Simple BASH backup script.

backup.sh

#!/bin/bash

KEEP_DAILY=3
KEEP_WEEKLY=1
KEEP_MONTHLY=1
KEEP_YEARLY=1

# Folder being backed up
SRC_DIR="data"
# Backup location
TARGET_DIR="bkp"

DURATION_SELECTOR="$1"

# Directory name for today's date
FOLDER_NAME=`date -u +"%Y-%m-%d"`
FOLDER_NAME="$TARGET_DIR/${DURATION_SELECTOR}_$FOLDER_NAME"

backup_directory(){
  TARGET_PATH="$1"
  echo "backing up $SRC_DIR into $TARGET_PATH..."
  mkdir -p $TARGET_PATH
  #TODO: Replace with rsync or something similar
  cp -r $SRC_DIR $TARGET_PATH
}

remove_oldest_n(){
  TIMES=$(ls $TARGET_DIR | grep "$DURATION_SELECTOR\_" | sed "s/$DURATION_SELECTOR\_//g" | xargs -I _ date -d _ +"%s")
  # Turn the string with newlines to an array
  readarray -t TIMES <<< "$TIMES"
  if [[ ${#TIMES[@]} -gt $1 ]];then
    for time in "${TIMES[@]}"; do
      if [[ $time -lt ${TIMES[-$1]} ]]; then
        DNAME=`date -d @$time +"%Y-%m-%d"`
        echo "rm -rf $TARGET_DIR/${DURATION_SELECTOR}_$DNAME"
        rm -rf $TARGET_DIR/${DURATION_SELECTOR}_$DNAME
      fi
    done
  fi
}

if [ "$1" == "d" ];then
  echo "Starting daily backup..."
  backup_directory $FOLDER_NAME
  remove_oldest_n $KEEP_DAILY
elif [ "$1" == "w" ]; then
  echo "Starting weekly backup..."
  backup_directory $FOLDER_NAME
  remove_oldest_n $KEEP_WEEKLY
elif [ "$1" == "m" ]; then
  echo "Starting monthly backup..."
  backup_directory $FOLDER_NAME
  remove_oldest_n $KEEP_MONTHLY
elif [ "$1" == "y" ]; then
  echo "Starting yearly backup..."
  backup_directory $FOLDER_NAME
  remove_oldest_n $KEEP_YEARLY
fi