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:

$ ./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.

#!/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:

$ bash script.sh
one
three
3

Bash conditional construct can be used to decide whether to execute a specific command. Below an example script.sh.

#!/usr/bin/env bash

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

And its output:

$ bash script.sh
false

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

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:

true
false