topic Re: Shell script problem in Operating System - HP-UX

Shell script problem

bibith dathan — Thu, 16 Oct 2008 15:27:50 GMT

Hi All

can any one tell is their any limitation in lengh of numeric value that expr function can operate ?

means ,in shell script if i have set a value Y=100000000000( more than 10 digit) and Z =100000000000 ( more than 10 digit).
and do "expr $Y + $Z" i should get 200000000000, but i am getting some negative value . If i use 9 digit numbers for Y and Z i will get correct output .

Please tell me why it is happeing and how to over come the same

Bibith Dathan

Re: Shell script problem

James R. Ferguson — Thu, 16 Oct 2008 15:35:41 GMT

Hi:

The shell is using 32-bit arithmetic and you are seeing an overflow. See our discussion here:

http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1273761

Regards!

...JRF...

Re: Shell script problem

Laurent Menase — Fri, 17 Oct 2008 07:30:56 GMT

Hi Bibith,

If you want to use large numbers you need to use bc as coprocess.
i.e.:
a=$(echo "$Z+$Y" |bc)
or ksh coprecess

bc |& # start bc as coprocess
exec 3>&p 4<&p
echo "$Z+$Y" >&3
read result <&4
echo $result

echo ".+$Z" >&3
read result <&4
echo $result

echo ".*$Z" >&3
read result <&4
echo $result
exec 3<&- 4<&- # to exit the coprocess

bc is using unlimited arithmetic.
if yu want floating points or mathematical functions use "bc -l"