Merge pull request #114 from neddy70/no-auto-expire

Add option to disable automatic purging of backups

.gitignore

@@ -0,0 +1,5 @@
+.idea
+test.sh
+*~
+tests/TestDest/
+tests/TestSource/

README.md

@@ -1,14 +1,49 @@
 # Rsync time backup
 
-Time Machine style backup with rsync. Should work on Linux, Mac OS X and Windows with Cygwin.
+This script offers Time Machine-style backup using rsync. It creates incremental backups of files and directories to the destination of your choice. The backups are structured in a way that makes it easy to recover any file at any point in time.
 
-# Installation
+It works on Linux, macOS and Windows (via WSL or Cygwin). The main advantage over Time Machine is the flexibility as it can backup from/to any filesystem and works on any platform. You can also backup, for example, to a Truecrypt drive without any problem.
+
+On macOS, it has a few disadvantages compared to Time Machine - in particular it does not auto-start when the backup drive is plugged (though it can be achieved using a launch agent), it requires some knowledge of the command line, and no specific GUI is provided to restore files. Instead files can be restored by using any file explorer, including Finder, or the command line.
+
+## Installation
 
 	git clone https://github.com/laurent22/rsync-time-backup
 
-# Usage
+## Usage
 
-	rsync_tmbackup.sh <source> <destination> [excluded-pattern-path]
+	Usage: rsync_tmbackup.sh [OPTION]... <[USER@HOST:]SOURCE> <[USER@HOST:]DESTINATION> [exclude-pattern-file]
+
+	Options
+	 -p, --port           SSH port.
+	 -h, --help           Display this help message.
+	 --rsync-get-flags    Display the default rsync flags that are used for backup.
+	 --rsync-set-flags    Set the rsync flags that are going to be used for backup.
+	 --log-dir            Set the log file directory. If this flag is set, generated files will
+	                      not be managed by the script - in particular they will not be
+	                      automatically deleted.
+	 --strategy           Set the expiration strategy. Default: "1:1 30:7 365:30" means after one
+	                      day, keep one backup per day. After 30 days, keep one backup every 7 days.
+	                      After 365 days keep one backup every 30 days.
+	 --no-auto-expire     Set option to disable automatically purging old backups when out of space.
+
+## Features
+
+* Each backup is on its own folder named after the current timestamp. Files can be copied and restored directly, without any intermediate tool.
+
+* Backup to/from remote destinations over SSH.
+
+* Files that haven't changed from one backup to the next are hard-linked to the previous backup so take very little extra space.
+
+* Safety check - the backup will only happen if the destination has explicitly been marked as a backup destination.
+
+* Resume feature - if a backup has failed or was interrupted, the tool will resume from there on the next backup.
+
+* Exclude file - support for pattern-based exclusion via the `--exclude-from` rsync parameter.
+
+* Automatically purge old backups - within 24 hours, all backups are kept. Within one month, the most recent backup for each day is kept. For all previous backups, the most recent of each month is kept.
+
+* "latest" symlink that points to the latest successful backup.
 
 ## Examples
 	
@@ -20,34 +55,84 @@ Time Machine style backup with rsync. Should work on Linux, Mac OS X and Windows
 	
 		rsync_tmbackup.sh /home /mnt/backup_drive excluded_patterns.txt
 
-## Exclude file
+* Backup to remote drive over SSH, on port 2222:
 
-An optional exclude file can be provided as a third parameter. It should be compabible with the `--exclude-from` parameter of rsync. See [this tutorial] (https://sites.google.com/site/rsync2u/home/rsync-tutorial/the-exclude-from-option) for more information.
-
-# Features
-
-* Each backup is on its own folder named after the current timestamp. Files can be copied and restored directly, without any intermediate tool.
-
-* Files that haven't changed from one backup to the next are hard-linked to the previous backup so take very little extra space.
-
-* Safety check - the backup will only happen if the destination has explicitely been marked as a backup destination.
-
-* Resume feature - if a backup has failed or was interrupted, the tool will resume from there on the next backup.
-
-* Exclude file - support for pattern-based exclusion via the `--exclude-from` rsync parameter.
-
-* The application is one bash script that can be easily edited.
-
-# TODO
-
-* Check if there's enough space in the destination before doing the backup. Also automatically delete old backups.
-
-* Manage the backups in a way similar to Time Machine - hourly backups for the past 24 hours; daily backups for the past month; weekly backups for the previous months.
-
-# LICENSE
-
-[MIT](http://opensource.org/licenses/MIT)
+		rsync_tmbackup.sh -p 2222 /home user@example.com:/mnt/backup_drive
 
 
-[![Bitdeli Badge](https://d2weczhvl823v0.cloudfront.net/laurent22/rsync-time-backup/trend.png)](https://bitdeli.com/free "Bitdeli Badge")
+* Backup from remote drive over SSH:
 
+		rsync_tmbackup.sh user@example.com:/home /mnt/backup_drive
+
+* To mimic Time Machine's behaviour, a cron script can be setup to backup at regular interval. For example, the following cron job checks if the drive "/mnt/backup" is currently connected and, if it is, starts the backup. It does this check every 1 hour.
+
+		0 */1 * * * if [[ -d /mnt/backup ]]; then rsync_tmbackup.sh /home /mnt/backup; fi
+
+## Backup expiration logic
+
+Backup sets are automatically deleted following a simple expiration strategy defined with the `--strategy` flag. This strategy is a series of time intervals with each item being defined as `x:y`, which means "after x days, keep one backup every y days". The default strategy is `1:1 30:7 365:30`, which means:
+
+- After **1** day, keep one backup every **1** day (**1:1**).
+- After **30** days, keep one backup every **7** days (**30:7**).
+- After **365** days, keep one backup every **30** days (**365:30**).
+
+Before the first interval (i.e. by default within the first 24h) it is implied that all backup sets are kept. Additionally, if the backup destination directory is full, the oldest backups are deleted until enough space is available.
+
+## Exclusion file
+
+An optional exclude file can be provided as a third parameter. It should be compatible with the `--exclude-from` parameter of rsync. See [this tutorial](https://sites.google.com/site/rsync2u/home/rsync-tutorial/the-exclude-from-option) for more information.
+
+## Built-in lock
+
+The script is designed so that only one backup operation can be active for a given directory. If a new backup operation is started while another is still active (i.e. it has not finished yet), the new one will be automaticalled interrupted. Thanks to this the use of `flock` to run the script is not necessary.
+
+## Rsync options
+
+To display the rsync options that are used for backup, run `./rsync_tmbackup.sh --rsync-get-flags`. It is also possible to add or remove options using the `--rsync-set-flags` option. For example, to exclude backing up permissions and groups:
+
+	rsync_tmbackup --rsync-set-flags "--numeric-ids --links --hard-links \
+	--one-file-system --archive --no-perms --no-groups --itemize-changes" /src /dest
+
+## No automatic backup expiration
+
+An option to diable the default behaviour to purge old backups when out of space. This option is set with the `--no-auto-expire` flag.
+	
+	
+## How to restore
+
+The script creates a backup in a regular directory so you can simply copy the files back to the original directory. You could do that with something like `rsync -aP /path/to/last/backup/ /path/to/restore/to/`. Consider using the `--dry-run` option to check what exactly is going to be copied. Use `--delete` if you also want to delete files that exist in the destination but not in the backup (obviously extra care must be taken when using this option).
+
+## Extensions
+
+* [rtb-wrapper](https://github.com/thomas-mc-work/rtb-wrapper): Allows creating backup profiles in config files. Handles both backup and restore operations.
+* [time-travel](https://github.com/joekerna/time-travel): Smooth integration into OSX Notification Center
+
+## TODO
+
+* Check source and destination file-system (`df -T /dest`). If one of them is FAT, use the --modify-window rsync parameter (see `man rsync`) with a value of 1 or 2
+* Add `--whole-file` arguments on Windows? See http://superuser.com/a/905415/73619
+* Minor changes (see TODO comments in the source).
+
+## LICENSE
+
+The MIT License (MIT)
+
+Copyright (c) 2013-2018 Laurent Cozic
+
+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.

rsync_tmbackup.sh

@@ -1,19 +1,20 @@
 #!/usr/bin/env bash
 
+APPNAME=$(basename $0 | sed "s/\.sh$//")
+
 # -----------------------------------------------------------------------------
 # Log functions
 # -----------------------------------------------------------------------------
 
-fn_log_info() {
-	echo "[RB INFO] $1"
-}
-
-fn_log_warn() {
-	echo "[RB WARN] $1"
-}
-
-fn_log_error() {
-	echo "[RB ERROR] $1"
+fn_log_info()  { echo "$APPNAME: $1"; }
+fn_log_warn()  { echo "$APPNAME: [WARNING] $1" 1>&2; }
+fn_log_error() { echo "$APPNAME: [ERROR] $1" 1>&2; }
+fn_log_info_cmd()  {
+	if [ -n "$SSH_DEST_FOLDER_PREFIX" ]; then
+		echo "$APPNAME: $SSH_CMD '$1'";
+	else
+		echo "$APPNAME: $1";
+	fi
 }
 
 # -----------------------------------------------------------------------------
@@ -21,19 +22,289 @@ fn_log_error() {
 # -----------------------------------------------------------------------------
 
 fn_terminate_script() {
-	echo "SIGINT caught"
+	fn_log_info "SIGINT caught."
 	exit 1
 }
 
 trap 'fn_terminate_script' SIGINT
 
+# -----------------------------------------------------------------------------
+# Small utility functions for reducing code duplication
+# -----------------------------------------------------------------------------
+fn_display_usage() {
+	echo "Usage: $(basename $0) [OPTION]... <[USER@HOST:]SOURCE> <[USER@HOST:]DESTINATION> [exclude-pattern-file]"
+	echo ""
+	echo "Options"
+	echo " -p, --port           SSH port."
+	echo " -h, --help           Display this help message."
+	echo " --rsync-get-flags    Display the default rsync flags that are used for backup."
+	echo " --rsync-set-flags    Set the rsync flags that are going to be used for backup."
+	echo " --log-dir            Set the log file directory. If this flag is set, generated files will"
+	echo "                      not be managed by the script - in particular they will not be"
+	echo "                      automatically deleted."
+	echo "                      Default: $LOG_DIR"
+	echo " --strategy           Set the expiration strategy. Default: \"1:1 30:7 365:30\" means after one"
+	echo "                      day, keep one backup per day. After 30 days, keep one backup every 7 days."
+	echo "                      After 365 days keep one backup every 30 days."
+	echo " --no-auto-expire     Disable automatically deleting backups when out of space. Instead an error"
+	echo "                      is logged, and the backup is aborted."
+	echo ""
+	echo "For more detailed help, please see the README file:"
+	echo ""
+	echo "https://github.com/laurent22/rsync-time-backup/blob/master/README.md"
+}
+
+fn_parse_date() {
+	# Converts YYYY-MM-DD-HHMMSS to YYYY-MM-DD HH:MM:SS and then to Unix Epoch.
+	case "$OSTYPE" in
+		linux*) date -d "${1:0:10} ${1:11:2}:${1:13:2}:${1:15:2}" +%s ;;
+		cygwin*) date -d "${1:0:10} ${1:11:2}:${1:13:2}:${1:15:2}" +%s ;;
+		darwin8*) yy=`expr ${1:0:4}`
+			mm=`expr ${1:5:2} - 1`
+			dd=`expr ${1:8:2}`
+			hh=`expr ${1:11:2}`
+			mi=`expr ${1:13:2}`
+			ss=`expr ${1:15:2}`
+			# Because under MacOS X Tiger 'date -j' doesn't work, we do this:
+			perl -e 'use Time::Local; print timelocal('$ss','$mi','$hh','$dd','$mm','$yy'),"\n";' ;;
+		darwin*) date -j -f "%Y-%m-%d-%H%M%S" "$1" "+%s" ;;
+		FreeBSD*) date -j -f "%Y-%m-%d-%H%M%S" "$1" "+%s" ;;
+	esac
+}
+
+fn_find_backups() {
+	fn_run_cmd "find "$DEST_FOLDER/" -maxdepth 1 -type d -name \"????-??-??-??????\" -prune | sort -r"
+}
+
+fn_expire_backup() {
+	# Double-check that we're on a backup destination to be completely
+	# sure we're deleting the right folder
+	if [ -z "$(fn_find_backup_marker "$(dirname -- "$1")")" ]; then
+		fn_log_error "$1 is not on a backup destination - aborting."
+		exit 1
+	fi
+
+	fn_log_info "Expiring $1"
+	fn_rm_dir "$1"
+}
+
+fn_expire_backups() {
+	local current_timestamp=$EPOCH
+	local last_kept_timestamp=9999999999
+
+	# Process each backup dir from most recent to oldest
+	for backup_dir in $(fn_find_backups | sort -r); do
+		local backup_date=$(basename "$backup_dir")
+		local backup_timestamp=$(fn_parse_date "$backup_date")
+
+		# Skip if failed to parse date...
+		if [ -z "$backup_timestamp" ]; then
+			fn_log_warn "Could not parse date: $backup_dir"
+			continue
+		fi
+
+		# Find which strategy token applies to this particular backup
+		for strategy_token in $(echo $EXPIRATION_STRATEGY | tr " " "\n" | sort -r -n); do
+			IFS=':' read -r -a t <<< "$strategy_token"
+
+			# After which date (relative to today) this token applies (X)
+			local cut_off_timestamp=$((current_timestamp - ${t[0]} * 86400))
+
+			# Every how many days should a backup be kept past the cut off date (Y)
+			local cut_off_interval=$((${t[1]} * 86400))
+
+			# If we've found the strategy token that applies to this backup
+			if [ "$backup_timestamp" -le "$cut_off_timestamp" ]; then
+
+				# Special case: if Y is "0" we delete every time
+				if [ $cut_off_interval -eq "0" ]; then
+					fn_expire_backup "$backup_dir"
+					break
+				fi
+
+				# Check if the current backup is in the interval between
+				# the last backup that was kept and Y
+				local interval_since_last_kept=$((last_kept_timestamp - backup_timestamp))
+				if [ "$interval_since_last_kept" -lt "$cut_off_interval" ]; then
+					# Yes: Delete that one
+					fn_expire_backup "$backup_dir"
+				else
+					# No: Keep it
+					last_kept_timestamp=$backup_timestamp
+				fi
+				break
+			fi
+		done
+	done
+}
+
+fn_parse_ssh() {
+	# To keep compatibility with bash version < 3, we use grep
+	if echo "$DEST_FOLDER"|grep -Eq '^[A-Za-z0-9\._%\+\-]+@[A-Za-z0-9.\-]+\:.+$'
+	then
+		SSH_USER=$(echo "$DEST_FOLDER" | sed -E  's/^([A-Za-z0-9\._%\+\-]+)@([A-Za-z0-9.\-]+)\:(.+)$/\1/')
+		SSH_HOST=$(echo "$DEST_FOLDER" | sed -E  's/^([A-Za-z0-9\._%\+\-]+)@([A-Za-z0-9.\-]+)\:(.+)$/\2/')
+		SSH_DEST_FOLDER=$(echo "$DEST_FOLDER" | sed -E  's/^([A-Za-z0-9\._%\+\-]+)@([A-Za-z0-9.\-]+)\:(.+)$/\3/')
+		SSH_CMD="ssh -p $SSH_PORT ${SSH_USER}@${SSH_HOST}"
+		SSH_DEST_FOLDER_PREFIX="${SSH_USER}@${SSH_HOST}:"
+	elif echo "$SRC_FOLDER"|grep -Eq '^[A-Za-z0-9\._%\+\-]+@[A-Za-z0-9.\-]+\:.+$'
+	then
+		SSH_USER=$(echo "$SRC_FOLDER" | sed -E  's/^([A-Za-z0-9\._%\+\-]+)@([A-Za-z0-9.\-]+)\:(.+)$/\1/')
+		SSH_HOST=$(echo "$SRC_FOLDER" | sed -E  's/^([A-Za-z0-9\._%\+\-]+)@([A-Za-z0-9.\-]+)\:(.+)$/\2/')
+		SSH_SRC_FOLDER=$(echo "$SRC_FOLDER" | sed -E  's/^([A-Za-z0-9\._%\+\-]+)@([A-Za-z0-9.\-]+)\:(.+)$/\3/')
+		SSH_CMD="ssh -p $SSH_PORT ${SSH_USER}@${SSH_HOST}"
+		SSH_SRC_FOLDER_PREFIX="${SSH_USER}@${SSH_HOST}:"
+	fi
+}
+
+fn_run_cmd() {
+	if [ -n "$SSH_DEST_FOLDER_PREFIX" ]
+	then
+		eval "$SSH_CMD '$1'"
+	else
+		eval $1
+	fi
+}
+
+fn_find() {
+	fn_run_cmd "find '$1'"  2>/dev/null
+}
+
+fn_get_absolute_path() {
+	fn_run_cmd "cd '$1';pwd"
+}
+
+fn_mkdir() {
+	fn_run_cmd "mkdir -p -- '$1'"
+}
+
+# Removes a file or symlink - not for directories
+fn_rm_file() {
+	fn_run_cmd "rm -f -- '$1'"
+}
+
+fn_rm_dir() {
+	fn_run_cmd "rm -rf -- '$1'"
+}
+
+fn_touch() {
+	fn_run_cmd "touch -- '$1'"
+}
+
+fn_ln() {
+	fn_run_cmd "ln -s -- '$1' '$2'"
+}
+
 # -----------------------------------------------------------------------------
 # Source and destination information
 # -----------------------------------------------------------------------------
+SSH_USER=""
+SSH_HOST=""
+SSH_DEST_FOLDER=""
+SSH_SRC_FOLDER=""
+SSH_CMD=""
+SSH_DEST_FOLDER_PREFIX=""
+SSH_SRC_FOLDER_PREFIX=""
+SSH_PORT="22"
 
-SRC_FOLDER=${1%/}
-DEST_FOLDER=${2%/}
-EXCLUSION_FILE=$3
+SRC_FOLDER=""
+DEST_FOLDER=""
+EXCLUSION_FILE=""
+LOG_DIR="$HOME/.$APPNAME"
+AUTO_DELETE_LOG="1"
+EXPIRATION_STRATEGY="1:1 30:7 365:30"
+AUTO_EXPIRE="1"
+
+RSYNC_FLAGS="-D --compress --numeric-ids --links --hard-links --one-file-system --itemize-changes --times --recursive --perms --owner --group --stats --human-readable"
+
+while :; do
+	case $1 in
+		-h|-\?|--help)
+			fn_display_usage
+			exit
+			;;
+		-p|--port)
+			shift
+			SSH_PORT=$1
+			;;
+		--rsync-get-flags)
+			shift
+			echo $RSYNC_FLAGS
+			exit
+			;;
+		--rsync-set-flags)
+			shift
+			RSYNC_FLAGS="$1"
+			;;
+		--strategy)
+			shift
+			EXPIRATION_STRATEGY="$1"
+			;;
+		--log-dir)
+			shift
+			LOG_DIR="$1"
+			AUTO_DELETE_LOG="0"
+			;;
+		--no-auto-expire)
+			AUTO_EXPIRE="0"
+			;;
+		--)
+			shift
+			SRC_FOLDER="$1"
+			DEST_FOLDER="$2"
+			EXCLUSION_FILE="$3"
+			break
+			;;
+		-*)
+			fn_log_error "Unknown option: \"$1\""
+			fn_log_info ""
+			fn_display_usage
+			exit 1
+			;;
+		*)
+			SRC_FOLDER="$1"
+			DEST_FOLDER="$2"
+			EXCLUSION_FILE="$3"
+			break
+	esac
+
+	shift
+done
+
+# Display usage information if required arguments are not passed
+if [[ -z "$SRC_FOLDER" || -z "$DEST_FOLDER" ]]; then
+	fn_display_usage
+	exit 1
+fi
+
+# Strips off last slash from dest. Note that it means the root folder "/"
+# will be represented as an empty string "", which is fine
+# with the current script (since a "/" is added when needed)
+# but still something to keep in mind.
+# However, due to this behavior we delay stripping the last slash for
+# the source folder until after parsing for ssh usage.
+
+DEST_FOLDER="${DEST_FOLDER%/}"
+
+fn_parse_ssh
+
+if [ -n "$SSH_DEST_FOLDER" ]; then
+	DEST_FOLDER="$SSH_DEST_FOLDER"
+fi
+
+if [ -n "$SSH_SRC_FOLDER" ]; then
+	SRC_FOLDER="$SSH_SRC_FOLDER"
+fi
+
+# Now strip off last slash from source folder.
+SRC_FOLDER="${SRC_FOLDER%/}"
+
+for ARG in "$SRC_FOLDER" "$DEST_FOLDER" "$EXCLUSION_FILE"; do
+	if [[ "$ARG" == *"'"* ]]; then
+		fn_log_error 'Source and destination directories may not contain single quote characters.'
+		exit 1
+	fi
+done
 
 # -----------------------------------------------------------------------------
 # Check that the destination drive is a backup drive
@@ -41,24 +312,14 @@ EXCLUSION_FILE=$3
 
 # TODO: check that the destination supports hard links
 
-fn_backup_marker_path() {
-	echo "$1/backup.marker"
-}
+fn_backup_marker_path() { echo "$1/backup.marker"; }
+fn_find_backup_marker() { fn_find "$(fn_backup_marker_path "$1")" 2>/dev/null; }
 
-fn_is_backup_destination() {
-	DEST_MARKER_FILE="$(fn_backup_marker_path $1)"
-	if [ -f "$DEST_MARKER_FILE" ]; then
-		echo "1"
-	else
-		echo "0"
-	fi
-}
-
-if [ "$(fn_is_backup_destination $DEST_FOLDER)" != "1" ]; then
+if [ -z "$(fn_find_backup_marker "$DEST_FOLDER")" ]; then
 	fn_log_info "Safety check failed - the destination does not appear to be a backup folder or drive (marker file not found)."
 	fn_log_info "If it is indeed a backup folder, you may add the marker file by running the following command:"
 	fn_log_info ""
-	fn_log_info "touch \"$(fn_backup_marker_path $DEST_FOLDER)\""
+	fn_log_info_cmd "mkdir -p -- \"$DEST_FOLDER\" ; touch \"$(fn_backup_marker_path "$DEST_FOLDER")\""
 	fn_log_info ""
 	exit 1
 fi
@@ -67,167 +328,183 @@ fi
 # Setup additional variables
 # -----------------------------------------------------------------------------
 
-BACKUP_FOLDER_PATTERN="\d\d\d\d-\d\d-\d\d-\d\d\d\d\d\d"
+# Date logic
 NOW=$(date +"%Y-%m-%d-%H%M%S")
-PROFILE_FOLDER="$HOME/.rsync_tmbackup"
-LOG_FILE="$PROFILE_FOLDER/$NOW.log"
-DEST=$DEST_FOLDER/$NOW
-LAST_TIME=$(ls -1 $DEST_FOLDER | grep "$BACKUP_FOLDER_PATTERN" | tail -n 1)
-PREVIOUS_DEST=$DEST_FOLDER/$LAST_TIME
-INPROGRESS_FILE=$DEST_FOLDER/backup.inprogress
+EPOCH=$(date "+%s")
+KEEP_ALL_DATE=$((EPOCH - 86400))       # 1 day ago
+KEEP_DAILIES_DATE=$((EPOCH - 2678400)) # 31 days ago
+
+export IFS=$'\n' # Better for handling spaces in filenames.
+DEST="$DEST_FOLDER/$NOW"
+PREVIOUS_DEST="$(fn_find_backups | head -n 1)"
+INPROGRESS_FILE="$DEST_FOLDER/backup.inprogress"
+MYPID="$$"
 
 # -----------------------------------------------------------------------------
-# Create profile folder if it doesn't exist
+# Create log folder if it doesn't exist
 # -----------------------------------------------------------------------------
 
-if [ ! -d "$PROFILE_FOLDER" ]; then
-	fn_log_info "Creating profile folder in '$PROFILE_FOLDER'..."
-	mkdir -- "$PROFILE_FOLDER"
+if [ ! -d "$LOG_DIR" ]; then
+	fn_log_info "Creating log folder in '$LOG_DIR'..."
+	mkdir -- "$LOG_DIR"
 fi
 
 # -----------------------------------------------------------------------------
 # Handle case where a previous backup failed or was interrupted.
 # -----------------------------------------------------------------------------
 
-if [ -f "$INPROGRESS_FILE" ]; then
-	if [ "$LAST_TIME" != "" ]; then
+if [ -n "$(fn_find "$INPROGRESS_FILE")" ]; then
+	if [ "$OSTYPE" == "cygwin" ]; then
+		# 1. Grab the PID of previous run from the PID file
+		RUNNINGPID="$(fn_run_cmd "cat $INPROGRESS_FILE")"
+
+		# 2. Get the command for the process currently running under that PID and look for our script name
+		RUNNINGCMD="$(procps -wwfo cmd -p $RUNNINGPID --no-headers | grep "$APPNAME")"
+
+		# 3. Grab the exit code from grep (0=found, 1=not found)
+		GREPCODE=$?
+
+		# 4. if found, assume backup is still running
+		if [ "$GREPCODE" = 0 ]; then
+			fn_log_error "Previous backup task is still active - aborting (command: $RUNNINGCMD)."
+			exit 1
+		fi
+	else
+		RUNNINGPID="$(fn_run_cmd "cat $INPROGRESS_FILE")"
+		if [ "$RUNNINGPID" = "$(pgrep -o -f "$APPNAME")" ]; then
+			fn_log_error "Previous backup task is still active - aborting."
+			exit 1
+		fi
+	fi
+
+	if [ -n "$PREVIOUS_DEST" ]; then
 		# - Last backup is moved to current backup folder so that it can be resumed.
 		# - 2nd to last backup becomes last backup.
-		fn_log_info "$INPROGRESS_FILE already exists - the previous backup failed or was interrupted. Backup will resume from there."
-		LINE_COUNT=$(ls -1 $DEST_FOLDER | grep "$BACKUP_FOLDER_PATTERN" | tail -n 2 | wc -l)
-		mv $PREVIOUS_DEST $DEST
-		if [ "$LINE_COUNT" -gt 1 ]; then
-			SECOND_LAST_TIME=$(ls -1 $DEST_FOLDER | grep "$BACKUP_FOLDER_PATTERN" | tail -n 2 | head -n 1)
-			LAST_TIME=$SECOND_LAST_TIME
+		fn_log_info "$SSH_DEST_FOLDER_PREFIX$INPROGRESS_FILE already exists - the previous backup failed or was interrupted. Backup will resume from there."
+		fn_run_cmd "mv -- $PREVIOUS_DEST $DEST"
+		if [ "$(fn_find_backups | wc -l)" -gt 1 ]; then
+			PREVIOUS_DEST="$(fn_find_backups | sed -n '2p')"
 		else
-			LAST_TIME=""
+			PREVIOUS_DEST=""
 		fi
-		PREVIOUS_DEST=$DEST_FOLDER/$LAST_TIME
+		# update PID to current process to avoid multiple concurrent resumes
+		fn_run_cmd "echo $MYPID > $INPROGRESS_FILE"
 	fi
 fi
 
-# -----------------------------------------------------------------------------
-# Check if we are doing an incremental backup (if previous backup exists) or not
-# -----------------------------------------------------------------------------
+# Run in a loop to handle the "No space left on device" logic.
+while : ; do
 
-LINK_DEST_OPTION=""
-if [ "$LAST_TIME" == "" ]; then
-	fn_log_info "No previous backup - creating new one."
-else
-	# If the path is relative, it needs to be relative to the destination. To keep
-	# it simple, just use an absolute path. See http://serverfault.com/a/210058/118679
-	PREVIOUS_DEST=`cd \`dirname "$PREVIOUS_DEST"\`; pwd`"/"`basename "$PREVIOUS_DEST"`
-	fn_log_info "Previous backup found - doing incremental backup from $PREVIOUS_DEST"
-	LINK_DEST_OPTION="--link-dest=$PREVIOUS_DEST"
-fi
+	# -----------------------------------------------------------------------------
+	# Check if we are doing an incremental backup (if previous backup exists).
+	# -----------------------------------------------------------------------------
 
-# -----------------------------------------------------------------------------
-# Create destination folder if it doesn't already exists
-# -----------------------------------------------------------------------------
+	LINK_DEST_OPTION=""
+	if [ -z "$PREVIOUS_DEST" ]; then
+		fn_log_info "No previous backup - creating new one."
+	else
+		# If the path is relative, it needs to be relative to the destination. To keep
+		# it simple, just use an absolute path. See http://serverfault.com/a/210058/118679
+		PREVIOUS_DEST="$(fn_get_absolute_path "$PREVIOUS_DEST")"
+		fn_log_info "Previous backup found - doing incremental backup from $SSH_DEST_FOLDER_PREFIX$PREVIOUS_DEST"
+		LINK_DEST_OPTION="--link-dest='$PREVIOUS_DEST'"
+	fi
 
-if [ ! -d "$DEST" ]; then
-	fn_log_info "Creating destination $DEST"
-	mkdir -p $DEST
-fi
+	# -----------------------------------------------------------------------------
+	# Create destination folder if it doesn't already exists
+	# -----------------------------------------------------------------------------
 
-# -----------------------------------------------------------------------------
-# Start backup
-# -----------------------------------------------------------------------------
+	if [ -z "$(fn_find "$DEST -type d" 2>/dev/null)" ]; then
+		fn_log_info "Creating destination $SSH_DEST_FOLDER_PREFIX$DEST"
+		fn_mkdir "$DEST"
+	fi
 
-# Run in a loop to handle the "No space left on device" logic
-while [ "1" ]; do
-	LOG_FILE="$PROFILE_FOLDER/$(date +"%Y-%m-%d-%H%M%S").log"
+	# -----------------------------------------------------------------------------
+	# Purge certain old backups before beginning new backup.
+	# -----------------------------------------------------------------------------
+
+	fn_expire_backups
+
+	# -----------------------------------------------------------------------------
+	# Start backup
+	# -----------------------------------------------------------------------------
+
+	LOG_FILE="$LOG_DIR/$(date +"%Y-%m-%d-%H%M%S").log"
 
 	fn_log_info "Starting backup..."
-	fn_log_info "From: $SRC_FOLDER"
-	fn_log_info "To:   $DEST"
+	fn_log_info "From: $SSH_SRC_FOLDER_PREFIX$SRC_FOLDER/"
+	fn_log_info "To:   $SSH_DEST_FOLDER_PREFIX$DEST/"
 
 	CMD="rsync"
-	CMD="$CMD --compress"
-	CMD="$CMD --numeric-ids"
-	CMD="$CMD --links"
-	CMD="$CMD --hard-links"
-	CMD="$CMD --delete"
-	CMD="$CMD --delete-excluded"
-	CMD="$CMD --one-file-system"
-	CMD="$CMD --archive"
-	CMD="$CMD --progress"
-	CMD="$CMD --itemize-changes"
-	CMD="$CMD --verbose"
+	if [ -n "$SSH_CMD" ]; then
+		CMD="$CMD  -e 'ssh -p $SSH_PORT -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null'"
+	fi
+	CMD="$CMD $RSYNC_FLAGS"
 	CMD="$CMD --log-file '$LOG_FILE'"
-	if [ "$EXCLUSION_FILE" != "" ]; then
-		CMD="$CMD --exclude-from \"$EXCLUSION_FILE\""
+	if [ -n "$EXCLUSION_FILE" ]; then
+		# We've already checked that $EXCLUSION_FILE doesn't contain a single quote
+		CMD="$CMD --exclude-from '$EXCLUSION_FILE'"
 	fi
 	CMD="$CMD $LINK_DEST_OPTION"
-	CMD="$CMD $SRC_FOLDER/ $DEST/"
-	CMD="$CMD | grep -E '^deleting|[^/]$'"
+	CMD="$CMD -- '$SSH_SRC_FOLDER_PREFIX$SRC_FOLDER/' '$SSH_DEST_FOLDER_PREFIX$DEST/'"
 
 	fn_log_info "Running command:"
 	fn_log_info "$CMD"
 
-	touch $INPROGRESS_FILE
+	fn_run_cmd "echo $MYPID > $INPROGRESS_FILE"
 	eval $CMD
-	RSYNC_EXIT_CODE=$?
 
 	# -----------------------------------------------------------------------------
 	# Check if we ran out of space
 	# -----------------------------------------------------------------------------
 
-	# TODO: find better way to check for out of space condition without parsing log.
-	grep --quiet "No space left on device (28)" "$LOG_FILE"
-	NO_SPACE_LEFT="$?"
-	if [ "$NO_SPACE_LEFT" != "0" ]; then
-		# This error might also happen if there is no space left
-		grep --quiet "Result too large (34)" "$LOG_FILE"
-		NO_SPACE_LEFT="$?"
-	fi
+	NO_SPACE_LEFT="$(grep "No space left on device (28)\|Result too large (34)" "$LOG_FILE")"
 
-	rm -- "$LOG_FILE"
+	if [ -n "$NO_SPACE_LEFT" ]; then
 
-	if [ "$NO_SPACE_LEFT" == "0" ]; then
-		read -p "It looks like there is no space left on the destination. Delete old backup? (Y/n) " yn
-		case $yn in
-			[Nn]* ) exit 0;;
-		esac
+		if [[ $AUTO_EXPIRE == "0" ]]; then
+			fn_log_error "No space left on device, and automatic purging of old backups is disabled."
+			exit 1
+		fi
 
 		fn_log_warn "No space left on device - removing oldest backup and resuming."
 
-		BACKUP_FOLDER_COUNT=$(ls -1 $DEST_FOLDER | grep "$BACKUP_FOLDER_PATTERN" | wc -l)
-		if [ "$BACKUP_FOLDER_COUNT" -lt "2" ]; then
+		if [[ "$(fn_find_backups | wc -l)" -lt "2" ]]; then
 			fn_log_error "No space left on device, and no old backup to delete."
 			exit 1
 		fi
 
-		# TODO: handle case where only two backup folders are left. In which case, need to remove --link-dest option
-		
-		OLDEST_BACKUP=$(ls -1 $DEST_FOLDER | grep "$BACKUP_FOLDER_PATTERN" | head -n 1)
-		if [ "$OLDEST_BACKUP" == "" ]; then
-			fn_log_error "No space left on device, and cannot get path to oldest backup to delete."
-			exit 1
-		fi
-		
-		OLD_BACKUP_PATH="$DEST_FOLDER/$OLDEST_BACKUP"
-		
-		# Double-check that we're on a backup destination to be completely sure we're deleting the right folder
-		OLD_BACKUP_PARENT_PATH=$(dirname -- "$OLD_BACKUP_PATH")
-		if [ "$(fn_is_backup_destination $OLD_BACKUP_PARENT_PATH)" != "1" ]; then
-			fn_log_error "'$OLD_BACKUP_PATH' is not on a backup destination - aborting."
-			exit 1
-		fi
-		
-		fn_log_info "Deleting '$OLD_BACKUP_PATH'..."
-		rm -rf -- "$OLD_BACKUP_PATH"
+		fn_expire_backup "$(fn_find_backups | tail -n 1)"
 
 		# Resume backup
 		continue
 	fi
 
-	if [ "$RSYNC_EXIT_CODE" != "0" ]; then
-		fn_log_error "Exited with error code $RSYNC_EXIT_CODE"
-		exit $RSYNC_EXIT_CODE
+	# -----------------------------------------------------------------------------
+	# Check whether rsync reported any errors
+	# -----------------------------------------------------------------------------
+
+	EXIT_CODE="1"
+	if [ -n "$(grep "rsync error:" "$LOG_FILE")" ]; then
+		fn_log_error "Rsync reported an error. Run this command for more details: grep -E 'rsync:|rsync error:' '$LOG_FILE'"
+	elif [ -n "$(grep "rsync:" "$LOG_FILE")" ]; then
+		fn_log_warn "Rsync reported a warning. Run this command for more details: grep -E 'rsync:|rsync error:' '$LOG_FILE'"
+	else
+		fn_log_info "Backup completed without errors."
+		if [[ $AUTO_DELETE_LOG == "1" ]]; then
+			rm -f -- "$LOG_FILE"
+		fi
+		EXIT_CODE="0"
 	fi
 
-	rm $INPROGRESS_FILE
-	fn_log_info "Backup completed without errors."
-	exit 0
+	# -----------------------------------------------------------------------------
+	# Add symlink to last backup
+	# -----------------------------------------------------------------------------
+
+	fn_rm_file "$DEST_FOLDER/latest"
+	fn_ln "$(basename -- "$DEST")" "$DEST_FOLDER/latest"
+
+	fn_rm_file "$INPROGRESS_FILE"
+
+	exit $EXIT_CODE
 done

tests/populate_dest.php

@@ -0,0 +1,30 @@
+<?php
+
+// This PHP script can be used to test the expiration strategy.
+// It is going to populate a directory with fake backup sets (directories named Y-m-d-His) over several months.
+// Then the backup script can be run on it to check what directories are going to be deleted.
+
+// rm -rf ./tests/TestDest/201* && php ./tests/populate_dest.php && ./rsync_tmbackup.sh ./tests/TestSource/ ./tests/TestDest/
+
+$baseDir = dirname(__FILE__);
+$destDir = $baseDir . '/TestDest';
+
+$backupsPerDay = 2;
+$totalDays = 500;
+
+$intervalBetweenBackups = null;
+if ($backupsPerDay === 1) {
+	$intervalBetweenBackups = 'PT1D';
+} else if ($backupsPerDay === 2) {
+	$intervalBetweenBackups = 'PT12H';
+} else {
+	throw new Exception('Not implemented');
+}
+
+$d = new DateTime();
+$d->sub(new DateInterval('P' . $totalDays . 'D'));
+
+for ($i = 0; $i < $backupsPerDay * $totalDays; $i++) {
+	$d->add(new DateInterval($intervalBetweenBackups));
+	mkdir($destDir . '/' . $d->format('Y-m-d-His'), 0777, true);
+}