Compare Decimal Values

rbautch · 04-13-2008, 02:28 PM

How do I run test with decimal values? For example

x=5.2
if [ $x >= 5.1 ]; then
echo "good"
fi

This of course only works with integers, but what about decimals?

MensaWater · 04-13-2008, 02:53 PM

Don't use symbol for numeric comparison. Use the "test" special comparisons (you can see all of them with "man test").

-eq = Equals
-ne = Not equal
-gt = Greater than
-ge = Greater than or equal

So what you need is:

Code:

x=5.2
if [ $x -ge 5.1 ]; then
echo "good"
fi

H_TeXMeX_H · 04-13-2008, 03:05 PM

You could do:

Code:

x=5.2
if test $(echo "$x >= 5.1" | bc) == 1
  then
  echo "good"
fi

rbautch · 04-13-2008, 03:44 PM

Quote:

Originally Posted by jlightner

So what you need is:

Code:

x=5.2
if [ $x -ge 5.1 ]; then
echo "good"
fi

This still gives me "integer expression expected".

rbautch · 04-13-2008, 03:47 PM

Quote:

Originally Posted by H_TeXMeX_H

You could do:

Code:

x=5.2
if test $(echo "$x >= 5.1" | bc) == 1
  then
  echo "good"
fi

Thanks. This works, but the script will be run on machines that will likely not have bc. I thought about moving the decimal around to try to normalize values into integers but that seems a little convoluted. Is there any other way?

H_TeXMeX_H · 04-14-2008, 05:26 AM

You could probably do it with awk, don't have time to research it now, so check here in the meantime:
http://www.grymoire.com/Unix/Awk.html

colucix · 04-14-2008, 06:16 AM

You can try perl like this

Code:

#!/bin/bash
x=5.2
if [ $(perl -e "($x >= 5.1) ? print 1 : print 0") -eq 1 ]
then
    echo good
fi

In perl this is an alternate statement: if the expression is true, execute the statement after the question mark; if the expression is false, execute the statement after the colon.

H_TeXMeX_H · 04-14-2008, 11:14 AM

With awk you can do:

Code:

echo | awk '{ if (5.2 <= 5.1) print "good" }'
# or for passing variables
x=5.2
echo "$x 5.1" | awk '{ if ($1 <= $2) print "good" }'

Somehow, I'm thinking if those machines don't have bc, they ain't gonna have perl either. If they don't have awk, then throw those machines out the window.

MensaWater · 04-14-2008, 12:53 PM

Quote:

Originally Posted by rbautch

This still gives me "integer expression expected".

My bad. I happened to be running ksh on Linux and it worked in that.

What I typically use for math operations if they aren't handled by simple syntax or expr is the bc command. In bc if a greater than is true then it results in value 1. Test for that:

Something like:

Code:

x=5.2
if [ `echo 6.0\>5.1 |bc` -eq 1 ]; then echo good; fi

Notice you need the backslash in front of the greater than operator to keep the shell from interpreting it as a redirect.

rbautch · 04-21-2008, 06:20 PM

Quote:

Originally Posted by H_TeXMeX_H

With awk you can do:

Code:

echo | awk '{ if (5.2 <= 5.1) print "good" }'
# or for passing variables
x=5.2
echo "$x 5.1" | awk '{ if ($1 <= $2) print "good" }'

Somehow, I'm thinking if those machines don't have bc, they ain't gonna have perl either. If they don't have awk, then throw those machines out the window.

This was the winner. Thanks.

konsolebox · 04-22-2008, 04:11 AM

you can also try the function testfloat():

http://www.linuxquestions.org/questi...69#post3101569