変数の例CSVデータを考えると、次のようになります$csv。

gawk '
    function timestamp2epoch(ts,       m) {
        if(match(ts, /([0-9]{4})-([0-9]{2})-([0-9]{2})T([0-9]{2}):([0-9]{2}):([0-9]{2})\..*/, m)) 
            return mktime(m[1] " " m[2] " " m[3] " " m[4] " " m[5] " " m[6])
        else
            return -1
    }

    BEGIN {
        FS = ";"
        interval = 2 * 3600     # 2 hours
    }

    { t = timestamp2epoch($3) }
    t > start + interval { start = t; n++ }
    { batch[n] = batch[n] (batch[n] == "" ? "" : "/") $0 }

    END {
        PROCINFO["sorted_in"] = "@ind_num_asc"
        for (i in batch)
            print batch[i]
    }
' <<<"$csv"

出力

abc;square;2021-05-27T14:15:39.315Z/def;circle;2021-05-27T14:17:03.416Z/ghi;triang;2021-05-27T14:45:13.520Z/abc;circle;2021-05-27T15:25:47.624Z
ghi;square;2021-05-27T17:59:33.641Z/def;triang;2021-05-27T18:15:33.315Z
abc;circle;2021-05-27T21:12:13.350Z/ghi;triang;2021-05-27T21:15:31.135Z

これはシェル配列として読み取ることができます。たとえば、次のようになります。

mapfile -t batches < <(gawk '...' <<<"$csv")
declare -p batches

declare -a batches=([0]="abc;square;2021-05-27T14:15:39.315Z/def;circle;2021-05-27T14:17:03.416Z/ghi;triang;2021-05-27T14:45:13.520Z/abc;circle;2021-05-27T15:25:47.624Z" [1]="ghi;square;2021-05-27T17:59:33.641Z/def;triang;2021-05-27T18:15:33.315Z" [2]="abc;circle;2021-05-27T21:12:13.350Z/ghi;triang;2021-05-27T21:15:31.135Z")

次に、次のように対話します。

for ((i = 0; i < "${#batches[@]}"; i++)); do
    IFS="/" read -ra records <<<"${batches[i]}"
    echo "batch $i"
    for record in "${records[@]}"; do echo "  $record"; done
    echo
done

batch 0
  abc;square;2021-05-27T14:15:39.315Z
  def;circle;2021-05-27T14:17:03.416Z
  ghi;triang;2021-05-27T14:45:13.520Z
  abc;circle;2021-05-27T15:25:47.624Z

batch 1
  ghi;square;2021-05-27T17:59:33.641Z
  def;triang;2021-05-27T18:15:33.315Z

batch 2
  abc;circle;2021-05-27T21:12:13.350Z
  ghi;triang;2021-05-27T21:15:31.135Z