Bash Pattern matching and regular expressions Check if a string matches a regular expression
Example
3.0
Check if a string consists in exactly 8 digits:
$ date=20150624
$ [[ $date =~ ^[0-9]{8}$ ]] && echo "yes" || echo "no"
yes
$ date=hello
$ [[ $date =~ ^[0-9]{8}$ ]] && echo "yes" || echo "no"
no
