Added --min-size

Added an option to inhibit generation of empty (or very small) snapshots.

src/zfs-auto-snapshot.sh

@@ -42,6 +42,7 @@ opt_verbose=''
 opt_pre_snapshot=''
 opt_post_snapshot=''
 opt_do_snapshots=1
+opt_min_size=0
 
 # Global summary statistics.
 DESTRUCTION_COUNT='0'
@@ -161,7 +162,23 @@ do_snapshots () # properties, flags, snapname, oldglob, [targets...]
 
 	for ii in $TARGETS
 	do
-		if [ -n "$opt_do_snapshots" ]
+                # 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 "$size_check_skip" -eq 0 ]
 		then
 			if [ "$opt_pre_snapshot" != "" ]
 			then
@@ -212,7 +229,8 @@ GETOPT=$(getopt \
   --longoptions=event:,keep:,label:,prefix:,sep: \
   --longoptions=debug,help,quiet,syslog,verbose \
   --longoptions=pre-snapshot:,post-snapshot:,destroy-only \
-  --options=dnshe:l:k:p:rs:qgv \
+  --longoptions=min-size: \
+  --options=dnshe:l:k:p:rs:qgvm: \
   -- "$@" ) \
   || exit 128
 
@@ -271,6 +289,10 @@ 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'