Simple arithmetic in shell

Linux and Unix-Like Fedora
1

Hey, I just wanted to know how one can write simple arithmetic like addition, subtraction, multiplication and division in shell-script.

2 
matt@matt-macbook$ cat math.sh
#!/bin/sh

NUMBER1=10
NUMBER2=5

((sum=NUMBER1-NUMBER2))
echo $sum
echo "\n"

((difference=NUMBER1-NUMBER2))
echo $difference
echo "\n"

((product=NUMBER1*NUMBER2))
echo $product
echo "\n"

((quotient=NUMBER1/NUMBER2))
echo $quotient
echo "\n"
3

you can use different commnds such as
1)expr
2)bc
3)shell ("echo $((4+5))")

likewise..
read man page for more info

4

Thanks. What if I want to perform more than one operation in an equation. Like I want to do (910)/100. I just learnt that expr \ is used for multiplication and expr / for division but the bracket doesn't work here so what do you use instead? Like I want to output (9*10)/100.

5

Hey sorry, thanks. Without a bracket, it works. So you just say 9*\10 /100.

Just another questions: how can I get the lines of a command in man page. Like I just typed man expr and I want to know the number of lines that come in that command, and then maybe number of the string division in that man page of the command.

6

Hey I learnt now how to perform basic threat. However I am stuck with doing basic arithmetic for non-integer values. For example I want to perform the operation (120/220) *100.

7

The shell usually can't do floating-point operations. Use bc for that, eg

VAR=$( echo "(120/220)*100" | bc )
8

It says non-numeric argument when I try to execute it

9

What did you try to execute?

$ echo "(120/220)*100" | bc
54.54545454545454545400
$ VAR=$( echo "(120/220)*100" | bc )
$ echo $VAR
54.54545454545454545400
$ div1=120
$ div2=220
$ VAR=$( echo "($div1/$div2)*100" | bc )
$ echo $VAR
54.54545454545454545400
10

the best is to use awk for any kind of mathematical operation

awk 'BEGIN{print 100/10}'
awk 'BEGIN{print (10/100)*12}' etc etc....
11

I used the fast one which is

$ echo "(120/220)*100" | bc

but it didn't work. Says command not found.

12

Then you don't have bc installed. Try the awk approach as suggested by vidyadhar (you can pass variables to awk with the -v switch) or install bc.

13

How can I install bc then? From the terminal, maybe there is a simple way to do it?

14

Which OS? In Linux it's one of

  • apt-get install bc #Debian & derivates
  • zypper install bc #OpenSuSE / SLES
  • yum install bc #Red Hat / Fedora / CentOS
  • emerge bc #Gentoo
15

The only common shells that fully support floating point arithmetic are ksh93 and zsh.