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NAME
X - a portable, network-transparent window system
OVERVIEW
The X Window System is a network transparent window system which runs on a wide range of computing and
graphics machines. It should be relatively straightforward to build the X.Org Foundation software
distribution on most ANSI C and POSIX compliant systems. Commercial implementations are also available
for a wide range of platforms.
The X.Org Foundation requests that the following names be used when referring to this software:
X
X Window System
X Version 11
X Window System, Version 11
X11
X Window System is a trademark of The Open Group.
DESCRIPTION
X Window System servers run on computers with bitmap displays. The server distributes user input to and
accepts output requests from various client programs through a variety of different interprocess
communication channels. Although the most common case is for the client programs to be running on the
same machine as the server, clients can be run transparently from other machines (including machines with
different architectures and operating systems) as well.
X supports overlapping hierarchical subwindows and text and graphics operations, on both monochrome and
color displays. For a full explanation of the functions that are available, see the Xlib - C Language X
Interface manual, the X Window System Protocol specification, the X Toolkit Intrinsics - C Language
Interface manual, and various toolkit documents.
The number of programs that use X is quite large. Programs provided in the core X.Org Foundation
distribution include: a terminal emulator, xterm; a window manager, twm; a display manager, xdm; a
console redirect program, xconsole; a mail interface, xmh; a bitmap editor, bitmap; resource
listing/manipulation tools, appres, editres; access control programs, xauth, xhost, and iceauth; user
preference setting programs, xrdb, xcmsdb, xset, xsetroot, xstdcmap, and xmodmap; clocks, xclock and
oclock; a font displayer, xfd; utilities for listing information about fonts, windows, and displays,
xlsfonts, xwininfo, xlsclients, xdpyinfo, xlsatoms, and xprop; screen image manipulation utilities, xwd,
xwud, and xmag; a performance measurement utility, x11perf; a font compiler, bdftopcf; a font server and
related utilities, xfs, fsinfo, fslsfonts, fstobdf; a display server and related utilities, Xserver, rgb,
mkfontdir; a clipboard manager, xclipboard; keyboard description compiler and related utilities, xkbcomp,
setxkbmap xkbprint, xkbbell, xkbevd, xkbvleds, and xkbwatch; a utility to terminate clients, xkill; a
firewall security proxy, xfwp; a proxy manager to control them, proxymngr; a utility to find proxies,
xfindproxy; web browser plug-ins, libxrx.so and libxrxnest.so; an RX MIME-type helper program, xrx; and a
utility to cause part or all of the screen to be redrawn, xrefresh.
Many other utilities, window managers, games, toolkits, etc. are included as user-contributed software in
the X.Org Foundation distribution, or are available on the Internet. See your site administrator for
details.
STARTING UP
There are two main ways of getting the X server and an initial set of client applications started. The
particular method used depends on what operating system you are running and whether or not you use other
window systems in addition to X.
Display Manager
If you want to always have X running on your display, your site administrator can set your
machine up to use a Display Manager such as xdm, gdm, or kdm. This program is typically started
by the system at boot time and takes care of keeping the server running and getting users logged
in. If you are running one of these display managers, you will normally see a window on the
screen welcoming you to the system and asking for your login information. Simply type them in as
you would at a normal terminal. If you make a mistake, the display manager will display an error
message and ask you to try again. After you have successfully logged in, the display manager
will start up your X environment. The documentation for the display manager you use can provide
more details.
xinit (run manually from the shell)
Sites that support more than one window system might choose to use the xinit program for starting
X manually. If this is true for your machine, your site administrator will probably have
provided a program named "x11", "startx", or "xstart" that will do site-specific initialization
(such as loading convenient default resources, running a window manager, displaying a clock, and
starting several terminal emulators) in a nice way. If not, you can build such a script using
the xinit program. This utility simply runs one user-specified program to start the server, runs
another to start up any desired clients, and then waits for either to finish. Since either or
both of the user-specified programs may be a shell script, this gives substantial flexibility at
the expense of a nice interface. For this reason, xinit is not intended for end users.
DISPLAY NAMES
From the user's perspective, every X server has a display name of the form:
hostname:displaynumber.screennumber
This information is used by the application to determine how it should connect to the server and which
screen it should use by default (on displays with multiple monitors):
hostname
The hostname specifies the name of the machine to which the display is physically connected. If
the hostname is not given, the most efficient way of communicating to a server on the same
machine will be used.
displaynumber
The phrase "display" is usually used to refer to a collection of monitors that share a common set
of input devices (keyboard, mouse, tablet, etc.). Most workstations tend to only have one
display. Larger, multi-user systems, however, frequently have several displays so that more than
one person can be doing graphics work at once. To avoid confusion, each display on a machine is
assigned a display number (beginning at 0) when the X server for that display is started. The
display number must always be given in a display name.
screennumber
Some displays share their input devices among two or more monitors. These may be configured as a
single logical screen, which allows windows to move across screens, or as individual screens,
each with their own set of windows. If configured such that each monitor has its own set of
windows, each screen is assigned a screen number (beginning at 0) when the X server for that
display is started. If the screen number is not given, screen 0 will be used.
On POSIX systems, the default display name is stored in your DISPLAY environment variable. This variable
is set automatically by the xterm terminal emulator. However, when you log into another machine on a
network, you may need to set DISPLAY by hand to point to your display. For example,
% setenv DISPLAY myws:0
$ DISPLAY=myws:0; export DISPLAY
The ssh program can be used to start an X program on a remote machine; it automatically sets the DISPLAY
variable correctly.
Finally, most X programs accept a command line option of -display displayname to temporarily override the
contents of DISPLAY. This is most commonly used to pop windows on another person's screen or as part of
a "remote shell" command to start an xterm pointing back to your display. For example,
% xeyes -display joesws:0 -geometry 1000x1000+0+0
% rsh big xterm -display myws:0 -ls </dev/null &
X servers listen for connections on a variety of different communications channels (network byte streams,
shared memory, etc.). Since there can be more than one way of contacting a given server, The hostname
part of the display name is used to determine the type of channel (also called a transport layer) to be
used. X servers generally support the following types of connections:
local
The hostname part of the display name should be the empty string. For example: :0, :1, and
:0.1. The most efficient local transport will be chosen.
TCPIP
The hostname part of the display name should be the server machine's hostname or IP address.
Full Internet names, abbreviated names, IPv4 addresses, and IPv6 addresses are all allowed. For
example: x.org:0, expo:0, [::1]:0, 198.112.45.11:0, bigmachine:1, and hydra:0.1.
ACCESS CONTROL
An X server can use several types of access control. Mechanisms provided in Release 7 are:
Host Access Simple host-based access control.
MIT-MAGIC-COOKIE-1 Shared plain-text "cookies".
XDM-AUTHORIZATION-1 Secure DES based private-keys.
SUN-DES-1 Based on Sun's secure rpc system.
Server Interpreted Server-dependent methods of access control
Xdm initializes access control for the server and also places authorization information in a file
accessible to the user.
Normally, the list of hosts from which connections are always accepted should be empty, so that only
clients with are explicitly authorized can connect to the display. When you add entries to the host list
(with xhost), the server no longer performs any authorization on connections from those machines. Be
careful with this.
The file from which Xlib extracts authorization data can be specified with the environment variable
XAUTHORITY, and defaults to the file .Xauthority in the home directory. Xdm uses $HOME/.Xauthority and
will create it or merge in authorization records if it already exists when a user logs in.
If you use several machines and share a common home directory across all of the machines by means of a
network file system, you never really have to worry about authorization files, the system should work
correctly by default. Otherwise, as the authorization files are machine-independent, you can simply copy
the files to share them. To manage authorization files, use xauth. This program allows you to extract
records and insert them into other files. Using this, you can send authorization to remote machines when
you login, if the remote machine does not share a common home directory with your local machine. Note
that authorization information transmitted ``in the clear'' through a network file system or using ftp or
rcp can be ``stolen'' by a network eavesdropper, and as such may enable unauthorized access. In many
environments, this level of security is not a concern, but if it is, you need to know the exact semantics
of the particular authorization data to know if this is actually a problem.
For more information on access control, see the Xsecurity(7) manual page.
GEOMETRY SPECIFICATIONS
One of the advantages of using window systems instead of hardwired terminals is that applications don't
have to be restricted to a particular size or location on the screen. Although the layout of windows on
a display is controlled by the window manager that the user is running (described below), most X programs
accept a command line argument of the form -geometry WIDTHxHEIGHT+XOFF+YOFF (where WIDTH, HEIGHT, XOFF,
and YOFF are numbers) for specifying a preferred size and location for this application's main window.
The WIDTH and HEIGHT parts of the geometry specification are usually measured in either pixels or
characters, depending on the application. The XOFF and YOFF parts are measured in pixels and are used to
specify the distance of the window from the left or right and top and bottom edges of the screen,
respectively. Both types of offsets are measured from the indicated edge of the screen to the
corresponding edge of the window. The X offset may be specified in the following ways:
+XOFF The left edge of the window is to be placed XOFF pixels in from the left edge of the screen
(i.e., the X coordinate of the window's origin will be XOFF). XOFF may be negative, in which
case the window's left edge will be off the screen.
-XOFF The right edge of the window is to be placed XOFF pixels in from the right edge of the screen.
XOFF may be negative, in which case the window's right edge will be off the screen.
The Y offset has similar meanings:
+YOFF The top edge of the window is to be YOFF pixels below the top edge of the screen (i.e., the Y
coordinate of the window's origin will be YOFF). YOFF may be negative, in which case the
window's top edge will be off the screen.
-YOFF The bottom edge of the window is to be YOFF pixels above the bottom edge of the screen. YOFF may
be negative, in which case the window's bottom edge will be off the screen.
Offsets must be given as pairs; in other words, in order to specify either XOFF or YOFF both must be
present. Windows can be placed in the four corners of the screen using the following specifications:
+0+0 upper left hand corner.
-0+0 upper right hand corner.
-0-0 lower right hand corner.
+0-0 lower left hand corner.
In the following examples, a terminal emulator is placed in roughly the center of the screen and a load
average monitor, mailbox, and clock are placed in the upper right hand corner:
xterm -fn 6x10 -geometry 80x24+30+200 &
xclock -geometry 48x48-0+0 &
xload -geometry 48x48-96+0 &
xbiff -geometry 48x48-48+0 &
WINDOW MANAGERS
The layout of windows on the screen is controlled by special programs called window managers. Although
many window managers will honor geometry specifications as given, others may choose to ignore them
(requiring the user to explicitly draw the window's region on the screen with the pointer, for example).
Since window managers are regular (albeit complex) client programs, a variety of different user
interfaces can be built. The X.Org Foundation distribution comes with a window manager named twm which
supports overlapping windows, popup menus, point-and-click or click-to-type input models, title bars,
nice icons (and an icon manager for those who don't like separate icon windows).
See the user-contributed software in the X.Org Foundation distribution for other popular window managers.
FONT NAMES
Collections of characters for displaying text and symbols in X are known as fonts. A font typically
contains images that share a common appearance and look nice together (for example, a single size,
boldness, slant, and character set). Similarly, collections of fonts that are based on a common type
face (the variations are usually called roman, bold, italic, bold italic, oblique, and bold oblique) are
called families.
Fonts come in various sizes. The X server supports scalable fonts, meaning it is possible to create a
font of arbitrary size from a single source for the font. The server supports scaling from outline fonts
and bitmap fonts. Scaling from outline fonts usually produces significantly better results than scaling
from bitmap fonts.
An X server can obtain fonts from individual files stored in directories in the file system, or from one
or more font servers, or from a mixtures of directories and font servers. The list of places the server
looks when trying to find a font is controlled by its font path. Although most installations will choose
to have the server start up with all of the commonly used font directories in the font path, the font
path can be changed at any time with the xset program. However, it is important to remember that the
directory names are on the server's machine, not on the application's.
Bitmap font files are usually created by compiling a textual font description into binary form, using
bdftopcf. Font databases are created by running the mkfontdir program in the directory containing the
source or compiled versions of the fonts. Whenever fonts are added to a directory, mkfontdir should be
rerun so that the server can find the new fonts. To make the server reread the font database, reset the
font path with the xset program. For example, to add a font to a private directory, the following
commands could be used:
% cp newfont.pcf ~/myfonts
% mkfontdir ~/myfonts
% xset fp rehash
The xfontsel and xlsfonts programs can be used to browse through the fonts available on a server. Font
names tend to be fairly long as they contain all of the information needed to uniquely identify
individual fonts. However, the X server supports wildcarding of font names, so the full specification
-adobe-courier-medium-r-normal--10-100-75-75-m-60-iso8859-1
might be abbreviated as:
-*-courier-medium-r-normal--*-100-*-*-*-*-iso8859-1
Because the shell also has special meanings for * and ?, wildcarded font names should be quoted:
% xlsfonts -fn '-*-courier-medium-r-normal--*-100-*-*-*-*-*-*'
The xlsfonts program can be used to list all of the fonts that match a given pattern. With no arguments,
it lists all available fonts. This will usually list the same font at many different sizes. To see just
the base scalable font names, try using one of the following patterns:
-*-*-*-*-*-*-0-0-0-0-*-0-*-*
-*-*-*-*-*-*-0-0-75-75-*-0-*-*
-*-*-*-*-*-*-0-0-100-100-*-0-*-*
To convert one of the resulting names into a font at a specific size, replace one of the first two zeros
with a nonzero value. The field containing the first zero is for the pixel size; replace it with a
specific height in pixels to name a font at that size. Alternatively, the field containing the second
zero is for the point size; replace it with a specific size in decipoints (there are 722.7 decipoints to
the inch) to name a font at that size. The last zero is an average width field, measured in tenths of
pixels; some servers will anamorphically scale if this value is specified.
FONT SERVER NAMES
One of the following forms can be used to name a font server that accepts TCP connections:
tcp/hostname:port
tcp/hostname:port/cataloguelist
The hostname specifies the name (or decimal numeric address) of the machine on which the font server is
running. The port is the decimal TCP port on which the font server is listening for connections. The
cataloguelist specifies a list of catalogue names, with '+' as a separator.
Examples: tcp/x.org:7100, tcp/198.112.45.11:7100/all.
COLOR NAMES
Most applications provide ways of tailoring (usually through resources or command line arguments) the
colors of various elements in the text and graphics they display. A color can be specified either by an
abstract color name, or by a numerical color specification. The numerical specification can identify a
color in either device-dependent (RGB) or device-independent terms. Color strings are case-insensitive.
X supports the use of abstract color names, for example, "red", "blue". A value for this abstract name
is obtained by searching one or more color name databases. Xlib first searches zero or more client-side
databases; the number, location, and content of these databases is implementation dependent. If the name
is not found, the color is looked up in the X server's database. The text form of this database is
commonly stored in the file usr/share/X11/rgb.txt.
A numerical color specification consists of a color space name and a set of values in the following
syntax:
<color_space_name>:<value>/.../<value>
An RGB Device specification is identified by the prefix "rgb:" and has the following syntax:
rgb:<red>/<green>/<blue>
<red>, <green>, <blue> := h | hh | hhh | hhhh
h := single hexadecimal digits
Note that h indicates the value scaled in 4 bits, hh the value scaled in 8 bits, hhh the value scaled in
12 bits, and hhhh the value scaled in 16 bits, respectively. These values are passed directly to the X
server, and are assumed to be gamma corrected.
The eight primary colors can be represented as:
black rgb:0/0/0
red rgb:ffff/0/0
green rgb:0/ffff/0
blue rgb:0/0/ffff
yellow rgb:ffff/ffff/0
magenta rgb:ffff/0/ffff
cyan rgb:0/ffff/ffff
white rgb:ffff/ffff/ffff
For backward compatibility, an older syntax for RGB Device is supported, but its continued use is not
encouraged. The syntax is an initial sharp sign character followed by a numeric specification, in one of
the following formats:
#RGB (4 bits each)
#RRGGBB (8 bits each)
#RRRGGGBBB (12 bits each)
#RRRRGGGGBBBB (16 bits each)
The R, G, and B represent single hexadecimal digits. When fewer than 16 bits each are specified, they
represent the most-significant bits of the value (unlike the "rgb:" syntax, in which values are scaled).
For example, #3a7 is the same as #3000a0007000.
An RGB intensity specification is identified by the prefix "rgbi:" and has the following syntax:
rgbi:<red>/<green>/<blue>
The red, green, and blue are floating point values between 0.0 and 1.0, inclusive. They represent linear
intensity values, with 1.0 indicating full intensity, 0.5 half intensity, and so on. These values will
be gamma corrected by Xlib before being sent to the X server. The input format for these values is an
optional sign, a string of numbers possibly containing a decimal point, and an optional exponent field
containing an E or e followed by a possibly signed integer string.
The standard device-independent string specifications have the following syntax:
CIEXYZ:<X>/<Y>/<Z> (none, 1, none)
CIEuvY:<u>/<v>/<Y> (~.6, ~.6, 1)
CIExyY:<x>/<y>/<Y> (~.75, ~.85, 1)
CIELab:<L>/<a>/<b> (100, none, none)
CIELuv:<L>/<u>/<v> (100, none, none)
TekHVC:<H>/<V>/<C> (360, 100, 100)
All of the values (C, H, V, X, Y, Z, a, b, u, v, y, x) are floating point values. Some of the values are
constrained to be between zero and some upper bound; the upper bounds are given in parentheses above.
The syntax for these values is an optional '+' or '-' sign, a string of digits possibly containing a
decimal point, and an optional exponent field consisting of an 'E' or 'e' followed by an optional '+' or
'-' followed by a string of digits.
For more information on device independent color, see the Xlib reference manual.
KEYBOARDS
The X keyboard model is broken into two layers: server-specific codes (called keycodes) which represent
the physical keys, and server-independent symbols (called keysyms) which represent the letters or words
that appear on the keys. Two tables are kept in the server for converting keycodes to keysyms:
modifier list
Some keys (such as Shift, Control, and Caps Lock) are known as modifier and are used to select
different symbols that are attached to a single key (such as Shift-a generates a capital A, and
Control-l generates a control character ^L). The server keeps a list of keycodes corresponding
to the various modifier keys. Whenever a key is pressed or released, the server generates an
event that contains the keycode of the indicated key as well as a mask that specifies which of
the modifier keys are currently pressed. Most servers set up this list to initially contain the
various shift, control, and shift lock keys on the keyboard.
keymap table
Applications translate event keycodes and modifier masks into keysyms using a keysym table which
contains one row for each keycode and one column for various modifier states. This table is
initialized by the server to correspond to normal typewriter conventions. The exact semantics of
how the table is interpreted to produce keysyms depends on the particular program, libraries, and
language input method used, but the following conventions for the first four keysyms in each row
are generally adhered to:
The first four elements of the list are split into two groups of keysyms. Group 1 contains the first and
second keysyms; Group 2 contains the third and fourth keysyms. Within each group, if the first element
is alphabetic and the the second element is the special keysym NoSymbol, then the group is treated as
equivalent to a group in which the first element is the lowercase letter and the second element is the
uppercase letter.
Switching between groups is controlled by the keysym named MODE SWITCH, by attaching that keysym to some
key and attaching that key to any one of the modifiers Mod1 through Mod5. This modifier is called the
``group modifier.'' Group 1 is used when the group modifier is off, and Group 2 is used when the group
modifier is on.
Within a group, the modifier state determines which keysym to use. The first keysym is used when the
Shift and Lock modifiers are off. The second keysym is used when the Shift modifier is on, when the Lock
modifier is on and the second keysym is uppercase alphabetic, or when the Lock modifier is on and is
interpreted as ShiftLock. Otherwise, when the Lock modifier is on and is interpreted as CapsLock, the
state of the Shift modifier is applied first to select a keysym; but if that keysym is lowercase
alphabetic, then the corresponding uppercase keysym is used instead.
OPTIONS
Most X programs attempt to use the same names for command line options and arguments. All applications
written with the X Toolkit Intrinsics automatically accept the following options:
-display display
This option specifies the name of the X server to use.
-geometry geometry
This option specifies the initial size and location of the window.
-bg color, -background color
Either option specifies the color to use for the window background.
-bd color, -bordercolor color
Either option specifies the color to use for the window border.
-bw number, -borderwidth number
Either option specifies the width in pixels of the window border.
-fg color, -foreground color
Either option specifies the color to use for text or graphics.
-fn font, -font font
Either option specifies the font to use for displaying text.
-iconic
This option indicates that the user would prefer that the application's windows initially not be
visible as if the windows had be immediately iconified by the user. Window managers may choose
not to honor the application's request.
-name
This option specifies the name under which resources for the application should be found. This
option is useful in shell aliases to distinguish between invocations of an application, without
resorting to creating links to alter the executable file name.
-rv, -reverse
Either option indicates that the program should simulate reverse video if possible, often by
swapping the foreground and background colors. Not all programs honor this or implement it
correctly. It is usually only used on monochrome displays.
+rv
This option indicates that the program should not simulate reverse video. This is used to
override any defaults since reverse video doesn't always work properly.
-selectionTimeout
This option specifies the timeout in milliseconds within which two communicating applications
must respond to one another for a selection request.
-synchronous
This option indicates that requests to the X server should be sent synchronously, instead of
asynchronously. Since Xlib normally buffers requests to the server, errors do not necessarily
get reported immediately after they occur. This option turns off the buffering so that the
application can be debugged. It should never be used with a working program.
-title string
This option specifies the title to be used for this window. This information is sometimes used
by a window manager to provide some sort of header identifying the window.
-xnllanguage language[_territory][.codeset]
This option specifies the language, territory, and codeset for use in resolving resource and
other filenames.
-xrm resourcestring
This option specifies a resource name and value to override any defaults. It is also very useful
for setting resources that don't have explicit command line arguments.
RESOURCES
To make the tailoring of applications to personal preferences easier, X provides a mechanism for storing
default values for program resources (e.g. background color, window title, etc.) that is used by programs
that use toolkits based on the X Toolkit Intrinsics library libXt. (Programs using the common Gtk+ and
Qt toolkits use other configuration mechanisms.) Resources are specified as strings that are read in
from various places when an application is run. Program components are named in a hierarchical fashion,
with each node in the hierarchy identified by a class and an instance name. At the top level is the
class and instance name of the application itself. By convention, the class name of the application is
the same as the program name, but with the first letter capitalized (e.g. Bitmap or Emacs) although some
programs that begin with the letter ``x'' also capitalize the second letter for historical reasons.
The precise syntax for resources is:
ResourceLine = Comment | IncludeFile | ResourceSpec | <empty line>
Comment = "!" {<any character except null or newline>}
IncludeFile = "#" WhiteSpace "include" WhiteSpace FileName WhiteSpace
FileName = <valid filename for operating system>
ResourceSpec = WhiteSpace ResourceName WhiteSpace ":" WhiteSpace Value
ResourceName = [Binding] {Component Binding} ComponentName
Binding = "." | "*"
WhiteSpace = {<space> | <horizontal tab>}
Component = "?" | ComponentName
ComponentName = NameChar {NameChar}
NameChar = "a"-"z" | "A"-"Z" | "0"-"9" | "_" | "-"
Value = {<any character except null or unescaped newline>}
Elements separated by vertical bar (|) are alternatives. Curly braces ({...}) indicate zero or more
repetitions of the enclosed elements. Square brackets ([...]) indicate that the enclosed element is
optional. Quotes ("...") are used around literal characters.
IncludeFile lines are interpreted by replacing the line with the contents of the specified file. The
word "include" must be in lowercase. The filename is interpreted relative to the directory of the file
in which the line occurs (for example, if the filename contains no directory or contains a relative
directory specification).
If a ResourceName contains a contiguous sequence of two or more Binding characters, the sequence will be
replaced with single "." character if the sequence contains only "." characters, otherwise the sequence
will be replaced with a single "*" character.
A resource database never contains more than one entry for a given ResourceName. If a resource file
contains multiple lines with the same ResourceName, the last line in the file is used.
Any whitespace character before or after the name or colon in a ResourceSpec are ignored. To allow a
Value to begin with whitespace, the two-character sequence ``\space'' (backslash followed by space) is
recognized and replaced by a space character, and the two-character sequence ``\tab'' (backslash followed
by horizontal tab) is recognized and replaced by a horizontal tab character. To allow a Value to contain
embedded newline characters, the two-character sequence ``\n'' is recognized and replaced by a newline
character. To allow a Value to be broken across multiple lines in a text file, the two-character
sequence ``\newline'' (backslash followed by newline) is recognized and removed from the value. To allow
a Value to contain arbitrary character codes, the four-character sequence ``\nnn'', where each n is a
digit character in the range of ``0''-``7'', is recognized and replaced with a single byte that contains
the octal value specified by the sequence. Finally, the two-character sequence ``\\'' is recognized and
replaced with a single backslash.
When an application looks for the value of a resource, it specifies a complete path in the hierarchy,
with both class and instance names. However, resource values are usually given with only partially
specified names and classes, using pattern matching constructs. An asterisk (*) is a loose binding and
is used to represent any number of intervening components, including none. A period (.) is a tight
binding and is used to separate immediately adjacent components. A question mark (?) is used to match
any single component name or class. A database entry cannot end in a loose binding; the final component
(which cannot be "?") must be specified. The lookup algorithm searches the resource database for the
entry that most closely matches (is most specific for) the full name and class being queried. When more
than one database entry matches the full name and class, precedence rules are used to select just one.
The full name and class are scanned from left to right (from highest level in the hierarchy to lowest),
one component at a time. At each level, the corresponding component and/or binding of each matching
entry is determined, and these matching components and bindings are compared according to precedence
rules. Each of the rules is applied at each level, before moving to the next level, until a rule selects
a single entry over all others. The rules (in order of precedence) are:
1. An entry that contains a matching component (whether name, class, or "?") takes precedence over
entries that elide the level (that is, entries that match the level in a loose binding).
2. An entry with a matching name takes precedence over both entries with a matching class and entries
that match using "?". An entry with a matching class takes precedence over entries that match using
"?".
3. An entry preceded by a tight binding takes precedence over entries preceded by a loose binding.
Programs based on the X Toolkit Intrinsics obtain resources from the following sources (other programs
usually support some subset of these sources):
RESOURCE_MANAGER root window property
Any global resources that should be available to clients on all machines should be stored in the
RESOURCE_MANAGER property on the root window of the first screen using the xrdb program. This is
frequently taken care of when the user starts up X through the display manager or xinit.
SCREEN_RESOURCES root window property
Any resources specific to a given screen (e.g. colors) that should be available to clients on all
machines should be stored in the SCREEN_RESOURCES property on the root window of that screen.
The xrdb program will sort resources automatically and place them in RESOURCE_MANAGER or
SCREEN_RESOURCES, as appropriate.
application-specific files
Directories named by the environment variable XUSERFILESEARCHPATH or the environment variable
XAPPLRESDIR (which names a single directory and should end with a '/' on POSIX systems), plus
directories in a standard place (usually under /usr/share/X11/, but this can be overridden with
the XFILESEARCHPATH environment variable) are searched for for application-specific resources.
For example, application default resources are usually kept in /usr/share/X11/app-defaults/. See
the X Toolkit Intrinsics - C Language Interface manual for details.
XENVIRONMENT
Any user- and machine-specific resources may be specified by setting the XENVIRONMENT environment
variable to the name of a resource file to be loaded by all applications. If this variable is
not defined, a file named $HOME/.Xdefaults-hostname is looked for instead, where hostname is the
name of the host where the application is executing.
-xrm resourcestring
Resources can also be specified from the command line. The resourcestring is a single resource
name and value as shown above. Note that if the string contains characters interpreted by the
shell (e.g., asterisk), they must be quoted. Any number of -xrm arguments may be given on the
command line.
Program resources are organized into groups called classes, so that collections of individual resources
(each of which are called instances) can be set all at once. By convention, the instance name of a
resource begins with a lowercase letter and class name with an upper case letter. Multiple word
resources are concatenated with the first letter of the succeeding words capitalized. Applications
written with the X Toolkit Intrinsics will have at least the following resources:
background (class Background)
This resource specifies the color to use for the window background.
borderWidth (class BorderWidth)
This resource specifies the width in pixels of the window border.
borderColor (class BorderColor)
This resource specifies the color to use for the window border.
Most applications using the X Toolkit Intrinsics also have the resource foreground (class Foreground),
specifying the color to use for text and graphics within the window.
By combining class and instance specifications, application preferences can be set quickly and easily.
Users of color displays will frequently want to set Background and Foreground classes to particular
defaults. Specific color instances such as text cursors can then be overridden without having to define
all of the related resources. For example,
bitmap*Dashed: off
XTerm*cursorColor: gold
XTerm*multiScroll: on
XTerm*jumpScroll: on
XTerm*reverseWrap: on
XTerm*curses: on
XTerm*Font: 6x10
XTerm*scrollBar: on
XTerm*scrollbar*thickness: 5
XTerm*multiClickTime: 500
XTerm*charClass: 33:48,37:48,45-47:48,64:48
XTerm*cutNewline: off
XTerm*cutToBeginningOfLine: off
XTerm*titeInhibit: on
XTerm*ttyModes: intr ^c erase ^? kill ^u
XLoad*Background: gold
XLoad*Foreground: red
XLoad*highlight: black
XLoad*borderWidth: 0
emacs*Geometry: 80x65-0-0
emacs*Background: rgb:5b/76/86
emacs*Foreground: white
emacs*Cursor: white
emacs*BorderColor: white
emacs*Font: 6x10
xmag*geometry: -0-0
xmag*borderColor: white
If these resources were stored in a file called .Xresources in your home directory, they could be added
to any existing resources in the server with the following command:
% xrdb -merge $HOME/.Xresources
This is frequently how user-friendly startup scripts merge user-specific defaults into any site-wide
defaults. All sites are encouraged to set up convenient ways of automatically loading resources. See the
Xlib manual section Resource Manager Functions for more information.
ENVIRONMENT
DISPLAY
This is the only mandatory environment variable. It must point to an X server. See section
"Display Names" above.
XAUTHORITY
This must point to a file that contains authorization data. The default is $HOME/.Xauthority. See
Xsecurity(7), xauth(1), xdm(1), Xau(3).
ICEAUTHORITY
This must point to a file that contains authorization data. The default is $HOME/.ICEauthority.
LC_ALL, LC_CTYPE, LANG
The first non-empty value among these three determines the current locale's facet for character
handling, and in particular the default text encoding. See locale(7), setlocale(3), locale(1).
XMODIFIERS
This variable can be set to contain additional information important for the current locale
setting. Typically set to @im=<input-method> to enable a particular input method. See
XSetLocaleModifiers(3).
XLOCALEDIR
This must point to a directory containing the locale.alias file and Compose and XLC_LOCALE file
hierarchies for all locales. The default value is /usr/share/X11/locale.
XENVIRONMENT
This must point to a file containing X resources. The default is $HOME/.Xdefaults-<hostname>.
Unlike $HOME/.Xresources, it is consulted each time an X application starts.
XFILESEARCHPATH
This must contain a colon separated list of path templates, where libXt will search for resource
files. The default value consists of
/etc/X11/%L/%T/%N%C%S:\
/etc/X11/%l/%T/%N%C%S:\
/etc/X11/%T/%N%C%S:\
/etc/X11/%L/%T/%N%S:\
/etc/X11/%l/%T/%N%S:\
/etc/X11/%T/%N%S:\
/usr/share/X11/%L/%T/%N%C%S:\
/usr/share/X11/%l/%T/%N%C%S:\
/usr/share/X11/%T/%N%C%S:\
/usr/share/X11/%L/%T/%N%S:\
/usr/share/X11/%l/%T/%N%S:\
/usr/share/X11/%T/%N%S:\
/usr/lib/x86_64-linux-gnu/X11/%L/%T/%N%C%S:\
/usr/lib/x86_64-linux-gnu/X11/%l/%T/%N%C%S:\
/usr/lib/x86_64-linux-gnu/X11/%T/%N%C%S:\
/usr/lib/x86_64-linux-gnu/X11/%L/%T/%N%S:\
/usr/lib/x86_64-linux-gnu/X11/%l/%T/%N%S:\
/usr/lib/x86_64-linux-gnu/X11/%T/%N%S
A path template is transformed to a pathname by substituting:
%D => the implementation-specific default path
%N => name (basename) being searched for
%T => type (dirname) being searched for
%S => suffix being searched for
%C => value of the resource "customization"
(class "Customization")
%L => the locale name
%l => the locale's language (part before '_')
%t => the locale's territory (part after '_` but before '.')
%c => the locale's encoding (part after '.')
XUSERFILESEARCHPATH
This must contain a colon separated list of path templates, where libXt will search for user
dependent resource files. The default value is:
$XAPPLRESDIR/%L/%N%C:\
$XAPPLRESDIR/%l/%N%C:\
$XAPPLRESDIR/%N%C:\
$HOME/%N%C:\
$XAPPLRESDIR/%L/%N:\
$XAPPLRESDIR/%l/%N:\
$XAPPLRESDIR/%N:\
$HOME/%N
$XAPPLRESDIR defaults to $HOME, see below.
A path template is transformed to a pathname by substituting:
%D => the implementation-specific default path
%N => name (basename) being searched for
%T => type (dirname) being searched for
%S => suffix being searched for
%C => value of the resource "customization"
(class "Customization")
%L => the locale name
%l => the locale's language (part before '_')
%t => the locale's territory (part after '_` but before '.')
%c => the locale's encoding (part after '.')
XAPPLRESDIR
This must point to a base directory where the user stores the application dependent resource
files. The default value is $HOME. Only used if XUSERFILESEARCHPATH is not set.
XKEYSYMDB
This must point to a file containing nonstandard keysym definitions. The default value is
/usr/share/X11/XKeysymDB.
XCMSDB This must point to a color name database file. The default value is
/usr/lib/x86_64-linux-gnu/X11/Xcms.txt.
RESOURCE_NAME
This serves as main identifier for resources belonging to the program being executed. It defaults
to the basename of pathname of the program.
SESSION_MANAGER
Denotes the session manager to which the application should connect. See xsm(1), rstart(1).
XF86BIGFONT_DISABLE
Setting this variable to a non-empty value disables the XFree86-Bigfont extension. This extension
is a mechanism to reduce the memory consumption of big fonts by use of shared memory.
XKB_FORCE
XKB_DISABLE
XKB_DEBUG
_XKB_CHARSET
_XKB_LOCALE_CHARSETS
_XKB_OPTIONS_ENABLE
_XKB_LATIN1_LOOKUP
_XKB_CONSUME_LOOKUP_MODS
_XKB_CONSUME_SHIFT_AND_LOCK
_XKB_IGNORE_NEW_KEYBOARDS
_XKB_CONTROL_FALLBACK
_XKB_COMP_LED _XKB_COMP_FAIL_BEEP
These variables influence the X Keyboard Extension.
EXAMPLES
The following is a collection of sample command lines for some of the more frequently used commands. For
more information on a particular command, please refer to that command's manual page.
% xrdb $HOME/.Xresources
% xmodmap -e "keysym BackSpace = Delete"
% mkfontdir /usr/local/lib/X11/otherfonts
% xset fp+ /usr/local/lib/X11/otherfonts
% xmodmap $HOME/.keymap.km
% xsetroot -solid 'rgbi:.8/.8/.8'
% xset b 100 400 c 50 s 1800 r on
% xset q
% twm
% xmag
% xclock -geometry 48x48-0+0 -bg blue -fg white
% xeyes -geometry 48x48-48+0
% xbiff -update 20
% xlsfonts '*helvetica*'
% xwininfo -root
% xdpyinfo -display joesworkstation:0
% xhost -joesworkstation
% xrefresh
% xwd | xwud
% bitmap companylogo.bm 32x32
% xcalc -bg blue -fg magenta
% xterm -geometry 80x66-0-0 -name myxterm $*
DIAGNOSTICS
A wide variety of error messages are generated from various programs. The default error handler in Xlib
(also used by many toolkits) uses standard resources to construct diagnostic messages when errors occur.
The defaults for these messages are usually stored in usr/share/X11/XErrorDB. If this file is not
present, error messages will be rather terse and cryptic.
When the X Toolkit Intrinsics encounter errors converting resource strings to the appropriate internal
format, no error messages are usually printed. This is convenient when it is desirable to have one set
of resources across a variety of displays (e.g. color vs. monochrome, lots of fonts vs. very few, etc.),
although it can pose problems for trying to determine why an application might be failing. This behavior
can be overridden by the setting the StringConversionWarnings resource.
To force the X Toolkit Intrinsics to always print string conversion error messages, the following
resource should be placed in the file that gets loaded onto the RESOURCE_MANAGER property using the xrdb
program (frequently called .Xresources or .Xres in the user's home directory):
*StringConversionWarnings: on
To have conversion messages printed for just a particular application, the appropriate instance name can
be placed before the asterisk:
xterm*StringConversionWarnings: on
SEE ALSO
XOrgFoundation(7), XStandards(7), Xsecurity(7), appres(1), bdftopcf(1), bitmap(1), editres(1), fsinfo(1),
fslsfonts(1), fstobdf(1), iceauth(1), imake(1), makedepend(1), mkfontdir(1), oclock(1), proxymngr(1),
rgb(1), resize(1), rstart(1), smproxy(1), twm(1), x11perf(1), x11perfcomp(1), xauth(1), xclipboard(1),
xclock(1), xcmsdb(1), xconsole(1), xdm(1), xdpyinfo(1), xfd(1), xfindproxy(1), xfs(1), xfwp(1), xhost(1),
xinit(1), xkbbell(1), xkbcomp(1), xkbevd(1), xkbprint(1), xkbvleds(1), xkbwatch(1), xkill(1), xlogo(1),
xlsatoms(1), xlsclients(1), xlsfonts(1), xmag(1), xmh(1), xmodmap(1), xprop(1), xrdb(1), xrefresh(1),
xrx(1), xset(1), xsetroot(1), xsm(1), xstdcmap(1), xterm(1), xwd(1), xwininfo(1), xwud(1). Xserver(1),
Xorg(1), Xdmx(1), Xephyr(1), Xnest(1), Xquartz(1), Xvfb(1), Xvnc(1), XWin(1). Xlib - C Language X
Interface, and X Toolkit Intrinsics - C Language Interface
TRADEMARKS
X Window System is a trademark of The Open Group.
AUTHORS
A cast of thousands, literally. Releases 6.7 and later are brought to you by the X.Org Foundation. The
names of all people who made it a reality will be found in the individual documents and source files.
Releases 6.6 and 6.5 were done by The X.Org Group. Release 6.4 was done by The X Project Team. The
Release 6.3 distribution was from The X Consortium, Inc. The staff members at the X Consortium
responsible for that release were: Donna Converse (emeritus), Stephen Gildea (emeritus), Kaleb Keithley,
Matt Landau (emeritus), Ralph Mor (emeritus), Janet O'Halloran, Bob Scheifler, Ralph Swick, Dave Wiggins
(emeritus), and Reed Augliere.
The X Window System standard was originally developed at the Laboratory for Computer Science at the
Massachusetts Institute of Technology, and all rights thereto were assigned to the X Consortium on
January 1, 1994. X Consortium, Inc. closed its doors on December 31, 1996. All rights to the X Window
System have been assigned to The Open Group.
X Version 11 xorg-docs 1.7.1 X(7)