Need help with date arithmetic please

Shell Programming and Scripting
1

Hello fellow forum members,

I wrote below piece of code to calculate the date after a given date -

date=$DATE_FINAL
declare -a  max_month=(0 31 28 31 30 31 30 31 31 30 31 30 31)
eval $(echo $date|sed 's!\(....\)\(..\)\(..\)!year=\1;month=\2;day=\3!')
(( year4=year%4 ))
(( year100=year%100 ))
(( year400=year%400 ))
if [ \( $year4 -eq 0 -a \
        $year100 -ne 0 \) -o \
     $year400 -eq 0 ]
then
declare -a  max_month=(0 31 28 31 30 31 30 31 31 30 31 30 31)
fi
day=$((day+1))
if [ $day -gt ${max_month[$month]} ] >| /wload/baot/home/baoted9/logs_bde27_conversion_1/ataa_display.logs 2>&1
then
  day=1
  month=$((month+1))
  if [ $month -gt 12 ]
  then
    year=$((year+1))
    month=1
  fi
fi
if [ $month -eq "08" ] ||  [ $month -eq "09" ]
then
future_date_final=$(echo $year"$month"$day)
else
future_date_final=$(printf "%4.4d%2.2d%2.2d" $year $month $day)
fi
echo "this is your final business date $future_date_final"

It calculates the date correctly however throws an error at the end of the code as below -

line 79: 08: value too great for base (error token is "08")

It just looks too ugly, not sure how to remove it as otherwise code is working fine, tried redirecting it to a log file still appearing.
Also, I am facing issue with below code for a plain cd command with code highlighted in red -

echo "pset  date $Param_date_1"
cd /wload/baot/home/baotasa0/sandboxes_finance/ext_ukba_bde/pset >| /wload/baot/home/baoted9/logs_bde27_conversion_1/at_display.logs 2>&1
sh UKBA_publish.sh UKBA $Param_date_1 3 >| /wload/baot/home/baoted9/logs_bde27_conversion_1/ate_display.logs 2>&1

Error is -

./auto2.sh: line 190: syntax error: unexpected end of file

Any leads will be greatly appreciated.

2

My opinion is that coding date arithmetic and not using existing tools is foolish and error prone. I cannot tell what system you are on, most systems have perl.

#!/bin/sh
# ago.shl
# usage: ago.shl [number] 
#       for date [number] days ago,
#       ./ago.shl -3 
#   parm $1 == days in past e.g., yesterday = -1,
#              days in future e.g., tomorrow = 1 

ago()
{
   perl -e ' my $delta = $ARGV[0];
             $delta*=86400;          #  seconds in a day
             $delta=time + $delta;   #  epoch seconds today plus ( or minus) delta
              ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
                                                            localtime($delta);
             
             printf("%04d%02d%02d%02d%02d.%02d\n",
                     $year+1900, $mon+1, $mday;
             ' $1
}

# example usage of the function ago

when=$(ago $1)
echo "$when"

exit 0

If you are on Linux I would HIGHLY recommend that you use the date command which is very reliable and actually supports options like yesterday and tomorrow. Skip using the perl above.

3

The "value too great for base" happens because there is a number with a leading zero, and bash assumes octal, and 8 is too high for an octal number.
It happens with

day=$((day+1))

or later with month .
As always there is an escape from such (mis)feature: a 10# prefix forces a base10=decimal

day=$((10#$day+1))
month=$((10#$month))

Now the leading zero are removed.

---------- Post updated at 11:15 ---------- Previous update was at 10:52 ----------

You certainly want

if [ \( $year4 -eq 0 -a \
        $year100 -ne 0 \) -o \
     $year400 -eq 0 ]
then
declare -a  max_month=(0 31 29 31 30 31 30 31 31)
fi

As Jim said, such calculations are error prone.
perl is safer because it uses the libc routines.

4

Also try my general purpose date script which is a limited gnu-date-alike written in Perl.

5

You might like this for the leap year stuff:

function mthdays { TA=312831303130313130313031; printf "%d\n" $(( ${TA:($1-1)*2:2} + ($1!=2?0:!($2%4) && ($2%100) || !($2%400)))); }
echo $(mthdays 2 2016)
29
echo $(mthdays 2 2015)
28

For the function definition, you need to switch off bash 's history : set +H

6

Hi.

A collection of suggestions:

Date, time arithmetic, math

        1) gnu date

        2) ksh ( version 93, not 88; ksh93 M 93t+ ) printf, e.g:
           printf "%(%Y-%m-%d)T\n" "yesterday"
           Many more examples ( as of 2017.07 ):
           http://blog.fpmurphy.com/2008/10/ksh93-date-manipulation.html

        3) date.pl (limited arithmetic, but "date.pl -d '- 1 day'" works)
           ( http://www.unix.com/tips-tutorials/
           239167-general-purpose-date-script.html )

        4) dconv et al, e.g. ddiff, dconv, strptime (parsing), etc.
           ( dateutils: http://www.fresse.org/dateutils/ )

        5) tm2tm (, OK in 32-bit; fails to compile in 64-bit)
           ( http://www.unix.com/shell-programming-scripting/
           146216-date-difference-between-freebsd-linux.html#post302463136 )

        6) perl custom formatting (with function POSIX::strftime, "perldoc POSIX")

        7) date-cpan.pl, cpan perl date
           ( http://cpansearch.perl.org/src/CWEST/ppt-0.14/src/date/date.jgross )

        8) For small changes, say, "yesterday" in bash, ksh
           TZ=CST+24 date +%Y%m%d
           csh, tcsh
           setenv TZ CST+24 ; date +%Y%m%d

        9) Check for legal date:
           manstat:validata ( http://oldwww.acm.org/perlman/stat/ )

        10) Check for legal date:
            validate (local perl code)

        11) Shell, ksh, date calculations:
            www.unix.com/unix-for-dummies-questions-and-answers/4870-days-elapsed-between-2-dates.html

Best wishes ... cheers, drl

7

Thanks madeingermany...I tried but the error is still because of line I mentioned in my first post n I am using AIX so most of the commands don't work...I need to do date calculation for an arbitrary date so tz doesn't work for me either :frowning:
~Ekta

8

Did you replace the day=$((day+1)) by the two lines I gave you?
And do you run your script with bash?
Run it with

bash -xv ./scriptname ...

and you see what it does.

9

I tried that, but it didn't work and threw error on the same line I mentioned in the first post :frowning: ...will run with -xv option tomorrow n share the logs

10

Exactly the situation my general purpose date script was designed for - when you need the GNU tools and don't have them.