Tuesday, June 7, 2022

[SOLVED] How to start tmux with several windows in different directories?

Issue

I want to use a script to open a tmux session with 6 windows, each in a different directory. I started with href="http://blog.hawkhost.com/2010/07/02/tmux-%E2%80%93-the-terminal-multiplexer-part-2/#tmux-shell-scripting" rel="noreferrer">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?


Solution

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).



Answered By - Chris Johnsen
Answer Checked By - Cary Denson (WPSolving Admin)
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