public/subjects/devops/array-selector/README.md

## array-selector

### Instructions

Create a script `array-selector.sh`, which will have an array declared with the
following values (in this order): `red`, `blue`, `green`, `white`, `black`.

When executed, the script will try to print the element at the position specified in the first argument passed to the script. The script will interpret the position `1` as the element in the array position `0`.

The script should return `Error` when:

- the number of given arguments is different from one,

- the given argument is not a number,

- the given argument is a number outside the range of the array.

Expected output:

```console
$ ./array-selector.sh 2
blue
$ ./array-selector.sh 5
black
$ ./array-selector.sh 6
Error
$ ./array-selector.sh
Error
$
```

### Hints

`array` is a special variable type that can hold more than one value. Below an example on how to define an array, select an element in the specific position, and how find out the length of an array. Below an example `script.sh`.

```bash
#!/usr/bin/env bash

array=("one" "two" "three")

echo ${array[0]} # display element in position 0
echo ${array[2]} # display element in position 2
echo ${#array[@]} # display length of array
```

And its output:

```console
$ bash script.sh
one
three
3
```

[Bash conditional construct](https://www.gnu.org/software/bash/manual/bash.html#Conditional-Constructs) can be used to decide whether to execute a specific command. Below an example `script.sh`.

```bash
#!/usr/bin/env bash

if [[ 1 > 2 ]]; then
    echo "true"
else
    echo "false"
fi
```

And its output:

```console
$ bash script.sh
false
```

It is possible to combine several conditions with the **AND** (`&&`) and **OR** (`||`) logical operators. Below and example `script.sh`.

```bash
if [[ 1 > 2 ]] || [[ 1 == 1 ]]; then
    echo "true"
else
    echo "false"
fi

if [[ 1 > 2 ]] && [[ 1 == 1 ]]; then
    echo "true"
else
    echo "false"
fi
```

And its output:

```console
true
false
```