Re: bash string RE pattern matching

[Greg Wooledge]

On Wed, Jul 26, 2023 at 07:13:38PM -0400, Lee wrote:
> Why doesn't =~ match strings inside of double quotes?
> 
> $ bash bashre
> os = "Linux"   re = "^Linux"
> "$os" =~ ${re} is true
> "$os" =~ "${re}" is False

Because any quoted character within the RE is taken literally, instead
of having a special regular expression meaning.

"^" acts exactly like \^ because they are both ways of quoting the
character.

This is true even if the ^ is part of an expansion, instead of written
literally within the [[ ]] command.

If you put your RE in a variable, and you want it to be matched as an RE
instead of as a string, you must not use quotes around the variable
expansion.