how to check folder exists or not in linux shell code example

Example 1: linux command if directory exists

DIR="/etc/httpd/"
if [ -d "$DIR" ]; then
  ### Take action if $DIR exists ###
  echo "Installing config files in ${DIR}..."
else
  ###  Control will jump here if $DIR does NOT exists ###
  echo "Error: ${DIR} not found. Can not continue."
  exit 1
fi

Example 2: linux shell check if directory does not exists

if [ ! -d directory ]; then
  mkdir directory
fi