solutions.md

Solutions - Bash Basics

Tier 1

1.1 ~/sandbox/hello.sh:

#!/bin/bash
echo "Hello, DevOps"

chmod +x ~/sandbox/hello.sh
./hello.sh

1.2 ~/sandbox/count.sh:

#!/bin/bash
count=3
echo "Count is $count"

Tier 2

2.1 ~/sandbox/greet.sh - $1 is the first parameter:

#!/bin/bash
echo "Hello, $1"

2.2 ~/sandbox/add.sh - $(( )) performs arithmetic:

#!/bin/bash
echo $(( $1 + $2 ))

Tier 3

3.1 ~/sandbox/rect.sh:

#!/bin/bash
length=$1
width=$2
area=$(( length * width ))
perimeter=$(( 2 * (length + width) ))
echo "Area: $area"
echo "Perimeter: $perimeter"

Answers

1. The shebang (#!/bin/bash) tells the system which interpreter to run the file with; chmod +x marks it runnable so ./hello.sh works (otherwise you'd have to call bash hello.sh).
2. $1 is the first argument, $2 the second, … and $@ is all of them.
3. $(( )) evaluates its contents as arithmetic, so 3 + 4 becomes 7. In a plain string the characters are just text.