Script for validating a date e.g. 11291985

Garrett85 · 01-03-2013, 08:22 PM

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 days 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.

Code:

#! /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 #}

unSpawn · 01-03-2013, 09:17 PM

Quote:

Originally Posted by Garrett85

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

As long as you figure out how to determine / restrict input as MMDDYYYY or whatever else format 'date' can figure out if a date is OK on its own:

Code:

#!/bin/bash
set -vxe; LANG=C; LC_ALL=C; export LANG LC_ALL; 
INPUT="$1"; M=${INPUT:0:2}; D=${INPUT:2:2}; Y=${INPUT:4:4}; 
date --date="${Y}-${M}-${D}" >/dev/null 2>&1; 
case $? in 0) echo "ERANU!";; *) echo "Uvavu"; esac; exit 0

Garrett85 · 01-04-2013, 11:55 AM

This is a learning project I have been given. I need to write the script.

Quote:

Originally Posted by unSpawn

As long as you figure out how to determine / restrict input as MMDDYYYY or whatever else format 'date' can figure out if a date is OK on its own:

Code:

#!/bin/bash
set -vxe; LANG=C; LC_ALL=C; export LANG LC_ALL; 
INPUT="$1"; M=${INPUT:0:2}; D=${INPUT:2:2}; Y=${INPUT:4:4}; 
date --date="${Y}-${M}-${D}" >/dev/null 2>&1; 
case $? in 0) echo "ERANU!";; *) echo "Uvavu"; esac; exit 0

suicidaleggroll · 01-04-2013, 12:32 PM

A couple of things

What's with all of the C-style { } blocks around your if statements that are commented out? It makes the code difficult to read and doesn't add anything

You put the entire leap year test and february test in quotes, eg: [ "${result} == true" ], which is probably why it's not evaluating correctly

You should use $() rather than ``, such as: part1=$(expr $yy % 4)

Why did you put part1 and part2 of the leap year test in their own variables, then rolled part3 into the if statement? It makes it awkward to read.

All caps variable names are generally reserved for environment variables. Variables inside your code should probably use lower case or mixed upper/lower case to prevent confusion

There's no need to use the echo in your len assignment, just do: len=${#date}

Variables substitutions rarely need to be surrounded by {}. There's no harm in it, but I only see a couple of instances in your script where it was actually necessary, just FYI

A simpler way to do your leap year test would be to have the is_leap_year function return a 1 or a 0, rather than the strings "true" or "false", and simply add the result to calendar[2] to make it 29 in the event of a leap year. Then you only need one test in your main code, it would cut the number of lines significantly.

unSpawn · 01-04-2013, 12:59 PM

Then run the script as

Code:

/bin/bash -vx /path/to/script [args] 2>&1 > /path/to/logfile.0

twice with a different date one of which you know represents a leap year, then compare output with

Code:

diff --side-by-side /path/to/logfile.0 /path/to/logfile.1 | less

and spot the differences. BTW you shouldn't do

Code:

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

but use one style of variable naming and quoting

Code:

if [ "${RESULT}" = "TRUE" ]; then

and use that consistently.