A bash script maintains rotate zfs snapshots

snapshot.sh

#!/bin/bash

function add_slash {
    echo $1 | sed -e 's/\//\\\//'
}

function list_snapshot {
    local v=$(add_slash $VOL)
    zfs list -t snapshot | awk "/$v@$SNAPSHOT-/"'{print $1}'
}

function count_snapshot {
    list_snapshot | wc -l
}

function make_snapshot {
    local n=$VOL@$SNAPSHOT-`date +%Y%m%d%H%M%S`
    if [[ 1 -eq "$VERBOSE" ]] ; then
        echo "Create snapshot $n"
    fi
    zfs snapshot $n
}

function remove_snapshot {
    local c=$(count_snapshot)
    local h=`expr $c '-' $KEEP`
    if [[ 1 -eq "$VERBOSE" ]] ; then
        echo "$h snapshot(s) to be deleted"
    fi
    if [[ $h -ge 0 ]]
    then
  local line
        local i=0
        for line in $(list_snapshot)
        do
            i=`expr $i + 1`
            if [[ $h -ge $i ]]
            then
                if [[ 1 -eq "$VERBOSE" ]] ; then
                    echo "Delete snapshot $line"
                fi
                zfs destroy $line
            fi
        done
    fi
}

usage()
{
cat << EOF
usage: $0 options zfsvol

This script run the test1 or test2 over a machine.

OPTIONS:
   -h      Show this message
   -s      Snapshot prefix, required.
   -k      Number of snapshots to be kept, required without -l
   -l      List snapshots
   -v      Verbose
EOF
}

SNAPSHOT=
KEEP=
while getopts “hs:k:lv” OPTION
do
     case $OPTION in
         h)
             usage
             exit 1
             ;;
         s)
             SNAPSHOT=$OPTARG
             ;;
         l)
             LIST=1
             ;;
         k)
             KEEP=$OPTARG
             ;;
         v)
             VERBOSE=1
             ;;
         ?)
             usage
             exit
             ;;
     esac
done
shift $((OPTIND-1))
VOL=$1

if [[ 1 -eq "$LIST" ]]
then
   list_snapshot
   exit 0
fi

if [[ -z $VOL ]] || [[ -z $SNAPSHOT ]] || [[ -z $KEEP ]]
then
    usage
    exit 1
fi

make_snapshot
remove_snapshot