Comparing float values in bash

Question

Hi I would like to compare 2 float numbers in bash but I haven't find anything that works properly. My actual code is the following:

 if [ $(echo " 0.5 > $X " | bc -l )==1 ] echo grande fi if [ "$(bc <<< "$X - 0.5")" > 0 ] ; then echo 'Yeah!' fi

What happens is that no matter if the X is bigger or smaller than 0.5, it always echos both sentences and I don't know why. I know the X is bigger or smaller than 0.5 because I also echo it and I can see it.

Possible duplicate of stackoverflow.com/questions/15224581/… — Eric Renouf
– Eric Renouf, Commented Apr 30, 2015 at 0:04
when compare numeric with [ ] you should use -gt not >. tldp.org/LDP/abs/html/refcards.html — Dyno Fu
– Dyno Fu, Commented Apr 30, 2015 at 0:14

ctt · Accepted Answer · 2015-04-30 00:05:23Z

In bash, you need to be very careful about spacing. For example:

if [ $(echo " 0.5 > $X " | bc -l )==1 ]; then echo grande fi

Here, there are no spaces around the ==, so it'll be interpreted as:

if [ 0==1 ]; then fi

Believe it or not, this condition is always true.

Consider:

if [ "$(echo " 0.5 > $X " | bc -l )" == 1 ]; then echo grande fi

.

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