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In linux I can use the key combinations Alt-Ctrl-F1,Alt-Ctrl-F2... to switch to different tty1 as I could use man chvt.

using the command tty I also get displayed the teletype/linux virtual console I am on.

However if I am in xterm or in gnome-terminal tty will display the relevant pseude-terminal.

Given all that:

  • How can I tell which is the currently "active" tty (meaning it being displayed on the screen)?

This would be somewhat the solution (however it seems contorted and relies on loginctl logind, there must be a non-systemd to find out):

for sessionid in $(loginctl list-sessions --no-legend | awk '{ print $1 }'); do loginctl show-session -p State -p TTY  $sessionid; done | grep "State=active" -B1 | head -n 1 | sed 's/.*=//g'
fraleone
  • 797
  • I'm sorry, but I'm not sure I understand the question. Are you asking which of the virtual ttys (tty1 through tty12) is the one being shown to the console user? If so, what would you expect to be reported when a GUI is running on (say) tty8? What if the GUI is running remotely as an X Windows session over XDMCP and the user isn't local? – Chris Davies Nov 28 '19 at 11:28
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    @roaima thanks for the comment. There will be only local GUIs on ttys. I would like to get the tty for which loginctl show-session -p State {SESSION_ID} would yield State=active. Hence the tty on which either wayland compositor or Xorg server are running on if they are displayed. No remote GUIs. – fraleone Nov 28 '19 at 11:32
  • @KamilMaciorowski :) Yes, that seems to work. cat /sys/devices/virtual/tty/tty*/active yields tty2 which is the tty wayland-compositor is running on currently – fraleone Nov 28 '19 at 12:16

1 Answers1

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cat /sys/devices/virtual/tty/tty0/active

tty0 refers to the current virtual console (compare this answer). By reading /sys/devices/virtual/tty/tty0/active you can learn which console this is.

"Current" means what you see, not where cat is running. E.g. if you start this loop

while sleep 1; do
   cat /sys/devices/virtual/tty/tty0/active
done

let in run, manually switch to another console, wait few seconds and switch back, then you will see the other console was reported when you were looking at it.

Kamil Maciorowski
  • 21,864
  • A while back I wrote improved manual pages covering this: http://jdebp.uk./Proposals/linux-kvt-manual-pages.html http://jdebp.uk./Softwares/nosh/guide/commands/linux-vt.xml – JdeBP Nov 28 '19 at 16:08
  • what about pts / pseudoterminals within a tty? E.g. with tmux, it's possible to have several panes open, each having its own dedicated pts, e.g. /dev/pts/3 and /dev/pts/56. – Abdull Oct 26 '23 at 14:51
  • @Abdull Uhm… tty from the second sentence of the question? In tmux the format variable pane_tty should also tell you this, but it's more powerful since you can target any pane; e.g. tmux display-message -t %0 -p '#{pane_tty}'. – Kamil Maciorowski Oct 26 '23 at 18:27