Arithmetic Operations in bash

Arithmetic Operations in Bash:

Operators +,-, *,/, and %

Declare:

-I: integer variable

-X: environment variable, similar to export

1. Let: performs arithmetic operations in the format of let varname = arithmetic expression

If the calculation result is decimal, the fractional part is omitted.

For example, let sum = 4 + 1 and the result is 5.

Echo $ sum

Let s = 16/3, the result is 5

Echo $ s

2. varname = $ [arithmetic expression]

3. varname = $ (arithmetic expression ))

4. varname = 'expr $ num1 + $ num2'. Note that there must be spaces before and after +. If not, a hyphen is required.

For example, to write a script, calculate the sum of 1 to 100.

#! /Bin/bash

Declare-I sum = 0;

For num in {1 .. 100}

Do

Let sum = $ sum + $ num

Done

Echo $ sum

For example, write a script to calculate the sum of the odd and even numbers between 1 and 100.

#! /Bin/bash

Delcare-I oddsum = 0, evensum = 0

For I in 'seq 1 2 100'

Do

Let oddsum = $ oddsum + $ I

Done

Echo $ oddsum

For I in 'seq 2 2 100'

Do

Let evensum = $ evensum + $ I

Done

Echo $ evensum

Example: Calculate the sum of all current user IDs

#! /Bin/bash

Declare-I useridsum = 0

For I in 'cut-D: F3/etc/passwd'

Do

Useridsum = $ useridsum + $ I

Done

Echo $ useridsum

For example, calculate the characters of the three files/etc/rc. d/rc. sysinit/etc/init. d/functions/etc/issue.

#! /Bin/bash

Declare-I charsum = 0

For file in/etc/rc. d/rc. sysinit/etc/init. d/functions/etc/issue

Do

Charsum = $ charsum + 'wc-C $ file | cut-d'-f1'

Done

Example: create 10 users, tmpUser1-tmpUser10, and calculate the sum of their IDs

#! /Bin/bash

Declare-I useridsum = 0

For I in {1 .. 10}

Do

Useradd tmpuser $ I

Let useridsum = $ useridsum + 'id-u tmpuser $ I'

Done

Arithmetic Operations in bash