Smart file backup script

smart-backup.sh

#!/bin/bash

cd "$(dirname "$0")"

function limit {
  
  COUNT=$(find . -name "*.tar.gz" | wc -l)
  if (( $COUNT > $1))
  then
    rm "$(ls -t | tail -1)"
    limit $1
  fi
}

function cleanup {

  LIMIT=$(cat .limit)
  limit "$LIMIT"
}

function changed {

  LATEST_FILE=$(ls -rt | tail -1)
  if [ -z $LATEST_FILE ];
  then
    echo 1
  else  
    A_CONTENTS=$(tar -tvf $1 | sort)
    B_CONTENTS=$(tar -tvf $LATEST_FILE | sort)
    diff <(echo "$A_CONTENTS") <(echo "$B_CONTENTS") | wc -l
  fi  
}

pushd $1
BACKUP_TMP_FILE=$(mktemp)
BACKUP_FILE=$(tar -zcvf "$BACKUP_TMP_FILE" $2)
DATE=$(date '+%Y-%m-%d_%H-%M')
BACKUP_NAME="$DATE.tar.gz"

CHANGED=$(changed "$BACKUP_TMP_FILE")
  
if (( $CHANGED > 0 ))
then
  echo "Differences found, saving backup"
  mv "$BACKUP_TMP_FILE" "$BACKUP_NAME"
  cleanup
else
  echo "No differences found"
fi

popd