Contents

• What is XTERM?
• Who wrote XTERM?
• What platforms does it run on?
• What is the latest version?
• What versions are available?
• How do I...
• Frequent problems
• Known bugs
• How do I build xterm?
• How do I report bugs?
• Ongoing/future work

What is XTERM?

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?

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.

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?

• 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)
• 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?

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

What versions are available?

• ansi_xterm
• color_xterm
• dtterm
• emu (from X Consortium)
• nxterm
• kterm
• rxvt
• xiterm
• xterm (from X Consortium)

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. 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 ...

• How do I change the font size?
• How do I print the screen?
• How do I set up function keys?
• How do I set the title?

How do I change the font size?

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?

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.

• 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).

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.

• 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.

How do I set up function keys?

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

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

	#!/bin/sh

	# 		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
	Usage(){
		echo
		echo " Usage  : vax -options"
		echo
		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
		echo "          If you need additional help, please call Workstation"
		echo "          Services at x92396."
		echo
		exit 1
	}


	# Default to a black foreground with a white background.
	# Use the 9x15 and 9x15bold fonts. Connect to castor by default.
	#
	FG=black
	BG=white
	HOST=castor
	FONT=9x15
	BFONT=9x15bold
	COLS=80


	# Parse the command line arguments
	#
	while [ $# != 0 ];
	do
		case $1 in
			-80)	COLS=80
				FONT=spc12x24c
				BFONT=spc12x24b
				shift
				;;
			-132)	COLS=132
				FONT=9x15
				BFONT=9x15b
				shift
				;;
			-fg)	shift
				FG=$1
				shift;;
			-bg)	shift
				BG=$1
				shift;;
			-fn)	shift
				FONT=$1
				shift;;
			-fb)	shift
				BFONT=$1
				shift;;
			-host)	shift
				HOST=$1
				shift;;
			-help)	Usage;;
			*)	Usage;;
		esac
	done


	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 &

How do I set the title?

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="$ "
	else
		PS1='\u@\h:\w\$ '
	fi

add:

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

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:

	#!/bin/ksh
	# 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 $old
	b=${a#???}
	print -R "${b%??}"

	$ xprop -id $WINDOWID | grep WM_NAME
	WM_NAME(STRING) = "this is my title"
	current_title=$(xprop -id $WINDOWID | grep WM_NAME | cut -d= -f2)

Frequent problems

• My terminal doesn't show box characters
• My terminal doesn't recognize color
• What $TERM should I use?
• I need libncurses.so.3.0
• I need /etc/termcap
• Xterm does not run (no available pty's)
• Why is my screen size not set?
• Why can't I use the pageup/pagedown keys?
• Why can't I cut/paste in xterm?
• Reverse video is not reset
• Resizing under FVWM does weird things
• Why doesn't the screen clear when running vi?
• Why is the cursor misplaced after running vi?
• Why doesn't my delete key work?
• Why did my delete key stop working?
• Why doesn't my keypad work?
• Why can't I input 8-bit characters?
• Why are the menus tiny?
• What is this warning message?

My terminal doesn't show box characters

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.

My terminal doesn't recognize color

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?

• 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 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.

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

	setenv LINES 24
	setenv COLUMNS 80

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

	/usr/lib/X11/app-defaults/XTerm

	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

Why can't I cut/paste in xterm

I need libncurses.so.3.0

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.

I need /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)

Perhaps your system does not have enough pty's, or (a recent problem reported with newer Linux kernels, especially RedHat 6.0) the major device numbers of the pty's may have changed during a kernel upgrade.

Reverse video is not reset

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. 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.

FVWM does weird things when I try to resize xterm

• 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.

Why doesn't the screen clear when running vi?

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

XFree86 3.9s xterm implements a different set of controls which addresses 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.

Why is the cursor misplaced after running vi?

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).

Why doesn't my delete key work?

You are probably talking about the backarrow key (on my keyboard, at the upper right of the QWERTY block), or the key labeled delete. 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 (from VT320) that changes this key between the two styles (backspace or delete).

With XFree86 xterm patch number 95, 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?

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 (^?).

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.

Unset $TERMCAP in xterms in which you expect to run screen. That works.

Why doesn't my keypad work?

Here's a picture of the VT100 numeric keypad:

	+-----+-----+-----+-----+
	| PF1 | PF2 | PF3 | PF4 |
	+-----+-----+-----+-----+
	|  7  |  8  |  9  |  -  |
	+-----+-----+-----+-----+
	|  4  |  5  |  6  |  ,  |
	+-----+-----+-----+-----+
	|  1  |  2  |  3  |     |
	+-----+-----+-----+ ENT +
	|     0     |  .  |     |
	+-----+-----+-----+-----+

	+-----+-----+-----+-----+
	| NUM |  /  |  *  |  -  |
	+-----+-----+-----+-----+
	|  7  |  8  |  9  |     |
	+-----+-----+-----+  +  +
	|  4  |  5  |  6  |     |
	+-----+-----+-----+-----+
	|  1  |  2  |  3  |     |
	+-----+-----+-----+ ENT +
	|     0     |  .  |     |
	+-----+-----+-----+-----+

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.

Why can't I input 8-bit characters

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

	*customization: -color

Why are the menus tiny

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

	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.

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.

• 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.

X11R6.3 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.

COLOR_XTERM download

• 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).

ANSI_XTERM download

• implements non-bce color model
• fails vttest by not rendering reverse-video screen

DTTERM

• 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

KTERM download

• implements non-bce color model
• implements status line, but uses non-DEC escape sequences for this.

NXTERM

• 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.

RXVT link

• 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.

XITERM link

How do I build XTERM?

• 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.

	xmkmf
	make

	configure --help

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?

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