Tmux in bash script executing too fast

Question

I am trying to write a bash script that performs the following actions:

• open 8 tmux terminals
• each of the terminals connects in ssh to a remote server
• start a script X on 3 server, and when it's done
• start another script Y in 3 different servers

The operations (especially the last two) must be executed in this precise order. I managed to create all tmux terminals, but I see that for some reasons tmux is so fast at executing commands that it does not wait the command to finish.

For example, writing just:

tmux send-keys -t 0 "ls" 

in the script not always produce the full list of files contained in the home folder.

Same happens with the two scripts on different servers, sometimes it executes Y before X.

This is my script:

######################################
# Setup tmux
######################################
tmux new-session -d -s sss
tmux new-window -t sss

for (( i = 0; i < 3; i++ )); do
  tmux split
  tmux select-layout even-vertical
done

for (( i = 0; i < 8; i=i+2 )); do
  tmux select-pane -t $i
  tmux split-window -h
done
######################################




######################################
# Ssh Connection
######################################
for (( i = 0; i < 8; i++ )); do
  tmux send-keys -t $i "$connection ${port[$i]}" C-m
done
######################################


for (( i = 0; i < 3; i++ )); do
  tmux send-keys -t $i "cd scripts" C-m
  tmux send-keys -t $i "./X.sh" C-m
done

for (( i = 3; i < 6; i++ )); do
  tmux send-keys -t $i "cd scripts" C-m
  tmux send-keys -t $i "./Y.sh ${servers_ips[${i}-3]}" C-m
done

Update

Also, how can I wait for a command to finish in the same tmux pane? Like doing something else only after a long command has been running

Thank you in advance.

Answer 1

If you really need to use tmux, and your commands are not interactive, then you can add a second command to the first command that signals somehow that the first command has finished. A simple way to do this using a built-in tmux command is wait-for with the option -L channel to lock, and -U channel to unlock. You can have many arbitrary channels. When you lock a channel, further attempts to lock will block until an unlock.

Here's an example:

tmux wait-for -L my1\; \
  send-keys 'sleep 5' Enter 'tmux wait-for -U my1' Enter\; \
  wait-for -L my1

This locks channel my1, sends the command sleep 5 to the shell, immediately followed by the tmux wait-for unlock shell command, then tries to get the lock again, so it blocks.

After 5 seconds, the sleep finishes, the shell executes the tmux unlock, and now the lock can be taken, and only then does the above tmux command return.

To get back to normal, a wait-for -U should now be done, perhaps by issuing another send-keys ... wait-for -U ... combined command as above.