awk printf problem


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# 1  
awk printf problem

Hi Friends,

Can anyone guide me how to compute sum of column4 from the below file x using awk command? when i do using awk I'm getting sum 7482350198352648.000000 which is not accurate.

$ cat x
56,232,dfgjkhdfj,,56,anand
56,22,dfgjkhdfj,7482347823453123.97834 ,56,Khan
56,23,dfgjkhdfj, ,56,krishna
56,232,dfgjkhdfj,45.68 ,56,Hari
56,232,dfgjkhdfj,2374899477.99235 ,56,Gopa
56,232,dfgjkhdfj, ,56,Gopa

$ echo 7482347823453123.97834+45.68+2374899477.99235|bc -l
7482350198352647.65069 ===> accurate result

$ awk -F, '{a+=$4} END {printf("%20.6f\n",a)}' x
7482350198352648.000000 ===> why I'm not getting correct result?

Thanks in advance
Krishna
# 2  
awk uses double precision floating point. There is a limit to its accuracy and your data exceeds that limit.
# 3  
Re: awk printf problem

Perderabo,

Can you tell me what is the maximum number it can hadle
example 99999999999999999999.999999 ???
# 4  
It varies. On my Sun it's 1.7976931348623157E+308

But do a "man limits" or find your <limits.h> and look up your value for DBL_MAX.
# 5  
I've checked the setting is
#define DBL_MAX 1.79769313486231570e+308

what I want to ask is how many total digits can hadled by awk?
# 6  
It can handle 308 digits. What you're looking for is a guarantee of n digits of integer-like arithmetic accuracy. Floating point arithmetic doesn't behave like that. Don't try to squeeze integer arithmetic behavior out of floating point. If you need integer arithmetic, simply switch to integer arithmetic. You already have the solution to your problem: use bc.

There probably is some number of digits of integer arithmetic style accuracy to had from floating point if you limit yourself to the addition of positive integers (something you were not doing). I don't know what that limit is. Nor do I care. But as soon as you start doing stuff like 9999.9999 you leave floating point behind very quickly. Not all decimal rationals can even be represented in floating point.
# 7  
Friend,

$ cat x
56,232,dfgjkhdfj,,56,anand
56,22,dfgjkhdfj,7482347823453123.97834 ,56,Khan
56,23,dfgjkhdfj, ,56,krishna
56,232,dfgjkhdfj,45.68 ,56,Hari
56,232,dfgjkhdfj,2374899477.99235 ,56,Gopa
56,232,dfgjkhdfj, ,56,Gopa

$ awk -F, '{a+=$4} END {printf("%20.6f\n",a)}' x
7482350198352648.000000 ===> why I'm not getting correct result?

what is the equivalent bc command for the above awk command?

Thanks in advance
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