In bash shell script how do I convert a string to an number [duplicate]

Answer 1

If your values are guaranteed to be in the same form and range, you can do string comparisons:

if [[ $x > 0.70 ]]
then
    echo "It's true"
fi

This will fail if x is ".8" (no leading zero), for example.

However, while Bash doesn't understand decimals, its builtin printf can format them. So you could use that to normalize your values.

$ x=.8
$ x=$(printf %.2 $x)
$ echo $x
0.80

Answer 2

For some reason, this solution appeals to me:

if ! echo "$x $y -p" | dc | grep > /dev/null ^-; then
  echo "$x > $y"
else
  echo "$x < $y"
fi

You'll need to be sure that $x and $y are valid (eg contain only numbers and zero or one '.') and, depending on how old your dc is, you may need to specify something like '10k' to get it to recognize non-integer values.

Answer 3

The bash language is best characterized as a full-featured macro processor, as such there is no difference between numbers and strings. The problem is that test(1) works on integers.

Answer 4

Bash doesn't understand floating-point numbers. It only understands integers.

You can either step up to a more powerful scripting language (Perl, Python, Ruby...) or do all the math through bc or similar.

Answer 5

Here is my simple solution:

 BaseLine=70.0         
 if [ $string \> $BaseLine ]
 then
      echo $string
 else
      echo "TOO SMALL"
 fi

Answer 6

you can use bc

$ echo "0.8 > 0.7" | bc
1
$ echo "0.8 < 0.7" | bc
0
$ echo ".08 > 0.7" | bc
0

therefore you can check for 0 or 1 in your script.