Pattern matching and regular expressions:
*Check if a string matches a regular expression
Check if a string matches a regular expression
suggest changeCheck 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
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