awk, grep, sed, ag, cut, sort,etc for most of the stuff. Elasticsearch, logstash, kibana for more complex queries
A great little tool is 'since' - a stateful tail. http://welz.org.za/projects/since
since is a unix utility similar to tail.
Unlike tail, since only shows the lines
appended since the last time. It is useful
to monitor growing log files.
It's a bit hard to websearch for because 'since' is a common word.