topic Re: Division Operation in Operating System - HP-UX

Division Operation

Gilbert Standen_1 — Wed, 23 Feb 2005 11:30:13 GMT

how do i set precision of a result ? At command line:
#let m=7
#let n=2
#let r=$m/$n
#echo $r
3

Only want the integer portion of calc so this is result needed.

How to guarantee that when run code on an arbitrary UNIX box it's going to return same precision ? How to incorporate precision of result into the code ?

Re: Division Operation

RAC_1 — Wed, 23 Feb 2005 11:40:19 GMT

Shell arithmatic oprations are not precise and has limitations.

You can do "echo "4/3"|bc"

Anil

Re: Division Operation

Rajeev Tyagi — Wed, 23 Feb 2005 11:42:47 GMT

Gilbert,

One of the method you can use is.

touch /tmp/anyfile
export m=7
export n=2
cat /tmp/anyfile | awk '{print '$m'/'$n'}'

Re: Division Operation

A. Clay Stephenson — Wed, 23 Feb 2005 11:54:07 GMT

You don't need to concern yourself at all because all shell arithmatic is integer (there is one shell that can do floating-point math but you must be explicit in your shell commands) and thus all will truncate (not round) the result.

It's generally considered better form to type your variables so that

typeset -i m=7
is better than
let m=7

Re: Division Operation

Gilbert Standen_1 — Wed, 23 Feb 2005 11:54:23 GMT

Got it. Much appreciated!
echo "scale=0; 10/3" | bc
3
echo "scale=2; 10/3" | bc

Re: Division Operation

A. Clay Stephenson — Wed, 23 Feb 2005 12:21:07 GMT

You really don't have it. There is no reason to call the external utility bc (or awk, Perl) because the shell can only do integer math. It's already done it for you. Your original approach is perfectly portable. The times that external programs like bc are called are those in which non-integer math are needed.

Re: Division Operation

Gilbert Standen_1 — Wed, 23 Feb 2005 12:28:31 GMT

Had replied before seeing your post, see now that integer math is the default, which is good for me.

Regarding your pointer on the uses of "let" vs. "typeset" what are the advantages of "typeset" :-)

here's a related question:

typeset -i p=50
typeset -i q=$p
typeset -i r=1

Have made the change you suggested for my uses of "let" but when "read" is used, what are the implications ? Is there a way to sort of use "typeset" when using "read" at the end of a string of piped ops ?

ls | wc -l | sed 's/^[ \t]*//;s/[ \t]*$//' | read histfilect

Re: Division Operation

A. Clay Stephenson — Wed, 23 Feb 2005 12:35:05 GMT

Yes, simply put the typeset in another statement.

typeset -i histfileect=0
ls | wc -l | sed 's/^[ \t]*//;s/[ \t]*$//' | read histfilect

The typeset applies to all following references of the variable.