Use `printf '%s\n'` rather than `echo` to echo strings about bashstyle

[progrium]

I'm not opposed to echo in general, but I do think it's worth getting comfortable with printf rather than just assuming echo everything.

[stuartpb]

I see this style guide as being aimed toward bulletproofing the leaky, channeling-attack-prone sieve that is Bash, and not using arguments that can be interpreted as commands is a core principle of that, right up there with not using eval. (Normally, to avoid this hole, you'd use -- to separate arguments, like I was showing you the other day with set and ssh, but echo doesn't have any such mechanism.)

[progrium]

I just don't want to rule against echo in the simple cases where it's obviously okay. Larger systems will probably benefit from specialized output commands, perhaps wrapping printf.

[stuartpb]

I don't rule echo out either, in the sole situation where you're specifying a complete string (with any variable substitutions coming after known static text) for human messages. Those are the only places where echo is used in Plushu.

For anywhere where a string is being echoed for technical purposes, there's no reason your function should choke on arbitrary two-character strings: all non-message output is printf '%s\n' (or similar) only.

[progrium]

Also if it's quoted it's not an issue. And you should quote all variables. So this is basically a non-issue.

EDIT: Sorry, that's not true. But that case is now that you are outputting just -n ... I'm not going to change my behavior for a fairly obvious edge case situation like that.