[Unix / Linux Shell Tutorial - Lession7] Arithmetic

1. #!/bin/bash
2. # Basic arithmetic using let
4. let a=5+4
5. echo $a # 9
7. let "a = 5 + 4"
8. echo $a # 9
10. let a++
11. echo $a # 10
13. let "a = 4 * 5"
14. echo $a # 20
16. let "a = $1 + 30"
17. echo $a # 30 + first command line argument

Operator	Operation
+, -, \*, /	addition, subtraction, multiply, divide
var++	Increase the variable var by 1
var--	Decrease the variable var by 1
%	Modulus (Return the remainder after division)

Example2

1. #!/bin/bash
2. # Basic arithmetic using expr
4. expr 5 + 4
6. expr "5 + 4"
8. expr 5+4
10. expr 5 \* $1
12. expr 11 % 2
14. a=$( expr 10 - 3 )
15. echo $a # 7

Example3

1. #!/bin/bash
2. # Basic arithmetic using double parentheses
4. a=$(( 4 + 5 ))
5. echo $a # 9
7. a=$((3+5))
8. echo $a # 8
10. b=$(( a + 3 ))
11. echo $b # 11
13. b=$(( $a + 4 ))
14. echo $b # 12
16. (( b++ ))
17. echo $b # 13
19. (( b += 3 ))
20. echo $b # 16
22. a=$(( 4 * 5 ))
23. echo $a # 20

Example4

1. #!/bin/bash
2. # Show the length of a variable.
4. a='Hello World'
5. echo ${#a} # 11
7. b=4953
8. echo ${#b} # 4