Operator	Description	Example
+	Addition - Adds values on either side of the operator	`expr $a + $b` will give 30
-	Subtraction - Subtracts right hand operand from left hand operand	`expr $a - $b` will give -10
*	Multiplication - Multiplies values on either side of the operator	`expr $a \* $b` will give 200
/	Division - Divides left hand operand by right hand operand	`expr $b / $a` will give 2
%	Modulus - Divides left hand operand by right hand operand and returns remainder	`expr $b % $a` will give 0
=	Assignment - Assign right operand in left operand	a=$b would assign value of b into a
==	Equality - Compares two numbers, if both are same then returns true.	[ $a == $b ] would return false.
!=	Not Equality - Compares two numbers, if both are different then returns true.	[ $a != $b ] would return true.

Operator	Description	Example
-eq	Checks if the value of two operands are equal or not, if yes then condition becomes true.	[ $a -eq $b ] is not true.
-ne	Checks if the value of two operands are equal or not, if values are not equal then condition becomes true.	[ $a -ne $b ] is true.
-gt	Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.	[ $a -gt $b ] is not true.
-lt	Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.	[ $a -lt $b ] is true.
-ge	Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.	[ $a -ge $b ] is not true.
-le	Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.	[ $a -le $b ] is true.

Operator	Description	Example
!	This is logical negation. This inverts a true condition into false and vice versa.	[ ! false ] is true.
-o	This is logical OR. If one of the operands is true then condition would be true.	[ $a -lt 20 -o $b -gt 100 ] is true.
-a	This is logical AND. If both the operands are true then condition would be true otherwise it would be false.	[ $a -lt 20 -a $b -gt 100 ] is false.

Operator	Description	Example
=	Checks if the value of two operands are equal or not, if yes then condition becomes true.	[ $a = $b ] is not true.
!=	Checks if the value of two operands are equal or not, if values are not equal then condition becomes true.	[ $a != $b ] is true.
-z	Checks if the given string operand size is zero. If it is zero length then it returns true.	[ -z $a ] is not true.
-n	Checks if the given string operand size is non-zero. If it is non-zero length then it returns true.	[ -z $a ] is not false.
str	Check if str is not the empty string. If it is empty then it returns false.	[ $a ] is not false.

Operator	Description	Example
-b file	Checks if file is a block special file if yes then condition becomes true.	[ -b $file ] is false.
-c file	Checks if file is a character special file if yes then condition becomes true.	[ -b $file ] is false.
-d file	Check if file is a directory if yes then condition becomes true.	[ -d $file ] is not true.
-f file	Check if file is an ordinary file as opposed to a directory or special file if yes then condition becomes true.	[ -f $file ] is true.
-g file	Checks if file has its set group ID (SGID) bit set if yes then condition becomes true.	[ -g $file ] is false.
-k file	Checks if file has its sticky bit set if yes then condition becomes true.	[ -k $file ] is false.
-p file	Checks if file is a named pipe if yes then condition becomes true.	[ -p $file ] is false.
-t file	Checks if file descriptor is open and associated with a terminal if yes then condition becomes true.	[ -t $file ] is false.
-u file	Checks if file has its set user id (SUID) bit set if yes then condition becomes true.	[ -u $file ] is false.
-r file	Checks if file is readable if yes then condition becomes true.	[ -r $file ] is true.
-w file	Check if file is writable if yes then condition becomes true.	[ -w $file ] is true.
-x file	Check if file is execute if yes then condition becomes true.	[ -x $file ] is true.
-s file	Check if file has size greater than 0 if yes then condition becomes true.	[ -s $file ] is true.
-e file	Check if file exists. Is true even if file is a directory but exists.	[ -e $file ] is true.

#!/bin/sh

val=`expr 2 + 2`
echo "Total value : $val"

						

Total value : 4