Question

I want to use a script to open a tmux session with 6 windows, each in a different directory. I started with a script I found and tried this first:

tmux new-session -s xyz   -n etc -d 'cd /etc'
tmux new-window  -t xyz:1 -n var    'cd /var/log'

But I soon found out that this will not work as I expected — the window will be closed after the shell command completes.

So my next idea was to start a new shell like this:

tmux new-session -s xyz   -n etc -d 'cd /etc; bash -i'
tmux new-window  -t xyz:1 -n var    'cd /var/log; bash -i'
tmux new-window  -t xyz:2 -n var2   'cd /var/log; bash -i'
tmux new-window  -t xyz:3 -n var3   'cd /var/log; bash -i'
tmux new-window  -t xyz:4 -n var4   'cd /var/log; bash -i'
tmux new-window  -t xyz:5 -n var5   'cd /var/log; bash -i'
tmux new-window  -t xyz:6 -n var6   'cd /var/log; bash -i'

tmux select-window -t xyz:1
tmux -2 attach-session -t xyz

This almost works. But if I start more than about 4 windows, I frequently see the following bash errors in one of the windows after startup:

bash: [: =: unary operator expected
bash: [: too many arguments
bash: [: =: unary operator expected
bash: [: =: unary operator expected
bash: [: =: unary operator expected
bash: [: =: unary operator expected
bash: [: too many arguments
bash: [: =: unary operator expected
bash: [: =: unary operator expected
bash: [: =: unary operator expected
bash: [: =: unary operator expected
bash: [: =: unary operator expected

I have no idea why this happens, but I still think that I’m not doing this right. Is there a better way to set up a tmux session over several directories?

Answer 1

The shell errors are probably due to some problem in your startup files (or something they run).

As shellter commented, temporarily including the command set -vx early in your startup sequence is a good way to find out where the errors are occurring.
If you find the -vx output too verbose, you could try “printf debugging” (manually adding debug statements to your startup files until you can narrow down exactly which lines are causing the errors):

• Put echo start of .bashrc and echo end of .bashrc at the start/end of your .bashrc to see if the error occurs during your .bashrc. If not, instrument your other startup files: .bash_profile/.bash_login/.profile. If the errors happen before that file, then the problem may be in /etc/profile.
• Once you know which file is being processed when the errors occur, add more debug outputs around each “major block” or line to narrow down the responsible section/line.
• The errors may not actually be in your startup file itself, but in a script that it runs.

Note: These debug additions need to be temporary since they will cause problems if you ever use a program that makes automated logins (e.g. rsync, SSH-based Git access, etc.) since these programs expect a “clean” connection without such debugging noise present.

---

There should be no need to use cd command like that in the shell-command argument given to either tmux new-session or tmux new-window.

A new window will “inherit”^† the current working directory when using new-session and new-window from the command line (i.e. when done through the tmux binary, instead of via a binding or at a tmux–: prompt). According to the CHANGES file, it looks like this has been the case since tmux 0.6 (at least for new-window).

^† This is tmux-mediated inheritance, not the parent–child inheritance that is the usual mechanism for passing along the cwd.

This script works for me with tmux 1.5:

#!/bin/bash
# var for session name (to avoid repeated occurences)
sn=xyz

# Start the session and window 0 in /etc
#   This will also be the default cwd for new windows created
#   via a binding unless overridden with default-path.
cd /etc
tmux new-session -s "$sn" -n etc -d

# Create a bunch of windows in /var/log
cd /var/log
for i in {1..6}; do
    tmux new-window -t "$sn:$i" -n "var$i"
done

# Set the default cwd for new windows (optional, otherwise defaults to session cwd)
#tmux set-option default-path /

# Select window #1 and attach to the session
tmux select-window -t "$sn:1"
tmux -2 attach-session -t "$sn"

This might also (as a side-effect) alleviate your shell startup errors since the way tmux starts a shell is different from a plain bash -i (it is more akin to bash -l, which uses your .bash_profile/.bash_login/.profile instead of (just) your .bashrc).