Validate date format in a shell script

Question

I have to create a Shell Script wherein one of the parameters will be the date in the format dd/mm/yyyy. My question is, how can I check if the Date passed as parameter real

Answer 1

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