Funny that this should come up. Being an old Unix grouch, I started a prototype GTD system where I just have all of my next actions in a single file — one task per line with “[Context]” thrown on the end. I was pulling the relevant context using grep at the command line. Frex, if I wanted to look at my “Out of House]” context I typed:

grep -i “out of house” nextactions.txt

This looked promising as Hell, but in the end I decided to stick with OmniOutliner for the time being because I decided that I was shaving the proverbial yak. The urge to tinker with the system was overtaking me, and I made myself stop.