Count non blank lines

Question

I am using wc -l to count the number of lines I get as output from docker ps command. Sometimes there are no containers in the list and it just gives empty line but wc -l counts that as well and says the answer as 1. How can I avoid this

Answer 1

try the count option of grep and dot means any character which is not blank.

docker ps|grep -c .

Answer 2

Use instead a better-for-programs docker ps output -q. It only displays containers ids

docker ps -q | wc -l