How to split a new window and run a command in this new window using tmux?

Use:

tmux split-window "shell command"

The split-window command has the following syntax:

 split-window [-dhvP] [-c start-directory] [-l size | -p percentage] [-t
         target-pane] [shell-command] [-F format]

(from man tmux, section "Windows and Panes"). Note that the order is important - the command has to come after any of those preceding options that appear, and it has to be a single argument, so you need to quote it if it has spaces.

For commands like ping -c that terminate quickly, you can set the remain-on-exit option first:

tmux set-option remain-on-exit on
tmux split-window 'ping -c 3 127.0.0.1'

The pane will remain open after ping finishes, but be marked "dead" until you close it manually.

If you don't want to change the overall options, there is another approach. The command is run with sh -c, and you can exploit that to make the window stay alive at the end:

tmux split-window 'ping -c 3 127.0.0.1 ; read'

Here you use the shell read command to wait for a user-input newline after the main command has finished. In this case, the command output will remain until you press Enter in the pane, and then it will automatically close.


bash --rcfile

This technique opens a new shell, runs commands, and leaves you there after the commands finish:

tmux-split-cmd() ( tmux split-window -dh -t $TMUX_PANE "bash --rcfile <(echo '. ~/.bashrc;$*')" )
tmux-split-cmd 'cd; pwd; ping google.com'

Or if the command has no special terminal characters like ; just:

tmux-split-cmd ping google.com

This uses:

  • --rcfile: How to invoke bash, run commands inside the new shell, and then give control back to user? | Stack Overflow
  • TMUX_PANE: How to split the window that ran the "tmux split-window" command instead of the current one?

Another interesting variant is:

tmux-split-cmd-uniq() (
  if [ "$(tmux list-panes | wc -l | cut -d' ' -f1)" -ne 1 ]; then
    tmux kill-pane -t 1
  fi
  tms "$@"
)

which kills the previous split if it already exists, and helps to keep only one extra split at all times.

Tags:

Tmux

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