FAQ - tmux - Rivoreo Source Code Repositories

 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? What else does it offer?

 tmux offers several advantages over screen:

 - a clearly-defined client-server model: windows are independent entities which
   may be attached simultaneously to multiple sessions and viewed from multiple
   clients (terminals), as well as moved freely between sessions within the same
   tmux server;
 - a consistent, well-documented command interface, with the same syntax
   whether used interactively, as a key binding, or from the shell;
 - easily scriptable from the shell;
 - multiple paste buffers;
 - choice of vi or emacs key layouts;
 - an option to limit the window size;
 - a more usable status line syntax, with the ability to display the first line
   of output of a specific command;
 - a cleaner, modern, easily extended, BSD-licensed codebase.

 There are still a few features screen includes that tmux omits:

 - builtin serial and telnet support; this is bloat and is unlikely to be added
   to tmux;
 - 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.

 * 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.

 $Id: FAQ,v 1.36 2010-02-04 21:01:59 nicm Exp $
	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? What else does it offer?

	tmux offers several advantages over screen:

	- a clearly-defined client-server model: windows are independent entities which
	may be attached simultaneously to multiple sessions and viewed from multiple
	clients (terminals), as well as moved freely between sessions within the same
	tmux server;
	- a consistent, well-documented command interface, with the same syntax
	whether used interactively, as a key binding, or from the shell;
	- easily scriptable from the shell;
	- multiple paste buffers;
	- choice of vi or emacs key layouts;
	- an option to limit the window size;
	- a more usable status line syntax, with the ability to display the first line
	of output of a specific command;
	- a cleaner, modern, easily extended, BSD-licensed codebase.

	There are still a few features screen includes that tmux omits:

	- builtin serial and telnet support; this is bloat and is unlikely to be added
	to tmux;
	- 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.

	* 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.

	$Id: FAQ,v 1.36 2010-02-04 21:01:59 nicm Exp $