I found a script online that compares two dates and gives output as
number of days in between both the dates. It works perftecly fine.
Here is the script I found online

---------------------------------------------------------------------------------

# days-between.sh: Number of days between two dates.
# Usage: ./days-between.sh [M]M/[D]D/YYYY [M]M/[D]D/YYYY
#
# Note: Script modified to account for changes in Bash, v. 2.05b +,
#+ that closed the loophole permitting large negative
#+ integer return values.

ARGS=2 # Two command line parameters expected.
E_PARAM_ERR=65 # Param error.

REFYR=1600 # Reference year.
CENTURY=100
DIY=365
ADJ_DIY=367 # Adjusted for leap year + fraction.
MIY=12
DIM=31
LEAPCYCLE=4

MAXRETVAL=255 # Largest permissible
#+ positive return value from a function.

diff= # Declare global variable for date difference.
value= # Declare global variable for absolute value.
day= # Declare globals for day, month, year.
month=
year=


Param_Error () # Command line parameters wrong.
{
echo "Usage: `basename $0` [M]M/[D]D/YYYY [M]M/[D]D/YYYY"
echo " (date must be after 1/3/1600)"
exit $E_PARAM_ERR
}


Parse_Date () # Parse date from command line params.
{
month=${1%%/**}
dm=${1%/**} # Day and month.
day=${dm#*/}
let "year = `basename $1`" # Not a filename, but works just the
same.
}


check_date () # Checks for invalid date(s) passed.
{
[ "$day" -gt "$DIM" ] || [ "$month" -gt "$MIY" ] ||
[ "$year" -lt "$REFYR" ] && Param_Error
# Exit script on bad value(s).
# Uses or-list / and-list.
#
# Exercise: Implement more rigorous date checking.
}


strip_leading_zero () # Better to strip possible leading zero(s)
{ #+ from day and/or month
return ${1#0} #+ since otherwise Bash will interpret them
} #+ as octal values (POSIX.2, sect 2.9.2.1).


day_index () # Gauss' Formula:
{ # Days from March 1, 1600 to date passed as
param.
# ^^^^^^^^^^^^^
day=$1
month=$2
year=$3

let "month = $month - 2"
if [ "$month" -le 0 ]
then
let "month += 12"
let "year -= 1"
fi

let "year -= $REFYR"
let "indexyr = $year / $CENTURY"


let "Days = $DIY*$year + $year/$LEAPCYCLE - $indexyr \
+ $indexyr/$LEAPCYCLE + $ADJ_DIY*$month/$MIY + $day -
$DIM"
# For an in-depth explanation of this algorithm, see
#+ http://weblogs.asp.net/pgreborio/arc...06/347968.aspx


echo $Days

}


calculate_difference () # Difference between two day
indices.
{
let "diff = $1 - $2" # Global variable.
}


abs () # Absolute value
{ # Uses global "value" variable.
if [ "$1" -lt 0 ] # If negative
then #+ then
let "value = 0 - $1" #+ change sign,
else #+ else
let "value = $1" #+ leave it alone.
fi
}



if [ $# -ne "$ARGS" ] # Require two command line params.
then
Param_Error
fi

Parse_Date $1
check_date $day $month $year # See if valid date.

strip_leading_zero $day # Remove any leading zeroes
day=$? #+ on day and/or month.
strip_leading_zero $month
month=$?

let "date1 = `day_index $day $month $year`"


Parse_Date $2
check_date $day $month $year

strip_leading_zero $day
day=$?
strip_leading_zero $month
month=$?

date2=$(day_index $day $month $year) # Command substitution.


calculate_difference $date1 $date2

abs $diff # Make sure it's positive.
diff=$value

echo $diff

exit 0

# Compare this script with
#+ the implementation of Gauss' Formula in a C program at:
#+ http://buschencrew.hypermart.net/software/datedif
-------------------------------------------------------------------------------------------------------------------------

Now I want to use about script in my awk program. I tried to do that
by creating it as a shell function and then call it from with in awk
like this.

DIFF_DATE='
function diff_date {
# ABOVE MENTIONED SCRIPT IS COPIED HERE
} #End of shell function diff_DATE
' #End of DIFF_DATE

export DIFF_DATE

awk 'BEGIN{
#some awk business

date1=1/1/2007
date2=2/2/2008

system(ENVIRON["DIFF_DATE"]"diff_date" "date1" "date2)

#more awk stuff
}'

But this does not work. Then I tried the following


function diff_date {
# ABOVE MENTIONED SCRIPT IS COPIED HERE
} #End of shell function diff_DATE

CALL='
function call_diff_date {
diff_date $1 $2
} # End of function.
' #End of CALL
export DIFF_DATE

awk 'BEGIN{
#some awk business

date1=1/1/2007
date2=2/2/2008

system(ENVIRON["DIFF_DATE"]"diff_date" "date1" "date2)


But this gives me an error that date_diff not found.

In the above script if I call call_diff_date function with in shell
script (not in awk) then it works fine. like this

function diff_date {
# ABOVE MENTIONED SCRIPT IS COPIED HERE
} #End of shell function diff_DATE


function call_diff_date {
diff_date $1 $2
} # End of function.

call_diff_date

above script works fine. but it gives errors with I try to call it
from awk. Here I would like to mention that the way of calling shell
functions mentioned above works fine. But in case of nested shell
functions it is a problem.

Any ideas why?

Reargds,
Rachit Bhatia.

rachit7@gmail.com wrote:

> I found a script online that compares two dates and gives output as
> number of days in between both the dates. It works perftecly fine.

<snip>

> above script works fine. but it gives errors with I try to call it
> from awk. Here I would like to mention that the way of calling shell
> functions mentioned above works fine. But in case of nested shell
> functions it is a problem.
>
> Any ideas why?

Already answered in comp.lang.awk. Please don't multi-post.

Ed.

On Jul 30, 3:56 pm, Ed Morton <mor...@lsupcaemnt.com> wrote:
> rach...@gmail.com wrote:
> > I found a script online that compares two dates and gives output as
> > number of days in between both the dates. It works perftecly fine.
>
> <snip>
>
> > above script works fine. but it gives errors with I try to call it
> > from awk. Here I would like to mention that the way of calling shell
> > functions mentioned above works fine. But in case of nested shell
> > functions it is a problem.
>
> > Any ideas why?
>
> Already answered in comp.lang.awk. Please don't multi-post.
>
> Ed.

How is this a multi-post if the answer is in a different Usenet group?
Do we have to join ALL the groups just to participate in this one?
That seems Draconian. If it's posted somewhere in this group, then I
see how it's a multi-post, otherwise, could you explain your position?

FYI: I'm a newbie to this group, but I'm stubborn and opinionated. ;-)

Dave

On 31 Jul., 16:12, EvilDave <dave.tur...@verizonwireless.com> wrote:
> On Jul 30, 3:56 pm, Ed Morton <mor...@lsupcaemnt.com> wrote:
>
> > Already answered in comp.lang.awk. Please don't multi-post.
>
> > Ed.
>
> How is this a multi-post if the answer is in a different Usenet group?
> Do we have to join ALL the groups just to participate in this one?
> That seems Draconian. If it's posted somewhere in this group, then I
> see how it's a multi-post, otherwise, could you explain your position?

http://en.wikipedia.org/wiki/Crossposting

And see also the parts where multi-posting is mentioned.

Janis

>
> FYI: I'm a newbie to this group, but I'm stubborn and opinionated. ;-)
>
> Dave

On 31 Jul., 16:12, EvilDave <dave.tur...@verizonwireless.com> wrote:
> On Jul 30, 3:56 pm, Ed Morton <mor...@lsupcaemnt.com> wrote:
>
> > Already answered in comp.lang.awk. Please don't multi-post.
>
> > Ed.
>
> How is this a multi-post if the answer is in a different Usenet group?
> Do we have to join ALL the groups just to participate in this one?
> That seems Draconian. If it's posted somewhere in this group, then I
> see how it's a multi-post, otherwise, could you explain your position?

http://en.wikipedia.org/wiki/Crossposting

And see also the parts where multi-posting is mentioned.

Janis

>
> FYI: I'm a newbie to this group, but I'm stubborn and opinionated. ;-)
>
> Dave

Janis wrote:
> On 31 Jul., 16:12, EvilDave <dave.tur...@verizonwireless.com> wrote:
>
>>On Jul 30, 3:56 pm, Ed Morton <mor...@lsupcaemnt.com> wrote:
>>
>>
>>>Already answered in comp.lang.awk. Please don't multi-post.
>>
>>> Ed.
>>
>>How is this a multi-post if the answer is in a different Usenet group?
>>Do we have to join ALL the groups just to participate in this one?
>>That seems Draconian. If it's posted somewhere in this group, then I
>>see how it's a multi-post, otherwise, could you explain your position?
>
>
> http://en.wikipedia.org/wiki/Crossposting
>
> And see also the parts where multi-posting is mentioned.

See also http://www.blakjak.demon.co.uk/mul_crss.htm.

Ed.

I'm inferring the query of the thread only through the subject
line: posters, don't elide the original text -- and least not the
first person to respond!

What if you didn't have to leave awk(1) to calculate date-time
differences? How about dateplus, by Bob Orlando.

"dateplus.awk":
http://www.orlandokuntao.com/dateplus.html
http://www.unixreview.com/documents/s=8989/ur0403c/
http://www.unixreview.com/documents/...3c/ur0403c.htm

And I might as well include:

"Secular American Holidays"
http://www.orlandokuntao.com/holidays_awk.txt

=Brian