outfile="${backup_dir}${backup_dir:+/}${hostname}-${src_basename}_${postfix}_${backup_type}${gnupg_key:+.gpg.}.t${compress_format:-ar}"
 	else
 		outfile=$backup_filename
 	fi
 }
 
-function compress # compress to stdout
+# compress to stdout
+function compress
 {
-	tar cf$compress_flag - -C $src_basedir $src_basename $snapshot_option $snapshot_file $exclude_option $exclude_list --ignore-failed-read
+	# snapshot file is per directory so we cannot test it within apply_config()
+	if [[ -n $snapshot_file ]]; then
+		if printf '' >> $snapshot_file; then
+			snapshot_option='-g'
+		else
+			err "Snapshot file $snapshot_file cannot be written. Proceeding with full backup."
+		fi
+	fi
+	# do the magic and spit to stdout
+	tar -C $src_basedir -c$compress_flag $snapshot_option $snapshot_file $exclude_option $exclude_list --ignore-failed-read $src_basename
 }
 
-function store # store to local or remote
+# store to local or remote
+function store
 {
+	# take from stdin and do the magic
 	case $protocol in
 		('local') dd of=$outfile ;;
-		('ssh') ssh -p$remote_port $remote_user@$remote_host "dd of=$outfile" ;;
-		('sftp'|'ftp'|'ftps') curl -ksS -T - $protocol://$remote_host:$remote_port/$outfile -u $remote_user:$remote_pass ;;
-		(*) err 1 'Wrong protocol!' ;;
+		('ssh') ssh -p$port $remote_user@$remote_host "dd of=$outfile" ;;
+		('sftp'|'ftp'|'ftps') curl -ksS -T - $protocol://$remote_host:$port/$outfile -u $remote_user:$remote_pass ;;
 	esac
 }
 
+# encrypt asymmetrically via gpg
+function encrypt
+{
+	gpg -r $gnupg_key -e -
+}
+
+# self explanatory, using case statement, so one dash multiple opts is not supported
 function parse_opts
 {
 	while [[ -n $1 ]]; do
 		case $1 in
-			('--help'|'-h') usage; return 0;;
-			('--config'|'-c') shift; opt_cfg=$1; shift;;
+			('--help'|'-h') usage; exit 0;;
+			('--conf'|'-c') shift; opt_cfg=$1; return 0;;
+			(*) err "unknown parameter $1"; exit 127;;
 		esac
 	done
 }
 
+# the main logic
 function main
 {
-	parse_opts
-	if [[ -z $opt_cfg ]]; then
-		cfg=$default_cfg
-	else
-		cfg=$opt_cfg
-	fi
+	# parse options
+	parse_opts $@
+	# set default config if $opt_cfg is not defined via an option
+	cfg=${opt_cfg:-$default_cfg}
+	# run config tests and fill in defaults
 	apply_config
+	# fail in case something goes wrong
+	local exit_code=$?
+	(( exit_code )) && return $exit_code
+	unset exit_code
+	# run backups per directory
 	for i in $source_dirs; do
+		# prepare the set of variables
 		unset src_basename src_basedir outfile
-		IFS=':' read source_dir snap_file <<< $i
+		IFS=':' read source_dir snapshot_file <<< $i
 		src_basename=${source_dir:t}
 		src_basedir=${source_dir:h}
+		# generate the backups path
 		generate_fullpath
-		compress | store
+		err "Creating a backup of $source_dir via $protocol to store it in $outfile."
+		# pipe magic into magic
+		if [[ -n $gnupg_key ]]; then
+			compress | encrypt | store
+		else
+			compress | store
+		fi
 	done
 	return 0
 }

backup.zsh.cfg

@@ -0,0 +1,56 @@
+#### general options ####
+## The protocol we want to use to store our backups.
+## Can be ftp, sftp, ftps, ssh or local.
+protocol='ssh'
+
+## The directory to store backups in, locally or remotely.
+backup_dir='relative_or_full_path'
+
+## The list of patterns to exclude from backups, for
+## more details look into tar -X option.
+#exclude_list='/usr/local/etc/backup/excludes.list'
+
+## The compression algorithm for backups.
+## Can be gz, bz2, xz or empty (for non-compressed).
+compress_format='xz'
+
+## An array with the set of directories within it.
+## Optionally snapshot file can be added to store
+## incremental diffs (tar -g option used).
+## You'll have to deal with snapshots on your own:
+## backup.zsh only handles backups (i.e. you can remove
+## snapshot via cron on regular basis to ensure that
+## full backups are created from time to time.)
+source_dirs=( '/home/user/source1:/var/backup/snapshot.list'
+              '/etc' '/var/spool/mail:/var/backup/spool_snapshot.list' )
+
+## Use with caution, the file existance is not checked
+## on execution.
+## Since this config is sourced, I advise adding some
+## logic for that, or you can handle filename collisions
+## externally.
+#backup_filename='somebackup'
+
+## GPG key to encrypt backups, uses name of the private
+## key in your keyring. It is also entirely possible to
+## add the GNUPGHOME environment variable export here in
+## order to use the private key from a specific location.
+#gnupg_key='keyname'
+
+#### remote options ####
+## Remote host.
+remote_host='hostname.tld'
+
+## Remote user.
+remote_user='username'
+
+## Password, due to how openssh handles security it only
+## works for *ftp* protocols; backups via ssh protocol
+## work interactively. Later versions will have support
+## for ssh keys... If I ever decide to make it happen.
+remote_pass='PassWd'
+
+## Port is optional, the defaults are hardcoded.
+#remote_port='443'
+
+# vim: ft=zsh