Shell Programming and Scripting

Hello All,

I'm trying to issue a conditional expression using "bc" on floating point numbers. I had this working on my linux box,
but as soon as I transferred the file over to an AIX Server, it would not work anymore...

This is the "WORKING" command on linux (below), which I can't seem to figure out how to do on AIX's Version of "bc". I've read
the manpage which didn't have a very good explaination for it, except that, I believe the ONLY way you can use those
relational operators is in an if|for|while statements/loops...

Code:

condition=$(echo "$size == 0" | bc 2>/dev/null)

So I think I have to somehow convert this to a "bc" If Statement.
Anyone know how this is done?


Thanks in Advance,
Matt

Matt, can you explain your requirement? What input do you have and what output do you expect?

Are you trying to check if a variable value is equal to 0?

Hey bipinajith, thanks for the reply!

Ok, basically yes...
For the expression below, $size COULD possibly be a floating point number, OR it could be a '0'. And since I'm writing this in a
shell script I can't exactly use a float in a Shell If Statement.

Code:

condition=$(echo "$size == 0" | bc 2>/dev/null

And for what I'm looking for as output, I really just need 0|1 (i.e. TRUE or FALSE) result.

Does that make sense?


Thanks Again,
Matt

Yes.

You can use awk for floating point comparison. Here is an example:-

Code:

echo | awk -v size1=5.65 -v size2=3.14e-22  '{if (size1<size2) printf ("%s\n", "Less-than"); else printf ("%s\n", "Greater-than"); }

I hope this helps.

Oh, cool. That should work too! Thanks...

Any idea how something like that would look for "bc" though?
I'm kinda curious now how that would work....

Thanks Again,
Matt

Can you replace letter E or e in the exponential notation with ^ sign and re-try:-

Code:

export size1=5.65
export size2=3.14^22
echo "$size1 < $size2" | bc

Hey, thanks again for the reply.

Ok, tried your "bc" example, but I got an error...

Code:

# export SIZE_1=5.65            
# export SIZE_2=3.14
# echo "$SIZE_1 < $SIZE_2" | bc
syntax error on line 1 stdin

I'm pretty sure I need to somehow do this in a "If Statement" in the bc command. I just can't figure out the syntax.

Thanks Again,
Matt