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

2

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

.

answered Apr 30, 2015 at 0:05

ctt

1,4459 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Comparing float values in bash

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related