#!/bin/bash 
# 
# purge old zfs snapshots
# work on Solaris 10, not tested in other environment
# by Igor Velkov <dober-aeons.lv>
# v 0.2.1
# based on snap_zfs by trevor.pretty@sun.com

SCRIPT_NAME=$0
FILESYSTEM=$1

ID=/usr/xpg4/bin/id
ZFS=/usr/sbin/zfs
NOW="date +%Y-%m-%d.%H:%M:%S "
DEBUG=N

# very bad!!!!!
# get the current date in unixtime format
DATE=`/usr/bin/truss /usr/bin/date 2>&1 |  nawk -F= '/^time\(\)/ {gsub(/ /,"",$2);print $2}'`


## Usage
# 
Usage()
{
    echo "Recursively removes all snapshots of filesystem "
    echo "older min_age, or between (min_age..max_age)"
    echo "Usage: $SCRIPT_NAME filesystem @snapprefix min_age [max_age]"
    echo ""
    echo "Examples"
    echo "        $SCRIPT_NAME pool/name @snap 3"
    echo "        $SCRIPT_NAME pool/name @snap 3 10"
    echo ""
    echo "Note: The filesystem cannot have a trailing \"/\""
    echo "snapprefix must always start with \"@\""
    echo ""
    exit 1
}

########### Main Part ###################

## Check Usage
#
if [ $# -lt 3 ]; then
    echo 'You have to provide at least 3 arguments'
    Usage
fi

# check if parameter 3 is number
# [0-9]+
case "$3" in
*[^0-9]*)
    echo '3rd argument must be a number'
    Usage
    exit 1
    ;;
*)
   MIN="$3"
    ;;
esac

# check if parameter 4 is present and is number
# [0-9]+
case "$4" in
*[^0-9]*)
    echo '4rd argument must be a number if present'
    Usage
    exit 1
    ;;
# 4rd parametr is number
[0-9]*)
    MAX=$4 
    ;;
*)
    ;;
esac

# sheck for snapshot pattern starts with "@" ant not contain more @
# it must for not erase filesystem if no "@" will be supplied
SNAPPTN="$2"
if [ "@${SNAPPTN#@}" != "$SNAPPTN" ]; then
    echo "Second parameter must start with @ and not contain \"@\" more"
    Usage
fi

## See if we have right authorization: Either we are root or allowed to manage ZFS
#
WHO=`/usr/xpg4/bin/id -n -u`
PROF=`/bin/profiles | grep "ZFS File System Management"`
if [ "$PROF" != "ZFS File System Management" ]; then
        if [  "$WHO" != "root"  ]; then
                echo "$SCRIPT_NAME: ERROR: you are not authorized to run this script."
                exit 1
        fi
fi


# get list in format fsname, used bytes, creation time, mountpoint
# we will work only where type=snapshot
$ZFS get -H -o value -rp name,used,creation,type "$FILESYSTEM" \
    | sed '$!N;s/\n/ /' | sed '$!N;s/\n/ /' | grep "$SNAPPTN" \
    | while read SNNAME SNUSED SNTIME SNTYPE; 
do 
    if [ "$DEBUG" = 'Y' ] ; then
        echo "$SNNAME $SNUSED $SNTIME $SNTYPE"
    fi
    #work only with snapshots, not filesystem or something other
    if [ "$SNTYPE" != 'snapshot' ]; then
        if [ "$DEBUG" = 'Y' ] ; then
            echo "type is \"$SNTYPE\", not processed"
        fi
        continue;
    fi
    
    # AGE is snapshot age in days, count from unixtime dy /sec in min/min in a hour/hour in a day
    AGE=`expr \( $DATE - $SNTIME \) / 60 / 60 / 24`

    # target expression (!$MAX & ($AGE >= $MIN)) | ($MAX & ($AGE < $MAX) & ($AGE >= $MIN))
    #  inverse: not remove if $AGE < $MIN or (isset($MAX)  and $AGE>$MAX)
    ERASE=Y
    if [ "$AGE" -lt "$MIN" ]; then 
        ERASE=N
    elif [ "$MAX" ]; then
        if [ "$AGE" -gt "$MAX" ]; then 
          ERASE="N"
        fi
    fi
    if [ "$DEBUG" = 'Y' ] ; then
        echo "snap:$SNNAME snaptime:$SNAPTIME age:$AGE min:$MIN max:$MAX erase:$ERASE"
    fi
    if [ "$ERASE" != 'N' ]; then
        if [ "$DEBUG" = 'Y' ] ; then
            echo "want run zfs remove $SNNAME"
        else
            # not using -R swich to protect child objects if exists
            $ZFS destroy "$SNNAME"
            if [ $? -gt 0 ] ; then
                echo "error destroying $SNNAME"
            else
                echo "$SNNAME destroyed"
            fi
        fi
    fi
          
done
exit