The tmux attach
command acts more like a combination of screen -r
and screen -x
-- first it trys to attach to the most recently detached session, and then if none is available it will attach to a currently attached session. I want to emulate the behavior of screen -R
: first try to attach to a detached session, then start a new session if there were no detached sessions. What is the best way to achieve this in tmux?
After consulting the wizards of IRC I am confident there is no single tmux command that has this behavior. Luckily, it is fairly easy to emulate using the shell:
(tmux ls | grep -vq attached && tmux at) || tmux
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Minor edit to squelch the "failed to connect to server: Connection refused" output in the event that you're launching a new session:
(tmux ls 2>/dev/null | grep -vq attached && tmux at) || tmux
– l8nite Jul 20 '15 at 3:07
Despite what it says in tmux manual:
The target-session rules for attach-session are slightly
adjusted: if tmux needs to select the most recently used session,
it will prefer the most recently used unattached session.
Drew's answer won't work properly in a situation like:
0: 1 windows (created Wed Nov 7 23:51:08 2012) [177x47]
1: 1 windows (created Wed Nov 7 23:51:33 2012) [177x47] (attached)
tmux at
will attach to the last session (#1) (even though this session is still attached somewhere else). This ruins the whole idea of running several tmux sessions and attaching only to a detached one (to use mosh + tmux + iterm2 to create a perfect roaming terminal).
Another approach would be to manually select a non-attached session:
tmux ls | grep -vq attached && tmux at `tmux ls | grep -vm1 attached | cut -d: -f1`
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Good catch! The documentation is out of sync with the actual behavior. I created a bug report for this. – Drew Frank Nov 26 '12 at 18:59
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A patch is out that fixes this, so by the next release it should behave as advertised. – Drew Frank Nov 26 '12 at 23:00
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I tend to only have two tmux sessions at a time, so I do something like this in each terminal window.
terminal window 0:
tmux attach -t 0 || tmux new
terminal window 1:
tmux attach -t 1 || tmux new
This has worked the best for me:
if [ -z "$TMUX" ]; then
(tmux ls | grep -vq attached && tmux at -t `tmux ls | grep -vm1 attached | cut -d: -f1`) || tmux new
fi
The -t is needed to attach to the proper session.
What about
tmux attach || tmux new
or instead just create the file ~/.tmux.conf
if it doesn't exist, and add
new-session
to it such that it creates a new session when there is none when you run tmux attach
.
It might also be handy to make tmux
an alias to tmux attach
.
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The first proposal would attach to currently attached tmux sessions (similar to screen -x), which is something I want to avoid. The second proposal exhibits this same problem and also has the undesirable consequence of creating "extra" tmux sessions when I use the tmux source-file command to reload the config. – Drew Frank Oct 13 '12 at 21:53