Olli has this excellent question which asks for a file integrity checker. I'm sure many of us could write up a quick shell script and cron
entry that will do exactly what he needs.
We seem to have established that offering to write code for an asker is bad mojo. But what if, instead of an offer to write it, we just provide the complete code right there in the answer?
Would this be considered any different from linking to your own open-source project on Github? And in that line of thought, would it be better to just write the code, publish it github, and link to it in the answer?