How to compare reals and integers?

Question

I have tried all possible combinations that I could find to compare a real and an integer, but they all seemed to fail.

For example

if (( "10.0" == "10" )); then
    echo "Joy"
else
    echo "Damn it"
fi

I tried square brackets, I tried without quotes, I tried -eq, but that was for integers only. So not sure how I am supposed to make this work in bash.

Bash doesn't do floating point comparisons. [`bc`](http://www.gnu.org/software/bc/manual/html_chapter/bc_toc.html) is the standard unix system tool for doing arithmetic or comparisons using floating point numbers. — John B, Aug 15 '14 at 11:08
Or use a shell that does support floating-point, like ksh93. — cdarke, Aug 15 '14 at 12:52

konsolebox · Accepted Answer · 2014-08-15T10:40:15.170

2

Using bc:

if [[ $(echo "10.0 == 10" | bc) -eq 1 ]]; then
    echo "Joy"
else
    echo "Damn it"
fi

awk is also possible:

if awk -v op="10.0" 'BEGIN { exit !(op == 10) }'; then

edited Aug 15 '14 at 10:40

answered Aug 15 '14 at 10:29

konsolebox

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`expr` didn't work though. I still got `Damn it` – Peter Raeves Aug 15 '14 at 10:31
Your version perhaps doesn't return a code. Try `if [[ $(expr 10.0 == 10) == 1 ]]; then` – konsolebox Aug 15 '14 at 10:32
Didn't work either, I'm using `GNU bash, version 4.3.11(1)` – Peter Raeves Aug 15 '14 at 10:33
Doesn't seem to work here either; `--version` is `expr (GNU coreutils) 8.23` – Martin Tournoij Aug 15 '14 at 10:33
Mine is even older. 8.21 – konsolebox Aug 15 '14 at 10:34
`if [ $(echo " 10.0 == 10" | bc) -eq 1 ]` bc seemed to work though. Edit: I was using `--versionexpr (GNU coreutils) 8.21` too – Peter Raeves Aug 15 '14 at 10:35
Nevermind. I think I might be wrong about how `expr` works. Just use `bc`. It actually becomes string comparison already, not comparison of floats. – konsolebox Aug 15 '14 at 10:38

score 1 · Answer 2 · answered Aug 15 '14 at 11:29

1

Convert both to float and make string comparison:

printf -v a "%f" 10.0
printf -v b "%f" 10
echo $a
echo $b

Output:

10.000000
10.000000

answered Aug 15 '14 at 11:29

Cyrus

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How to compare reals and integers?

2 Answers2