Validating parameters using conditional statements

Variables can be tested and compared against other variables when using a variable as a number.

Here is a list of some of the operators that can be used:

Operator	Description
-eq	This stands for equal to
-ne	This stands for not equal to
-gt	This stands for greater than
-lt	This stands for less than
-ge	This stands for greater than or equal to
-le	This stands for less than or equal to
!	This stands for the negation operator

Let's take a look at this in our next example script:

Chapter 2 - Script 2

#!/bin/sh
#
# 6/13/2017
#
echo "script2"

# Numeric variables
a=100
b=100
c=200
d=300

echo a=$a b=$b c=$c d=$d     # display the values

# Conditional tests
if [ $a -eq $b ] ; then
 echo a equals b
fi

if [ $a -ne $b ] ; then
 echo a does not equal b
fi

if [ $a -gt $c ] ; then
 echo a is greater than c
fi

if [ $a -lt $c ] ; then
 echo a is less than c
fi

if [ $a -ge $d ] ; then
 echo a is greater than...