#!/bin/bash
LIMIT=500000
NO=0
#Get the number of files, that has `*.pcap` in its name, with last modified time 5 days     ago

NUMBER=$(find /mnt/md0/capture/DCN/ -maxdepth 1 -name "*.pcap" |wc -l)
if [[ $NUMBER -gt $LIMIT ]]  #if number greater than limit
 then
  del=$(($NUMBER-$LIMIT))
   if [ "$del" -lt "$NO" ]
    then
     del=$(($del*-1))
   fi
   echo $del
   FILES=$(
     find /mnt/md0/capture/DCN/ -maxdepth 1 -type f -name "*.pcap" -print0 |
       xargs -0 ls -lt |
       tail -$del |
       awk '{print $8}'
   )
  rm -f ${FILES[@]}
  #delete the originals

 fi

find /mnt/md0/capture/DCN/ -maxdepth 1 -type f -name "*.pcap" -print0 |
  xargs -0 ls -lt | tail -n "$del" | awk '{print $8}'

ls -dt /mnt/md0/capture/DCN/*.pcap | tail -n "$del"

ls -dt /mnt/md0/capture/DCN/*.pcap | tail -n "$del" | xargs rm

ls -dt --quoting-style=shell-always /mnt/md0/capture/DCN/*.pcap |
  tail -n "$del" | xargs rm

#! /bin/zsh -
keep=5000
rm -f /mnt/md0/capture/DCN/*.pcap(D.om[$((keep+1)),-1])

cd /mnt/md0/capture/DCN/ &&
  find . -maxdepth 1 -name '*.pcap' -type f -printf '%T@@%p' |
    sort -zrn | sed -z "s/[^@]*@//;1,$keep d" | xargs -r0 rm -f

cd /mnt/md0/capture/DCN/ &&
  find . -maxdepth 1 -name '*.pcap' -type f -printf '%T@@%p' |
    tr 'n' 'n' | sort -rn | tail -n "+$(($keep+1))" |
    cut -d @ -f2- | tr  'n' 'n' | xargs -r0 rm -f

shopt -s dotglob
cd /mnt/md0/capture/DCN/ &&
  eval "files=($(ls -dt --quoting-style=shell-always -- *.pcap))" &&
  rm -f -- "${files[@]:$keep}"

cd /mnt/md0/capture/DCN/ &&
  ls -dt ./.pcap ./.*.pcap ./*.pcap | awk -v keep="$keep" '
    function process() {
      if (++n > keep) {
        gsub(/[ tn"\''']/,"\\&", file)
        print file
        file = ""
      }
    }
    /// {
      if (NR > 1) process()
      file=$0
      next
    }
    {file = file "n" $0}
    END {if (NR > 0) process()}' | xargs rm -f

mkdir t && cd t

# 50500 files, 500 to delete
touch {000001..050500}

limit=50000

ls -t|tail -n "+$(($limit + 1))"|xargs rm

ls|wc -l
50000

limit=5000
Cnt=0
for line in `ls -t`
do
  if [[ $Cnt -gt $limit ]]
  then
    rm $line
  fi
  Cnt=`expr $Cnt + 1`
done