Im learning bash, confused with command line arguments

Question

I need to create a script that allows a command line argument to be passed and checked to see if it exists as a directory within the directory im running the script in. If it does list the contents and if it doesnt print a error message. So at the command line I should type ./check.sh test(existing directory) and the script should run. Now I don't understand how to use test which should be $1. In the script I want to take $1 and check it against existing directories. however if i do something like:

#!/bin/bash
DIR=$1
cd DIR
ls

it doesn't work because DIR doesn't take on the argument(in this case test) I know I need to use an if-else block but I dont understand how to get the information I need to begin with. Please someone help me figure this out.

Answer 1

I think you wanted something like

#!/bin/bash
DIR="$1"
#test if $DIR is a directory.
if [ -d "$DIR" ]; then
    cd "$DIR"
    ls
fi

Or, you could have used $1 throughout (it's shorter than $DIR, and I would prefer to use env to search for bash - it isn't always /bin/bash ).

#!/usr/bin/env bash
if [ -d "$1" ]; then
    cd "$1"
    ls
fi