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XTERM - Frequently Asked Questions (FAQ)
Copyright 1997,1998,2000 by Thomas E. Dickey


What is XTERM?

From the manual page:
The xterm program is a terminal emulator for the X Window System. It provides DEC VT102 and Tektronix 4014 compatible terminals for programs that can't use the window system directly. If the underlying operating system supports terminal resizing capabilities (for example, the SIGWINCH signal in systems derived from 4.3bsd), xterm will use the facilities to notify programs running in the window whenever it is resized.

Who wrote XTERM?

A lot of people, cited at the bottom of the manual page wrote the original xterm program, maintained by the X Consortium (now part of the Open Group). There is no changelog, and it is not clear who did what. Email from Jim Gettys provides some background:
Cast of thousands...

To give a bit of history, xterm predates X!

It was originally written as a stand-alone terminal emulator for the VS100 by Mark Vandevoorde, as my coop student the summer that X started.

Part way through the summer, it became clear that X was more useful than trying to do a stand alone program, so I had him retarget it to X. Part of why xterm's internals are so horrifying is that it was originally intended that a single process be able to drive multiple VS100 displays. Don't hold this against Mark; it isn't his fault.

I then did a lot of hacking on it, and merged several improved versions from others back in.

Notable improvements include the proper ANSI parser, that Bob McNamara did.

The Tek 4010 support came from a guy at Smithsonian Astrophysical Observatory whose name slips my mind at the moment.

Ported to X11 by Loretta Guarino.

Then hacked on at the X Consortium by uncounted people.

Email from Doug Mink provides more background:
I was checking out the newly revised AltaVista search engine to see what was on the net about xterm, and I found your pages. I can add to the FAQ in that I was the "guy at the Smithsonian Astrophysical Observatory" Jim Gettys refers to. I am listed at the end of the man page under authors. What happened was that I was hired by SAO (after leaving the research staff at MIT) in October 1985 to write analysis software for the Spacelab 2 Infrared Telescope which was to fly on the Space Shuttle in 1985 less than six months after I was hired. I came with a tar tape full of software I had written for Unix and Tektronix terminals, but I was presented with a VS100 terminal which had an early version (X6 or so) of xterm, with no graphics capabilities. SAO is at Harvard, across Cambridge from MIT, where Jim Gettys was detailed from DEC to the X project, and Jim had connections with SAO, having worked here after college (MIT, where we had both worked at the observatory at various times); he was still sharing an apartment with an SAO colleague of mine, too. Anyway, everyone decided that since I knew Tektronix commands pretty well, and our group desparately needed the graphics capabilities, it would be a good use of my time to implement a Tektronix terminal emulator under X. So I set to work learning more C--I had only written a couple of wrappers to C I/O routines so I could use them with my Fortran software--and wrote a Tektronix emulator. The only X documentation at the time was the code itself. While I was at it, I wrote an improved Tektronix emulator for our Imagen laser printer which used the full resolution of that 300 dpi printer instead of the effective 100 dpi (i.e. jaggy) emultator distributed with the printer. The original xterm Tek emulator shared a window with the VT100 emulator, much like on the VT240 terminals which I had been using at MIT before I came to Harvard. With a VAX 750 running several VS100's, window creation was sloowww, so sharing a window was the quickest way to do things, and all of my software was written for that mode of operation, anyway. While I wrote the emulator so that my software would work on it, it was tested by the X group against a BBN graphics package, the name of which slips my mind right now.

Anyway, 15 years later, I am still using xterm and some of the same mapping software I wrote the emulator for. And I am still at the Smithsonian Astrophysical Observatory.

This FAQ is oriented toward the version of xterm distributed with XFree86 3.3, which is based on the X11R6.3 xterm, with the addition of ANSI color and VT220 controls.

What platforms does it run on?

Xterm runs in all of the implementations of X11. I've built and run these since I started working on xterm:
  • AIX 3.2.5 (cc)
  • Digital Unix 3.2, 4.0 (cc)
  • FreeBSD 2.2.6 (gcc 2.8)
  • HP-UX 9.05 (gcc 2.7.2)
  • IRIX 5.2, 6.2 (cc, gcc 2.7.2, gcc 2.8)
  • Linux 2.0.0, 2.0.29 (gcc 2.7.2)
  • SCO OpenServer 5 (cc, gcc).
  • Solaris 2.4, 2.5, 2.5.1, 2.6 (cc, gcc 2.7.2)
  • SunOS 4.1.1, 4.1.3 (gcc 2.7.2)

Most of these configurations have X11R5 libraries. Only minor changes are needed to make xterm work on those systems. However, with X11R6 you can obtain better locale support, as well as new features such as the active icon.

What is the latest version?

The most recent (and well supported) version of xterm is the XFree86 version. I have a copy at

Ftp: ftp://dickey.his.com/xterm/xterm.tar.gz

What versions are available?

There are several other versions of xterm, as well as similar programs. These include (I am aware of a few others, such as xcterm and mterm, but have not seen a working version of these).

There are actually two versions of XFree86 xterm. Starting with my patch 88, there are the stable (beta) and unstable (alpha) versions, which currently are XFree86 3.3.6 and XFree86 4.0, respectively. I have been making only critical changes to the stable version since patch 88; ongoing development (including all non-critical fixes) is focused on the "unstable".

XFree86 4.0 should have incorporated my patch 131, but it was overlooked at the last moment (though it was listed in the ChangeLog, the patch itself was not applied). Unfortunately, the patch 130 version which was released renders colors incorrectly on most platforms, in particular FreeBSD. Ironically, the change in patch 129 which introduced this bug was designed to work around a bug which I have seen only running with FreeBSD. To compound the irony, there is some resistance at this time (2000/4/5) by that organization to incorporating the fix because it might be confused with the 4.0 release version.

How do I ...

Not really problems, but frequently asked questions (the point of this, after all):

How do I change the font size?

This is in the manpage, in MENUS.

X Consortium xterm provides popup menus, by pressing the control key together with the mouse button. Control right mouse button pops up the VT FONTS menu, from which you can select fonts that are specified in xterm's resources. Usually these are in increasing order of size.

XFree86 xterm provides the menu, plus a feature adapted from rxvt: pressing the shifted keypad plus or minus keys steps through the font menu selections, in order of their size.

How do I print the screen?

That depends on why you want to print it.

If you want a trace of an interactive session, you should use the script program. It records every character sent to the screen, recording them in a file typescript. There are two drawbacks to this approach:

  • Every character is recorded. Even cursor movement, if you run an editor.
  • You must start a new shell to capture the typescript file.
Well, what about logging? Some versions of xterm support logging to a file. In fact XFree86 xterm does. Logging was dropped from X Consortium xterm during X11R5 due to security concerns. Those were addressed, but logging was not reinstated (in fact there is a related bug in xterm). Some people prefer this, because it is convenient: you can start and stop logging a popup menu entry. However
  • Every character is recorded. Even cursor movement, if you run an editor.
  • Line drawing characters are translated to control characters, i.e., codes 0-31 (this may be fixed sometime, it is a problem inherited from X Consortium xterm).
Both script and logging are useful for recording, but they require interpretation to make sense of the trace. You probably would not send that trace to a printer (not twice, anyway).

If you want to print the contents of the screen, XFree86 xterm implements, as part of the VT100 emulation, an "attached" printer.

  • The printer is really a pipe command, to which xterm writes.
  • You can print the current line, page, or continuously with the corresponding control sequences. That takes an application program which knows how to print the screen.
  • If you do not have an application, xterm has a popup menu entry to print the window.
There are limitations and tradeoffs using the "attached" printer, because it is an emulation:
  • The emulation is based on detailed documentation for a VT320. This states that control sequences are sent in each line to reset bold, underlining and other printable attributes, and to set them as needed. Your printer probably does not understand this sort of input. Use the xterm resource printAttributes to get more easily printed output.
  • The printer may hang. Not really, but it seems that way. If you use the "attached" printer from an application designed for the VT100 terminal, it is written with the assumption that the printer is a dedicated piece of hardware, printing onto a continuous form. Use the printerAutoClose resource to change xterm's behavior to close the printer pipe whenever the terminal is told to switch the printer offline.
If you use the popup menu to print the screen, this will close the printer pipe unless it was already opened by the application running in xterm.

How do I set up function keys?

With XFree86 xterm, this is relatively simple. So I'll answer that first.

With X Consortium xterm, you have partial support for DEC VTxxx function keys. Function keys F1 to F12 correspond to DEC's F1 to F12 (sort of). Actually, DEC's VT220 terminals do not have codes for F1 through F5. They are reserved for local functions. And the VT220 (and up) terminals have 20 function keys. So you cannot do anything with the F13 through F20 (i.e., DO, HELP and SELECT). Finally, though xterm is reputed to be VT100-compatible, it has no support for the VT100 keypad (PF1 to PF4, and the "," key).

XFree86 xterm changes the X Consortium codes for F1 to F4 to match the VT100 PF1 to PF4, except when the emulation level is VT220 and up. In this case, it generates the same F1 to F4 codes as X Consortium xterm. Moreover, it adds a new resource sunKeyboard, which tells the program whether it has only 12 function keys (i.e., a Sun or PC keyboard). If so (this is selectable from the popup menu), you can use the control key with F1 to F12 to get F13 to F24, and use the "+" key on the keypad as an alias for "," (comma).

The emulation level for XFree86 xterm is set via the resource decTerminalID, e.g., to 220 for a VT220. Once set, applications can set the emulation level up or down within that limit. DEC's terminals are configured in much the same way by a setup option.

That is the simple way, using a couple of new resources. The traditional way to get function keys involves translations. I have seen a few postings on the newsgroups that do this. Here is one from Bruce Momjian <root@candle.pha.pa.us> for a VT220:

	xterm $XTERMFLAGS +rw +sb +ls $@ -tm 'erase ^? intr ^c' \
		-name vt220 -title vt220 -tn xterm-220 "$@" &

with the corresponding resources:

	XTerm*VT100.Translations: #override \n\
		<Key>Home: string(0x1b) string("[3~") \n \
		<Key>End: string(0x1b) string("[4~") \n
	vt220*VT100.Translations: #override \n\
	~Shift	<Key>F1: string(0x1b) string("OP") \n \
	~Shift	<Key>F2: string(0x1b) string("OQ") \n \
	~Shift	<Key>F3: string(0x1b) string("OR") \n \
	~Shift	<Key>F4: string(0x1b) string("OS") \n \
	~Shift	<Key>F5: string(0x1b) string("[16~") \n \
	~Shift	<Key>F6: string(0x1b) string("[17~") \n \
	~Shift	<Key>F7: string(0x1b) string("[18~") \n \
	~Shift	<Key>F8: string(0x1b) string("[19~") \n \
	~Shift	<Key>F9: string(0x1b) string("[20~") \n \
	~Shift	<Key>F10: string(0x1b) string("[21~") \n \
	~Shift	<Key>F11: string(0x1b) string("[28~") \n \
	~Shift	<Key>F12: string(0x1b) string("[29~") \n \
	Shift	<Key>F1: string(0x1b) string("[23~") \n \
	Shift	<Key>F2: string(0x1b) string("[24~") \n \
	Shift	<Key>F3: string(0x1b) string("[25~") \n \
	Shift	<Key>F4: string(0x1b) string("[26~") \n \
	Shift	<Key>F5: string(0x1b) string("[K~") \n \
	Shift	<Key>F6: string(0x1b) string("[31~") \n \
	Shift	<Key>F7: string(0x1b) string("[31~") \n \
	Shift	<Key>F8: string(0x1b) string("[32~") \n \
	Shift	<Key>F9: string(0x1b) string("[33~") \n \
	Shift	<Key>F10: string(0x1b) string("[34~") \n \
	Shift	<Key>F11: string(0x1b) string("[28~") \n \
	Shift	<Key>F12: string(0x1b) string("[29~") \n \
		<Key>Print: string(0x1b) string("[32~") \n\
		<Key>Cancel: string(0x1b) string("[33~") \n\
		<Key>Pause: string(0x1b) string("[34~") \n\
		<Key>Insert: string(0x1b) string("[2~") \n\
		<Key>Delete: string(0x1b) string("[3~") \n\
		<Key>Home: string(0x1b) string("[1~") \n\
		<Key>End: string(0x1b) string("[4~") \n\
		<Key>Prior: string(0x1b) string("[5~") \n\
		<Key>Next: string(0x1b) string("[6~") \n\
		<Key>BackSpace: string(0x7f) \n\
		<Key>Num_Lock: string(0x1b) string("OP") \n\
		<Key>KP_Divide: string(0x1b) string("Ol") \n\
		<Key>KP_Multiply: string(0x1b) string("Om") \n\
		<Key>KP_Subtract: string(0x1b) string("OS") \n\
		<Key>KP_Add: string(0x1b) string("OM") \n\
		<Key>KP_Enter: string(0x1b) string("OM") \n\
		<Key>KP_Decimal: string(0x1b) string("On") \n\
		<Key>KP_0: string(0x1b) string("Op") \n\
		<Key>KP_1: string(0x1b) string("Oq") \n\
		<Key>KP_2: string(0x1b) string("Or") \n\
		<Key>KP_3: string(0x1b) string("Os") \n\
		<Key>KP_4: string(0x1b) string("Ot") \n\
		<Key>KP_5: string(0x1b) string("Ou") \n\
		<Key>KP_6: string(0x1b) string("Ov") \n\
		<Key>KP_7: string(0x1b) string("Ow") \n\
		<Key>KP_8: string(0x1b) string("Ox") \n\
		<Key>KP_9: string(0x1b) string("Oy") \n

	!	<Key>Up: string(0x1b) string("[A") \n\
	!	<Key>Down: string(0x1b) string("[B") \n\
	!	<Key>Right: string(0x1b) string("[C") \n\
	!	<Key>Left: string(0x1b) string("[D") \n\

	*visualBell:	true
	*saveLines:    1000
	*cursesemul:	true
	*scrollKey: true
	*scrollBar: true
Note that real VT220 terminals use shifted function keys to mean something different: the user-programmable keys (i.e., DECUDK). XFree86 xterm supports this, but the translations do not (they're using shift to select F13 to F20).

Here's another one, from Robert Ess <ress@spd.dsccc.com>:


	#		vax
	# 09-17-96	Bob Ess      - initial creation
	# 09-26-96	Shig Katada  - Additional keybindings
	#		Script file to incorporate keybindings and command line
	#		options for connecting to a VAX node

	# Usage statement
		echo " Usage  : vax -options"
		echo " Options: -80   for 80 column terminal"
		echo "          -132  for 132 column terminal"
		echo "          -fg colorname"
		echo "          -bg colorname"
		echo "          -fn fontname"
		echo "          -fb bold fontname"
		echo "          -host [altair] [devel] [leonis] [castor]"
		echo ""
		echo " Example: \"vax -80 -fg white -bg black -fn 9x15 -fb 9x15b -host castor\""
		echo "          Starts a VAX session with an 80 column terminal"
		echo "          with a black background, white foreground, a normal"
		echo "          font of 9x15 and a bold font of 9x15b, and connects"
		echo "          to the node 'castor'"
		echo "          If you need additional help, please call Workstation"
		echo "          Services at x92396."
		exit 1

	# Default to a black foreground with a white background.
	# Use the 9x15 and 9x15bold fonts. Connect to castor by default.

	# Parse the command line arguments
	while [ $# != 0 ];
		case $1 in
			-80)	COLS=80
			-132)	COLS=132
			-fg)	shift
			-bg)	shift
			-fn)	shift
			-fb)	shift
			-host)	shift
			-help)	Usage;;
			*)	Usage;;

	xterm  -title "VAX" -sb -sl 1200 -geo ${COLS}x24 -fg ${FG} -bg ${BG} \
		-cr red -fn ${FONT} -fb ${BFONT} -xrm \
		"XTerm*vt100.translations:     #override \n\
		<Key>Insert:            string(\001) \n\
		Shift <Key>Up:          scroll-back(1,lines) \n\
		Shift <Key>Down:        scroll-forw(1,lines) \n\
		Shift <Key>Right:       string(0x1b) string("f") \n\
		Shift <Key>Left:        string(0x1b) string("b") \n\
		Shift <Key>Delete:      string(0x1b) string(0x08) \n\
		Shift <Key>Tab:         string(0x1b) string("*") \n\
		<Key>0x1000FF0D:        scroll-back(1,page) \n\
		<Key>0x1000FF0E:        scroll-forw(1,page) \n\
		<Key>0x1000FF09:        string(\010) \n\
		<Key>0x1000FF0A:        string(\005) \n\
		<Key>BackSpace:         string(0xff) \n\
		<Key>Select:            select-start() \n\
		<Key>0x1000FF02:        select-end(PRIMARY,CUT_BUFFER0) \n\
		Meta <Key>0x1000FF02:   select-end(CLIPBOARD) \n\
		<Key>0x1000FF04:        insert-selection(PRIMARY,CUT_BUFFER0) \n\
		Meta <Key>0x1000FF04:   insert-selection(CLIPBOARD) \n\
		<Key>F1:                string(0x1b) string("OP") \n\
		<Key>F2:                string(0x1b) string("OQ") \n\
		<Key>F3:                string(0x1b) string("OR") \n\
		<Key>F4:                string(0x1b) string("OS") \n\
		<Key>F5:                string(0x1b) string("OA") \n\
		<Key>F11:               string(0x1b) string("[23~") \n\
		<Key>F12:               string(0x1b) string("[24~") \n\
		<Key>KP_0:              string(0x1b) string("Op") \n\
		<Key>KP_1:              string(0x1b) string("Oq") \n\
		<Key>KP_2:              string(0x1b) string("Or") \n\
		<Key>KP_3:              string(0x1b) string("Os") \n\
		<Key>KP_4:              string(0x1b) string("Ot") \n\
		<Key>KP_5:              string(0x1b) string("Ou") \n\
		<Key>KP_Divide:         string(0x1b) string("OP") \n\
		<Key>KP_Multiply:       string(0x1b) string("[29~") \n\
		<Key>KP_Enter:          string(0x1b) string("OM") \n\
		<Key>KP_Subtract:       string(0x1b) string("Om") \n\
		<Key>KP_Add:            string(0x1b) string("Ol") \n\
		<Key>KP_Decimal:        string(0x1b) string("On") \n\
		<Btn1Down>:             select-start() \n\
		<Btn1Motion>:           select-extend() \n\
		<Btn1Up>:               select-end(PRIMARY,CUT_BUFFER0) \n\
		Button1<Btn2Down>:      select-end(CLIPBOARD) \n\
		Button1<Btn2Up>:        ignore()" \
		-e telnet $HOST &
Finally (for the moment) is a further modification of Robert Ess's script by Erik Ahlefeldt, <oahlefel@metz.une.edu.au>. From his readme file, for vmsterm:
This script is for people who wish to connect from a Linux or Unix computer to a VMS computer using telnet and get a good VT100 or VT220 emulation. The key mappings have been specifically designed to emulate the VT terminal auxiliary numeric keypad, so that you can use VMS EDT and TPU editors, as well as the many VMS applications use keys PF1 to PF4. The script should work with any recent version of Xterm using a standard extended IBM PC keyboard or a Sun keyboard.

About the keymappings. First the auxiliary numeric keypad. My prime objective with these mappings was to produce a setup that I could use with the EDT and TPU editors which make extensive use of the numeric keypad. The top row of keys PC numeric keypad (Num Lock, Divide, Multiply, Subtract) are where you find PF1, PF2, PF3, PF4 on a VT keyboard, so I have mapped them to PF1 thru PF4. The PC numeric keypad Add key (+) takes up the space of two keys which are Minus and Comma on the VT keyboard - I have mapped it to Comma (Delete Character in the EDT editor). I have then used the PC Pause key to map to VT key Minus (Delete Word in the EDT editor). The remaining keys on the auxiliary numeric keypad are the same for PC and VT.

The six keys between the main and numeric keypads on the PC (Insert, Home, Page Up, Delete End, Page Down) are usually mapped to the VT keys by either position or by (approximate) function. As I rarely use these keys I have mapped them by function as follows: PC key Insert to VT Insert Here, PC Home to VT Find, PC Page Up to VT Prev, PC Delete to VT Remove, PC End to VT Select, PC Page Down to VT Next.

Function keys.
There are 12 function keys on the PC keyboard and 20 on the VT keyboard, so I map PC F1 thru F12 to VT F1 thru F12 (except for F1 thru F5 as noted below) and PC Shift F1 thru Shift F10 to VT F11 thru F20.

The VT keys F1 thru F5 are local hardware function keys so there is nothing to emulate, however some PC to VT emulations in the past have mapped PF1 thru PF4 here, so I have done that too, even though they are already mapped on the auxiliary numeric keypad.

Xterm functionality.
You lose some xterm functions when you remap the keyboard, however this script implements a scroll back buffer of 1000 lines which you scroll through using Shift and Up (a.k.a. Up Arrow or Cursor Up key) or Shift and Down.
a summary of the keyboard mapping:
		PC Key     maps to   VT Key.
		------               ------
		F1                   PF1
		F2                   PF2
		F3                   PF3
		F4                   PF4
		F5                   unused
		F6                   F6
		F7                   F7
		F8                   F8
		F9                   F9
		F10                  F10
		F11                  F11
		F12                  F12
		Shift F1             F11
		Shift F2             F12
		Shift F3             F13
		Shift F4             F14
		Shift F5             F15 (Help)
		Shift F6             F16 (Do)
		Shift F7             F17
		Shift F8             F18
		Shift F9             F19
		Shift F10            F20
		Shift F11            F11
		Shift F12            F12
		Print                Help (F15)
		Cancel               Do   (F16)
		Pause                Keypad Minus

		Insert               Insert Here
		Delete               Remove
		Home                 Find
		End                  Select
		Prior                Prev
		Next                 Next
		BackSpace            BackSpace (sends DEL - ascii 127)

		Num_Lock             PF1
		KP_Divide            PF2
		KP_Multiply          PF3
		KP_Subtract          PF4
		KP_Add               Keypad Comma
		KP_Enter             Enter
		KP_Decimal           Period
		KP_0                 Keypad 0
		KP_1                 Keypad 1
		KP_2                 Keypad 2
		KP_3                 Keypad 3
		KP_4                 Keypad 4
		KP_5                 Keypad 5
		KP_6                 Keypad 6
		KP_7                 Keypad 7
		KP_8                 Keypad 8
		KP_9                 Keypad 9
		Up                   Up
		Shift Up             Scroll Back
		Down                 Down
		Shift Down           Scroll Forward
		Right                Right
		Left                 Left
and the script:

	#               vmsterm
	#               from an original script by Bob Ess
	#               key translations by Erik Ahlefeldt
	#               Script file using Xterm and telnet to connect to a VMS host
	#               and give a decent vt220 emulation.
	# Usage statement
		echo " Usage  : vmsterm -options"
		echo " Options: -80   for 80 column terminal"
		echo "          -132  for 132 column terminal"
		echo "          -bg colorname"
		echo "          -fg colorname"
		echo "          -fn fontname"
		echo "          -fb bold fontname"
		echo "          -host [crusher.saltmine.com] [earth] []"
		echo ""
		echo " Example: \"vmsterm -80 -fg white -bg black -fn 9x15 -fb 9x15b -host earth\""
		echo "          Starts a VMS session with an 80 column terminal"
		echo "          with a black background, white foreground, a normal"
		echo "          font of 9x15 and a bold font of 9x15b, and connects"
		echo "          to the node 'earth'"
		echo ""
		echo " Example: \"vmsterm -host earth\""
		echo "          Starts a VMS session with default terminal settings "
		echo ""
		echo " Example: \"vmsterm -help\""
		echo "          Displays vmsterm options "
		exit 1

	# Default to a black foreground with a white background.
	# Use the 9x15 and 9x15bold fonts. Connect to by default.

	# Parse the command line arguments
	while [ $# != 0 ];
		case $1 in
			-80)    COLS=80
			-132)   COLS=132
			-fg)    shift
			-bg)    shift
			-fn)    shift
			-fb)    shift
			-host)  shift
			-help)  Usage;;
			*)      Usage;;

	xterm	-title "VMSTERM" -sb -sl 1000 -geo ${COLS}x24 -fg ${FG} -bg ${BG} \
		-cr blue -fn ${FONT} -fb ${BFONT} -xrm \
		"XTerm*vt100.translations: #override \n \
		~Shift	<Key>F1:	string(0x1b)	string("OP") \n \
		~Shift	<Key>F2:	string(0x1b)	string("OQ") \n \
		~Shift	<Key>F3:	string(0x1b)	string("OR") \n \
		~Shift	<Key>F4:	string(0x1b)	string("OS") \n \
		~Shift	<Key>F5:	string("Break") \n \
		~Shift	<Key>F6:	string(0x1b)	string("[17~") \n \
		~Shift	<Key>F7:	string(0x1b)	string("[18~") \n \
		~Shift	<Key>F8:	string(0x1b)	string("[19~") \n \
		~Shift	<Key>F9:	string(0x1b)	string("[20~") \n \
		~Shift	<Key>F10:	string(0x1b)	string("[21~") \n \
		~Shift	<Key>F11:	string(0x1b)	string("[23~") \n \
		~Shift	<Key>F12:	string(0x1b)	string("[24~") \n \
		Shift   <Key>F1:	string(0x1b)	string("[23~") \n \
		Shift   <Key>F2:	string(0x1b)	string("[24~") \n \
		Shift   <Key>F3:	string(0x1b)	string("[25~") \n \
		Shift   <Key>F4:	string(0x1b)	string("[26~") \n \
		Shift   <Key>F5:	string(0x1b)	string("[28~") \n \
		Shift   <Key>F6:	string(0x1b)	string("[29~") \n \
		Shift   <Key>F7:	string(0x1b)	string("[31~") \n \
		Shift   <Key>F8:	string(0x1b)	string("[32~") \n \
		Shift   <Key>F9:	string(0x1b)	string("[33~") \n \
		Shift   <Key>F10:	string(0x1b)	string("[34~") \n \
		Shift   <Key>F11:	string(0x1b)	string("[28~") \n \
		Shift   <Key>F12:	string(0x1b)	string("[29~") \n \
			<Key>Print:	string(0x1b)	string("[28~") \n \
			<Key>Cancel:	string(0x1b)	string("[29~") \n \
			<Key>Pause:	string(0x1b)	string("Om") \n \
			<Key>Insert:	string(0x1b)	string("[2~") \n \
			<Key>Delete:	string(0x1b)	string("[3~") \n \
			<Key>Home:	string(0x1b)	string("[1~") \n \
			<Key>End:		string(0x1b)	string("[4~") \n \
			<Key>Prior:	string(0x1b)	string("[5~") \n \
			<Key>Next:	string(0x1b)	string("[6~") \n \
			<Key>BackSpace:	string(0x7f)	\n \
			<Key>Num_Lock:	string(0x1b)	string("OP") \n \
			<Key>KP_Divide:	string(0x1b)	string("OQ") \n \
			<Key>KP_Multiply: string(0x1b)	string("OR") \n \
			<Key>KP_Subtract: string(0x1b)	string("OS") \n \
			<Key>KP_Add:	string(0x1b)	string("Ol") \n \
			<Key>KP_Enter:	string(0x1b)	string("OM") \n \
			<Key>KP_Decimal: string(0x1b)	string("On") \n \
			<Key>KP_0:	string(0x1b)	string("Op") \n \
			<Key>KP_1:	string(0x1b)	string("Oq") \n \
			<Key>KP_2:	string(0x1b)	string("Or") \n \
			<Key>KP_3:	string(0x1b)	string("Os") \n \
			<Key>KP_4:	string(0x1b)	string("Ot") \n \
			<Key>KP_5:	string(0x1b)	string("Ou") \n \
			<Key>KP_6:	string(0x1b)	string("Ov") \n \
			<Key>KP_7:	string(0x1b)	string("Ow") \n \
			<Key>KP_8:	string(0x1b)	string("Ox") \n \
			<Key>KP_9:	string(0x1b)	string("Oy") \n \
		~Shift	<Key>Up:		string(0x1b)	string("[A") \n \
		Shift	<Key>Up:		scroll-back(1,lines) \n \
		~Shift	<Key>Down:	string(0x1b)	string("[B") \n \
		Shift	<Key>Down:	scroll-forw(1,lines) \n \
			<Key>Right:	string(0x1b)	string("[C") \n \
			<Key>Left:	string(0x1b)	string("[D")" \
		-e telnet $HOST

How do I set the title?

The control sequences are documented in ctlseqs.ms; a copy is contained in the xterm.tar.gz file.

The usual context for this question is setting the title according to the current working directory. People post answers to this periodically on the newsgroups. Here is one that I have seen, from Roy Wright <nobody@roystoy.dseg.ti.com>. In your /etc/profile after:

	if [ "$SHELL" = "/bin/pdksh" -o "$SHELL" = "/bin/ksh" ]; then
		PS1="! $ "
	elif [ "$SHELL" = "/bin/zsh" ]; then
		PS1="%m:%~%# "
	elif [ "$SHELL" = "/bin/ash" ]; then
		PS1="$ "
		PS1='\u@\h:\w\$ '


	if [ "$TERM" = "xterm" ]; then
		PS1="\033]2;\u@\h:\w\007bash$ "

The terminator "\007" is a problem area. Xterm historically uses this character, though it is non-ANSI. The "correct" character should be a "\233" string terminator, or "\033\\", which is the 7-bit equivalent. XFree86 xterm recognizes either (the "\007" or string terminator); waiting for the first of these.

You may have resource or environment problems that prevent you from setting the title at all. Newer xterms (starting somewhere in X11R5) use the $LANG variable. If your locale is incorrectly installed, you will be unable to set the xterm's title. As noted by Mikhail Teterin <mi@rtfm.ziplink.net>: Make sure that the locale (LANG and/or LOCALE environment variable) is known to X Window System. Check ${X11ROOT}/lib/X11/locale.* for it. If it is not listed in either one of the files, find the nearest match and add an alias to it. Restart X if you have made changes.

On a related note, some people want to know how to read the title from an xterm. This works for XFree86 xterm and dtterm, but not for other variations:

	# Echo the current X term title bar to standard output.
	# Written by Icarus Sparry <icarus@bath.ac.uk> 11 Apr 1997
	exec </dev/tty
	old=$(stty -g)
	stty raw -echo min 0  time ${1-10}
	print "\033[21t\c" > /dev/tty
	IFS='' read -r a
	stty $old
	print -R "${b%??}"
But it is possible to avoid escape sequences altogether (from Hemant Shah <shah@typhoon.xnet.com>):

	$ xprop -id $WINDOWID | grep WM_NAME
	WM_NAME(STRING) = "this is my title"
	current_title=$(xprop -id $WINDOWID | grep WM_NAME | cut -d= -f2)
Here's another source of information: Xterm-Title HowTo

How do I make the cursor blink?

Standard xterm does not implement a blinking cursor. Some of the variations do: dtterm, Gnome terminal, and XFree86 xterm (from mid 1999, patch 107).

By default, XFree86 xterm's blinking cursor is not enabled because there is a minor problem with it: when writing large amounts of text to the screen, it may pause until you press a key (even the shift key). For normal use it works well.

Frequent problems

My terminal doesn't show box characters

Xterm displays the 7-bit ASCII and VT100 graphic characters (including box corners) using specially arranged fixed-pitch fonts. The first 32 glyph positions (which would correspond to nonprinting control characters) are used to hold the VT100 graphic characters. Some fonts that otherwise look fine (such as courier) do not have glyphs defined for these positions. So they display as blanks. Use xfd to display the font.

XFree86 xterm can form its own line-drawing characters (see patch 90, for example). It does not draw all of the graphic characters, only those that may be done with straight lines. But those are the most used, making most of the fixed-pitch fonts useful for xterm.

You may also have a problem with the terminfo description. As distributed, the X11R6 terminfo for xterm does not have the acsc string defined, so most implementations of curses do not try to use the alternate character set.

Finally, some people confuse the VT100 graphic characters with the VT220 support for DEC technical character set. These are distinct (7-bit) character sets. Xterm currently does not support this.

I see little dots on the screen

Well, I do. Perhaps you do not. It depends on the fonts you choose, and how you use them.

Standard xterm has a "normal" font for which a bold font can be chosen, and several alternative fonts, useful for changing the font size. The alternative fonts do not have corresponding bold fonts. Xterm simulates bold fonts in this case by overstriking the character one pixel offset. That can make an bold character extend into the area that another character occupies. When erasing a bold character from the screen, xterm does not erase the extra pixel. This is corrected in XFree86 xterm, subject to the available fonts (from late 1998, patch 85). For each font, it asks the font server for a corresponding bold font. Your font server may not have the bold font (or it may incorrectly report that it does). But it usually works.

My terminal doesn't recognize color

First, ensure that you have set up xterm to render color. The XFree86 xterm renders color only if you have set resources to do this; the default behavior is monochrome to maintain compatibility with older applications. The manual page describes these resources. I set them in my .Xdefaults file.

Even if you set the resources properly, there may be another application running which prevents xterm from allocating the colors you have specified. But you should see a warning message for this.

Check the terminal description, to see if it is installed properly, e.g., for ncurses, which uses terminfo.

Finally, some applications (that do not interface properly with terminfo or termcap) may need the environment variable $COLORTERM to be set.

Why is my screen size not set?

Well, it may be set, but not correctly. You may notice these symptoms:
  • When editing with vi, you cannot see the beginning of the file, or
  • Running
    	stty -a
    shows the rows and/or columns values as 0, or some other value (such as 65) which has nothing to do with the actual window size.
Xterm knows how big the screen is (of course), and tries to tell your applications (e.g., by invoking ioctl's and sending SIGWINCH). But sometimes it cannot:
  • Xterm itself may have been built incorrectly (the #ifdef's that make the logic work are inactive).
  • You may be running xterm via a remote connection which refuses to pass that information. This can happen even on "modern" networks where the connection crosses domain boundaries.
  • You may be running su'd to another account. SIGWINCH is just another signal; signals do not propagate for security reasons.
Most full-screen applications such as vi are designed to use the ioctl calls that return the screen size. When they fail, the applications use the size defined in the terminal's terminfo or termcap description.

You may be able to use the resize program to issue the ioctl's that will notify your application of the actual screen size. This does not always work for the reasons just mentioned. Newer versions of stty let you specify the screen size, though it will not be updated if you resize the xterm window:

	stty rows 24 columns 80
Most full-screen applications also check if the $LINES and $COLUMNS variables are set, using those values to override the terminal description:

	setenv LINES 24
	setenv COLUMNS 80
Why 65 lines? The standard xterm terminfo description specifies 65 lines, perhaps because someone liked it that way. Real VT100's are 24 lines. I once used (and wrote applications for) a Bitgraph terminal, which emulated Vt100, but displayed 65 lines.

Why can't I use the pageup/pagedown keys?

Some vendors, e.g,. Sun, have added key translations which make the pageup and pagedown keys talk to the xterm's scrollbar instead of your application. You can override this by specifying your own translations in your resource file. Use the translations in

as a guide. For example,

	XTerm.VT100.Translations:       #override \
		~Shift<Key>Home:  string(\033[1~)\n\
		~Shift<Key>End:   string(\033[4~)\n\
		~Shift<Key>Prior: string(\033[5~)\n\
		~Shift<Key>Next:  string(\033[6~)\n\
		Shift<Key>Prior:  scroll-back(100,page) \n\
		Shift<Key>Next:   scroll-forw(100,page) \n\
		Shift<Key>Home:   scroll-back(100,page) \n\
		Shift<Key>End:    scroll-forw(100,page) \n
makes the home/end and pageup/pagedown keys usable by your editor, while leaving their shifted equivalents available for the scrollbar.

Why can't I cut/paste in xterm?

When an application sets xterm to any of its mouse tracking modes, it reserves the unshifted mouse button clicks for the application's use. Unless you have modified the treatment of the shifted mouse button events (e.g., with your window manager), you can always do cut/paste by pressing the shift key while clicking with the mouse.

I need libncurses.so.3.0

During initialization, xterm checks to see if the value of $TERM is legal, i.e., is defined via the termcap interface. Some people have linked xterm against ncurses, which provides a similar interface, since they do not want to package termcap on their system.

The libncurses.so.3.0 corresponds to ncurses 1.9.8a; while there have been interface changes to ncurses past this point (the current version of ncurses), the termcap interface should still be compatible. So (for xterm) it doesn't matter much which version of ncurses you have installed. However, other applications may not work properly. Some people have advised just linking libncurses.so.2.0 to libncurses.so.3.0, but that won't work well at all (one person simply linked libncurses.so.3.0 to the libtermcap.so, which may work...). A better solution would be to install the later version of ncurses, with a link (if you must) from the newer version to the older library.

Since there is little agreement on the set of shared libraries that are assumed to be present on the user's system, XFree86 distributes xterm statically linked against termcap because that is simplest, and because you lose functionality (the $TERMCAP variable) when linked against terminfo libraries such as ncurses.

Why does $LD_LIBRARY_PATH get reset?

If xterm is running setuid (which is needed on some systems which have no wrappers for opening pty's and updating utmp), newer systems automatically set or reset environment variables which are considered security problems. These include $PATH and $LD_LIBRARY_PATH, since they affect the choice of which programs are run if not specified via a full pathname.

This means, for example, that if you attempt to run

	xterm -e foo
where foo is a program that uses shared libraries in /usr/local/lib, then the command will fail, because /usr/local/lib is not considered part of root's environment.

Modern Unix systems (such as recent Solaris and HPUX versions) do not require you to run xterm setuid. Some will result in odd malfunctions if you do this.

Why do the -e and -ls options not work together?

Xterm has two useful options for controlling the shell that is run:
tells xterm to execute a command using the remaining parameters after this option.
tells xterm to invoke a login shell, making it read your .login file, for instance.
The two are not compatible. If you specify both, xterm uses -e, and if that fails for whatever reason will fall through to the -ls option. It cannot (in general) combine the two, since some shells permit this (e.g., bash), and others do not (e.g., tcsh).

I need /etc/termcap

If you have a termcap version of xterm on a system with no termcap libraries, you may also be missing /etc/termcap.

A workaround is to copy /usr/X11R6/lib/X11/etc/xterm.termcap to /etc/termcap.

This is fixed another way starting with XFree86 3.3.1. If xterm cannot find the terminal description, it will accept that, though it will print a warning. If xterm does not find the termcap entry, it will not set the $TERMCAP variable.

Xterm does not run (no available pty's)

Your copy of xterm may not have enough permissions to use existing pty's:
  • you may have to make xterm run setuid to root (though newer systems have wrappers that make this unnecessary).
  • the pty's permissions may be restrictive (that is ok, but you have to make xterm agree with it). Usually this is done by making the group ownership of the pty's "tty", and requiring that xterm run setgid to "tty". This is done rather than make xterm run setuid to root, since that presents problems with security.
  • newer systems (with Unix98 pty's) have a single entry under /dev which has to have the right permissions. For example:
    	# ls -l /dev/ptmx
    	crw-rw----    1 root     tty        5,   2 Aug 21 20:19 /dev/ptmx

Perhaps your system does not have enough pty's, or (problems reported with newer Linux kernels supporting Unix98 pty's, beginning with RedHat 6.0) the major device numbers of the pty's may have changed during a kernel upgrade. (This is described in /usr/src/linux/Documentation).

See also the MAKEDEV script, which usually exists under /dev.

Reverse video is not reset

When running less or other programs that do highlighting, you see the highlighting not turned off properly.

This may be due to incompatible terminal descriptions for xterm. With XFree86 3.2, I modified the terminal description for XFree86 xterm to use the VT220 (aka ISO 6429) controls that allow an application to turn off highlighting (or bold, underline) without modifying the other attributes. The X Consortium xterm does not recognize these controls.

If, for example, you are running an older xterm and rlogin to a system where the newer xterm has been installed, you will have this problem, because both programs default to $TERM set to xterm. The solution for mixed systems is to install the newer terminal description as as a different name (e.g., xterm-color) and set the termName resource accordingly in the app-defaults file for the system which has the newer xterm.

However - see below.

What $TERM should I use?

The xterm-color value for $TERM is a bad choice for XFree86 xterm because it is commonly used for a terminfo entry which happens to not support bce. Use the xterm-xfree86 entry which is distributed with XFree86 xterm (or the similar one distributed with ncurses).

The term "bce" stands for "back color erase". Terminals such as XFree86 xterm and rxvt implement back color erase, others such as dtterm do not. (Roughly half of the emulators that I know about implement bce). When an application clears the screen, a terminal that implements back color erase will retain the last-set background color. A terminal that does not implement back color erase will reset the background color to the default or initial colors. Applications that paint most of the screen in a single color are more efficient on terminals that support back color erase.

Curses libraries that support color know about bce and do the right thing - provided that you tell them what the terminal does. That is the whole point of setting $TERM. The "xterm-color" description distributed with ncurses does not list bce, because it was applied originally to a terminal type which does not implement back color erase. It will "work" for XFree86 xterm, though less efficient. Some other applications such as the slang library have hardcoded support for terminals that implement back color erase. Given the "xterm-color" description, those will be efficient - and fortuitously work. However, slang (through version 1.4.0) does not work properly for the terminals that xterm-color was designed for. See this page for an example of (n)curses and slang running on dtterm. That bug in slang is reported to be fixed for succeeding versions, though your application may require changes to use this fix. (The demo which comes with slang to illustrate the use of bce does not work properly, for instance).

The xterm-color value for $TERM is also (for the same reason) a bad choice for rxvt, but "works" due to the large number of hard-coded applications that override this.

FVWM does weird things when I try to resize xterm

I have an old (3.1.2G) bug report for xterm which may be related to the second (3.9s) problem:
  • Steven Lang <tiger@ecis.com> reports a problem with extra resize events for xterm.

    When I change font size often I will get the double-refresh, and when that happens the text program gets 2 resize events.. Running a quick test, I got this: Going to a bigger font, it got a 53x20 resize, then a 80x24 resize. Going to a smaller font, it got a 120x27 resize, then a 80x24 resize.

    Earlier I made a mention of changing font size in rxvt (And xterm does it to) causing 2 resize events. Well I just happened to do it in fvwm (Instead of fvwm 95) and found it seems to be a 'feature' of fvwm95, not XFree86 as I'd initially assumed.

  • Stephen Marley <stephen@memex.com> reports a problem with the active icon (from X11R6.3 xterm):

    Using the XFree86 xterm-53 with the active icon feature on, I get some problems resizing where the xterm window shrinks as small as possible and won't stay at whatever size you set it thereafter.

    Comment out the PixmapPath and IconPath from your .fvwmrc file to disable the fvwm icons and restart the WM. Start an xterm. Iconify xterm and maximize it again. Use resize button or corners to resize the xterm.

    The xterm now shrinks to a tiny size and attempts to resize it result in it shrinking again.

    I've tried this with fvwm 1.23 and fvwm 2.0.46 with the same results. Olvm, olvwm and twm all behave correctly so it may be a fvwm problem.

I have not observed the first, but have reproduced the second.

Why doesn't the screen clear when running vi?

Under SunOS 4.x, the termcap description for xterm embeds in the ti and te capabilities a command to switch to xterm's alternate screen (e.g., while running vi), and return to the normal screen on exit. This has the effect of clearing the screen. Under Solaris 2.x, the terminfo description does not use the alternate screen (it is a matter of preference after all), so that the text from vi remains on the screen after exit. There are corresponding terminfo symbols for ti and te: smcup and rmcup, respectively.

This is configurable.

For example (from Bjorn Helgaas <helgaas@dhc.net>) this procedure adds these capabilities to the "xterm" terminfo definition on HP-UX 10.20:

	cp /usr/lib/terminfo/x/xterm /usr/lib/terminfo/x/xterm.orig
	untic xterm > /tmp/xterm.src
	echo " smcup=\E7\E[?47h, rmcup=\E[2J\E[?47l\E8," >> /tmp/xterm.src
	tic /tmp/xterm.src
In this example, the terminfo strings are a series of operations:
\E7 saves the cursor's position
\E[?47h switches to the alternate screen
\E[2J clears the screen (assumed to be the alternate screen)
\E[?47l switches back to the normal screen
\E8 restores the cursor's position.

However, xterms that are linked with termcap are more flexible in this area than those linked with terminfo libraries. The xterm program supports a resource titeInhibit which manipulates the $TERMCAP variable to accomplish this. It sets the $TERMCAP variable for the client with the ti and te capabilities suppressed. Systems that use terminfo cannot do this. If you are running terminfo with the alternate screen controls in the terminal description, then you can suppress the switching to the alternate screen by the titeInhibit, but not the associated cursor save/restore and clear-screen operations.

XFree86 3.9s xterm implements a different set of controls (codes 1047, 1048 and 1049) which address this (in addition to the older set of controls, for compatibility). The new set of controls implements the entire ti sequence (save cursor, switch to alternate screen, clear screen) and te (switch to normal screen, restore cursor) as two control sequences that can be disabled by titeInhibit.

The 1049 code is a refinement of 1047 and 1048, clearing the alternate screen before switching to it rather than after switching back to the normal screen. This allows you (with a popup menu entry designed to exploit this behavior) to switch the display back to the alternate screen to select text from it, to paste into the normal screen. You can also set or clear the titeInhibit resource using another popup menu entry (Enable Alternate Screen Switching).

Why is the cursor misplaced after running vi?

Vi and other full-screen applications use the termcap ti/te (terminfo smcup/rmcup) strings to initiate and end cursor addressing mode. As mentioned in the discussion of titeInhibit, full-screen applications can expect the initialization string to save the cursor's position, and the end-string to restore it.

A few applications (reportedly IRIX 5.x and 6.x vi incorrectly move the cursor before initializing cursor-addressing. This will cause the end-string to restore the cursor to its position when it was saved by the initialization string (typically at the upper left corner of the screen).

The usual reason is due to the cursor save/restore controls in the ti/te strings. If your application runs a subprocess which in turn runs another full-screen application (or when reinitializing the screen after the shell process), it will save the cursor position again, so the position which is restored when finally exiting your program is the last one saved, not the first. XFree86 xterm (from late 1998, patch 90) changes the behavior of the cursor save/restore operations so they apply only to the current screen. That makes it less likely to misplace your cursor.

Why doesn't my delete key work?

This seems to be a problem with the older XFree86 release (3.1.2). I have picked up pieces of the story (xterm and the keyboard work as designed under XFree86 3.2 and up).

The underlying problem is that we've accumulated three things that are being equated as "Delete":

	ASCII backspace (code 8)
	ASCII delete (code 127)
	VT220 "remove" aka "delete" (ESC [ 3 ~)

You are probably talking about the backarrow key (on my keyboard, at the upper right of the QWERTY block), or the key labeled delete which is on the 6-key "editing keypad". Since xterm is emulating a VT100/VT220, the backarrow key should generate a 127 (often displayed as ^?). You would use a control/H to obtain a backspace on a real VT220.

Tastes differ on Unix, people expect the backarrow key to generate a backspace (or not). As I understand it, at one point, XFree86 picked up the sense of the erase character during initialization, so that xterm would in effect use the same erase character as the console. The current scheme (X11R6) uses keyboard mapping tables that are independent of the environment.

XFree86 xterm provides a resource toggle backarrowKey (and an escape sequence from VT320) that changes this key between the two styles (backspace or delete).

With XFree86 xterm patch 95 (also in the stable version as "88b"), you may have an xterm which can automatically initialize the backarrow key to backspace or delete depending on the pseudo terminal's sense, or based on the termcap setting of kbs (backspace key). This feature is controlled by the resource setting ptyInitialErase.

Why did my delete key stop working?

Well, something changed. You have to determine what did.

This may be because an upgrade introduced different X resource settings, or because you are using the newer xterm with the ptyInitialErase resource (or perhaps both). Use

	appres XTerm
to see the X resources that you are using, in particular the translation (or Translation) resource for the vt100 widget.

One unexpected scenario came out of hiding when I was implementing the ptyInitialErase resource. When xterm is (by default) built to support this, it sets the pty's erase character to match the termcap entry. Xterm also sets the $TERMCAP environment variable to match. So everything is consistent, and everything defined. The stty erase character is either backspace (^H) or delete (^?).

The problem arises because there are two things called "delete", which were not well-defined: ASCII delete (127) and the PC-style adaptation of VT220 remove assigned to the key Delete.

However, the screen program prefers to make the termcap delete (kD) an <escape>[3~, which corresponds to the VT220 remove key. If $TERMCAP is set when starting screen, it will translate stty's erase character into the <escape>[3~, making most curses and termcap applications work. But stty still has the original erase character. So low-level applications which check stty will not work. I found that unsetting $TERMCAP before running would work, but this was not a good solution. Someone pointed out (see patch 129), that the problem really was because termcap kD should delete the character at the current position. So it cannot be the same as stty erase.

As a matter of fact, stty erase has to be a single character, so <escape>[3~ would not work anyway.

Well, how can I set my delete key?

When people first started asking this question in 1995-1996, it appeared in the context of making Netscape work. Netscape's use of the delete key running in X did not match user's expectations when compared to that other platform. They were commonly advised to use xmodmap, e.g.,

	keysym BackSpace = Delete

	keycode 22 = 0xff08
Either way is a bad technical solution - it works for some people but not others (on my keyboard at work, keycode 22 is the numeric keypad '9').

Alternatively, you can set resources. This works reasonably well for environments where you have different versions of xterm, e.g.,

	XTerm*vt100.translations: #override <Key>Delete: string(0x7f)
I do not do that either, because it is not flexible. Not all programs use the same sense of stty erase; some use termcap or terminfo, and some are hardcoded. So I prefer to be able to switch the xterm's keyboard at runtime. You cannot do that with resources. (Or not really - xterm has a keymap() action which could support this if you provided a rather complex resource settings, but the X library support for that is broken in X11R6). Instead, I have added to XFree86 a set of resources (and popup menu entries) to allow simple switching between the different styles of keyboard, in particular for the backspace/delete issues. See the manual page for backarrowKey backarrowKeyIsErase and deleteIsDEL as well as sunKeyboard.

Why doesn't my keypad work?

A few people have commented that the keypad does not work properly. Aside from bugs (I have fixed a few), the most common problem seems to be misconception.

Here's a picture of the VT100 numeric keypad:

	| PF1 | PF2 | PF3 | PF4 |
	|  7  |  8  |  9  |  -  |
	|  4  |  5  |  6  |  ,  |
	|  1  |  2  |  3  |     |
	+-----+-----+-----+ ENT +
	|     0     |  .  |     |
and the similar Sun and PC keypads:
	| NUM |  /  |  *  |  -  |
	|  7  |  8  |  9  |     |
	+-----+-----+-----+  +  +
	|  4  |  5  |  6  |     |
	|  1  |  2  |  3  |     |
	+-----+-----+-----+ ENT +
	|     0     |  .  |     |
Working in X11, the NUM (NumLock) key has better uses than an alias for PF1 (and is sometimes reserved). I use the F1 through F4 on the keyboard to implement PF1 through PF4, alias the keypad "+" to "," and use the existing "-" key.

VT220 emulation uses the VT100 numeric keypad as well as a 6-key editing keypad. Here's a picture of the VT220 numeric keypad:

	| Find   | Insert | Remove |
	| Select | Prev   | Next   |
and the similar Sun and PC keypads:
	| Insert | Home   | PageUp |
	| Delete | End    | PageDn |

I chose to use keys that are mnemonic rather than in the "same" positions, though some emulators (e.g., Tera Term) use the same positions:

	| Insert | Find   | Prev   |
	| Remove | Select | Next   |

I test the keyboard (for VT52/VT100/VT220) using vttest. If you find (or think that you have found) a problem with the keyboard handling of xterm, please test it with vttest first.

Other arrangements of the keyboard are possible of course. If you prefer to use the top row of the numeric keypad as PF1 through PF4, you should do this using xterm's X resources.

Why can't I input 8-bit characters?

You must have the eightBitInput resource set to do this.

My .Xdefaults for XTERM

	XTerm*internalBorder:  10
	XTerm*highlightSelection:  true
	XTerm*VT100*colorBDMode:  on
	XTerm*VT100*colorBD:  blue
	XTerm*VT100*colorULMode:  on
	XTerm*VT100*colorUL:  magenta
	XTerm.VT100.eightBitInput:  true
	XTerm.VT100.eightBitOutput:  true
	XTerm*scrollBar:  true
	XTerm.VT100.titeInhibit:  true

	XTerm.VT100*colorMode:  on
	XTerm.VT100*dynamicColors:  on

	! Uncomment this to use color for underline attribute
	XTerm.VT100*colorULMode:  on
	XTerm.VT100*underLine:  off

	! Uncomment this to use color for the bold attribute
	XTerm.VT100*colorBDMode: on

	XTerm.VT100*color0: black
	XTerm.VT100*color1: red3
	XTerm.VT100*color2: green3
	XTerm.VT100*color3: yellow3
	XTerm.VT100*color4: blue3
	XTerm.VT100*color5: magenta3
	XTerm.VT100*color6: cyan3
	XTerm.VT100*color7: gray90
	XTerm.VT100*color8: gray30
	XTerm.VT100*color9: red
	XTerm.VT100*color10: green
	XTerm.VT100*color11: yellow
	XTerm.VT100*color12: blue
	XTerm.VT100*color13: magenta
	XTerm.VT100*color14: cyan
	XTerm.VT100*color15: white
	XTerm.VT100*colorUL: yellow
	XTerm.VT100*colorBD: white

	XTerm.VT100*cursorColor: lime green

XFree86 xterm comes with two copies of the resource file, one with color only (XTerm-col.ad, which is installed as XTerm-color), and the regular one (XTerm.ad, installed as XTerm). To use the XTerm-color file in conjunction with a separate XTerm app-defaults file which does not contain color, add the following line to your .Xdefaults file:

	*customization: -color

Why are the menus tiny?

Everything seems to work, except that the xterm menus (VT options, fonts, etc.) do not display properly; the menus pop up, but only with a tiny display area in which none of the options are visible (and only part of the menu title is visible).

You have specified the geometry for xterm too high in the hierarchy, and that 24x80 (or whatever the -geometry parameter happens to be) is applying to the menus in pixels. This resource makes the geometry apply to the menus as well as the VT100 widget:

	XTerm*geometry: 80x24
while this applies only to the VT100 widget (which is probably what you intended):

	XTerm.VT100*geometry: 80x24
or better yet (to allow for the toolbar option, which uses a level of widget hierarchy):

	XTerm*VT100*geometry: 80x24

What is this warning message?

xterm: Error 11, errno 22: permission denied
Actually, any message like this denotes a failure which requires studying the xterm source to determine the exact problem.

You have either found a bug in xterm, or there is something wrong with your computer's configuration, e.g., not enough pty's, incorrect permissions, etc.

The first number is an internal code (defined in error.h in xterm's source), and the second is the system error number (defined in /usr/include/sys/errno.h). The system error number is easier to lookup, but the internal error code tells you where to look in the source.

input method doesn't support my preedit type
Ignore this if you do not know what input method is. Input methods are used to enter composite characters (e.g., umlauts, other types of punctuated characters, East Asian characters, etc). Your computer's libraries support this, but are missing configuration tables, and xterm is warning you.

If the message bothers you (e.g., if you aren't starting xterm from a window manager menu), you can suppress it by setting a resource:

Warning: Actions not found: ignore, "xxx"
The action "xxx" (for example "scroll-back") is specified in a resource file whose translations match widgets that do not support them. For example, this

		XTerm*Translations:     #override\n\
			<Leave>, ~Ctrl ~Meta <Btn2Up>: ignore()\n\
			~Shift <Key>KP_8: scroll-back(1,line)\n\
			~Shift <Key>KP_2: scroll-forw(1,line)\n\
			Shift <Key>KP_8: scroll-back(1,halfpage)\n\
			Shift <Key>KP_2: scroll-forw(1,halfpage)
will produce warnings such as

		Warning: Actions not found: ignore, scroll-back, scroll-forw
		Warning: Actions not found: ignore, scroll-back, scroll-forw
		Warning: Actions not found: ignore, scroll-back, scroll-forw
This is a correct form, assigning the actions to the "VT100" widget.

		XTerm*VT100.translations:     #override\n\
			<Leave>, ~Ctrl ~Meta <Btn2Up>: ignore()\n\
			~Shift <Key>KP_8: scroll-back(1,line)\n\
			~Shift <Key>KP_2: scroll-forw(1,line)\n\
			Shift <Key>KP_8: scroll-back(1,halfpage)\n\
			Shift <Key>KP_2: scroll-forw(1,halfpage)
Warning: Cannot allocate colormap entry for "xxx"
This comes from the X library. XFree86 xterm uses the default color map. What this means is that if your X server has insufficient space to store color information for more than one color map, other applications which could use other color maps may conflict with xterm. In practice, that is 256 unique colors on the screen at a time -- not enough for a fancy background or an application such as Netscape.

During resource initialization, xterm attempts to allocate an entry from the color map for each color which it might use. If there are not enough free slots in the color map, you will see a "Cannot allocate" message for each color that xterm failed to allocate. Those colors will be rendered in the foreground color, making full-screen color applications such as dialog unreadable.

This problem is alleviated with patch 129, which modified xterm to delay the most color allocation until the colors are first needed. If a color is never needed (xterm allocates 20 colors in this manner), that reduces the number of slots in the color map that are needed. Even with this improvement, xterm must still allocate 4 colors during initialization to determine how to display the cursor. If none of those colors can be allocated, XFree86 xterm reverts to monochrome.

Known Bugs in XTERM

These are the known bugs (or limitations) in the XFree86 xterm. They are also present in the other versions based on the X Consortium sources (color_xterm, ansi_xterm, kterm).

Note that of the emulators that support color, most do not support bce (back color erase). The bce capability is also called the "new color model", though it has been implemented in the IBM PC for quite a while. Technically, not implementing bce (or allowing the choice between it and its complement) is not a bug, since few hardware terminals (with good reason) implemented this feature.

  • cut/paste does not select tabs; instead spaces are selected. This is because the selection works from the array of displayed characters, on which tab/space conversion has already been performed.
  • does not implement the autorepeat feature of VTxxx terminals.


The X Consortium version of xterm (and versions based on it) has additional bugs not in XFree86 xterm:
  • the program must be run with fixed (nonproportional) fonts.
  • the home and end keys do not generate usable escape sequences, due to an indexing error.
  • the Main Options menu is improperly constructed, due to incorrect indices after removing the logging toggle. This makes the list of signals off by one.
  • very large screens (e.g., by using nil2 for a font) cause core dumps because the program uses a fixed array (200 lines) for adjusting pointers.
  • certain types of key translations cause a core dump because the program does not check the event class before attempting to use events.
(These bugs are also present in the X11R5 version).

COLOR_XTERM download

This is based on the X Consortium X11R5 source, with the same bugs.
  • implements non-bce color model
  • moving the cursor is reported to leave trails of incorrect color
  • clearing the screen resets colors (arguably this is a limitation).
Not exactly a bug, but it does not build on Linux with X11R6.3

ANSI_XTERM download

This is based on the X Consortium source, with the same bugs.
  • implements non-bce color model
  • fails vttest by not rendering reverse-video screen

CXTERM download

CXterm stands for "Chinese Xterm". This is based on the X Consortium source.


This is distributed with CDE. It implements more of the DEC VT220 than the X Consortium xterm, and also adds controls to manipulate the window and icon.
  • implements non-bce color model
  • fails vttest by clearing its background to solid white rather than preserving its sense in response to ED.
  • under some circumstances, scrolling margins are not recognized. For instance, running vile which uses scrolling margins, we see text overwriting the status line.

EMU 1.3 download

This is not based on the X Consortium source. The authors state that it implements VT220 emulation. It is in need of maintenance, since it builds with some problems to produce an executable that (on Linux and SunOS) does not handle the carriage return and newline translations properly. So I am unable to run vttest on this emulator.

ETERM link

Eterm was based on rxvt, though the appearance differs. The terminal emulation capabilities appear similar, though I am not able to run the full suite of tests in vttest with this emulator (the core dump noted for rxvt, as well as hanging while awaiting response from one or more control sequences). Oddly, it appears that neither Eterm nor rxvt implement CPR (cursor position report). This applies to versions of Eterm through 0.9.


Gnome terminal appears to be developed separately from both xterm and rxvt, and is based on the zvt (zterm) widget. Like kvt), it appears to have been developed imitating other terminal emulators (Linux console and xterm) rather than strictly emulating a VT102. The documentation is fragmentary (with a comment suggesting that the author does not know where to find relevant information), and the program fares badly with vttest. Recent (since late 1999) reports indicate that it does not properly parse ANSI control sequences: the vim editor is using XFree86 xterm's vt220-style "Send Device Attributes" (Secondary DA) control sequence to obtain the terminal emulator's version. That is, it sends

expecting a response such as

for vt100. The bug report indicates that the "c" sent by vim is echoed rather than interpreted by the emulator.

But it suffices for vi.

HANTERM download

HanTerm stands for "Hangul term" (Korean). This is based on the XFree86 source.

KTERM download

KTerm stands for "Kanji term" (Japanese). This is based on the X Consortium source, with the same bugs (though the list of original authors has been removed; the modifications that comprise kterm is relatively small).
  • implements non-bce color model
  • implements status line, but uses non-DEC escape sequences for this.
There is a variation of xvt (ancestor of rxvt) properly known as kvt bundled with KDE which may be referred to as "kterm", but I do not find it interesting, other than to comment that it was a poor choice of name.


There are a few variants of this: the xterm bundled with some Motif clients is more common. More interesting, however is one which does not appear to be available any longer, attributed to "Der Mouse".
(mouse@Lightning.McRCIM.McGill.EDU) Available: larry.mcrcim.mcgill.edu ( in /X/mterm.src/mterm.ball-o-wax.
I've seen only an incomplete version of this, even while it was advertised, in the mid-90's. The fragment did not appear to be a patched version of xterm, though it was apparently written, like rxvt, as a clone of xterm.


There are several variants on this: xterm adapted for Motif libraries. I have seen none that work properly:
  • MXTERM: a motif Xterm with character attributes color rendered I've noticed this one only recently. It is a reworking of the earlier patches for color_xterm (credited to Erik Fortune at SGI) and the Motif widgets (apparently first done by Ivan M. Hajadi at SGI in 1991, but credited in this release to Mahesh Neelakanta, for Motif 1.2.4).
  • ANSI Xterm with Motif Scrollbar Usually seen as the ansi-xterm-R6-motif-sb patch, I used this as the starting point for changes to my #82 patch of xterm in August 1998.

    The original patch changes only the scrollbars to Motif, leaving the popup menus in Athena widgets. That was not what I wanted. My motivation for using Motif is not for performance or esthetics, of course, but to make it simpler to build on hosts that have no Athena widgets installed.

    I set those changes aside, having found (the hard way) that the Motif library has hardcoded behavior regarding the control right-mouse button. According to the O'Reilly book on Motif programming (volume 6), it does a server grab when processing menus. Making the menus behave just as in the Athena widgets can cause the X server to hang. (I was able to do this with both Lesstif and Motif libraries). Given that, I decided to restructure the menus entirely, making a toolbar which could support at compile-time either widget set.

  • mxterm This is a different reworking of the Motif widget patch, using a 1993 version (ignoring the more recent 1994 patches noted above). However, it appears to have the same technical defect that I noted above.


Distributed with Redhat Linux 5.2, it is a repackaging of xterm-sb_right-ansi, to use the Xaw3d widget set. This is based on the X Consortium X11R6 source, with the same bugs.
  • implements non-bce color model
  • does not implement SGR 39 and SGR 49, all attributes are reset when changing colors.
  • popup menus do not appear to work.
Starting with Redhat 6.0, nxterm is the XFree86 3.3.6 xterm. Unfortunately Redhat neglected to update their termcap for nxterm to match the program.

RXVT link

This applies to versions of rxvt through 2.21:
  • clearing the screen resets colors
  • does not have a delete key
  • the implementation of ech (erase characters) does not follow DEC VT220 (also ISO 6429), causing applications using this function to misbehave.
A new version (upgraded to an beta as of 2.6.PRE3, however, since it no longer dumps core in vttest) is reported to fix the ech bug. However, it is less VT100-compatible than the earlier versions such as 2.21b because it does not render reverse video (DECSCNM) properly. All versions do not update the screen frequently enough, making animation ineffective. See vttest, tests 1 and 2.


This appears to be rxvt 2.20, lightly reformatted, with a few ifdef's changed.

How do I build XTERM?

Building a copy of xterm is simple, provided that you have a development configuration for X11:
  • Header files and libraries. If you do not have the header files (usually under /usr/include/X11) for your system, you are better off building the libraries yourself. Xterm can be built with either X11R5 or X11R6 libraries; however X11R6 requires much more data to be installed before xterm will run. Xterm uses the Xaw library for popup menus.
  • imake and xmkmf. These utilities produce a Makefile from the Imakefile. They are not essential, but useful, particularly on systems with unusual configurations.
If you have a working xmkmf script (or correctly configured imake utility), all you need to do is type

I have written a simple configure script for xterm which uses imake (or xmkmf) to generate a Makefile from the Makefile.in. I plan to restructure xterm to eliminate the hardcoded #ifdef's, replacing them with definitions that can be derived with the configuration script. The configure script is more flexible than xmkmf, since it allows you to enable or disable a variety of features. Type
	configure --help
to get a list of options.

Though I plan to replace the hardcoded ifdef's with autoconfigured values, it will still continue to build properly with the imake environment, since that is how large distributions incorporate xterm.

How do I report bugs?

You should report bugs to report@XFree86.org; however I am continuing development as I find time; your input is valuable: mail. See also Analyzing problems with configure scripts

Additional Information

There appears to be no comprehensive source of information on xterm better than the documentation which comes with the source code. I have found Richard Shuford's archive to be invaluable for notes on the DEC VT220 and related terminals. Though not available at the time that I was collecting most of my notes, VT100.net is also a good source of primary information.

The command-line options, X resources and similar configurable options of xterm are documented in the manual page. Control sequences, i.e., programming information are in the ctlseqs.ms file which I bundle with the program source. (It used to be in the same directory in the X distribution, but was moved to a difference part of the tree some time ago). Note that you must format this file with different options than a manpage, e.g.,

	tbl ctlseqs.ms | nroff -ms >ctlseqs.txt
	tbl ctlseqs.ms | groff -ms >ctlseqs.ps
As a PostScript file, the individual letters of the control sequences are all boxed, for emphasis, but I find the text file equally readable.

Ongoing/future work

  • double-high/double-wide characters

    I have implemented double size characters in stages:

    • Like Kermit, XFree86 xterm can show normal characters spaced at the proper intervals.
    • If your font server cooperates (e.g., X11R6), you can display many fixed fonts in double-size, though not all.
    • XFree86 xterm can also generate its own line-drawing characters, which normally are missing from fixed fonts except for those that were designed for xterm.
    • Other than the limitations which the font server may impose, the double size characters are drawn properly.
  • soft (downloadable) fonts
  • search scrollback It would be nice to be able to search the scrollback buffer.
  • printer interface

    Done, except for the corresponding support in the VT52 emulation. It would be nice to have a dialog to control this.

  • allow alternate libraries for popup-menus and dialogs

    My configure script currently provides tests for the variations of Athena widgets (Xaw3D, neXtaw). I intend to make additional changes to support Motif scrollbars and menus.

  • blinking text.

    Just for completeness (though no one seems to want this feature).

  • Double-width font support for UTF-8 mode (for CJK users)
  • popup window that shows hex code for content of a character cell and hexadecimal keyboard entry for all Unicode characters (ISO 14755)
  • UTF-8 combining character support (simple glyph overstriking only)
  • correct cut&paste of TAB character