**Working with Shell Arithmetic and Boolean Operators in Unix:**

*In this tutorial, we will review the various operators that are supported by the Unix shell.*

Operators are used for manipulating variables and constants in shell programs. They are required to perform mathematical operations.

Here, we will explain to you more about working with Arithmetic Operators.

**Unix Video #14:**

Note that the back-tick (`) is often used here – when executing a command, everything between the back-ticks is executed and substituted with the result before the remainder of the command is executed.

In newer shells (**Example:** bash), the same result can be achieved by embedding the expression between ‘$(’ and ‘)’.

### Operators in Unix

#### #1) Shell Arithmetic Operators Example

**These consist of basic mathematical operations:**

- Addition: +
- Subtraction: –
- Multiplication: *
- Division: /
- Modulus: %

Each of these operators performs the operation on two integer variables or constants.

**For Example, the below program illustrates each of these operations:**

$ c=`expr $a + $b` $ echo “the value of addition=$c” $ d=`expr $a - $b` $ echo “the value of subtraction=$d” $ e= expr $a \* $b` $ echo “the value of multiplication=$e” $ f=`expr $a / $b` $ echo “the value of division=$f” $ g= echo `expr $a % $b` $ echo “the value of modulus=$c”

The Unix shell does not natively support floating point operations. A separate command-line tool must be used for this. The ‘bc’ co0mmand is the most standard tool for this.

**Example:**

$ c = `echo “$a + $b” | bc` $ d = `echo “$a + $b” | bc`

Note that each of the operators needs to be surrounded by a space on both sides, and the ‘*’ operators need to be escaped with a backslash ‘\’.

#### #2) Shell Logical Boolean Operators Example

**The logical operators in Unix are as follows:**

- Not:!
- And: -a
- Or: -o

**These operators and their usage will be covered in detail in the next tutorial.**