calculate 13 months ago

Shell Programming and Scripting
1

hi,
I have a big file that contains datas since 4 years ago.

I need re-create this file but just lines that are 13 months ago from today.

see what I have: ( I have a file.ksh that calls this file.scl ok !!)

======== file.scl ================
/STATISTICS=stderr
/STABLE
/NODUPLICATES
/EXECUTE " today=`date +%Y%m%d` "
/EXECUTE " 13m_ago=`expr ${today} - 10000` "
/INFILE=$PAR_SCL1
/FIELD=(CONTA_CORRENTE, POSITION=1, SIZE=13)
/FIELD=(DATA_VENCIMENTO, POSITION=50, SIZE=10)
/CONDITION=(cond1, TEST=(DATA_VENCIMENTO > ($13m_ago) )
/INCLUDE=(CONDITION=cond1)
/KEY=(NUMERO_FATURA, ASCENDING)
/OUTFILE=$PAR_SCL2
/FIELD=(CONTA_CORRENTE, POSITION=1, SIZE=13)
/FIELD=(DATA_VENCIMENTO, POSITION=50, SIZE=10)

============================================

"DATA_VENCIMENTO" is the date that have to be in the maximum equal 13 months ago.
the layout of DATA_VENCIMENTO is 20071115 , for exemple.

I've already see the topic ( http://www.unix.com/answers-frequently-asked-questions/13785-yesterdays-date-date-arithmetic.html\) but it didn't help me ...

My Unix is Solaris.

does somebody can help ?
thanks , Andrea.

2 
$ cat 13months_ago
#! /usr/bin/ksh

for input in 20071115 20071105 20070105 ; do

        year=${input%????}
        day=${input#??????}
        month=${input#????}
        month=${month%??}
        month=${month#0}
        day=${day#0}
        print -n $input $year $month $day

        ((year=year-1))
        ((month=month-1))
        if ((!month)) ; then
                ((year=year-1))
                month=12
        fi
        typeset -Z2 newday newmonth
        newday=$day
        newmonth=$month
        output=${year}${newmonth}${newday}
        print -- " -->" $year $month $day $output
done
exit 0
$ ./13months_ago
20071115 2007 11 15 --> 2006 10 15 20061015
20071105 2007 11 5 --> 2006 10 5 20061005
20070105 2007 1 5 --> 2005 12 5 20051205
$
3

Perderabo, thanks but your example didn�t works for me.

but I found the solution:

in my main program I calculate 13 months ago

hoje=`date +%Y%m%d`
data_13m=`expr ${hoje} - 10200`

and then, I've send the variable data_13m to the file.scl

export PAR_SCL3=${data_13m}

in the file.scl I did:

.
.
/EXECUTE "$PAR_SCL3"
/INFILE=$PAR_SCL1
/FIELD=(CONTA_CORRENTE, POSITION=1, SIZE=13)
/FIELD=(DATA_VENCIMENTO, POSITION=50, SIZE=10)
/CONDITION=(cond1, TEST=(DATA_VENCIMENTO > $PAR_SCL3 ))

and it worked !
by.

4

You are in effect subtracting 1 year and 2 months from the date. If that is your defintion of "13 months ago", you could change my script to
((month=month-2))
if ((month<1)) ; then

Note that your method will fail if the original date is in january or february.