[BUG] From tmux within SSH session, clipetty-kill-ring-save does not send to system clipboard

[jokem59]

Describe the bug
When I SSH onto my Amazon Linux instance. If I open terminal emacs WITHOUT a tmux session, clipetty-kill-ring-save works as intended and sends the region to my system clipboard.

From that same SSH session, if I launch tmux and open terminal emacs, clipetty-kill-ring-save does not send anything to the system clipboard. I don't see anything in the *Messages* buffer that indicates any error. toggle-debug-on-error also doesn't trip anything.

This was working prior and I'm unsure what changed (no changes to tmux/emacs configs recently).

To Reproduce
From Ubuntu 20.04 ssh to an Amazon Linux 2 instance. Launch tmux from this ssh session and launch emacs. Attempt clipetty-kill-ring-save and observe the contents are not present in the system clipboard.

Expected behavior
I expect the region clipetty-kill-ring-save is called on to be available on the system clipboard.

** System Info (please complete the following information):**

• OS: Ubuntu 20.04.6 LTS, 5.15.0-92-generic
• Emacs Version: 27.2
• Terminal program: st
• Any terminal multiplexers in play: tmux 3.3a
• Local or remote (over SSH): Remote

Additional context
N/A

[SteVwonder]

I had the same issue. Walking through the code, my issue turned out to be due to TMUX, TERM, and SSH_TTY env vars returning as nil from the call to (getenv "<ENVVAR>" (selected-frame)). Dropping the (selected-frame) bit makes things work again:

diff --git a/clipetty.el b/clipetty.el
index cb24eec..fc609a3 100644
--- a/clipetty.el
+++ b/clipetty.el
@@ -137,9 +137,9 @@ Optionally base64 encode it first if you specify non-nil for ENCODE."
 
 (defun clipetty--emit (string)
   "Emit STRING, optionally wrapped in a DCS, to an appropriate tty."
-  (let ((tmux    (getenv "TMUX" (selected-frame)))
-        (term    (getenv "TERM" (selected-frame)))
-        (ssh-tty (getenv "SSH_TTY" (selected-frame))))
+  (let ((tmux    (getenv "TMUX"))
+        (term    (getenv "TERM"))
+        (ssh-tty (getenv "SSH_TTY")))
     (if (<= (length string) clipetty--max-cut)
         (write-region
          (clipetty--dcs-wrap string tmux term ssh-tty)

I don't think this is a general solution that can be submitted as a PR since respecting the environment of each frame seems reasonable. But it is at least a temporary workaround. I'm not sure why that getenv is failing when targeting a specific frame. And I'm not sure why it works outside of tmux.

[yashaswikarnati]

I could not get it to work in a tmux session. I ssh into my ubuntu machine from my mac, start tmux session and run emacs (spacemacs). (getenv "TMUX" (selected-frame) returns me a valid value - /tmp/tmux-361936330/default,49641,0.

It works outside of tmux

tmux version - 3.4
spacemacs version - 0.999.0@29.3
iterm2 mac terminal