Comparing an integer and floating point in bash

Question

I'm trying to compare an integer and a floating point in bash script. I have tried the following:

if [ $? -eq 4.189 ];

which doesn't work because it wants 4.189 to be an integer, and

if [ $? = 4.186 ];

because I thought that that might work. I also tried bc. Any tips on how to do this? Bash newbie here. Thanks so much.

Note: $? is the output from an executable that calculates the volume of a sphere.

What exactly do you want to do? If $? is an integer, it is never equal to 4.186 — BeniBela
– BeniBela, Commented Feb 19, 2013 at 0:55
please go through the link : stackoverflow.com/questions/9939546/… — user1428716
– user1428716, Commented Feb 19, 2013 at 0:56
Oh, you're right. I guess the output is not an integer. -eq expects an integer, I just need a way to compare the output value to 4.189. Sorry, ignorant question. — scoots
– scoots, Commented Feb 19, 2013 at 0:56
linuxjournal.com/content/floating-point-math-bash they used bc — zb'
– zb', Commented Feb 19, 2013 at 1:01

amdn · Accepted Answer · 2013-02-19 01:20:34Z

5

This will work

#!/bin/bash
volume=4.189
if [[ $(echo "$volume == 4.189" | bc) -eq "1" ]]; then
    echo Equal
else
    echo Not Equal
fi

or simply put the literal in quotes

#!/bin/bash
volume=4.189
if [[ $volume == "4.189" ]]; then
    echo Equal
else
    echo Not Equal
fi

Notice that of the two ways I showed to compare floating point the preferred is to use bc, it will tell you that 4.1890 is equal to 4.189 whereas the second method is a dumb string compare, they will compare unequal.

edited Feb 19, 2013 at 1:20

answered Feb 19, 2013 at 0:58

amdn

11.7k37 silver badges45 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

scoots Over a year ago

Ok - so if I use your code, they all come out as correct, and if my code is used, they all come out as incorrect.

scoots Over a year ago

the output from the executable, which calculates the volume of a inputted radius. we have to use it because of the sample code that was given to us by the professor.

amdn Over a year ago

You are using $? which is the return code from a command, see stackoverflow.com/questions/6834487/… That will always be an integer. The return code is not a good way to do this, first because it is meant to indicate an error condition when not zero and second because you can't pass fractional digits.

scoots Over a year ago

Oh alright, that makes sense. I will take that into account. Thank you very much!

amdn Over a year ago

You are welcome. Notice that of the two ways I showed to compare floating point the preferred is to use bc, it will tell you that 4.1890 is equal to 4.189 whereas the second method is a dumb string compare, they will compare unequal.

|

Collectives™ on Stack Overflow

Comparing an integer and floating point in bash

1 Answer 1

7 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

7 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related