UNIX for Dummies Questions & Answers

$ echo "10/22/2013 10/30/2013" | \
awk '
    function dates(date){
                          split(date,A,"/")
                          return int(mktime(A[3]" "A[1]" "A[2]" " 00 " " 00 " " 00) / 86400)
                        }
                        {
                              print $0,dates($2)-dates($1), "Days"
                        }'

10/22/2013 10/30/2013 8 Days

$ echo "10/22/2013" | \
awk '

function Cmd(cmde,result){
                              while ((cmde | getline line) > 0)
                                  {
                                      result = result (result=="" ? "" : "\n")line
                                  }
                              close(cmde)
                              return result
                         }

    function dates(date){
                              split(date,A,"/")
                              return int(mktime(A[3]" "A[1]" "A[2]" " 00 " " 00 " " 00) / 86400)
                        }
                        {
                              diff = dates(Cmd("date +%m/%d/%Y"))-dates($1)
                              msg  = diff < 30 ? "true" : "False"
                              print $0,Cmd("date +%m/%d/%Y"),diff,"Days",msg 
                        }'

10/22/2013 11/25/2013 34 Days False

11/22/2013 11/25/2013 3 Days true

#!/usr/bin/env bash

# @(#) s1	Demonstrate days between dates with perl Date::Calc module.

# 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 perl divepm
pe
pe " Modules used by perl code p1:"
divepm -q -i p1

# Set test date and length:
length=30
TD=${1-"10/22/2013"}

pl " Results for date $TD:"
./p1 $TD && pe " Less than $length" || pe " Greater than $length"

TD="11/15/2013"
pl " Results for date $TD:"
./p1 $TD && pe " Less than $length" || pe " Greater than $length"

# Set a new length.
length=5
pl " Results for date $TD, length $length:"
./p1 $TD $length && pe " Less than $length" || pe " Greater than $length"

exit 0

$ ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian 5.0.8 (lenny, workstation) 
bash GNU bash 3.2.39
perl 5.10.0
divepm (local) 1.4

 Modules used by perl code p1:
 1.04	strict
 1.06	warnings
 5.4	Date::Calc

-----
 Results for date 10/22/2013:
 today is 2013, 11, 25, length = 30
 input date for comparison = 2013, 10, 22
 Difference = 34
 Greater than 30

-----
 Results for date 11/15/2013:
 today is 2013, 11, 25, length = 30
 input date for comparison = 2013, 11, 15
 Difference = 10
 Less than 30

-----
 Results for date 11/15/2013, length 5:
 today is 2013, 11, 25, length = 5
 input date for comparison = 2013, 11, 15
 Difference = 10
 Greater than 5