Merge pull request #14 from robru/master

Time Machine style backup pruning.

2 files changed, 81 insertions, 36 deletions

diff --git a/README.md b/README.md
index e36e090..b4417a6 100644
--- a/README.md
+++ b/README.md
@@ -40,14 +40,10 @@ An optional exclude file can be provided as a third parameter. It should be comp
 
 # TODO
 
-* 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.
-
-* Other minor changes (see TODO comments in the source).
+* Minor changes (see TODO comments in the source).
 
 # LICENSE
 
 [MIT](http://opensource.org/licenses/MIT)
 
-
 [![Bitdeli Badge](https://d2weczhvl823v0.cloudfront.net/laurent22/rsync-time-backup/trend.png)](https://bitdeli.com/free "Bitdeli Badge")
-
diff --git a/rsync_tmbackup.sh b/rsync_tmbackup.sh
index 45f8478..8b2a0e1 100644
--- a/rsync_tmbackup.sh
+++ b/rsync_tmbackup.sh
@@ -28,6 +28,34 @@ fn_terminate_script() {
 trap 'fn_terminate_script' SIGINT
 
 # -----------------------------------------------------------------------------
+# Small utility functions for reducing code duplication
+# -----------------------------------------------------------------------------
+
+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 ;;
+		darwin*) date -j -f "%Y-%m-%d-%H%M%S" "$1" "+%s" ;;
+	esac
+}
+
+fn_find_backups() {
+	find "$DEST_FOLDER" -type d -name "????-??-??-??????" -prune
+}
+
+fn_expire_backup() {
+	# Double-check that we're on a backup destination to be completely
+	# sure we're deleting the right folder
+	if [ -z "$(fn_is_backup_destination "$(dirname -- "$1")")" ]; then
+		fn_log_error "$1 is not on a backup destination - aborting."
+		exit 1
+	fi
+
+	fn_log_info "Expiring $1"
+	rm -rf -- "$1"
+}
+
+# -----------------------------------------------------------------------------
 # Source and destination information
 # -----------------------------------------------------------------------------
 
@@ -53,15 +81,10 @@ fn_backup_marker_path() {
 }
 
 fn_is_backup_destination() {
-	DEST_MARKER_FILE="$(fn_backup_marker_path $1)"
-	if [ -f "$DEST_MARKER_FILE" ]; then
-		echo "1"
-	else
-		echo "0"
-	fi
+	find "$(fn_backup_marker_path "$1")" 2>/dev/null
 }
 
-if [ "$(fn_is_backup_destination $DEST_FOLDER)" != "1" ]; then
+if [ -z "$(fn_is_backup_destination $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 ""
@@ -74,12 +97,18 @@ fi
 # Setup additional variables
 # -----------------------------------------------------------------------------
 
-BACKUP_FOLDER_PATTERN=????-??-??-??????
+# Date logic
 NOW=$(date +"%Y-%m-%d-%H%M%S")
+EPOCH=$(date "+%s")
+KEEP_ALL_DATE=$(($EPOCH - 86400))       # 1 day ago
+KEEP_DAILIES_DATE=$(($EPOCH - 2678400)) # 31 days ago
+
+
+export IFS=$'\n' # Better for handling spaces in filenames.
 PROFILE_FOLDER="$HOME/.rsync_tmbackup"
 LOG_FILE="$PROFILE_FOLDER/$NOW.log"
 DEST=$DEST_FOLDER/$NOW
-PREVIOUS_DEST=$(find "$DEST_FOLDER" -type d -name "$BACKUP_FOLDER_PATTERN" -prune | sort | tail -n 1)
+PREVIOUS_DEST=$(fn_find_backups | sort | tail -n 1)
 INPROGRESS_FILE=$DEST_FOLDER/backup.inprogress
 
 # -----------------------------------------------------------------------------
@@ -100,10 +129,10 @@ if [ -f "$INPROGRESS_FILE" ]; then
 		# - Last backup is moved to current backup folder so that it can be resumed.
 		# - 2nd to last backup becomes last backup.
 		fn_log_info "$INPROGRESS_FILE already exists - the previous backup failed or was interrupted. Backup will resume from there."
-		LINE_COUNT=$(find "$DEST_FOLDER" -type d -name "$BACKUP_FOLDER_PATTERN" -prune | sort | tail -n 2 | wc -l)
+		LINE_COUNT=$(fn_find_backups | sort | tail -n 2 | wc -l)
 		mv -- "$PREVIOUS_DEST" "$DEST"
 		if [ "$LINE_COUNT" -gt 1 ]; then
-			PREVIOUS_PREVIOUS_DEST=$(find "$DEST_FOLDER" -type d -name "$BACKUP_FOLDER_PATTERN" -prune | sort | tail -n 2 | head -n 1)
+			PREVIOUS_PREVIOUS_DEST=$(fn_find_backups | sort | tail -n 2 | head -n 1)
 			PREVIOUS_DEST=$PREVIOUS_PREVIOUS_DEST
 		else
 			PREVIOUS_DEST=""
@@ -139,6 +168,34 @@ while [ "1" ]; do
 	fi
 
 	# -----------------------------------------------------------------------------
+	# Purge certain old backups before beginning new backup.
+	# -----------------------------------------------------------------------------
+
+	# Default value for $prev ensures that the most recent backup is never deleted.
+	prev="0000-00-00-000000"
+	for fname in $(fn_find_backups | sort -r); do
+		date=$(basename "$fname")
+		stamp=$(fn_parse_date $date)
+
+		# Skip if failed to parse date...
+		[ -n "$stamp" ] || continue
+
+		if   [ $stamp -ge $KEEP_ALL_DATE ]; then
+			true
+
+		elif [ $stamp -ge $KEEP_DAILIES_DATE ]; then
+			# Delete all but the most recent of each day.
+			[ "${date:0:10}" == "${prev:0:10}" ] && fn_expire_backup "$fname"
+
+		else
+			# Delete all but the most recent of each month.
+			[ "${date:0:7}" == "${prev:0:7}" ] && fn_expire_backup "$fname"
+		fi
+
+		prev=$date
+	done
+
+	# -----------------------------------------------------------------------------
 	# Start backup
 	# -----------------------------------------------------------------------------
 
@@ -187,9 +244,9 @@ while [ "1" ]; do
 		grep --quiet "Result too large (34)" "$LOG_FILE"
 		NO_SPACE_LEFT="$?"
 	fi
-		
+
 	rm -- "$LOG_FILE"
-	
+
 	if [ "$NO_SPACE_LEFT" == "0" ]; then
 		# TODO: -y flag
 		read -p "It looks like there is no space left on the destination. Delete old backup? (Y/n) " yn
@@ -198,29 +255,21 @@ while [ "1" ]; do
 		esac
 
 		fn_log_warn "No space left on device - removing oldest backup and resuming."
-		
-		BACKUP_FOLDER_COUNT=$(find "$DEST_FOLDER" -type d -name "$BACKUP_FOLDER_PATTERN" -prune | wc -l)
+
+		BACKUP_FOLDER_COUNT=$(fn_find_backups | wc -l)
 		if [ "$BACKUP_FOLDER_COUNT" -lt "2" ]; then
 			fn_log_error "No space left on device, and no old backup to delete."
 			exit 1
 		fi
-				
-		OLD_BACKUP_PATH=$(find "$DEST_FOLDER" -type d -name "$BACKUP_FOLDER_PATTERN" -prune | head -n 1)
+
+		OLD_BACKUP_PATH=$(fn_find_backups | head -n 1)
 		if [ "$OLD_BACKUP_PATH" == "" ]; then
 			fn_log_error "No space left on device, and cannot get path to oldest backup to delete."
 			exit 1
 		fi
-				
-		# 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 "$OLD_BACKUP_PATH"
+
 		# Resume backup
 		continue
 	fi
@@ -229,16 +278,16 @@ while [ "1" ]; do
 		fn_log_error "Exited with error code $RSYNC_EXIT_CODE"
 		exit $RSYNC_EXIT_CODE
 	fi
-	
+
 	# -----------------------------------------------------------------------------
 	# Add symlink to last successful backup
 	# -----------------------------------------------------------------------------
-	
+
 	cd "$DEST_FOLDER"
 	rm -f -- "latest"
 	ln -s -- $(basename -- "$DEST") "latest"
 	cd -
-	
+
 	rm -- "$INPROGRESS_FILE"
 	# TODO: grep for "^rsync error:.*$" in log
 	fn_log_info "Backup completed without errors."