Equivalent of screen -R ?

[osennte]

Hello, with the old screen program I frequently used the -R option: With it I did not need to check if a screen session with the given name exists, because the program connected to it if present, or created it and connected if not. I failed to find a simple command line with tmux that behaves this way "idempotently" (with simple I mean without: if tmux ls ...; then attach...; else new ...; fi). Please help!

[aless3]

what about
tmux new-session -A -s NAME?
NAME is the name of the session, by default 0.
this can be shortened to tmux new -As0 if using the default session name, or changing the 0 the connect a specific tmux session (creating it if not already existing)
in a small test I just did it also seems that tmux new -A works if using only one session (haven't tested with more sessions)
I never used screen, but it seems to me that "-As" should be the equivalent of screen -R

A.

[osennte]

Yes that does the trick, thanks!

[anarcat]

is there a way to provide a short-hand alias for this like tmux A? i know how this sounds, but tmux new -A is quite long compared to screen -RD which is pretty tightly hardwired in my fingers.

i've tried the mysterious command-alias but this doesn't seem to do anything:

set command-alias[0] A="new-session -A"

it fails with no server running on /tmp/tmux-1000/default.

as for this:

I never used screen, but it seems to me that "-As" should be the equivalent of screen -R

Yes, tmux new-session -A is pretty similar to screen -R. Here is what my hardwired -RD does:

       -D -R   Attach  here  and now. In detail this means: If a session is run‐
               ning, then reattach. If  necessary  detach  and  logout  remotely
               first.  If it was not running create it and notify the user. This
               is the author's favorite.

-D is mostly irrelevant for tmux, as tmux happily reattaches to an existing session even if it's already attached elsewhere. In screen, you need to first detach the other with -D or use -x to have two clients attached to the same session.

-R, essentially, means "attach or create".