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Old 08-16-2004, 12:39 PM   #1
linuxboy69
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Registered: Oct 2003
Distribution: Redhat 9
Posts: 138

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how to compare decimals


I am writing a script where I need to check if a decimal number is higher than another given decimal number using an if statement.

I have the if setup so far as:

if [ $<dec. num> -lt 0.02 ]; then
...
..
fi

since the "-lt" operator only does integer I get an error that looks like this:

[: .000066041946411: integer expression expected

my second idea is that I should multiply the first number by a thousand and then round it off to create an integer. I googled "round decimal" and I get nothing productive.

Can someone help me either compare the decimal number or tell me how I round a decimal? I am guessing that rounding the decimal has something to do with the "bc" command.
 
Old 08-16-2004, 01:09 PM   #2
Komakino
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Registered: Feb 2004
Location: Somerset, England
Distribution: Slackware 10.2, Slackware 10.0, Ubuntu 9.10
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You could use the arbitrary precision calculator bc if it is installed on the system. It accepts equations like 1.2 < 1.3 and outputs 1 for true or 0 for false. e.g:
Code:
bc -q
bc -q starts bc without a welcome message.

You can echo expressions to bc from a script and receive the output:
Code:
echo "1.2 > 1.3" | bc
gives the result 0. Thus you can include piped input (as above) as part of a script.
(in Perl):
Code:
if(`echo \"1.2 > 1.1\" | bc` == 0){
 print "Something here...";
}
Sorry, I don't do much bash scripting, but the principle is the same.
 
Old 08-16-2004, 02:43 PM   #3
linuxboy69
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Registered: Oct 2003
Distribution: Redhat 9
Posts: 138

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I tried what you put and it worked. Thank you so much!!
 
  


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