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Maths in shell scripts

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# 1  
Old 01-11-2012
Maths in shell scripts


Need help on this. I need to increment a variable by 1 but retain as 2 characters.

I am using expr to do additions:

$SERIAL can range from 01-99. After adding "1", I need the result to be 2 characters, eg: 02+1 = 03. By default expr will truncate the zero such that 02+1 will become "3" not "03"

Please help. Much appreciated.


Last edited by Franklin52; 01-11-2012 at 07:24 AM.. Reason: Please use code tags for code and data samples, thank you
# 2  
Old 01-11-2012
one way ..
$ cnt=3
$ echo $cnt
$ [ $cnt -lt 10 ] && cnt=0$((cnt))
$ echo $cnt

# 3  
Old 01-11-2012
@jayan_jay: Wouldn't $cnt become 099, if [ $cnt -le 99 ] were in a loop incrementing $cnt by one each time?

@vchee: Try this.
NEWSERIAL=`printf "%02d" $(($SERIAL + 1))`

# 4  
Old 01-11-2012
Originally Posted by balajesuri
@jayan_jay: Wouldn't $cnt become 099, if [ $cnt -le 99 ] were in a loop incrementing $cnt by one each time?

@vchee: Try this.
NEWSERIAL=`printf "%02d" $(($SERIAL + 1))`

Thanks for all the help. It works.
# 5  
Old 01-12-2012
@balaje, yes correct.. while using in loop it might get fail .. Thanks .. Smilie

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