Hi,
I am trying to process the file for next month (if this month is 03 then I'll need to look at 04 files)
I use month = `date + %m` to get value of 03 for this month
If I use month='expr $month + 1` it will give me 4 instead of 04. I then use month=`"0"$month` to covert it to 04.
Also if use my way when it reach to >10 then I'll need to covert again.
I would like to know is there any better way to to this?

I was trying to do like this:
while [condition]; do
something...
#I want add if here like:
month=`date +%m`
month=`$month + 1`
if ($month<10) month=`"0"$month
if ($month=13) month=01
something...
done

for some reason it doesn't work.
anything wrong? Please advice.
Thanks

Once you are done with all your arithmetic, use the external printf command (similiar to the "C" version of printf). If the number is only 1 digit it'll prepend a 0:

#!/bin/sh

m=9
m=`printf "%02d\n" $m`
echo $m

n=11
n=`printf "%02d\n" $n`
echo $n

Alternatively, use:

date -d 'next month' '+%m'

if your 'date' command is fully featured.

Thank you all for the help.
Nails' way works for me perfect
unfortunately, my 'date' is not fully functioned so I can't use Wolfbone's way

Now I have another question: when I process next month
month=`expr $month + 1`
if $month=13 month=1 -- this one is not working. where I did wrong? it says:" 'if' unmatched"
please advice.

Thanks

You don't have the correct if syntax:

month=12
month=`expr $month + 1`
if [ $month == 13 ]
then
month=1
fi
echo $month