Is it possible to send input to a tmux session without connecting to it?

Question

Is there any command that I can use to send input or commands to a given tmux session / pane without connecting to it?

It's for unattended access,

I've a console application running on a tmux session. I want to restart it when a deploy (using capistrano) is done.

Is it possible?

Basically I want to send:

exit
cd ..
cd app
rails console

Answer 1

This question has a solution on ServerFault:

• Run command in detached tmux session

It uses the send-keys command, which is documented in the man-pages:

• General Commands: TMUX(1)

The following is a "Hello World" example illustrating the use of the send-keys command.

• Step 1. Create a detached session:

  user@host:~$ tmux new -d -s mySession
  

• Step 2: Execute a command in the detached session:

  user@host:$ tmux send-keys -t mySession.0 "echo 'Hello World'" ENTER
  

• Step 3: Attach to the session:

  user@host:$ tmux a -t mySession
  

You should see the following text displayed in the Tmux terminal window:

user@host:$ echo 'Hello World'
Hello World

user@host:$

This demonstrates that the echo command was successfully sent and executed inside of the tmux session.

An adaptation of this technique to your commands might look something like the following:

user@host:~$ tmux send-keys -t mySession.0 exit ENTER
user@host:~$ tmux send-keys -t mySession.0 "cd .." ENTER
user@host:~$ tmux send-keys -t mySession.0 "cd app" ENTER
user@host:~$ tmux send-keys -t mySession.0 "rails console" ENTER