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understanding part of an awk script

 
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# 1  
Old 01-23-2010
understanding part of an awk script
Hi

I have an awk script running in ksh in which a section of code is picking out the datetime as follows:
Code:
 
dia=`echo $starttime | nawk '{ printf "%02d\n", substr($1,9,2)}'`
mes=`echo $starttime | nawk '{ printf "%02d\n", substr($1,6,2)}'`
ano=`echo $starttime | nawk '{ printf "%02d\n", substr($1,1,4)}'`
hora=`echo ${starttime#* } | nawk '{ printf "%02d\n", substr($1,1,2)}'`
minuto=`echo ${starttime#* } | nawk '{ printf "%02d\n", substr($1,4,2)}'`
 
# startime='2010-01-03 15:00'

and then assigning it to ftime as ftime=$ano$mes$dia$hora$minuto

But I don't understand how the above code is picking out the year, month, day, hour and minute.

Bearing the above starttime in mind, what would ftime be?

If I've missed any info out, please excuse me and let me know what it is?

Regards
Last edited by Scott; 01-23-2010 at 10:21 AM.. Reason: Please use code tags
# 2  
Old 01-23-2010
Well you can just execute and see:
Code:
$ starttime='2010-01-03 15:00'
$ dia=`echo $starttime | nawk '{ printf "%02d\n", substr($1,9,2)}'`
$ mes=`echo $starttime | nawk '{ printf "%02d\n", substr($1,6,2)}'`
$ ano=`echo $starttime | nawk '{ printf "%02d\n", substr($1,1,4)}'`
$ hora=`echo ${starttime#* } | nawk '{ printf "%02d\n", substr($1,1,2)}'`
$ minuto=`echo ${starttime#* } | nawk '{ printf "%02d\n", substr($1,4,2)}'`
$ ftime=$ano$mes$dia$hora$minuto
$ echo $ftime
201001031500

It is rather inefficient code though, as this this would accomplish the same if your shell supports it:
Code:
ftime=${starttime//[^0-9]}

-or-
Code:
ftime=$(echo "$starttime" | sed 's/[^0-9]//g')

# 3  
Old 01-23-2010
Thanks so much...Appreciated.

Would it be possible just to explain how this is working:

dia=`echo $starttime | nawk '{ printf "%02d\n", substr($1,9,2)}'`

?

Regards
# 4  
Old 01-23-2010
Echo the contents of starttime into nawk (do not preserve spacing)
substr($1,9,2) means take position 9 and 10 from this string
printf "%02d\n means print to digits and prepad with a zeroes if it there are fewer than to digits and add a carriage return (which is not implicit in the case of printf)
The backticks (`) are used to assign the result to variable dia.
 
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