When I executed the command redis-cli --bigkeys, it returned Couldn't determine DBSIZE!.
My redis server version is 5.0.7. 

$ redis-cli --bigkeys
Couldn't determine DBSIZE!

Comment From: oranagra

please try to run redis-cli dbsize and see what it responds (if any).

Comment From: xiejx

oh, when I run redis-cli dbsize, it responded (error) NOAUTH Authentication required..
then I use redis-cli --bigkeys -a [my password]. it responds the expected result.
thanks for help!

Comment From: oranagra

I suppose this is a good opportunity to ask for improvement, to print a better error message in that case.

Comment From: huangzhw

@oranagra Maybe we just need output the error from server?

Comment From: oranagra

yes, i think that would be enough. something like DBSIZE failed: %s

Comment From: ccc-56

oh, when I run redis-cli dbsize, it responded (error) NOAUTH Authentication required.. then I use redis-cli --bigkeys -a [my password]. it responds the expected result. thanks for help!

its worked for me too

Comment From: wwlwxg

oh, when I run redis-cli dbsize, it responded (error) NOAUTH Authentication required.. then I use redis-cli --bigkeys -a [my password]. it responds the expected result. thanks for help!

its worked for me too