Earlier quoted context omitted.
ag is made to search code specifically. grep is a more general purpose text search tool and better suited (imho) for handling data (in contrast to code). Also, it’s always installed. I’ve never been on a machine with ag unless if I’ve installed it myself.
Errmm, yes, I'm familiar with the difference in motivations behind the tools. I guess what I'm looking for is specific examples of things that cause you to use grep instead of ag. Ubiquity is a good one. But let's say you have both ag and grep. When do you reach for one and why? (I should have said this in my first comment, but I'm the author of ripgrep, and I'm just generally interested in learning more about the di…
some | commands | grep ERROR
In fact I do this so often that I have it aliased to g: alias g=grep
Maybe I could achieve the same with ack/ag/ripgrep, but I somehow mentally associate these tools with searching over a filesystem.