Comparison of floating point numbers in bash


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Top Forums Shell Programming and Scripting Comparison of floating point numbers in bash
# 8  
Hi Chubler_XL...

This is the result, (including the missing 'if'):
Code:
Last login: Wed Oct 23 09:21:10 on ttys000
AMIGA:amiga~> num1=1.2345
AMIGA:amiga~> num2=0.9876
AMIGA:amiga~> if awk "BEGIN{exit !($num1 > $num2)}"; then echo "OK."; fi
-bash: !: event not found
AMIGA:amiga~> _

I am getting good at _fudging_ with single and double quotes.
But unless I use my Linux box I only have bash version 3.2.x, but almost everyone has POSIX compliance. <wink>






-------------------------
OT, in fact I used a method of exiting AudioScope.sh that was perfect until bash 4.4.x when someone must have noticed it was a serious bug and I thought it was a feature, post #7:
AudioScope Project.


EDIT:
My modified version also works in 'dash'.

Last edited by wisecracker; 10-23-2019 at 07:01 AM.. Reason: See EDIT:
# 9  
Perl is even shorter than awk.
It can even be hidden in a function:

Code:
fff(){
perl -e "exit ! ($*)"
}

num1=1.2345
num2=0.9876
if fff "$num1 > $num2"; then echo "OK"; fi

Or
Code:
if fff "$num1" ">" "$num2"; then echo "OK"; fi

This User Gave Thanks to MadeInGermany For This Post:
# 10  
Then, why not
Code:
bc <<< "$num1 > $num2"
1

?
This User Gave Thanks to RudiC For This Post:
# 11  
Quote:
Originally Posted by RudiC
Then, why not
Code:
bc <<< "$num1 > $num2"
1

?
Perhaps because the OP might mistake '1' as being a result or a '$?' as opposed to a 'true'.
(Also it does not work in POSIX but that is my reason not the OP's.)
This User Gave Thanks to wisecracker For This Post:
# 12  
Quote:
Originally Posted by wisecracker
Hi Chubler_XL...

This is the result, (including the missing 'if'):
Code:
Last login: Wed Oct 23 09:21:10 on ttys000
AMIGA:amiga~> num1=1.2345
AMIGA:amiga~> num2=0.9876
AMIGA:amiga~> if awk "BEGIN{exit !($num1 > $num2)}"; then echo "OK."; fi
-bash: !: event not found
AMIGA:amiga~> _

I am getting good at _fudging_ with single and double quotes.
But unless I use my Linux box I only have bash version 3.2.x, but almost everyone has POSIX compliance. <wink>
Oh, OK. ! is a command line history expansion thing. This is really quite sad as even this simple command will fail with a weird error about events:

Code:
echo "Hello, World!"

This expanson should only impact command line code, scripts using ! should work fine in 3.2.x. I also believe that if a whitespace character follows bash will not try to expand from the history. I don't have access to 3.2.x bash to test, but believe this should work OK from the command line:
Code:
if awk "BEGIN{exit ! ($num1 > $num2)}"; then echo "OK."; fi


Last edited by Chubler_XL; 10-23-2019 at 07:11 PM..
# 13  
Quote:
Originally Posted by Chubler_XL
Oh, OK. ! is a command line history expansion thing. This is really quite sad as even this simple command will fail with a weird error about events:

Code:
echo "Hello, World!"

This expanson should only impact command line code, scripts using ! should work fine in 3.2.x. I also believe that if a whitespace character follows bash will not try to expand from the history. I don't have access to 3.2.x bash to test, but believe this should work OK from the command line:
Code:
if awk "BEGIN{exit ! ($num1 > $num2)}"; then echo "OK."; fi

Works as expected now! <thumbs_up>

Code:
Last login: Wed Oct 23 21:29:52 on ttys000
AMIGA:amiga~> num1=1.2345
AMIGA:amiga~> num2=0.9876
AMIGA:amiga~> if awk "BEGIN{exit ! ($num1 > $num2)}"; then echo "OK."; fi
OK.
AMIGA:amiga~> if awk "BEGIN{exit ! ($num1 < $num2)}"; then echo "OK."; fi
AMIGA:amiga~> _

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