Shell Programming and Scripting

tdate=$( date +"%m/%d/%Y" ) #Today
ydate=$(date +"%m/$(date +"%d" | awk '{ printf ("%02d",($1-1)) }')/%Y") #Yesterday
bydate=$(date +"%m/$(date +"%d" | awk '{ printf ("%02d",($1-2)) }')/%Y") #Day before yesterday

$ tdate=$( date +"%m/%d/%Y" ) # Today

$ ydate=$( date -d" -1 day" +"%m/%d/%Y" ) # Yesterday OR

$ ydate=$( date --date yesterday  +"%m/%d/%Y" ) # Yesterday

$ dydate=$( date -d" -2 day" +"%m/%d/%Y" ) # Day before yesterday OR

$ dydate=$( date --date="2 days ago" +"%m/%d/%Y" ) # Day before yesterday

$ echo $tdate
12/15/2013

$ echo $ydate
12/14/2013

$ echo $dydate
12/13/2013

std=substr($2,4,2) ;                          #start date
end=substr($4,4,2) ;                         #end date
mul=((end-std)-1);                           #no: of full days elapsed in the interval
t1=(3600*substr($3,1,2)+60*substr($3,4,2)+substr($3,7,2)); #total no: of start time seconds
t2=(3600*substr($5,1,2)+60*substr($5,4,2)+substr($5,7,2)); #total no: of end time seconds
if (mul == "-1")                                 #both instances in the same day
t=t2-t1;
else                                               #instances occur in two different days
t=((24*3600)-t1)+(mul*24*3600)+t2;
printf("%02d:%02d:%02d\n",(t/3600),((t/60)%60),t%60);      #time elapsed in HH:MM:YY format

#!/usr/bin/env perl
use Time::Local;
use POSIX qw(strftime);

while (my $ln = <STDIN>) {
    my ($d, $smt, $sdy, $sy, $sh, $sm, $ss, $emt, $edy, $ey, $eh, $em, $es) = split(/[ \/:]/, $ln);
        my $t = abs(timelocal($es,$em,$eh,$edy,$emt-1,$ey) -
                timelocal($ss,$sm,$sh,$sdy,$smt-1,$sy));

    printf "%02d:%02d:%02d\n", $t / 3600, ($t / 60) % 60, $t % 60;
}

$ ./datediff.pl < infile
00:02:59
30:56:38

#!/usr/bin/env ksh

# @(#) s1       Demonstrate date arithmetic, differences, ddiff, dateutils.
# See:
# https://github.com/downloads/hroptatyr/dateutils/dateutils-0.2.3.tar.xz

# Utility functions: print-as-echo, print-line-with-visual-space, debug.
# export PATH="/usr/local/bin:/usr/bin:/bin"
pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }
C=$HOME/bin/context && [ -f $C ] && $C ksh ddiff

FILE=${1-data1}

pl " Input data file $FILE:"
cat $FILE

pl " Results, first-second, second-first:"
while :
do
  if read v1 d1 t1 d2 t2 v2
  then
    x1=${d1}T${t1}
    x2=${d2}T${t2}
    db "first date-time of pair, x1 [$x1]"
    db "last  date-time of pair, x2 [$x2]"
  else
    break
  fi
  ddiff $x1 $x2 -f '%d days and %S seconds' -i "%m/%d/%YT%T"
  ddiff $x2 $x1 -f '%d days and %S seconds' -i "%m/%d/%YT%T"
  pe
done < $FILE

exit 0

$ ./s1

Environment: LC_ALL = POSIX, LANG = POSIX
(Versions displayed with local utility "version")
OS, ker|rel, machine: SunOS, 5.10, i86pc
Distribution        : Solaris 10 10/08 s10x_u6wos_07b X86
bash GNU bash 3.00.16
ksh M-11/16/88i
ddiff 0.2.6

-----
 Input data file data1:
name1 12/16/2013 10:56:38 12/16/2013 10:59:37 value1
name2 12/16/2013 04:37:41 12/17/2013 11:34:19 value2

-----
 Results, first-second, second-first:
0 days and 179 seconds
0 days and -179 seconds

1 days and 24998 seconds
-1 days and -24998 seconds

NAME
     ddiff - Compute durations between dates and times

SYNOPSIS
     ddiff [OPTION]... DATE/TIME [DATE/TIME]...

DESCRIPTION
     ddiff 0.2.6

     Compute duration from DATE/TIME (the reference date/time) to
     the other DATE/TIMEs given and print the result as duration.
     If the other DATE/TIMEs are omitted read them from stdin.

-rwxr-xr-x   1  105904 Dec 22 12:35 ddiff