Jake McCrary

How to display a message to all tmux clients

Lately, I’ve been using tmux a lot. This resulted in me figuring out how to get lein-test-refresh to send notifications using tmux.

The setup linked above works great for when I’m doing work all by myself. It showed a problem when using ssh and tmux to pair with another developer. Instead of both developers receiving a notification, only one did. One is better than none but not ideal.

Below is a GIF showing the problem. Each window simulates a different developer.

tmux only showing one developer a notification

This wasn’t too hard to fix. A little digging through the tmux manpage shows that tmux display-message takes an optional flag telling it which client receives the message. If we can get a list of all the clients then iterating over them and sending a message to each is straightforward.

tmux list-clients give us this list. Below is the output.

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$ tmux list-clients
/dev/ttys002: 0 [78x41 xterm-256color] (utf8)
/dev/ttys006: 0 [78x42 xterm-256color] (utf8)

What we care about are the parts that look like /dev/ttys002. At first I used cut to grab these values but then I dug a bit deeper into the tmux manpage.

It turns out that you can specify a format to tmux list-clients. Running tmux list-clients -F "#{client_name}" gives us the output we care about.

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$ tmux list-clients -F "#{client_name}"
/dev/ttys002
/dev/ttys006

We can combine that with xargs to send a message to multiple clients.

tmux xargs example

That command is a bit much to put into lein-test-refresh’s configuration so I shoved it in a script called notify and configured lein-test-refresh to use it. Script and GIF of that below. Now both you and your pair can get notifications.

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#!/bin/bash

USAGE="Usage: notify <message>

example: notify 'Tests passed!'"

if [ -z "$1" ]; then
    echo "$USAGE"
    exit 1
fi

message="$1"

tmux list-clients -F "#{client_name}" \
    | xargs -n1 -I{} tmux display-message -c {} "$message"

Example using notify script

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