square root of number using sqrt and/or awk

skuz_ball · 08-04-2008, 02:41 AM

Hi all,

I'm trying to get the square root of a number and have used a couple of methods but neither has worked for me.

First method:

Quote:

sqrt($number)

Second method:

Quote:

awk '{print sqrt($number)}'

I have read somewhere that I must include <math.h> but am not exactly sure of what this is referring to and haven't seen this in any of the example scripts I have looked at. I am trying to write this using korn shell. Any help would be greatly appreciated.

Mr. C. · 08-04-2008, 02:44 AM

How about:

echo sqrt "($number)" | bc

skuz_ball · 08-04-2008, 02:58 AM

thanks heaps mate!

ghostdog74 · 08-04-2008, 03:54 AM

Quote:

Originally Posted by skuz_ball

Hi all,

I'm trying to get the square root of a number and have used a couple of methods but neither has worked for me.

First method:

Second method:

I have read somewhere that I must include <math.h> but am not exactly sure of what this is referring to and haven't seen this in any of the example scripts I have looked at. I am trying to write this using korn shell. Any help would be greatly appreciated.

you need BEGIN in you awk script since there's no file input

Code:

awk 'BEGIN{print sqrt(400)}'
# awk 'BEGIN{print 400**0.5}'

next time when it doesn't work, don't just say it doesn't work. Describe any errors or strange phenomena clearly.

matthewg42 · 08-04-2008, 04:18 AM

The math.h thing is for when you are writing a program in C. If you are using shell script, you will need to use some external program, as most shells do not include a built-in square root command.

bc is probably the best bet here as it is a very small program (so it is quicker to invoke than other programs), and it can give you a lot of precision, or as little as you want.

bc reads from standard input, so you can echo an expression to evaluate like these examples:

Code:

result1=$(echo "3 + 5" | bc -l)
result2=$(echo "sqrt(3)" | bc -l)