Small DateValidation bash script

Below is a program I'M trying to write that will take an 8 digit date and validate whether or not it's a valid date. I'M very new to shell scripting so I really a have no idea what I'M going. Could you take a look and let me know what all I'M doing wrong here? Thanks.

Code:

---

#! /bin/bash -x

# This is the calender array for the DateValidation program
CALENDER=(31 28 31 30 31 30 31 31 30 31 30 31)

read -p "Enter a date for validation: " DATE

# establish the varible LEN to hold the number of characters in Date, 8 is the only valid number
LEN=$(echo ${#DATE})

if [ $LEN -eq 8 ]; then #{
 
        # set date dariables MM, DD, & YY
        export MM=${DATE:0:2}
        export DD=${DATE:2:2}
        export YY=${DATE:4:4}

        if [ ${YY} -gt 0 ]; then #{
                if [ ${MM} -gt 0 & < 13 ]; then #{
                        if [ ${MM} -eq 2 ]; then #{
                                if [ is_leap_year ${YY} == 1 ]; then #{
                                        if [ ${DD} -gt 0 & -le 29 ]; then #{
                        elif [ ${DATE} -gt 0 & -le ${CALENDER[${MM}]}] #}}}}}}

        echo "${DATE} is a valid date"
else
        "${DATE} is an invalid date"
fi #}

#############################
### FUNCTION-is_leap_year ###
#############################

is_leap_year() {

if [ 0 -eg ${YY} % 4 & 0 -ne {YY} % 100 or 0 -eq ${YY} % 400 ]; then #{

        return true #}
else #{
        return false #}

exit
#END

---

hi,

function should be declared before it's used.

Code:

---

LEN=$(echo ${#DATE}) # echo is useless, so is command substitution
export MM=${DATE:0:2} # exports are useless
if [ ${MM} -gt 0 & < 13 ]; then # a single & puts the process in background, you need 2 to be an AND, but it doesn't work inside test [ ]
# < is redirection from file, 13 is not a file
#  if [ $MM -gt 0 ] && [ $MM -lt 13 ]
if [ is_leap_year ${YY} == 1 ]; then # you need command substitution : if [ "$(is_leap_year "$YY")" -eq 1 ]; then

---

Hi.

Perhaps this skeleton will help:

Code:

---

11 if [ ... ; then
 18  if [ ... ; then
 19    if [ ... ; then
 20      if [ ... ; then
 21        if [ ... ; then
 22          if [ ... ; then
 23          elif [
 24          elif [
 Expected then, but got at line 24:
 26        else
 36          if [ ... ; then
 39          else
 Unbalanced: (if - fi) count: 7

---

Best wishes ... cheers, drl

Thanks guys. Still don't have my script working but what you gave me was some much needed info. Thanks again.

remember that arrays are referenced from 0 and not 1.

1. I presume you have a reason for using the shell, rather than some more powerful scripting language such as perl or python?
2. Once you get your script working, may I suggest a bit of human engineering?
a) validate the input. i.e. months 1-12, etc.
b) allow user to enter dates with / or - as in mm-dd-yyyy
c) allow user to enter dates with yy
d) It always annoys me (as a non USA resident) when programs assume the date is mm-dd-yyyy. This seems to me to be a very illogical format. It is neither ascending order (dd-mm-yyyy) nor descending order. It is not that difficult to allow yyyy/mm/dd or yyyy-mm-dd which AFAIK is the international ISO standard way of doing dates, (as well as mm-dd-yyyy which is what your USA users will probably assume.).

Just my two cents worth.......
pgmer6809