Merge pull request #109 from mergwyn/master

Correct incorrect sh syntax

CHANGELOG

@@ -0,0 +1,9 @@
+[ 1.2.5 (Unreleased) ]
+
+ * Start a changelog
+ * Accept PR#94 from aimileus/macos
+   - Replace --utc longform option with -u for macos compatibility
+ * Accept PR#107 from ArakniD/master
+   - Add optional label for snap removals
+
+ -- Jonathan Carter 2019-09-25, 15:24 SAST

Makefile

@@ -1,17 +1,28 @@
+PREFIX := /usr/local
+
 all:
 
 install:
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.d
+	install -d $(DESTDIR)/etc/cron.d
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.daily
+	install -d $(DESTDIR)/etc/cron.daily
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.hourly
+	install -d $(DESTDIR)/etc/cron.hourly
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.weekly
+	install -d $(DESTDIR)/etc/cron.weekly
-	install -d $(DESTDIR)$(PREFIX)/etc/cron.monthly
+	install -d $(DESTDIR)/etc/cron.monthly
-	install etc/zfs-auto-snapshot.cron.frequent $(DESTDIR)$(PREFIX)/etc/cron.d/zfs-auto-snapshot
+	install -m 0644 etc/zfs-auto-snapshot.cron.frequent $(DESTDIR)/etc/cron.d/zfs-auto-snapshot
-	install etc/zfs-auto-snapshot.cron.hourly   $(DESTDIR)$(PREFIX)/etc/cron.hourly/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.hourly   $(DESTDIR)/etc/cron.hourly/zfs-auto-snapshot
-	install etc/zfs-auto-snapshot.cron.daily    $(DESTDIR)$(PREFIX)/etc/cron.daily/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.daily    $(DESTDIR)/etc/cron.daily/zfs-auto-snapshot
-	install etc/zfs-auto-snapshot.cron.weekly   $(DESTDIR)$(PREFIX)/etc/cron.weekly/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.weekly   $(DESTDIR)/etc/cron.weekly/zfs-auto-snapshot
-	install etc/zfs-auto-snapshot.cron.monthly  $(DESTDIR)$(PREFIX)/etc/cron.monthly/zfs-auto-snapshot
+	install etc/zfs-auto-snapshot.cron.monthly  $(DESTDIR)/etc/cron.monthly/zfs-auto-snapshot
 	install -d $(DESTDIR)$(PREFIX)/share/man/man8
-	install src/zfs-auto-snapshot.8 $(DESTDIR)$(PREFIX)/share/man/man8/zfs-auto-snapshot.8
+	install -m 0644 src/zfs-auto-snapshot.8 $(DESTDIR)$(PREFIX)/share/man/man8/zfs-auto-snapshot.8
 	install -d $(DESTDIR)$(PREFIX)/sbin
 	install src/zfs-auto-snapshot.sh $(DESTDIR)$(PREFIX)/sbin/zfs-auto-snapshot
+
+uninstall:
+	rm $(DESTDIR)/etc/cron.d/zfs-auto-snapshot
+	rm $(DESTDIR)/etc/cron.hourly/zfs-auto-snapshot
+	rm $(DESTDIR)/etc/cron.daily/zfs-auto-snapshot
+	rm $(DESTDIR)/etc/cron.weekly/zfs-auto-snapshot
+	rm $(DESTDIR)/etc/cron.monthly/zfs-auto-snapshot
+	rm $(DESTDIR)$(PREFIX)/share/man/man8/zfs-auto-snapshot.8
+	rm $(DESTDIR)$(PREFIX)/sbin/zfs-auto-snapshot

README

@@ -10,3 +10,12 @@ snapshots if it is installed.
 
 This program is a posixly correct bourne shell script.  It depends only on
 the zfs utilities and cron, and can run in the dash shell.
+
+
+Installation:
+-------------
+
+wget https://github.com/zfsonlinux/zfs-auto-snapshot/archive/upstream/1.2.4.tar.gz
+tar -xzf 1.2.4.tar.gz
+cd zfs-auto-snapshot-upstream-1.2.4
+make install

etc/zfs-auto-snapshot.cron.daily

@@ -1,2 +1,6 @@
 #!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+which zfs-auto-snapshot > /dev/null || exit 0
+
 exec zfs-auto-snapshot --quiet --syslog --label=daily --keep=31 //

etc/zfs-auto-snapshot.cron.frequent

@@ -1,3 +1,3 @@
-PATH="/usr/bin:/bin:/usr/sbin:/sbin"
+PATH="/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin"
 
-*/15 * * * * root zfs-auto-snapshot -q -g --label=frequent --keep=4  //
+*/15 * * * * root which zfs-auto-snapshot > /dev/null || exit 0 ; zfs-auto-snapshot --quiet --syslog --label=frequent --keep=4 //

etc/zfs-auto-snapshot.cron.hourly

@@ -1,2 +1,6 @@
 #!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+which zfs-auto-snapshot > /dev/null || exit 0
+
 exec zfs-auto-snapshot --quiet --syslog --label=hourly --keep=24 //

etc/zfs-auto-snapshot.cron.monthly

@@ -1,2 +1,6 @@
 #!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+which zfs-auto-snapshot > /dev/null || exit 0
+
 exec zfs-auto-snapshot --quiet --syslog --label=monthly --keep=12 //

etc/zfs-auto-snapshot.cron.weekly

@@ -1,2 +1,6 @@
 #!/bin/sh
+
+# Only call zfs-auto-snapshot if it's available
+which zfs-auto-snapshot > /dev/null || exit 0
+
 exec zfs-auto-snapshot --quiet --syslog --label=weekly --keep=8 //

src/zfs-auto-snapshot.8

@@ -64,6 +64,27 @@ Snapshot named filesystem and all descendants.
 \fB\-v\fR, \fB\-\-verbose\fR
 Print info messages.
 .TP
+\fB\-\-pre-snapshot\fR=\fICOMMAND\fR
+Command to run before each dataset is snapshotted. 
+It is passed the dataset and snapshot name. If it
+returns non-zero, snapshotting this dataset is 
+aborted.
+.TP
+\fB\-\-post-snapshot\fR=\fICOMMAND\fR
+Command to run after each dataset is snapshotted. 
+It is passed the dataset and snapshot name.
+.TP
+\fB\-\-destroy-only\fR
+Do not create new snapshots, but do destroy older 
+snapshots. Has no effect unless used with \fB\-k\fR.
+.IP
+A non-obvious use may be construction of cron jobs or
+scripts that run pre-snapshot command(s), then run 
+zfs-auto-snapshot (without \fB\-k\fR) to quickly
+snapshot all datasets, then run post-snapshot
+command(s) and clean up with zfs-auto-snapshot
+\fB\-\-destroy-only\fR.
+.TP
 name
 Filesystem and volume names, or '//' for all ZFS datasets.
 .SH SEE ALSO

src/zfs-auto-snapshot.sh

@@ -39,6 +39,10 @@ opt_setauto=''
 opt_syslog=''
 opt_skip_scrub=''
 opt_verbose=''
+opt_pre_snapshot=''
+opt_post_snapshot=''
+opt_do_snapshots=1
+opt_min_size=0
 
 # Global summary statistics.
 DESTRUCTION_COUNT='0'
@@ -59,10 +63,6 @@ print_usage ()
   -n, --dry-run      Print actions without actually doing anything.
   -s, --skip-scrub   Do not snapshot filesystems in scrubbing pools.
   -h, --help         Print this usage message.
-  -H, --hanoi=INT    Use the hanoi rotation scheme.
-		     INT how frequently the hanoi rotation is being run.
-		     It is a number followed by one of w, d, h, m, s for
-		     weeks, days, hours, minutes or seconds.
   -k, --keep=NUM     Keep NUM recent snapshots and destroy older snapshots.
   -l, --label=LAB    LAB is usually 'hourly', 'daily', or 'monthly'.
   -p, --prefix=PRE   PRE is 'zfs-auto-snap' by default.
@@ -73,6 +73,7 @@ print_usage ()
   -g, --syslog       Write messages into the system log.
   -r, --recursive    Snapshot named filesystem and all descendants.
   -v, --verbose      Print info messages.
+      --destroy-only Only destroy older snapshots, do not create new ones.
       name           Filesystem and volume names, or '//' for all ZFS datasets.
 " 
 }
@@ -110,7 +111,7 @@ print_log () # level, message, ...
 			;;
 		(inf*)
 			# test -n "$opt_syslog" && logger -t "$opt_prefix" -p daemon.info $*
-			test -n "$opt_verbose" && echo $*
+			test -z "$opt_quiet" && test -n "$opt_verbose" && echo $*
 			;;
 		(deb*)
 			# test -n "$opt_syslog" && logger -t "$opt_prefix" -p daemon.debug $*
@@ -144,123 +145,6 @@ do_run () # [argv]
 }
 
 
-do_rotate () # flags, oldglob, target
-{
-	local FLAGS="$1"
-	local GLOB="$2"
-	local TARGET="$3"
-	local KEEP=''
-
-	# global DESTRUCTION_COUNT
-	# global WARNING_COUNT
-	# global SNAPSHOTS_OLD
-
-	# Retain at most $opt_keep number of old snapshots of this filesystem,
-	# including the one that was just recently created.
-	KEEP="$opt_keep"
-
-	# ASSERT: The old snapshot list is sorted by increasing age.
-	for jj in $SNAPSHOTS_OLD
-	do
-		# Check whether this is an old snapshot of the filesystem.
-		if [ -z "${jj#$TARGET@$GLOB}" ]
-		then
-			KEEP=$(( $KEEP - 1 ))
-			if [ "$KEEP" -le '0' ]
-			then
-				if do_run "zfs destroy $FLAGS '$jj'" 
-				then
-					DESTRUCTION_COUNT=$(( $DESTRUCTION_COUNT + 1 ))
-				else
-					WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
-				fi
-			fi
-		fi
-	done
-}
-
-
-compute_hanoi_level() # date
-{
-	local DATE="$1"
-	local EPOCH_TIME=''
-	local HANOI_NUM=''
-	local HANOI_LEVEL='1'
-
-	# The h* is because on Solaris %H%M will have generated 12h34
-	EPOCH_TIME=$(date +%s --date="$(echo $DATE | sed 's/-\(..\)h*\(..\)$/ \1:\2/')")
-	HANOI_NUM=$(($EPOCH_TIME / $opt_hanoi));
-	while test "$HANOI_NUM" -ne "0"
-	do
-		case "${HANOI_NUM}" in
-			(*[13579])
-				break
-				;;
-		esac
-		HANOI_LEVEL=$(($HANOI_LEVEL + 1))
-		HANOI_NUM=$(($HANOI_NUM / 2))
-	done
-	echo $HANOI_LEVEL
-}
-
-
-do_hanoi () # flags, oldglob, target
-{
-	local FLAGS="$1"
-	local GLOB="$2"
-	local TARGET="$3"
-	local KEEP=''
-	local HANOI_LEVEL='0'
-	local SNAP_DATE=''
-	local SNAP_LEVEL=''
-	local POSSIBLY_DESTROY=''
-
-	# global DESTRUCTION_COUNT
-	# global WARNING_COUNT
-	# global SNAPSHOTS_OLD
-
-	HANOI_LEVEL=$(compute_hanoi_level "$DATE")
-
-	# Retain at most $opt_keep number of old snapshots of this filesystem,
-	# including the one that was just recently created.
-	KEEP="$opt_keep"
-
-	# ASSERT: The old snapshot list is sorted by increasing age.
-	for jj in $SNAPSHOTS_OLD
-	do
-		# Check whether this is an old snapshot of the filesystem.
-		if [ -z "${jj#$TARGET@$GLOB}" ]
-		then
-			# If younger snapshot was stored for possible
-			# deletion, delete it.
-			if [ -n "$POSSIBLY_DESTROY" ]
-			then
-				if do_run "zfs destroy $FLAGS '$POSSIBLY_DESTROY'"
-				then
-					DESTRUCTION_COUNT=$(( $DESTRUCTION_COUNT + 1 ))
-				else
-					WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
-				fi
-				POSSIBLY_DESTROY=''
-			fi
-
-			SNAP_DATE=$(echo $jj | sed 's/.*-\(....-..-..-..h*..\)$/\1/')
-			SNAP_LEVEL=$(compute_hanoi_level "$SNAP_DATE")
-			if test "$HANOI_LEVEL" -eq "$SNAP_LEVEL"
-			then
-				# By default the hanoi rotation scheme acts as
-				# though there are an infinite number of
-				# disks.  So instead of immediately destroying
-				# this snapshot, remember it as possibly
-				# needing to be destroyed and only do so if an
-				# older snapshot is found for this set.
-				POSSIBLY_DESTROY="$jj"
-			fi
-		fi
-	done
-}
-
-
 do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 {
 	local PROPS="$1"
@@ -268,27 +152,71 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 	local NAME="$3"
 	local GLOB="$4"
 	local TARGETS="$5"
+	local KEEP=''
+	local RUNSNAP=1
 
+	# global DESTRUCTION_COUNT
 	# global SNAPSHOT_COUNT
 	# global WARNING_COUNT
+	# global SNAPSHOTS_OLD
 
 	for ii in $TARGETS
 	do
-		if do_run "zfs snapshot $PROPS $FLAGS '$ii@$NAME'" 
+                # Check if size check is > 0
+                size_check_skip=0
+                if [ "$opt_min_size" -gt 0 ]
+                then
+                        bytes_written=`zfs get -Hp -o value written $ii`
+                        kb_written=$(( $bytes_written / 1024 ))
+                        if [ "$kb_written" -lt "$opt_min_size" ]
+                        then
+                                size_check_skip=1
+                                if [ $opt_verbose -gt 0 ]
+                                then
+                                        echo "Skipping target $ii, only $kb_written kB written since last snap. opt_min_size is $opt_min_size"
+                                fi
+                        fi
+                fi
+
+                if [ -n "$opt_do_snapshots" -a "$size_check_skip" -eq 0 ]
 		then
-			SNAPSHOT_COUNT=$(( $SNAPSHOT_COUNT + 1 ))
+			if [ "$opt_pre_snapshot" != "" ]
-		else
+			then
-			WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
+				do_run "$opt_pre_snapshot $ii $NAME" || RUNSNAP=0
-			continue
+			fi
+			if [ $RUNSNAP -eq 1 ] && do_run "zfs snapshot $PROPS $FLAGS '$ii@$NAME'"
+			then
+				[ "$opt_post_snapshot" != "" ] && do_run "$opt_post_snapshot $ii $NAME"
+				SNAPSHOT_COUNT=$(( $SNAPSHOT_COUNT + 1 ))
+			else
+				WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
+				continue
+			fi
 		fi
 
-		if test -z "$opt_hanoi"
+		# Retain at most $opt_keep number of old snapshots of this filesystem,
-		then
+		# including the one that was just recently created.
-			test -z "$opt_keep" && continue
+		test -z "$opt_keep" && continue
-			do_rotate "$FLAGS" "$GLOB" "$ii"
+		KEEP="$opt_keep"
-		else
+
-			do_hanoi  "$FLAGS" "$GLOB" "$ii"
+		# ASSERT: The old snapshot list is sorted by increasing age.
-		fi
+		for jj in $SNAPSHOTS_OLD
+		do
+			# Check whether this is an old snapshot of the filesystem.
+			if [ -z "${jj#$ii@$GLOB}" ]
+			then
+				KEEP=$(( $KEEP - 1 ))
+				if [ "$KEEP" -le '0' ]
+				then
+					if do_run "zfs destroy -d $FLAGS '$jj'"
+					then
+						DESTRUCTION_COUNT=$(( $DESTRUCTION_COUNT + 1 ))
+					else
+						WARNING_COUNT=$(( $WARNING_COUNT + 1 ))
+					fi
+				fi
+			fi
+		done
 	done
 }
 
@@ -296,11 +224,19 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 # main ()
 # {
 
-GETOPT=$(getopt \
+if [ "$(uname)" = "Darwin" ]; then
+  GETOPT_BIN="$(brew --prefix gnu-getopt 2> /dev/null || echo /usr/local)/bin/getopt"
+else
+  GETOPT_BIN="getopt"
+fi
+
+GETOPT=$($GETOPT_BIN \
   --longoptions=default-exclude,dry-run,fast,skip-scrub,recursive \
-  --longoptions=event:,hanoi:,keep:,label:,prefix:,sep: \
+  --longoptions=event:,keep:,label:,prefix:,sep: \
   --longoptions=debug,help,quiet,syslog,verbose \
-  --options=dnshH:e:l:k:p:rs:qgv \
+  --longoptions=pre-snapshot:,post-snapshot:,destroy-only \
+  --longoptions=min-size: \
+  --options=dnshe:l:k:p:rs:qgvm: \
   -- "$@" ) \
   || exit 128
 
@@ -346,29 +282,6 @@ do
 			print_usage
 			exit 0
 			;;
-		(-H|--hanoi)
-			HANOI_OPT="$2"
-			MULT="";
-			INT="";
-			case "$2" in
-				(*[0-9]s) MULT=1 ;;
-				(*[0-9]m) MULT=60 ;;
-				(*[0-9]h) MULT=3600 ;;
-				(*[0-9]d) MULT=86400 ;;
-				(*[0-9]w) MULT=604800 ;;
-				(*)
-					print_log error "Unrecognized interval $2 for the $1 parameter."
-					exit 139
-					;;
-			esac
-			INT=$(echo $2 | sed 's/.$//')
-			if ! test "$INT" -gt '0' 2>/dev/null
-			then
-				print_log error "The $2 parameter must be a positive integer."
-			fi
-			opt_hanoi=$(($INT * $MULT))
-			shift 2
-			;;
 		(-k|--keep)
 			if ! test "$2" -gt '0' 2>/dev/null
 			then
@@ -382,6 +295,10 @@ do
 			opt_label="$2"
 			shift 2
 			;;
+		(-m|--min-size)
+			opt_min_size="$2"
+			shift 2
+			;;
 		(-p|--prefix)
 			opt_prefix="$2"
 			while test "${#opt_prefix}" -gt '0'
@@ -433,6 +350,18 @@ do
 			opt_verbose='1'
 			shift 1
 			;;
+		(--pre-snapshot)
+			opt_pre_snapshot="$2"
+			shift 2
+			;;
+		(--post-snapshot)
+			opt_post_snapshot="$2"
+			shift 2
+			;;
+		(--destroy-only)
+			opt_do_snapshots=''
+			shift 1
+			;;
 		(--)
 			shift 1
 			break
@@ -459,11 +388,6 @@ then
 	exit 134
 fi
 
-if test -n "$opt_hanoi" -a -z "$opt_label"
-then
-	opt_label=hanoi
-fi
-
 # These are the only times that `zpool status` or `zfs list` are invoked, so
 # this program for Linux has a much better runtime complexity than the similar
 # Solaris implementation.
@@ -471,16 +395,33 @@ fi
 ZPOOL_STATUS=$(env LC_ALL=C zpool status 2>&1 ) \
   || { print_log error "zpool status $?: $ZPOOL_STATUS"; exit 135; }
 
+
 ZFS_LIST=$(env LC_ALL=C zfs list -H -t filesystem,volume -s name \
   -o name,com.sun:auto-snapshot,com.sun:auto-snapshot:"$opt_label") \
   || { print_log error "zfs list $?: $ZFS_LIST"; exit 136; }
 
 if [ -n "$opt_fast_zfs_list" ]
 then
-	SNAPSHOTS_OLD=$(env LC_ALL=C zfs list -H -t snapshot -o name -s name|grep $opt_prefix |awk '{ print substr( $0, length($0) - 14, length($0) ) " " $0}' |sort -r -k1,1 -k2,2|awk '{ print substr( $0, 17, length($0) )}') \
+	# Check if a snapshot label is being used, in which case restrict the old
-	  || { print_log error "zfs list $?: $SNAPSHOTS_OLD"; exit 137; }
+	# snapshot removal to only snapshots with the same label format
+	if [ -n "$opt_label" ]
+	then
+		SNAPSHOTS_OLD=$(env LC_ALL=C zfs list -H -t snapshot -o name -s name | \
+			grep "$opt_prefix"_"$opt_label" | \
+			awk '{ print substr( $0, length($0) - 14, length($0) ) " " $0}' | \
+			sort -r -k1,1 -k2,2 | \
+			awk '{ print substr( $0, 17, length($0) )}') \
+	  	|| { print_log error "zfs list $?: $SNAPSHOTS_OLD"; exit 137; }
+	else
+ 		SNAPSHOTS_OLD=$(env LC_ALL=C zfs list -H -t snapshot -o name -s name | \
+			grep $opt_prefix | \
+			awk '{ print substr( $0, length($0) - 14, length($0) ) " " $0}' | \
+			sort -r -k1,1 -k2,2 | \
+			awk '{ print substr( $0, 17, length($0) )}') \
+	  	|| { print_log error "zfs list $?: $SNAPSHOTS_OLD"; exit 137; }
+	fi
 else
-	SNAPSHOTS_OLD=$(env LC_ALL=C zfs list -H -t snapshot -S creation -o name) \
+        SNAPSHOTS_OLD=$(env LC_ALL=C zfs list -H -t snapshot -S creation -o name) \
 	  || { print_log error "zfs list $?: $SNAPSHOTS_OLD"; exit 137; }
 fi
 
@@ -540,11 +481,20 @@ do
 	# Just testing "$ii" != ${ii#$jj} would incorrectly match.
 	iii="$ii/"
 
-	# Exclude datasets that are not named on the command line.
+
+	# Exclude datasets
+	# * that are not named on the command line or
+	# * those whose prefix is not on the command line (if --recursive flag is set)
 	IN_ARGS='0'
 	for jj in "$@"
 	do
+		# Ibid regarding iii.
+		jjj="$jj/"
+
 		if [ "$jj" = '//' -o "$jj" = "$ii" ]
+		then
+			IN_ARGS=$(( $IN_ARGS + 1 ))
+		elif [ -n "$opt_recursive" -a "$iii" != "${iii#$jjj}" ]
 		then
 			IN_ARGS=$(( $IN_ARGS + 1 ))
 		fi
@@ -628,30 +578,43 @@ do
 	TARGETS_RECURSIVE="${TARGETS_RECURSIVE:+$TARGETS_RECURSIVE	}$ii" # nb: \t
 done
 
-# ISO style date; fifteen characters: YYYY-MM-DD-HHMM
-# On Solaris %H%M expands to 12h34.
-DATE=$(date --utc +%F-%H%M)
-
-if test -n "$opt_hanoi" -a "$opt_event" = "-"
-then
-	opt_event=hanoi-$HANOI_OPT-level-$(compute_hanoi_level $DATE)
-fi
-
 # Linux lacks SMF and the notion of an FMRI event, but always set this property
 # because the SUNW program does. The dash character is the default.
 SNAPPROP="-o com.sun:auto-snapshot-desc='$opt_event'"
 
+# ISO style date; fifteen characters: YYYY-MM-DD-HHMM
+# On Solaris %H%M expands to 12h34.
+# We use the shortfirm -u here because --utc is not supported on macos.
+DATE=$(date -u +%F-%H%M)
+
 # The snapshot name after the @ symbol.
-SNAPNAME="$opt_prefix${opt_label:+$opt_sep$opt_label}-$DATE"
+SNAPNAME="${opt_prefix:+$opt_prefix$opt_sep}${opt_label:+$opt_label}-$DATE"
 
 # The expression for matching old snapshots.  -YYYY-MM-DD-HHMM
-SNAPGLOB="$opt_prefix${opt_label:+?$opt_label}????????????????"
+SNAPGLOB="${opt_prefix:+$opt_prefix$opt_sep}${opt_label:+$opt_label}-???????????????"
 
-test -n "$TARGETS_REGULAR" \
+if [ -n "$opt_do_snapshots" ]
-  && print_log info "Doing regular snapshots of $TARGETS_REGULAR"
+then
+	test -n "$TARGETS_REGULAR" \
+	  && print_log info "Doing regular snapshots of $TARGETS_REGULAR"
 
-test -n "$TARGETS_RECURSIVE" \
+	test -n "$TARGETS_RECURSIVE" \
-  && print_log info "Doing recursive snapshots of $TARGETS_RECURSIVE"
+	  && print_log info "Doing recursive snapshots of $TARGETS_RECURSIVE"
+
+	if test -n "$opt_keep" && [ "$opt_keep" -ge "1" ]
+	then
+		print_log info "Destroying all but the newest $opt_keep snapshots of each dataset."
+	fi
+elif test -n "$opt_keep" && [ "$opt_keep" -ge "1" ]
+then
+	test -n "$TARGETS_REGULAR" \
+	  && print_log info "Destroying all but the newest $opt_keep snapshots of $TARGETS_REGULAR"
+
+	test -n "$TARGETS_RECURSIVE" \
+	  && print_log info "Recursively destroying all but the newest $opt_keep snapshots of $TARGETS_RECURSIVE"
+else
+	print_log notice "Only destroying snapshots, but count of snapshots to preserve not given. Nothing to do."
+fi
 
 test -n "$opt_dry_run" \
   && print_log info "Doing a dry run. Not running these commands..."