[SOLVED] Script for validating a date e.g. 11291985

[Garrett85]

This script whould be able to determine if a date that has been entered in as 8 digits is valid or not.

It will first check that there are 8 digits, if so everything is good.

It will then theck that the month value is > 0 & < 13, if so everything is good.

In order to get the day I need to fist find out if it's leap year or not to determin if the maximum number of da

ys is 28 or 29

I use a function "is_leap_year" to determine if it is or is not leap year.

I use a function "get_day" to check that the day is > 0 & <= CALENDER[MM]

For some reason my program is running the "get_day" function even when the function "is_leap_year" returns true, in that case it would only call "get_day" in the else clause of that code block. Please help I am stumped.

#! /bin/bash -x


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

is_leap_year()
{
        PART1=`expr ${YY} % 4`
        PART2=`expr ${YY} % 100`
        if [[ 0 -eq ${PART1} ]] && [[ 0 -ne ${PART2} ]] || [[ 0 -eq `expr ${YY} % 400` ]]; then
                result=true
	else
		result=false
        fi
}



####################
### END FUNCTION ###
####################

########################
### FUNCTION-get_day ###
########################

get_day()
{
	if [[ ${DD} -gt 0 ]] && [[ ${DD} -le ${CALENDER[${MM}]} ]]; then #{
		DAY="GOOD"
	else
		DAY="BAD"
	fi #}
}

####################
### END FUNCTION ###
####################

# 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
	MM=${DATE:0:2}
	DD=${DATE:2:2}
	YY=${DATE:4:4}

	if [ ${YY} -gt 0 ]; then #{
		if [ ${MM} -gt 0 ] && [ ${MM} -lt 13 ]; then
			if [ "${MM} -ne 02" ]; then
				get_day ${DD}
				if [ ${DAY} == GOOD ]; then
					echo "${DATE} is a valid date!"
				else
					echo "${DD} is invalid!"
				fi #}

			else
				is_leap_year ${YY} 
				if [ "${result} == true" ]; then
					if [ ${DD} -gt 0 ] && [ ${DD} -le 29 ]; then
						echo "${DATE} is a valid date"
					else
						echo "The day you entered for this date is invalid"
					fi #}
				else
					get_day ${DD}
					if [ ${DAY} == GOOD ]; then
						echo "${Date} is a valid date"
					else
						echo "Date ${DD} is invalid"
					fi #}
				fi #}
			fi #}

		else
			echo "${MM} is invalid!"
		fi #}


	else
		echo "${YY} is invalid!"
	fi #}

else
	echo "Incalid number of digits for a valid date"
fi #}

[atreyu]

Instead of evaluating like this:

if [ "${result} == true" ]; then

try evaluating like this:

if [ "$result" == 'true' ]; then

but what I generally do is return a 0 or 1 from a function, instead of messing with variables, e.g.:

#!/bin/bash

function testfunc() {
  local var=$1
  if [ "$var" == 'foo' ]; then
    return 0
  else
    return 1
  fi
}

# now call the function
testfunc foo && echo Successful || echo Failed

# you could also evaluate the return value, e.g.:
testfunc foo
if [ $? -eq 0 ]; then
  echo The function returned success
else
  echo The function returned with error
fi

[Garrett85]

I thought there was no returning in bash?

[Garrett85]

When I enter the date 02292001 I get "02292001 is a valid date' I don't understand. 29 should be invalid since there are only 28 days in FEB unless it's leap year and 2001 is not leap year. What am I doing wrong here?

[atreyu]

I thought there was no returning in bash?

You can return from a bash function, absolutely, but you must return an integer, not a string. It is then easy to evaluate that integer as a return value.

[atreyu]

When I enter the date 02292001 I get "02292001 is a valid date' I don't understand. 29 should be invalid since there are only 28 days in FEB unless it's leap year and 2001 is not leap year. What am I doing wrong here?

It is your use of arrays that is tripping you up. Arrays start at 0, not 1. So subtract 1 from your $MM before getting the max # of days for that month. E.g.:

# FUNCTION-get_day
get_day(){
  local mo=$(( $MM - 1 ))
  if [[ $DD -gt 0 ]] && [[ $DD -le ${CALENDER[${mo}]} ]]; then
    DAY="GOOD"
  else
    DAY="BAD"
  fi
}

Running this bit of code in your script will elucidate what your array holds:

CALENDER=(31 28 31 30 31 30 31 31 30 31 30 31)

for ((i=0;i<${#CALENDER[*]};i++)) {
  echo month $i days: ${CALENDER[$i]}
}

[Garrett85]

If I run the line if [[ ${DD} -gt 0 ]] && [[ ${DD} -le ${CALENDER[${SECONDDIGIT}]} ]]; DD is run against 31, I belive that 31 is from the [0] index because if I then change the line to { to if [[ ${DD} -gt 0 ]] && [[ ${DD} -le ${CALENDER[${SECONDDIGIT+1}]} ]]; then #{ DD is then run against 28 every time. It looks to me like my SECONDDIGIT & MM indexes are not being used. It looks like I'M always fetching the first index no matter wha,t and the second index if I add a + 1. Any ideas?

[atreyu]

It looks to me like my SECONDDIGIT & MM indexes are not being used. It looks like I'M always fetching the first index no matter wha,t and the second index if I add a + 1. Any ideas?

Where are you getting SECONDDIGIT from? Can you show the whole code?

[Garrett85]

Sorry, I didn't realize I had posted older code. The whole thing is below.

#! /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)


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

is_leap_year()
{
        PART1=`expr ${YY} % 4`
        PART2=`expr ${YY} % 100`
        if [[ 0 -eq ${PART1} ]] && [[ 0 -ne ${PART2} ]] || [[ 0 -eq `expr ${YY} % 400` ]]; then #{
                result=true
	else
		result=false
        fi #}
}


####################
### END FUNCTION ###
####################

########################
### FUNCTION-get_day ###
########################

get_day()
{
	DAY="BAD"
	FIRSTDIGIT=${MM:0:1}
	SECONDDIGIT=${MM:1:1}
	if [[ ${FIRSTDIGIT} -eq 0 ]]; then #{
		if [[ ${DD} -gt 0 ]] && [[ ${DD} -le ${CALENDER[${SECONDDIGIT+1}]} ]]; then #{
			DAY="GOOD"
		fi #}
	else
		if [[ ${DD} -gt 0 ]] && [[ ${DD} -le ${CALENDER[${MM}]} ]]; then #{
			DAY="GOOD"
		fi #}
	fi #}
}

####################
### END FUNCTION ###
####################

KEEPGOING=1
while [[ ${KEEPGOING} -eq 1 ]]; do

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 [[ "${DATE}" == exit ]]; then
	$KEEPGOING=0

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

	if [ ${YY} -gt 0 ]; then #{
		if [ ${MM} -gt 0 ] && [ ${MM} -lt 13 ]; then
			if [ ${MM} -eq 02 ]; then
				
				is_leap_year ${YY} 
				if [ $result == true ]; then
					if [ ${DD} -gt 0 ] && [ ${DD} -le 29 ]; then
						echo "${DATE} is a valid date!"
					else
						echo "${DD} is invalid for this date!"
					fi #}
				else
					get_day ${DD}
					if [ ${DAY} == GOOD ]; then
						echo "${Date} is a valid date!"
					else
						echo "${DD} is invalid for this date!"
					fi #}
				fi #}
			else
				get_day ${DD}
				if [ ${DAY} == GOOD ]; then
					echo "${DATE} is a valid date!"
				else
					echo "${DD} is invalid for this date!"
				fi #}
			fi #}

		else
			echo "${MM} is invalid for this date!"
		fi #}

	else
		echo "${YY} is invalid for this date!"
	fi #}

else
	echo "Invalid number of digits for a date!"
fi #}
done