How can Python heredoc be used as input for a Bash process substitution?

Question

I have a Python script that defines a configuration for tmux and then launches tmux with this configuration. The configuration is stored as a heredoc in Python and I want to use this in a Bash process substitution when executing the Bash launch command for tmux.

So, I'm looking to do something like this:

configuration = \
"""
set -g set-remain-on-exit on
new -s "FULL"
set-option -g prefix C-a
unbind C-b
bind - split-window -v
bind | split-window -h
## colours
set-option -g window-status-current-bg yellow
set-option -g pane-active-border-fg yellow
set -g status-fg black
set -g status-bg '#FEFE0A'
set -g message-fg black
set -g message-bg '#FEFE0A'
set -g message-command-fg black
set -g message-command-bg '#FEFE0A'
set-option -g mode-keys vi
set -g history-limit 5000
## mouse mode
set -g mode-mouse on
set -g mouse-select-pane on
set -g mouse-select-window on
set -g mouse-resize-pane on # resize panes with mouse (drag borders)
## status
set-option -g status-interval 1
set-option -g status-left-length 20
set-option -g status-left ''
set-option -g status-right '%Y-%m-%dT%H%M%S '
## run programs in panes
# split left-right
split-window -h
# split left up
select-pane -t 0
split-window -v
select-pane -t 0
split-window -v
select-pane -t 0
split-window -v
select-pane -t 3
split-window -v
select-pane -t 0
send-keys 'ranger' Enter
select-pane -t 1
send-keys 'clear' Enter
select-pane -t 2
#send-keys 'htop' Enter
select-pane -t 3
send-keys 'elinks http://arxiv.org/list/hep-ph/new' Enter
select-pane -t 4
send-keys 'cmus' Enter
select-pane -t 5
send-keys 'ranger' Enter
select-pane -t 4
set -g set-remain-on-exit off
"""

command = executable + " -f <(echo " + configuration + ") attach"
os.system(command)

What should I change to get this working?

Answer 1

Python's os.system() is defined in terms of C's system() function, which runs the given command via /bin/sh -c <the command>. Even if /bin/sh is an alias for bash, when bash is started as sh, it operates in POSIX mode, and POSIX does not provide process substitution (the <(<command>)).

It looks like your best bet is probably to write the configuration to a temporary file, and then specify that file's name in your command. If you have the mktemp command available to you, then it is a good candidate for making the temp file. Maybe something along these lines would do it:

command = "config=`mktemp` && { echo \"" + configuration + "\" > $config; "
        + executable + " -f $config attach; unlink $config; }"

Moreover, even if it were available to you, bash process substitution is a redirection. It affects the standard input (or standard output) if the process being launched, and does not take the place of a file name.