|  | tmux frequently asked questions | 
|  |  | 
|  | ****************************************************************************** | 
|  | * PLEASE NOTE: most display problems are due to incorrect TERM! Before       * | 
|  | * reporting problems make SURE that TERM settings are correct inside and     * | 
|  | * outside tmux.                                                              * | 
|  | *                                                                            * | 
|  | * Inside tmux TERM must be "screen" or similar (such as "screen-256color").  * | 
|  | * Don't bother reporting problems where it isn't!                            * | 
|  | *                                                                            * | 
|  | * Outside, it must match your terminal: particularly, use "rxvt" for rxvt    * | 
|  | * and derivatives.                                                           * | 
|  | ****************************************************************************** | 
|  |  | 
|  | * How is tmux different from GNU screen? | 
|  |  | 
|  | tmux and GNU screen have many similarities. Some of the main differences I am | 
|  | aware of are (bearing in mind I haven't used screen for a few years now): | 
|  |  | 
|  | - tmux uses a client-server model. Each server has single Unix domain socket in | 
|  | /tmp and within one server there are multiple sessions which may be attached | 
|  | to multiple clients (terminals). | 
|  |  | 
|  | This has advantages, notably: windows may be linked simultaneously to | 
|  | multiple sessions; windows may be moved freely between sessions; and a client | 
|  | may be switched between sessions easily (C-b D). There is one major | 
|  | disadvantage: if the server crashes, game over, all sessions die. In | 
|  | practice, however, tmux is quite stable and gets more so as people report any | 
|  | bugs they hit :-). | 
|  |  | 
|  | This model is different from screen, where typically each new screen instance | 
|  | is independent. tmux supports the same behaviour by using multiple servers | 
|  | with the -L option but it is not typically recommended. | 
|  |  | 
|  | - Different command interfaces. One of the goals of tmux is that the shell | 
|  | should be easily usable as a scripting language - almost all tmux commands | 
|  | can be used from the shell and behave identically whether used from the | 
|  | shell, from a key binding or from the command prompt. Personally I also find | 
|  | tmux's command interface much more consistent and clearer, but this is | 
|  | subjective. | 
|  |  | 
|  | - tmux calls window names (what you see in the status line) "names", screen | 
|  | calls them "titles". | 
|  |  | 
|  | - tmux has a multiple paste buffers. Not a major one but comes in handy quite a | 
|  | lot. | 
|  |  | 
|  | - tmux supports automatically renaming windows to the running application | 
|  | without gross hacks using escape sequences. Its even on by default. | 
|  |  | 
|  | - tmux has a choice of vi or emacs key layouts. Again, not major, but I use | 
|  | emacs so if tmux did support only one key set it would be emacs and then all | 
|  | the vi users would get humpy. Key bindings may be completely reconfigured in | 
|  | any case. | 
|  |  | 
|  | - tmux has an option to limit the window size. | 
|  |  | 
|  | - tmux has search in windows (C-b f). | 
|  |  | 
|  | - The window split (pane) model is different. tmux has two objects, windows and | 
|  | panes; screen has just windows. This difference has several implications: | 
|  |  | 
|  | * In screen you can have a window appear in several layouts, in tmux a pane | 
|  | can only be in one window (fixing this is a big todo item but quite | 
|  | invasive). | 
|  |  | 
|  | * tmux layouts are immutable and do not get changed unless you modify them. | 
|  |  | 
|  | * In tmux, all panes are closed when you kill a window. | 
|  |  | 
|  | * tmux panes do not have individual names, titles and so on. | 
|  |  | 
|  | I think tmux's model is much easier to manage and navigate within a window, | 
|  | but breaking panes off from and joining them to windows is more clumsy. | 
|  |  | 
|  | tmux also has support for preset pane layouts. | 
|  |  | 
|  | - tmux's status line syntax is more readable and easier to use. I think it'd be | 
|  | hard for anyone to argue with this. tmux doesn't support running a command | 
|  | constantly and always using the last line of its output, commands must be run | 
|  | again each time. | 
|  |  | 
|  | - tmux has modern, easily extended code. Again hard to argue screen is better | 
|  | if you have looked at the code. | 
|  |  | 
|  | - tmux depends on libevent. I don't see this as a disadvantage: libevent is | 
|  | small and portable, and on modern systems with current package management | 
|  | systems dependencies are not an issue. libevent brings advantages in code | 
|  | simplicity and performance. | 
|  |  | 
|  | - screen allows the window to be bigger than the terminal and can pan around | 
|  | it. tmux limits the size to the largest attached client. This is a big todo | 
|  | item for tmux but it is not trivial. | 
|  |  | 
|  | - screen has builtin serial and telnet support; this is bloat and is unlikely | 
|  | to be added to tmux. | 
|  |  | 
|  | - screen has support for updating utmp. Nobody has really come up with a clean, | 
|  | portable way to do this without making tmux setuid or setgid yet. | 
|  |  | 
|  | - Environment handling is different. | 
|  |  | 
|  | - tmux tends to be more demanding on the terminal so tends to show up terminal | 
|  | and application bugs which screen does not. | 
|  |  | 
|  | - screen has wider platform support, for example IRIX and HP-UX, and for odd | 
|  | terminals. | 
|  |  | 
|  | * I found a bug! What do I do? | 
|  |  | 
|  | Please send bug reports by email to nicm@users.sourceforge.net or | 
|  | tmux-users@lists.sourceforge.net. Please include as much of the following | 
|  | information as possible: | 
|  |  | 
|  | - the version of tmux you are running; | 
|  | - the operating system you are using and its version; | 
|  | - the terminal emulator you are using and the TERM setting when tmux was | 
|  | started; | 
|  | - a description of the problem; | 
|  | - if the problem is repeatable, the steps to repeat the problem; | 
|  | - for screen corruption issues, a screenshot and the output of "infocmp $TERM" | 
|  | from outside tmux are often very useful. | 
|  |  | 
|  | * Why doesn't tmux do $x? | 
|  |  | 
|  | Please send feature requests by email to nicm@users.sourceforge.net. | 
|  |  | 
|  | * Why do you use the screen terminal description inside tmux? It sucks. | 
|  |  | 
|  | It is already widely available. It is planned to change to something else such | 
|  | as xterm-xfree86 at some point, if possible. | 
|  |  | 
|  | * I don't see any colour in my terminal! Help! | 
|  |  | 
|  | On some platforms, common terminal descriptions such as xterm do not include | 
|  | colour. screen ignores this, tmux does not. If the terminal emulator in use | 
|  | supports colour, use a value for TERM which correctly lists this, such as | 
|  | xterm-color. | 
|  |  | 
|  | * tmux freezes my terminal when I attach to a session. I even have to kill -9 | 
|  | the shell it was started from to recover! | 
|  |  | 
|  | Some consoles really really don't like attempts to set the window title. Tell | 
|  | tmux not to do this by turning off the "set-titles" option (you can do this | 
|  | in .tmux.conf): | 
|  |  | 
|  | set -g set-titles off | 
|  |  | 
|  | If this doesn't fix it, send a bug report. | 
|  |  | 
|  | * Why is C-b the prefix key? How do I change it? | 
|  |  | 
|  | The default key is C-b because the prototype of tmux was originally developed | 
|  | inside screen and C-b was chosen not to clash with the screen meta key. It | 
|  | also has the advantage of not interfering with the use of C-a for start-of-line | 
|  | in emacs and the shell (although it does interfere with previous-character). | 
|  |  | 
|  | Changing is simple: change the "prefix-key" option, and - if required - move | 
|  | the binding of the "send-prefix" command from C-b (C-b C-b sends C-b by | 
|  | default) to the new key. For example: | 
|  |  | 
|  | set -g prefix C-a | 
|  | unbind C-b | 
|  | bind C-a send-prefix | 
|  |  | 
|  | * How do I use UTF-8? | 
|  |  | 
|  | When running tmux in a UTF-8 capable terminal, UTF-8 must be turned on in tmux; | 
|  | as of release 0.9, tmux attempts to autodetect a UTF-8-capable terminal by | 
|  | checking the LC_ALL, LC_CTYPE and LANG environment variables. list-clients may | 
|  | be used to check if this is detected correctly; if not, the -u command-line | 
|  | flag may be specified when creating or attaching a client to a tmux session: | 
|  |  | 
|  | $ tmux -u new | 
|  |  | 
|  | Since the 1.0 release, tmux will turn on UTF-8 related options automatically | 
|  | (ie status-utf8, and utf8) if the above conditions are met. | 
|  |  | 
|  | * How do I use a 256 colour terminal? | 
|  |  | 
|  | Provided the underlying terminal supports 256 colours, it is usually sufficient | 
|  | to add the following to ~/.tmux.conf: | 
|  |  | 
|  | set -g default-terminal "screen-256color" | 
|  |  | 
|  | Note that some platforms do not support "screen-256color" ("infocmp | 
|  | screen-256color" will return an error) - in this case see the next entry in | 
|  | this FAQ. | 
|  |  | 
|  | tmux attempts to detect a 256 colour terminal both by looking at the colors | 
|  | terminfo entry and by looking for the string "256col" in the TERM environment | 
|  | variable. | 
|  |  | 
|  | If both these methods fail, the -2 flag may be passed to tmux when attaching | 
|  | to a session to indicate the terminal supports 256 colours. | 
|  |  | 
|  | * vim or $otherprogram doesn't display 256 colours. What's up? | 
|  |  | 
|  | Some programs attempt to detect the number of colours a terminal is capable of | 
|  | by checking the colors terminfo or Co termcap entry. However, this is not | 
|  | reliable, and in any case is missing from the "screen" terminal description | 
|  | used inside tmux. | 
|  |  | 
|  | There are two options (aside from using "screen-256color") to allow programs to | 
|  | recognise they are running on a 256-colour terminal inside tmux: | 
|  |  | 
|  | - Manually force the application to use 256 colours always or if TERM is set to | 
|  | screen. For vim, you can do this by overriding the t_Co option, see | 
|  | http://vim.wikia.com/wiki/256_colors_in_vim. | 
|  | - Creating a custom terminfo file that includes colors#256 in ~/.terminfo and | 
|  | using it instead. These may be compiled with tic(1). | 
|  |  | 
|  | * How do I make Ctrl-PgUp and Ctrl-PgDn work in vim? | 
|  |  | 
|  | tmux supports passing through ctrl (and where supported by the client terminal, | 
|  | alt and shift) modifiers to function keys using xterm(1)-style key sequences. | 
|  | This may be enabled per window, or globally with the tmux command: | 
|  |  | 
|  | setw -g xterm-keys on | 
|  |  | 
|  | Because the TERM variable inside tmux must be set to "screen", vim will not | 
|  | automatically detect these keys are available; however, the appropriate key | 
|  | sequences can be overridden in .vimrc using the following: | 
|  |  | 
|  | if &term == "screen" | 
|  | set t_kN=^[[6;*~ | 
|  | set t_kP=^[[5;*~ | 
|  | endif | 
|  |  | 
|  | And similarly for any other keys for which modifiers are desired. | 
|  |  | 
|  | Please note that the "xterm-keys" setting may affect other programs, in the | 
|  | same way as running them in a standard xterm; for example most shells do not | 
|  | expect to receive xterm(1)-style key sequences so this setting may prevent keys | 
|  | such as ctrl-left and ctrl-right working correctly. tmux also passes through | 
|  | the ctrl (bit 5 set, for example ^[[5~ to ^[[5^) modifier in non-xterm(1) mode; | 
|  | it may be possible to configure vim to accept these, an example of how to do so | 
|  | would be welcome. | 
|  |  | 
|  | vim users may also want to set the "ttyfast" option inside tmux. | 
|  |  | 
|  | * Why doesn't elinks set the window title inside tmux? | 
|  |  | 
|  | There isn't a way to detect if a terminal supports setting the window title, so | 
|  | elinks attempts to guess by looking at the environment. Rather than looking for | 
|  | TERM=screen, it uses the STY variable to detect if it is running in screen; | 
|  | tmux does not use this so the check fails. A workaround is to set STY before | 
|  | running elinks. | 
|  |  | 
|  | The following shell function does this, and also clears the window title on | 
|  | exit (elinks, for some strange reason, sets it to the value of TERM): | 
|  |  | 
|  | elinks() { | 
|  | STY= `which elinks` $* | 
|  | echo -ne \\033]0\;\\007; | 
|  | } | 
|  |  | 
|  | * What is the proper way to escape characters with #(command)? | 
|  |  | 
|  | When using the #(command) construction to include the output from a command in | 
|  | the status line, the command will be parsed twice. First, when it's read by the | 
|  | configuration file or the command-prompt parser, and second when the status | 
|  | line is being drawn and the command is passed to the shell. For example, to | 
|  | echo the string "(test)" to the status line, either single or double quotes | 
|  | could be used: | 
|  |  | 
|  | set -g status-right "#(echo \\\\(test\\\\))" | 
|  | set -g status-right '#(echo \\\(test\\\))' | 
|  |  | 
|  | In both cases, the status-right option will be set to the string "#(echo | 
|  | \\(test\\))" and the command executed will be "echo \(test\)". | 
|  |  | 
|  | * tmux uses too much CPU. What do I do? | 
|  |  | 
|  | Automatic window renaming may use a lot of CPU, particularly on slow computers: | 
|  | if this is a problem, turn it off with "setw -g automatic-rename off". If this | 
|  | doesn't fix it, please report the problem. | 
|  |  | 
|  | * I use PuTTY and my tmux window pane separators are all qqqqqqqqq's! | 
|  |  | 
|  | PuTTY is using a character set translation that doesn't support ACS line | 
|  | drawing. With a Unicode font, try setting PuTTY to use a different translation | 
|  | on the Window -> Translation configuration page. For example, change UTF-8 to | 
|  | ISO-8859-1 or CP437. It may also be necessary to adjust the way PuTTY treats | 
|  | line drawing characters in the lower part of the same configuration page. | 
|  |  | 
|  | * What is the best way to display the load average? Why no #L? | 
|  |  | 
|  | It isn't possible to get the load average portably in code and it is preferable | 
|  | not to add portability goop. The following works on at least Linux, *BSD and OS | 
|  | X: | 
|  |  | 
|  | uptime|awk '{split(substr($0, index($0, "load")), a, ":"); print a[2]}' | 
|  |  | 
|  | * How do I attach the same session to multiple clients but with a different | 
|  | current window, like screen -x? | 
|  |  | 
|  | One or more of the windows can be linked into multiple sessions manually with | 
|  | link-window, or a grouped session with all the windows can be created with | 
|  | new-session -t. | 
|  |  | 
|  | * Ctrl and arrow keys doesn't work in putty! What do I do? | 
|  |  | 
|  | putty inverts the sense of the cursor key mode on ctrl, which is a bit hard for | 
|  | tmux to detect properly. To get ctrl keys right, change the terminfo settings | 
|  | so kUP5 (Ctrl-Up etc) are the adjusted versions, and disable smkx/rmkx so tmux | 
|  | doesn't change the mode. For example with this line in .tmux.conf (assuming you | 
|  | have TERM set to xterm): | 
|  |  | 
|  | set -g terminal-overrides "xterm*:kLFT5=\eOD:kRIT5=\eOC:kUP5=\eOA:kDN5=\eOB:smkx@:rmkx@" | 
|  |  | 
|  | Note that this will only work in tmux 1.2 and above. | 
|  |  | 
|  | * How can I blank the tmux window? | 
|  |  | 
|  | GNU screen has a feature whereby it will blank the screen after a period of | 
|  | inactivity. To do the same thing in tmux, use the lock-command setting, for | 
|  | example (with GNU bash): | 
|  |  | 
|  | set -g lock-command 'tput civis && read -s -n1' | 
|  |  | 
|  | This will remove the cursor and tell the shell to quit once a key has been | 
|  | pressed. For zsh, use "read -s -k1". | 
|  |  | 
|  | In addition, it's possible to have both blanking and locking (for instance via | 
|  | lock(1) or vlock(1)) by using the following: | 
|  |  | 
|  | bind x set lock-command '/usr/bin/vlock' \; lock-client \; set lock-command 'tput civis && read -s -n1' | 
|  |  | 
|  | * How can I open a new window in the same directory as the current window? | 
|  |  | 
|  | One option is to just run "TMUX= tmux" in the window. However, this only works if no | 
|  | command is running, so that you can input the command. | 
|  |  | 
|  | A workaround is to let tmux know about the current path through an environment | 
|  | variable. To do so, use the following command: | 
|  |  | 
|  | [ -n "$TMUX" ] && tmux setenv TMUXPWD_$(tmux display -p "#I") $PWD | 
|  |  | 
|  | Which sets TMUXPWD_i (where i is the number of the current window) to the path | 
|  | of the current directory. This command can be added to PS1, for example: | 
|  |  | 
|  | PS1='$([ -n "$TMUX" ] && tmux setenv TMUXPWD_$(tmux display -p "#I") $PWD)\h$ ' | 
|  |  | 
|  | When a new window is created, the shell should be asked to change | 
|  | directory. You can define a new binding (for example, if using GNU bash): | 
|  |  | 
|  | bind-key C-c run-shell 'tmux neww "cd $(tmux display -p "\$TMUXPWD_#I"); exec bash"' | 
|  |  | 
|  | This solution will work even if a command is currently running in the terminal, | 
|  | but it will not work from a window that has just been swapped with another | 
|  | because TMUXPWD_i will not be updated after a swap. However, once a new prompt | 
|  | is displayed, TMUXPWD_i is updated properly. | 
|  |  | 
|  | * tmux doesn't start with "daemon failed" | 
|  |  | 
|  | tmux shows something similar to this when started: | 
|  |  | 
|  | fatal: server_start: daemon failed: No such file or directory | 
|  | fatal: main_dispatch: imsg_read failed | 
|  |  | 
|  | A possible reason is that /dev/null is not a character device or is otherwise | 
|  | inaccessible. | 
|  |  | 
|  | Check with: | 
|  |  | 
|  | file /dev/null | 
|  | ls -l /dev/null | 
|  |  | 
|  | If it is not a character device or has incorrect permissions, it can typically | 
|  | be recreated with: | 
|  |  | 
|  | cd /dev && rm null && ./MAKEDEV null | 
|  |  | 
|  | * vim or $otherprogram displays reverse video instead of italics, even though | 
|  | tmux displays italics just fine in the status line. What's wrong? | 
|  |  | 
|  | Screen's terminfo description lacks italics mode and has standout mode in its | 
|  | place. To make applications aware that tmux supports italics, you'll need to | 
|  | create a new terminfo file with modified smso, rmso, sitm and ritm entries: | 
|  |  | 
|  | $ mkdir $HOME/.terminfo/ | 
|  | $ screen_terminfo="screen" | 
|  | $ infocmp "$screen_terminfo" | sed \ | 
|  | -e 's/^screen[^|]*\|[^,]*,/screen-it|screen with italics support,/' \ | 
|  | -e 's/smso=[^,]*,/smso=\\E[7m,/' \ | 
|  | -e 's/rmso=[^,]*,/rmso=\\E[27m,/' \ | 
|  | -e '$s/$/ sitm=\\E[3m, ritm=\\E[23m,/' > /tmp/screen.terminfo | 
|  | $ tic /tmp/screen.terminfo | 
|  |  | 
|  | And tell tmux to use it in ~/.tmux.conf: | 
|  |  | 
|  | set -g default-terminal "screen-it" | 
|  |  | 
|  | If your terminal supports 256 colors, use: | 
|  |  | 
|  | $ screen_terminfo="screen-256color" | 
|  |  | 
|  | instead of "screen". See the FAQ entry about 256 colors support for more info. | 
|  | Also note that tmux will still display reverse video on terminals that do not | 
|  | support italics. | 
|  |  | 
|  | $Id: FAQ,v 1.42 2011-04-11 07:14:54 nicm Exp $ |