Configuration files can be long and complex and it is hard to see which values have been set. There are numerous ways to do this however, grep with -v (–invert-match) is a quick way to achieve this. The following example removes all the comments from an elasticsearch configuration file:

ed@es01:~$ sudo grep -v '#' /etc/elasticsearch/elasticsearch.yml

Which returns: es es01 ["", ""]
discovery.zen.minimum_master_nodes: 2

Five lines where it is easy to see what has been configured. Rather than:

ed@es01:~$ sudo wc -l /etc/elasticsearch/elasticsearch.yml
94 /etc/elasticsearch/elasticsearch.yml

So we have removed 89 lines of comments and can review the configuration in five. Time saved!