On Mon, Jul 09, 2018 at 09:08:17AM -0400, Greg Wooledge wrote:
> On Sun, Jul 08, 2018 at 01:08:59PM +1000, Zenaan Harkness wrote:
> > With a bash fn like:
> > ttyGetNum () { return $(tty | grep -oE '[0-9]+$') ; }
> >
> > Then something like this will id your current tty:
> > ttyGetNum; export Xorg_vt=vt$?
>
> Ewwwww!
>
> The return status of a shell function is NOT intended to be used this way.
> It's analogous to the exit status of a shell command. It's a single
> byte, unsigned, so you can only return 0 to 255. It's intended to convey
> success or failure, not to carry an actual data payload.
>
> I recommend that you switch to using a regular variable for this purpose.
> I happen to like "r". With a regular variable, you're not restricted to
> integers from 0 to 255, and you retain the ability to convey succss/failure
> through the return code.
>
> As an aside, you can save the call to GNU grep by simply stripping the
> leading "/dev/tty" from the output of tty using a shell parameter
> expansion:
>
> ttyGetNum() {
> local t
> t=$(tty) || return 1
> [[ $t = /dev/tty+([0-9]) ]] || return 1
> r=${t#/dev/tty}
> }
>
> if ttyGetNum; then export Xorg_vt=vt"$r"; fi
>
fgconsole returns the current virtual terminal number.
chvt switches to a specified virtual terminal.
These are from package kbd.
-dsr-
