topic Re: integer math in ksh in Operating System - Linux

integer math in ksh

dictum9 — Tue, 07 Aug 2007 08:44:30 GMT

How does one multiple two variables in standard ksh?

Re: integer math in ksh

James R. Ferguson — Tue, 07 Aug 2007 08:49:43 GMT

Hi:

# X=2;Y=8;Z=$((X*Y));echo ${Z}
16

Regards!

...JRF...

Re: integer math in ksh

James R. Ferguson — Tue, 07 Aug 2007 08:53:25 GMT

Hi (again):

...I should add that if you are doing arithmetic in a shell, 'typeset'ing your variables to integers speeds things up a bit, too:

#!/usr/bin/ksh
typeset -i X=2
typeset -i Y=8
typeset -i Z
Z=$((X*Y))
echo ${Z}

Regards!

...JRF...

Re: integer math in ksh

dictum9 — Tue, 07 Aug 2007 09:01:58 GMT

The following works on the command line, but doesn't work in the shell script. The exact line that blows up is the multiplication line.

#!/bin/ksh

# find total space available in each VG

for VG in `strings /etc/lvmtab |grep -v dsk`
do
echo processing $VG
TOTAL_PE=`vgdisplay -v $VG | grep ^"Total PE" | awk '{print $3}'`

PE_SIZE=`vgdisplay -v $VG | grep ^"PE Size (Mbytes)" | awk '{print $4}'`

echo TOTAL_PE_=$TOTAL_PE
echo PE_SIZE=$PE_SIZE

((TOTAL_SIZE=$TOTAL_PE * $PE_SIZE)) # does not work in ksh
# ((TOTAL_SIZE=$TOTAL_PE * $PE_SIZE)) # works in dtksh

echo TOTAL_SIZE=$TOTAL_SIZE

done

Re: integer math in ksh

Oviwan — Tue, 07 Aug 2007 09:05:09 GMT

Hey

change this:
((TOTAL_SIZE=$TOTAL_PE * $PE_SIZE))
to this:

TOTAL_SIZE=$(( ${TOTAL_PE} * ${PE_SIZE} ))

Regards

Re: integer math in ksh

James R. Ferguson — Tue, 07 Aug 2007 09:13:51 GMT

Hi:

Exactly what error do you see? This works for me. You could try running with a trace:

# ksh -x my.sh 2>&1|more

Regards!

...JRF...

Re: integer math in ksh

dictum9 — Tue, 07 Aug 2007 09:30:57 GMT

Oviwan,

this worked beautifully, thanks.

Re: integer math in ksh

dictum9 — Tue, 07 Aug 2007 09:36:22 GMT

James Ferguson,

that one works well also:

total_size=$((total_pe*pe_size))