byobu attach exits with 0 when no sessions to attach unlike tmux

[Muneeb Shaikh]

Following is a walkthrough of the issue.

====
ubuntu@localhost:~$ byobu -L foo attach
[exited]
ubuntu@localhost:~$ echo $?
0
ubuntu@localhost:~$ tmux -L foo attach
no sessions
ubuntu@localhost:~$ echo $?
1
====

I came across this when trying to write an [auto]ssh function/alias along the following lines.

"tmux -L foo attach || sudo -H tmux -L foo attach"

which tries to attach to existing tmux session. Above works but if you substitute "tmux" with "byobu" it fails as first part exits with zero(success) status.

Package versions:
====
ubuntu@localhost:~$ apt-cache policy byobu | grep -B1 Installed
byobu:
  Installed: 5.106-0ubuntu1
ubuntu@localhost:~$ tmux -V
tmux 2.1
====

Is this an expected behaviour?

Similar question was asked on StackOverflow: https://stackoverflow.com/q/52129480