Tag Archives: terminal

Running tmux in Mac OS X Terminal

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I’ve been a fan of screen for … a while now. But since I like being one of the cool kids, I’ve been using tmux for the past year or so. Last week, I noticed that every time I launch a new terminal, I wind up typing tmux attach-session. Let’s streamline, a little bit.

In Mac OS X’s Terminal.app, you can change the shell that it runs. Here’s how I did it:

  • Open Preferences, and choose the Settings tab.

  • Duplicate your existing settings (since sometimes you might not want tmux after all). Pick your default session (mine’s “Pro”) and select “Duplicate settings” from the tool menu at the bottom. Name the new settings “Tmux” or something along those lines.

  • In the shell tab for your settings, select “Run command” and enter /usr/local/bin/tmux attach-session. Deselect “Run inside shell” since you don’t really need to. Since you’re not running inside a shell, /usr/local/bin probably isn’t in your $PATH so you’ll need to specify the full path name. Of course, if your tmux binary lives somewhere other than /usr/local/bin you’ll need to change the path.

  • If you’ve selected “Only if there are processes other than” for “Prompt before closing”, then you’ll probably want to add tmux to that list.

  • In the “Window” tab, I set “Scrollback” to limit the number of rows to ’0′, since tmux provides scroll back, and the Terminal one isn’t terribly useful when tmux is running inside it.

  • Make sure your Tmux session is set as the default one by clicking the “Default” button at the bottom of the settings lists while it’s selected.

That’s it. Close your existing terminal sessions and launch a new one. You should be launched into (one of) your existing tmux sessions. If tmux wasn’t already running, then this assumes that your ~/.tmux.conf sets up at least one session (which I think it required anyway). If you’ve got more than one tmux session running, I’ve no idea which one, offhand, it’ll choose, but you can always switch to the one you’re looking for with C-a s. (You have rebound the prefix to C-a, right?)

There’s (at least) one time where you don’t want tmux as your shell. That’s when you’re attempting to interact with launchd. I suspect it’s to do with launchd checking that you’re a child process as part of its permissions when you’re asking it to do stuff, where tmux works by detaching itself from its parent process so it’s not killed when the parent is. (Total guess, BTW.) Still, when you want to use launchctl, you’ll need to do it somewhere other than a tmux session. In Terminal, choose the Shell menu, choose “New Window” (or “New Tab”) and select one of the other settings profiles.

Give me back my # key!

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This particular tip may have an audience of approximately one, since:

  • It’s only going to bother Mac users;
  • who are in the UK;
  • who use the # (hash, pound, whatever you call it) key much; and
  • who have enabled “Use option as meta key” in Terminal.app in order to sanely use Emacs.

If you tick all these boxes, and have suddenly discovered that your # key (which is option-3 for UK-keyboard-wielding Mac users) no longer works, you’ve come to the right place!

The problem is that M-3 is bound to digit-argument. This allows you to repeat commands (e.g. if you type M-3 c, then it will output ccc) which I’ve got to admit I don’t use terribly often.

It turns out that the bindings for keys are controlled by the readline library and you can customise them with readline’s configuration file, ~/.inputrc. If you want to override the default behaviour of M-3 and turn it back to emitting the # symbol, put the following in that file:

"\e3": '#'

You’ll need to restart bash (or force it to reload its inputrc file with C-x C-r) in order for it to take effect.

Here’s another related tip, while I’m here. I picked this one up from Ross a few years ago. I almost never use the UK currency symbol (£) in a shell environment. On the other hand, there’s another operation I perform quite often at the command line: commenting out the command I’m currently typing. It usually happens when I’m doing a sequence of steps at the command line, and I realise that I’ve forgotten a prerequisite step. Rather than sticking the current line in the kill ring (C-e C-u or C-a C-k), then remembering to yank it (C-y) again, I tend to jump to the start of the line (C-a), stick a hash in (to comment the line out), then hit enter. That way it’s in my (searchable) bash history for when I next need it.

But that’s a fairly cumbersome sequence too, so let’s shorten it. Stick the following in ~/.inputrc:

"£": '\C-a#\C-m'

and restart your shell. Now when you’re part way through typing a command line and want to switch tracks, hit the £ sign and you’re done. When you want the command back, retrieve it from your shell history (C-r to search!), then hit C-a C-d to remove the comment sign and you’re good to go.

One last wee trick. You really can remap any key to any other key. Imagine the fun and hilarity of the following in your ~/.inputrc:

"l": 'r'
"s": 'm'

:-)

Update: My colleague, Mihai, points out that the only appreciable difference between the UK and US keyboard layout on the Mac is that the # and £ key combinations are swapped around (oh, and it’s easier to find the ™ than the € now, not that I use either). Since I’ve just discovered that my irb isn’t picking up the ~/.inputrc and doing the right thing, I reckon I’ll just switch to the US layout…