Possible Duplicate:
How do I get bc(1) to print the leading zero?
I have this problem:
x=$(echo "0.81+0.02" |bc)
echo $x
Result .83
I want see 0.83, but I don't make it.
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3 Answers
2
echo doesn't know anything about floating point numbers, it just knows about strings and integers.
You can use printf to deal with other data types and specify precise formatting options:
printf '%.2f\n' $x
Example:
imac:barmar $ x=$(echo "0.81+0.02" |bc)
imac:barmar $ printf '%.2f\n' $x
0.83
Barmar
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Is not than simple :-( x=$(echo "0.81+0.02" |bc) printf "$x.2f\n" $x, result 0.00 – bruli Oct 25 '12 at 11:25
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What happens when you try it? – Barmar Oct 25 '12 at 11:27
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1It should be `'%.2f\n'`, not `'$x.2f\n'` – Barmar Oct 25 '12 at 11:29
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Please read the documentation for `printf`, it explains the format string. – Barmar Oct 25 '12 at 11:30
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You can't put the printf on the same line as the assignment, they have to be separate statements. See example in my answer. – Barmar Oct 25 '12 at 11:37
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I would not use a printf with %.2f because it would print useless zeroes should the value be integer, and would round the numbers should they have more than two significant decimal digits. – Ferdinando Randisi Oct 25 '12 at 22:29
0
The simplest solution is to append the result to a string already containing the "0" character.
x=0
x+=$(echo "0.81+0.02" |bc)
echo $x
If you want to be able to handle the case in which the number could be greater than 1 you can use parameter substitution instead
x=$(echo "1.81+0.02" | bc )
x=${x/^./0.}
echo $x
unfortunately the previous code won't work. The second line is meant to replace the first character, if it is a dot, with the string 0., but obviously I made a syntax error. I'm not very knowledgeable of regexps, but this should be exactly what you are looking for.
The following is more cumbersome, but defenetively works.
x=$(echo "1.81+0.02" | bc )
if [[ $x == .* ]]; then
x=0$x
fi
Ferdinando Randisi
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$ x=0 $ x=$(echo "$x+0.81+0.02" |bc) $ echo $x -> result 0.83 ok. But. $ x=0 $ x+=$(echo "1.81+0.02" |bc) $ echo $x ->result 01.83 ->bad format. 01.83 – bruli Oct 25 '12 at 11:29
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0
Just do it in one line:
printf '%.2f\n' $(echo 0.82+0.01 | bc)
or
echo 0.82+0.01 | printf '%.2f\n' $(bc)
rici
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