Floating point comparison in shell

Question

Can you please suggest to me the syntax for doing floating point comparison in a Bash script? I would ideally like to use it as part of an if statement. Here is

Answer 1

another simple clear way with bc is this:

if ((`bc <<< "10.21>12.22"`)); then echo "true"; else echo "false"; fi

Answer 2

I was using bc until now, I found in some distros there was not bc installed, and I did not want to go through sudo apt install bc but python was there. Using python:

  if python -c "import sys; sys.exit(0 if float($float_1) > float($float_2) else 1)"; 
    then
    echo "true"
         else
           echo "false"
  fi

Answer 3

### The funny thing about bash is this:
> AA=10.3
> BB=10.4
### It needs `$` for compare
> [[ $AA > $BB ]] && echo Hello
> [[ $AA < $BB ]] && echo Hello
Hello

Yeah, I know it's cheating but it works. And scientific notation does not work here.

Answer 4

Using the exit() function of awk makes it almost readable.

key1=12.3
result=12.5

# the ! awk is because the logic in boolean tests 
# is the opposite of the one in shell exit code tests
if ! awk "{ exit ($result <= $key1) }" < /dev/null
then
        # some code here
fi

Note that there is not need to reuse the [ operator as if already uses the exit value.

Answer 5

bc is your friend:

key1="12.3"
result="12.2"
if [ $(bc <<< "$result <= $key1") -eq 1 ]
    then
    # some code here
fi

Note the somewhat obscure here string (<<<) notation, as a nice alternative to echo "$result <= $key1" | bc.

Also, the un-bash-like bc prints 1 for true and 0 for false.

Answer 6

yu can use this awk comparison inside a if clause, it will print 1 (true) if the condition is true else 0 (false), and those values will be interpreted as boolean vals by the if

if (( $(awk 'BEGIN {print ("'$result'" <= "'$key1'")}') )); then
    echo "true"
else
    echo "false"
fi