Example of the format of several control flow statements in Linux (if statement)

Examples of the format of several control flow statements for Linux:
Example of an if statement;
#!/bin/sh

a=10
B=20

if [$a = = $b]
Then
echo "A is equal to B"
elif [$a-gt $b]
Then
echo "A is greater than B"
elif [$a-lt $b]
Then
echo "A is less than B"
Else
echo "None of the condition met"
Fi

The IF ... else statement can also be written as a line and run as a command
if test $[2*3]-eq $[1+5]; Then echo ' The numbers is equal! '; Fi
The IF ... Else statement is also often used in conjunction with the test command
NUM1=$[2*3]
NUM2=$[1+5]
if test $[num1]-eq $[num2]
Then
Echo ' The numbers is equal! '
Else
Echo ' The numbers is not equal! '
Fi

Example of the format of several control flow statements in Linux (if statement)