Validate date format in a shell script

The simplest solution, that still works perfectly, is the following :

if [[ $1 =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]] && date -d "$1" >/dev/null 2>&1 ... 

It consists in combining 2 checks :

• the first part checks that $1 is of this format : NNNN-NN-NN
• the second part checks that it is a valid date

You need the two checks because :

• if you don't do the first check, date will exit with code 0 even if your variable is a valid date in another format
• if you don't do the second check, then you can end up with a 0 even for variables such as 2016-13-45

This function expects 2 strings,a format string, a date string

The format string uses the codes from the date command but does not include the '+'

The function returns 0 if the provided date matches the given format, otherwise it returns 1

Code (my_script.sh)

#!/bin/bash datecheck() { local format="$1" d="$2" [[ "$(date "+$format" -d "$d" 2>/dev/null)" == "$d" ]] } date_test="$1" echo $date_test if datecheck "%d %b %Y" "$date_test"; then echo OK else echo KO fi 

Output

$ ./my_script.sh "05 Apr 2020" 05 Apr 2020 OK $ ./my_script.sh "foo bar" foo bar KO 

First, check the form of the input using the regex. Then use awk to switch to mm/dd/yyyy and use date to validate. You can use the following expression in your if statement:

echo "$1" | egrep -q '^[0-3][0-9]/[0-1][0-9]/[0-9]{4}$' && date -d "$(echo "$1" | awk 'BEGIN{FS=OFS="/"}{print $2"/"$1"/"$3}')" >/dev/null 2>&1 

Simplest way for dd/mm/yyyy exactly in Bash is:

if [[ $1 == [0-3][0-9]/[0-1][0-9]/[0-9][0-9][0-9][0-9] ]] 

Or

if [[ $1 =~ ^[0-3][0-9]/[0-1][0-9]/[0-9]{4}$ ]] 

How about using awk:

echo "31/12/1999" | awk -F '/' '{ print ($1 <= 31 && $2 <= 12 && match($3, /^[1-9][1-9][1-9][1-9]$/)) ? "good" : "bad" }' 

It prints "good" if its valid date else prints "bad"

#! /bin/bash isDateInvalid() { DATE="${1}" # Autorized separator char ['space', '/', '.', '_', '-'] SEPAR="([ \/._-])?" # Date format day[01..31], month[01,03,05,07,08,10,12], year[1900..2099] DATE_1="((([123][0]|[012][1-9])|3[1])${SEPAR}(0[13578]|1[02])${SEPAR}(19|20)[0-9][0-9])" # Date format day[01..30], month[04,06,09,11], year[1900..2099] DATE_2="(([123][0]|[012][1-9])${SEPAR}(0[469]|11)${SEPAR}(19|20)[0-9][0-9])" # Date format day[01..28], month[02], year[1900..2099] DATE_3="(([12][0]|[01][1-9]|2[1-8])${SEPAR}02${SEPAR}(19|20)[0-9][0-9])" # Date format day[29], month[02], year[1904..2096] DATE_4="(29${SEPAR}02${SEPAR}(19|20(0[48]|[2468][048]|[13579][26])))" # Match the date in the Regex if ! [[ "${DATE}" =~ "^(${DATE_1}|${DATE_2}|${DATE_3}|${DATE_4})$" ]] then echo -e "ERROR - '${DATE}' invalid!" else echo "${DATE} is valid" fi } echo echo "Exp 1: "`isDateInvalid '12/13/3000'` echo "Exp 2: "`isDateInvalid '12/11/2014'` echo "Exp 3: "`isDateInvalid '12 01 2000'` echo "Exp 4: "`isDateInvalid '28-02-2014'` echo "Exp 5: "`isDateInvalid '12_02_2002'` echo "Exp 6: "`isDateInvalid '12.10.2099'` echo "Exp 7: "`isDateInvalid '31/11/2000'` 

Here's a function to do some data validation this:

# Script expecting a Date parameter in MM-DD-YYYY format as input verifyInputDate(){ echo ${date} | grep '^[0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]$' if [ $? -eq 0 ]; then echo "Date is valid" else echo "Date is not valid" fi } 

`X="2016-04-21" then check for the below value being 1 or 0.

cal echo $x | cut -c 6-7 echo $x | cut -c 1-4 2>/dev/null | grep -c echo $x | cut -c 9-10

If the value is 1, then it's valid, else it's not valid.

I would like to give an extended answer for a slightly different format, but this can easily be changed to the dd/mm/YY format with the answers already given; it's tested on busybox (posix shell)

This is one of the first hits for web searches similar to "busybox posix shell script date" and "test format" or "validate" etc, so here my solution for busybox (tested with 1.29.3, 1.23.1)

#!/bin/sh ########## # # check if date valid in busybox # tested in busybox 1.29.3, 1.23.1 # # call with: # $0 <yyyymmdd> # ########## mydate=$1 if echo $mydate | grep -qE '20[0-9][0-9](0[1-9]|1[0-2])([012][0-9]|3[01])'; then printf 'may be valid\n' date +%Y%m%d -d $mydate -D %Y%m%d > /dev/null 2>&1 is_valid=$? if [ $is_valid -ne 0 ]; then printf 'not valid\n' return 1 else mytestdate=$(date +%Y%m%d -d $mydate -D %Y%m%d) if [ $mydate -ne $mytestdate ]; then printf 'not valid, results in "%s"\n' "$mytestdate" return 1 else printf 'valid\n' fi fi else printf 'not valid (must be: <yyyymmdd>)\n' return 1 fi 

as in busybox (1.29.3 & 1.23.1) you have responds like:

lxsys:~# date +%Y%m%d -d 20110229 -D "%Y%m%d" 20110301 

I had the need to validate the date in some better way but i wanted to rely mostly on the system itself

so with

mytestdate=$(date +%Y%m%d -d $mydate -D %Y%m%d) if [ $mydate -ne $mytestdate ]; then ... fi 

there is a second test - do we have a difference between the wanted or given format (input, $mydate) and the system interpretation (output, $mytestdate) of it ... if it's not the same, discard the date

I wrote this bash script to validate date. I can accept mont as alphanumeric.

#!/bin/bash function isDateValid { DATE=$1 if [[ $DATE =~ ^[0-9]{1,2}-[0-9a-zA-Z]{1,3}-[0-9]{4}$ ]]; then echo "Date $DATE is a number!" day=`echo $DATE | cut -d'-' -f1` month=`echo $DATE | cut -d'-' -f2` year=`echo $DATE | cut -d'-' -f3` if [ "$month" == "01" ] || [ "$month" == "1" ]; then month="Jan" elif [ "$month" == "02" ] || [ "$month" == "2" ]; then month="Feb" elif [ "$month" == "03" ] || [ "$month" == "3" ]; then month="Mar" elif [ "$month" == "04" ] || [ "$month" == "4" ]; then month="Apr" elif [ "$month" == "05" ] || [ "$month" == "5" ]; then month="May" elif [ "$month" == "06" ] || [ "$month" == "6" ]; then month="Jun" elif [ "$month" == "07" ] || [ "$month" == "7" ]; then month="Jul" elif [ "$month" == "08" ] || [ "$month" == "8" ]; then month="Aug" elif [ "$month" == "09" ] || [ "$month" == "9" ]; then month="Sep" elif [ "$month" == "10" ]; then month="Oct" elif [ "$month" == "11" ]; then month="Nov" elif [ "$month" == "12" ]; then month="Dec" fi ymd=$year"-"$month"-"$day echo "ymd: "$ymd dmy=$(echo "$ymd" | awk -F- '{ OFS=FS; print $3,$2,$1 }') echo "dmy: "$dmy if date --date "$dmy" >/dev/null 2>&1; then echo "OK" return 0 else echo "NOK" return 1 fi else echo "Date $DATE is not a number" return 1 fi } if isDateValid "15-15-2014"; then echo "date is valid =)" else echo "bad format date" fi echo "===================" if isDateValid "15-12-2014"; then echo "date is valid =)" else echo "bad format date" fi echo "===================" if isDateValid "15-Dec-2014"; then echo "date is valid =)" else echo "bad format date" fi echo "===================" if isDateValid "1-May-2014"; then echo "date is valid =)" else echo "bad format date" fi echo "===================" if isDateValid "1-1-2014"; then echo "date is valid =)" else echo "bad format date" fi echo "===================" if isDateValid "12-12-2014"; then echo "date is valid =)" else echo "bad format date" fi 

Though the solution (if [[ $1 =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]] && date -d "$1" >/dev/null 2>&1) of @https://stackoverflow.com/users/2873507/vic-seedoubleyew is best one at least for linux, but it gives error as we can not directly compare/match regex in if statement. We should put the regex in a variable and then we should compare/match that variable in if statement. Moreover second part of if condition does not return a boolean value so this part will also cause error.

So I have done slight modification in the above formula and this modification can also be customized further for various other formats or combination of them.

DATEVALUE=2019-11-12 REGEX='^[0-9]{4}-[0-9]{2}-[0-9]{2}$' if [[ $DATEVALUE =~ $REGEX ]] ; then date -d $DATEVALUE if [ $? -eq 0 ] ; then echo "RIGHT DATE" else echo "WRONG DATE" fi else echo "WRONG FORMAT" fi 

Another regex to validate the date:

"$1" =~ [0-9]{4}/(0[1-9]|1[0-2])/(0[1-9]|[1-2][0-9]$|3[0-1]$) 

This regex has some shortcomings, it doesn't check if the day of month is valid for the specified month.

Blockquote

DATE = "$*" [[ "${DATE}" != @(((([123][0]|[012][1-9])|3[1])?([ \/._-])(0[13578]|1[02])?([ \/._-])(19|20)[0-9][0-9])|(([123][0]|[012][1-9])?([ \/._-])\ (0[469]|11)?([ \/._-])(19|20)[0-9][0-9])|(([12][0]|[01][1-9]|2[1-8])?([ \/._-])02?([ \/._-])(19|20)[0-9][0-9])|(29?([ \/._-])02?([ \/._-])\ (19|20(0[48]|[2468][048]|[13579][26])))) ]] && echo error || echo good)