Bash regex matching not working in 4.1

Question

Upgraded to Bash4 and found that it is not matching regexes:

$ echo $BASH_VERSION
4.1.2(1)-release

$ [[ "20110228" =~ "^[0-9]{8}$" ]] && echo matches

But Bash 3.0 is:

$ echo $BASH_VERSION
3.00.16(1)-release

$ [[ "20110228" =~ "^[0-9]{8}$" ]] && echo matches
matches

Why might this be? Have I not installed it correctly?

Solution

Check this answer on SO. Since you are using 3.00 version of bash 3, it might regard your problem. Shortly, starting from 3.2 version, quoting the string argument to the [[ command's =~ operator forces string matching, so the correct pattern for bash 4 should be:

$ [[ "20110228" =~ ^[0-9]{8}$ ]] && echo matches
matches