Divide two variables in bash

Question

I am trying to divide two var in bash, this is what I've got:

var1=3;
var2=4;

echo ($var1/$var2)

I always get a syntax error. Does anyone knows what's wrong?

The actual issue here is the mistake (subshell/arithmetic syntax). After fixing that, there's the integer division issue: [Bash Division Keeps giving 0 - Stack Overflow](https://stackoverflow.com/questions/45515025/bash-division-keeps-giving-0) — user202729, Oct 05 '21 at 23:57

score 108 · Accepted Answer · answered May 22 '15 at 13:40

108

shell parsing is useful only for integer division:

var1=8
var2=4
echo $((var1 / var2))

output: 2

instead your example:

var1=3
var2=4
echo $((var1 / var2))

ouput: 0

it's better to use bc:

echo "scale=2 ; $var1 / $var2" | bc

output: .75

scale is the precision required

answered May 22 '15 at 13:40

m47730

The output of `bc` should be a string or a float number? – Sigur Oct 01 '17 at 00:45
2

@Sigur the output is always a string – m47730 Oct 02 '17 at 11:12
2

Is it possible to convert it to float or int? – Sigur Oct 02 '17 at 11:31

score 25 · Answer 2 · answered Feb 06 '18 at 04:12

25

If you want to do it without bc, you could use awk:

$ awk -v var1=3 -v var2=4 'BEGIN { print  ( var1 / var2 ) }'
0.75

answered Feb 06 '18 at 04:12

rouble

2

What is "without bc"? – Jacob Birkett Jan 29 '22 at 07:20
1

bc is a terminal based calculator shipped with most distributions https://linux.die.net/man/1/bc – Nicolai Schmid Oct 25 '22 at 18:21

score 18 · Answer 3 · answered May 22 '15 at 13:36

18

There are two possible answers here.

To perform integer division, you can use the shell:

$ echo $(( var1 / var2 ))
0

The $(( ... )) syntax is known as an arithmetic expansion.

For floating point division, you need to use another tool, such as bc:

$ bc <<<"scale=2; $var1 / $var2"
.75

The scale=2 statement sets the precision of the output to 2 decimal places.

answered May 22 '15 at 13:36

Tom Fenech

1

P.S. in my .zshrc, I have `calc () { echo "scale=2;$*" | bc | sed 's/\.0*$//'}` to do calculations. The latter `sed` is to remove trailing zeros, E.g. `100/10` we get `10` instead of `10.00`... – Kent May 22 '15 at 13:47

score 2 · Answer 4 · answered May 22 '15 at 13:43

2

#!/bin/bash
var1=10
var2=5
echo $((var1/var2))

answered May 22 '15 at 13:43

Walter Wahlstedt

2

It would be nice if you explain what the error was. – MarkoHiel May 22 '15 at 14:50

score 2 · Answer 5 · answered Jul 01 '20 at 06:24

2

You can also use Python for this task.
Type python -c "print( $var1 / float($var2) )"

answered Jul 01 '20 at 06:24

Puspam

This is honestly the simplest solution I could get working. The `bc` solution wasn't working at all for me. – muad-dweeb Jun 09 '22 at 22:28

5 Answers5