Date is entered in mm/dd/yyyy format using a keyboard. Various conditions are applied to make sure date is valid. Read the program comments to get idea about program logic.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 | #!/bin/bash # Shell program to find the validity of a given date # ----------------------------------------------- # Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/> # This script is licensed under GNU GPL version 2.0 or above # ------------------------------------------------------------------------- # This script is part of nixCraft shell script collection (NSSC) # Visit http://bash.cyberciti.biz/ for more information. # ------------------------------------------------------------------------- # store day, month and year dd=0 mm=0 yy=0 # store number of days in a month days=0 # get day, month and year echo -n "Enter day (dd) : " read dd echo -n "Enter month (mm) : " read mm echo -n "Enter year (yyyy) : " read yy # if month is negative (<0) or greater than 12 # then it is invalid month if [ $mm -le 0 -o $mm -gt 12 ]; then echo "$mm is invalid month." exit 1 fi # Find out number of days in given month case $mm in 1) days=31;; 2) days=28 ;; 3) days=31 ;; 4) days=30 ;; 5) days=31 ;; 6) days=30 ;; 7) days=31 ;; 8) days=31 ;; 9) days=30 ;; 10) days=31 ;; 11) days=30 ;; 12) days=31 ;; *) days=-1;; esac # find out if it is a leap year or not if [ $mm -eq 2 ]; # if it is feb month then only check of leap year then if [ $((yy % 4)) -ne 0 ] ; then : # not a leap year : means do nothing and use old value of days elif [ $((yy % 400)) -eq 0 ] ; then # yes, it's a leap year days=29 elif [ $((yy % 100)) -eq 0 ] ; then : # not a leap year do nothing and use old value of days else # it is a leap year days=29 fi fi # if day is negative (<0) and if day is more than # that months days then day is invaild if [ $dd -le 0 -o $dd -gt $days ]; then echo "$dd day is invalid" exit 3 fi # if no error that means date dd/mm/yyyy is valid one echo "$dd/$mm/$yy is a vaild date" |