Per the documentation, when you create a detached session (new-session -d
), it defaults to a size of 80×24. If you attach with a terminal window that is actually 24 lines high (or 25, since tmux uses one for a status line), then you should find that the below-Vim pane does in fact end up with just five lines.
The problem comes when you attach to the session with a terminal window that is much taller than 24 lines. When you do this, tmux resizes the panes to fill the full terminal window. The lower pane grows past its original five lines when this happens.
One way to work around this problem is to create the detached session with an initial size that matches that of the terminal window from which you will eventually attach to the session. One semi-portable way to do this is to parse the output of stty size
(some shells also provide LINES and COLUMNS parameters (especially when in interactive mode), but these parameters are not always available and reliable in shell scripts).
set -- $(stty size) # $1 = rows $2 = columns
tmux -2 new-session -d -s "$SESSION" -x "$2" -y "$(($1 - 1))" # status line uses a row
The failed to connect to server: Connection refused
message comes from your tmux has-session
command. It is reporting that it there is no existing server. Since you are only interested in the exit code, you can probably just send the output to /dev/null
to avoid seeing it at all. You can also put the command directly into the if
statement:
if tmux has-session -t "$SESSION" 2>/dev/null; then
⋮
fi
Incidentally, you should almost always put your parameter expansions in double quotes (to avoid word splitting and glob expansion). You only have the one parameter and its value (copied from USER
) is (usually) probably safe not to quote, but it is a good habit to always quote your expansions in almost all contexts.
This is what is happening:
tmux new 'tmux source-file ~/.tmux/dev'
The new
commands creates a new session with a single window that has a single pane. The command tmux source-file ~/.tmux/dev
runs in this new pane.
- So, you have a new session
N
(where N is some number), with
- a single window
N:0
(or whatever you have base-index
set to), with
- a single pane
N:0.0
(or whatever you have base-pane-index
set to),
- running the command
tmux source-file ~/.tmux/dev
.
The source-file
command is processed.
- The extra panes are added.
- Pane 0 is (re)selected.
- The
send-keys
command then “types” vim .
+ Enter at pane 0.
This input is ignored because this pane is just running the tmux client that sent the source-file
command.
- The tmux client exits, thus closing pane 0.
So the unexpected bit is that pane 0 (i.e. N:0.0
) is running (only) the source-file
command which ignores your “typed” command. This pane never runs an interactive shell that could interpret the “typed” command.
There are at least a couple of ways you can fix this:
Start ~/.tmux/dev
with new-window
so that pane 0 is running your “default command” (i.e. probably an interactive shell).
This method has the benefit of not assuming that your current pane is running an interactive shell, and also not assuming that the current pane is 0
(i.e. what happens if you run your original series of commands against a pane that is part of an already split window?). It means you can safely bind source-file ~/.tmux/dev
to a key that you can run in any context (since it creates a new window for all of its panes). From the shell you can run either tmux source-file ~/.tmux/dev
(to create a new window in the current session), or your original tmux new 'tmux source-file ~/.tmux/dev'
to create a new session.
A minor drawback to this method is that when you run tmux new 'tmux source-file ~/.tmux/dev'
, the initial window will still run the client that sends source-file
and exit fairly quickly. This means that your “main window” (the one with the splits) will be one higher than your base-index
and a future new window will be placed before the “main window”. You could fix this by using something like this:
tmux new 'tmux move-window -t 99 \; source-file ~/.tmux/dev'
It moves the (ephemeral) initial window to a high index so that the new-window
in ~/.tmux/dev
will end up at base-index
.
Use (e.g.) tmux new 'tmux source-file ~/.tmux/dev ; zsh -l'
so that the pane ends up running an interactive shell after the source-file
command finishes.
The ugly bit about this is that you end up “hard coding” your preferred shell into this command. Also, the send-keys
input (vim .
+ Enter) is technically sent before the shell starts; this is probably okay, but may not always be completely reliable.
You could avoid “hard coding” your shell by querying tmux for the default-command
(or if that is not set, default-shell
(or if that is not set, using SHELL)), but that may be more work than you really want to do.
Best Answer
Turns out tmux has powerful formatting capabilities for the list-panes command:
The command above will print
for the active pane.
Fromatting options are described in
man tmux
:For the discussion of the term "first process in pane", see What does the "first pid of a pane" in tmux mean?