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I want to write a shell script which will attach to a named tmux session, select a window (or pane) in that session and run a command in that selected window (or pane).

How do I do this from a bash script?

I know

tmux new-window -n:mywindow 'exec something'

allows me to send commands to a freshly created window, but I need something like

tmux select-window -t:0 'my command'

I suppose I could use send-keys but seems like there should be something that takes a command or list of commands that get run.

3 Answers 3

107

Each tmux pane is an interface for a single pty (pseudo tty). Non-split windows have a single pane; split windows have multiple panes.

tmux does not supply a way to add extra processes to a pane once it has been started with its initial command. It is up to that initial command’s process (usually a shell) to supply job control1 for that terminal.

If you want to clobber whatever is currently running in the pane, you can use respawn-pane -k to kill the existing command and replace it with a new one (e.g., respawn-pane -t sessionname:0.4 -k 'some -new command').

But, if you want to maintain whatever is currently running in the pane, then there may be no better option that simply “typing at it” with send-keys.

You might script it like this (attach last, because otherwise the script will just wait for you to detach before continuing):

session=whatever
window=${session}:0
pane=${window}.4
tmux send-keys -t "$pane" C-z 'some -new command' Enter
tmux select-pane -t "$pane"
tmux select-window -t "$window"
tmux attach-session -t "$session"

Note that, on the send-keys command, you should actually type the letters E n t e r, to tell tmux to send a newline key to the window.  (Naturally, every command ends with the Enter key.)


1Job control is the arbitration between multiple process groups of a single session that uses the tty as its controlling terminal. I.e., the Ctrl+Z suspend key, and the jobs, fg, and bg shell commands.

2
  • 3
    Thanks for this! I put #{session_name}:#{window_index}.#{pane_index} in my status line so I can quickly see which pane to send commands to. May 24, 2017 at 23:32
  • That's nice to prevent the window to be removed when the command returns.
    – Alexis
    Jan 22 at 11:14
21

You can use C-m instead of Enter. It's the same thing. Also, tmux makes it easy to send to the right / left pane by using -t right or -t left. And if you want to address a pane in another window, just prefix it with the window number and period, like -t 0.right.

Now you can write a simple Bash function to get the sequence of keys as argument and send it over to the target pane easily.

1

Add commands to a simple text file queue:

This is only a last resort, if you really wanted to run the command after the last one without killing it.

Example

  1. Write a bash script that takes a [cli command] and a [tmux pane name] as variables
  2. The script adds the command to a queue file which it titles to pertain to that pane only
  3. However the queue file's first line is merely a 0 or 1
  4. The script loops through simple attempt at changing the 0 to a 1 via a tmux send-keys command to the corresponding tmux pane. (If there is a command presently running in the pane, the send-keys command naturally does nothing. Otherwise, it changes the 0 to a 1.)
  5. In the same loop, the script then attempts to detect a 1 in the queue file.
  6. When the script detects that the 0 is a 1, it runs the next command in the queue, and deletes it from the file. It changes the 1 back to a 0.

To store commands, you could also use an "associative array"

The script stops looping when the array is empty.

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