Regex to match the end of line

Question

I am looking for BASH regex to pull the 'db' agruments from the below commands. The order of the arguments is not guaranteed however. For some reason I cannot get it to work completely.

What I have so far

regex="--db (.*)($| --)"
[[ $@ =~ $regex ]]
DB_NAMES="${BASH_REMATCH[1]}"

# These are example lines
somecommand --db myDB --conf /var/home # should get "myDB"
somecommand --db myDB anotherDB manymoreDB --conf /home # should get "myDB anotherDB manymoreDB" 
somecommand --db myDB # should get "myDB"
somecommand --db myDB anotherDB # should get "myDB anotherDB"

Any suggestion on the regex?

Answer 1

The problem is that bash uses a flavor of regex that does not include non-greedy repetition operators (*?, +?). Because * is greedy and there is no way to tell it to not be greedy, the first parenthesized subexpression ((.*)) matches everything up to the end of line.

You can work around this if you know for that the values you want to capture do not contain a certain character and replace . with the character class that excludes that character.

For example, if the values after --db do not contain dashes (-) you can use this regex:

regex='--db ([^-]*)($| --)'

It matches all the examples posted in the question.