[ComputerGuru]

I disagree that your ‘ echo hello’ example is free of side effects. It writes to stdout. It overwrites $?. It changes the value of the last executed history command. Etc.

About the only side effect free operation at a blank line terminal prompt is _probably_ hitting enter or ctrl c. Or ‘#something<Enter>’

But your idempotency examples are spot on.

Basically, idempotency is a very useful concept. Side effect free isn’t.

[twic]

> I disagree that your ‘ echo hello’ example is free of side effects.

I posit that you understand perfectly well what i was getting at! If it helps, imagine that you are spawning a fresh shell to execute each command line, through system(3) or some such.

[ComputerGuru]

Fair enough!