Run command in detached tmux session

This is probably simple, but I really can't find out how you do it. I have read the man pages and googled without results.

Problem: How do I run a command in a detached tmux window?

Example: I want my detached window 'foo' to run 'ls', but I want to do it from another terminal.

I've tried stuff like: 'tmux -t foo ls' without results.

Solution 1:

The command is send. send is a key sequence, so treat it accordingly (e.g. you'll probably want ENTER). The target is specified with -t. You may want foo.0 or foo.1 depending on the pane you wish to hit.

tmux send -t foo.0 ls ENTER

send is short for send-keys, which is located in the man pages, but perhaps a bit difficult to find in that mile of text.