take snapshot_id volume_id snapshot_datestamp from ec2-describe-snapshots and remove from that list any IN-USE snapshots as described by ec2-describe-volumes

gistfile1.sh

#!/bin/bash

#Hey guys. This is really slow. with 1,000 snapshots and 15 excludes it's taking 40 seconds.

#this is the full list of all of a clients snapshots prepared in the format: "snapshot_id volume_id snapshot_datestamp"
#amazons describe-snapshots api does not contain information about whether a snapshot is IN-USE only describe-volumes has this information, so I must build an array of both datas and then compare them
fulllist=$(amazon_describe_snapshots | grep SNAPSHOT | awk '{ print $2 " " $3 " " $5 }' | sed 's,\+.*,,g' |  sort -k2)

#example of what the full list looks like

#snap-4b332d55 vol-044c9f6c 2013-11-15T05:03:46
#snap-a8b652b9 vol-044c9f6c 2013-11-16T05:04:23
#snap-bbd536aa vol-044c9f6c 2013-11-17T05:04:06
#snap-5b739d4a vol-044c9f6c 2013-11-18T05:04:22
#snap-5dca3e4c vol-044c9f6c 2013-11-19T05:04:31
#snap-35906224 vol-044c9f6c 2013-11-20T05:04:36
#snap-e56f96f4 vol-044c9f6c 2013-11-21T05:04:47
#snap-860ccb97 vol-044c9f6c 2013-11-22T05:04:31
#snap-85b77a94 vol-044c9f6c 2013-11-23T05:04:31
#snap-e74189f6 vol-044c9f6c 2013-11-24T05:04:08

#we must exclude the following snapshots_id's from the above list, the reason: they are currently in-use, so no matter how old they are we still don't want to try to delete them.
exclusionlist=$(amazon_describe_volumes | grep "in-use"  | grep snap | awk {'print $4'} | sort | uniq )

#example of what the exclusion list looks like
#snap-85b77a94
#snap-3f1fc554
#snap-84c28fef
#snap-89baa8a2
#snap-900156fb
#snap-940156ff
#snap-9ac28ff1
#snap-a8aae7c3
#snap-aeaae7c5
#snap-bc98d5d7

#Build the arrays
getexclusionlist=()
while read -d $'\n'; do
  getexclusionlist+=("$REPLY")
done < <(echo "$exclusionlist")

getfulllist=()
while read -d $'\n'; do
  getfulllist+=("$REPLY")
done < <(echo "$fulllist")


#for each element of the array we built of the full list we -->
for snapvoldate in "${getfulllist[@]}";
    do

            #compare it to the list of snapshot_id's that need to be excluded -->
            for excludethis in "${getexclusionlist[@]}";
            do

            #But wait, we only need the first element of our full list. -->
            #So build a temporary variable of only the first field of our full list array
                snaponly=$(echo $snapvoldate | awk '{print $1}')

                    #If we find a match then this element of the full list must be excluded, also we are done here we leave this loop ->
                    if [[ "$snaponly" == "$excludethis" ]]; then break
                    fi
            done
                    #If we just left the loop due to the above break then we know that $snaponly will equal $excludethis, if this is the case do nothing.
                    #If they dont match, we must have made it to the end of the exclusion list and the snapshot_id never matched the exclusion list, so we can print it.
                    if [[ "$snaponly" != "$excludethis" ]]; then excludedlist+="$snapvoldate"$'\n'
                    fi

    done


printfinishedlist=()
while read -d $'\n'; do
  printfinishedlist+=("$REPLY")
done < <(echo "$excludedlist")

echo $excludedlist