awk

Columns

Columns (made of empty space, tab etc.) with $ syntax:

cat data.log | grep :2[0-9] | awk '{print $4 " " $8 " " $10 " " $11}'

Example in docker:

Remove all docker images which don’t have a corresponding container anymore, i.e. grab all lines which begin with <none> and run the docker rmi command on its thrid column which happens to be the image’s name:

docker rmi $(docker images | grep "^<none>" | awk '{print $3}')