01backup.sh

#!/bin/bash

# This checks if the number of arguments is correct
# If the number of arguments is incorrect ( $# != 2) print error message and exit
if [[ $# != 2 ]]
then
  echo "backup.sh target_directory_name destination_directory_name"
  exit
fi

# This checks if argument 1 and argument 2 are valid directory paths
if [[ ! -d $1 ]] || [[ ! -d $2 ]]
then
  echo "Invalid directory path provided"
  exit
fi


targetDirectory="$1"
destinationDirectory="$2"


echo "Target dir : $targetDirectory"
echo "dest dir : $destinationDirectory"


currentTS=$(date +%s)


backupFileName="backup-$currentTS.tar.gz"

# We're going to:
  # 1: Go into the target directory
  # 2: Create the backup file
  # 3: Move the backup file to the destination directory

# To make things easier, we will define some useful variables...


origAbsPath=$(pwd)


cd "$destinationDirectory" # <-
destDirAbsPath=$(pwd)


cd  "$origAbsPath" # <-
cd "$targetDirectory" # <-


yesterdayTS=$((currentTS - 24 * 60 * 60))

declare -a toBackup

for file in $(ls) 
do
  if ((`date -r $file +%s` > $yesterdayTS))
  then
    toBackup+=($file)
  fi
done

tar -czvf $backupFileName ${toBackup[@]}

mv "$backupFileName" "$destDirAbsPath"