topic Numeric comparaison with ksh in Operating System - HP-UX

Numeric comparaison with ksh

Leo The Cat — Sat, 25 Oct 2008 19:11:47 GMT

Hello

I've a script with something like this :

SA=$(df -m -P | grep -i /logs | awk '{print $4}')

if [[ $SA < 900.25 ]] ;then
...

Here, is it a numeric compare or a string compare ?

Bests regards
Den

Re: Numeric comparaison with ksh

Leo The Cat — Sat, 25 Oct 2008 19:44:14 GMT

I think that I could the necessary -le as

if [[ $SA -le 900.25 ]] ;then

correct in any situation?

Regards
Den

Re: Numeric comparaison with ksh

Leo The Cat — Sat, 25 Oct 2008 19:49:22 GMT

sorry -gt

;-)

Re: Numeric comparaison with ksh

James R. Ferguson — Sat, 25 Oct 2008 20:51:15 GMT

Hi Den:

http://www.docs.hp.com/en/B2355-60130/ksh.1.html

For shells, the mathmatical symbol operators compare *strings* and the English-like ones (-lt, -gt, -le, -ge, -eq -ne) perform *numeric* comparisons.

Regards!

...JRF...

Re: Numeric comparaison with ksh

Hein van den Heuvel — Sat, 25 Oct 2008 21:57:59 GMT

Hmm, what version of Unix is that ?!

HP-UX 11.31 does not have a -m option for df, only -k.

Why not have awk do the grepping and the comparing?
A shell is not going to do the decimal fractions.
Awk is happy to.

What will your scipt do when someone mounts /logs_backup or some such?

SA=$(df -m -P | awk -i '/\/logs$/{print int ($4 - 900.25) }')

Note: hpux does not have a -i with the standard awk. gawk has that. either speel out the mount point in proper casing or activate IGNORECASE or lowercase() the column.

fwiw,
Hein.

Re: Numeric comparaison with ksh

Dennis Handly — Sun, 26 Oct 2008 11:09:27 GMT

>is it a numeric compare or a string compare?

As mentioned, this is a string compare unless you have it within arithmetic expressions, (( )) or use awk(1). And even there it will fail since ksh and sh don't do floating point. You need ksh93:
http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1151323

>Hein: activate IGNORECASE or lowercase() the column.

HP-UX's awk doesn't have IGNORECASE or lowercase() but has tolower().

Re: Numeric comparaison with ksh

Leo The Cat — Wed, 17 Dec 2008 21:31:33 GMT

Thanks guys.