On 25 Mar, 07:19, Stephane CHAZELAS <this.addr...@is.invalid> wrote:
> 2008-03-25, 07:07(-07), Spiros Bousbouras:
>
> > On 25 Mar, 14:03, Stephane CHAZELAS <this.addr...@is.invalid> wrote:
> >> 2008-03-25, 06:53(-07), Spiros Bousbouras:
> >> [...]
>
> >> >> Only '\a', '\b', '\f', '\n', '\r', '\t', '\v' are standard.
>
> >> > That's what I thought but can an implementation
> >> > output anything it wants with \e or is there a collection
> >> > of permitted behaviours ?
>
> >> \e is unspecified. If you want to output \e as opposed to the
> >> ESC character, use printf '\\e' or printf %s '\e'
>
> > What does unspecified mean in POSIX ? In the C standard
> > it means that the standard specifies a list of behaviours
> > and the implementation can choose any one of them without
> > needing to document it.
>
> That means that if your shell script has:
>
> printf '\e'
>
> you don't know what you'll get, that can be anything, so you
> should not use it in a POSIX script that intents to be portable.
>
> And if you're implementing a new "printf" utility, you can do
> whatever you want in that case as POSIX doesn't specify the
> behavior. So you can issue an error message, you can launch a
> web browser, shutdown the machine, output an ESC character,
> output an ASCII EOT, ETB, ETX... character, output \e, turn on
> terminal echo, erase a character...

If that's what unspecified means then what's the difference between
undefined behaviour and unspecified behaviour according to POSIX ?