Shell Script: How to see if a directory exists

General syntax to see if a directory exists or not
[ -d directory ]
OR
test directory
See if a directory exists or not with NOT operator:
[ ! -d directory ]
OR
! test directory

Find out if /tmp directory exists or not
Type the following command:
$ [ ! -d /tmp ] && echo 'Directory /tmp not found'
OR
$ [ -d /tmp ] && echo 'Directory found' || echo 'Directory /tmp not found'
Sample Shell Script to gives message if directory exists
Here is a sample shell script:

#!/bin/bash
DIR="$1"

if [ $# -ne 1 ]
then
echo "Usage: $0 {dir-name}"
exit 1
fi

if [ -d "$DIR" ]
then
echo "$DIR directory exists!"
else
echo "$DIR directory not found!"
fi