XPROP(1) MachTen Programmer’s Manual XPROP(1)

xprop - property displayer for X

xprop [-help] [-grammar] [-id id] [-root] [-name name]
[-frame] [-font font] [-display display] [-len n]
[-notype] [-fs file] [-remove property-name] [-spy] [-f
atom format [dformat]]* [format [dformat] atom]*

The xprop utility is for displaying window and font prop-
erties in an X server. One window or font is selected
using the command line arguments or possibly in the case
of a window, by clicking on the desired window. A list of
properties is then given, possibly with formatting infor-

-help Print out a summary of command line options.

Print out a detailed grammar for all command line

-id id This argument allows the user to select window id
on the command line rather than using the pointer
to select the target window. This is very useful
in debugging X applications where the target win-
dow is not mapped to the screen or where the use
of the pointer might be impossible or interfere
with the application.

-name name
This argument allows the user to specify that the
window named name is the target window on the com-
mand line rather than using the pointer to select
the target window.

-font font
This argument allows the user to specify that the
properties of font font should be displayed.

-root This argument specifies that X’s root window is
the target window. This is useful in situations
where the root window is completely obscured.

-display display
This argument allows you to specify the server to
connect to; see X(1).

-len n Specifies that at most n bytes of any property
should be read or displayed.

-notype Specifies that the type of each property should
not be displayed.

-fs file
Specifies that file file should be used as a
source of more formats for properties.

-frame Specifies that when selecting a window by hand
(i.e. if none of -name, -root, or -id are given),
look at the window manager frame (if any) instead
of looking for the client window.

-remove property-name
Specifies the name of a property to be removed
from the indicated window.

-spy Examine window properties forever, looking for
property change events.

-f name format [dformat]
Specifies that the format for name should be for-
mat and that the dformat for name should be dfor-
mat. If dformat is missing, " = $0+0 is

For each of these properties, its value on the selected
window or font is printed using the supplied formatting
information if any. If no formatting information is sup-
plied, internal defaults are used. If a property is not
defined on the selected window or font, "not defined" is
printed as the value for that property. If no property
list is given, all the properties possessed by the
selected window or font are printed.

A window may be selected in one of four ways. First, if
the desired window is the root window, the -root argument
may be used. If the desired window is not the root win-
dow, it may be selected in two ways on the command line,
either by id number such as might be obtained from xwin-
info, or by name if the window possesses a name. The -id
argument selects a window by id number in either decimal
or hex (must start with 0x) while the -name argument
selects a window by name.

The last way to select a window does not involve the com-
mand line at all. If none of -font, -id, -name, and -root
are specified, a crosshairs cursor is displayed and the
user is allowed to choose any visible window by pressing
any pointer button in the desired window. If it is
desired to display properties of a font as opposed to a
window, the -font argument must be used.

Other than the above four arguments and the -help argument
for obtaining help, and the -grammar argument for listing
the full grammar for the command line, all the other com-
mand line arguments are used in specifying both the format
of the properties to be displayed and how to display them.
The -len n argument specifies that at most n bytes of any
given property will be read and displayed. This is useful
for example when displaying the cut buffer on the root
window which could run to several pages if displayed in

Normally each property name is displayed by printing first
the property name then its type (if it has one) in paren-
theses followed by its value. The -notype argument speci-
fies that property types should not be displayed. The -fs
argument is used to specify a file containing a list of
formats for properties while the -f argument is used to
specify the format for one property.

The formatting information for a property actually con-
sists of two parts, a format and a dformat. The format
specifies the actual formatting of the property (i.e., is
it made up of words, bytes, or longs?, etc.) while the
dformat specifies how the property should be displayed.

The following paragraphs describe how to construct formats
and dformats. However, for the vast majority of users and
uses, this should not be necessary as the built in
defaults contain the formats and dformats necessary to
display all the standard properties. It should only be
necessary to specify formats and dformats if a new prop-
erty is being dealt with or the user dislikes the standard
display format. New users especially are encouraged to
skip this part.

A format consists of one of 0, 8, 16, or 32 followed by a
sequence of one or more format characters. The 0, 8, 16,
or 32 specifies how many bits per field there are in the
property. Zero is a special case meaning use the field
size information associated with the property itself.
(This is only needed for special cases like type INTEGER
which is actually three different types depending on the
size of the fields of the property)

A value of 8 means that the property is a sequence of
bytes while a value of 16 would mean that the property is
a sequence of words. The difference between these two
lies in the fact that the sequence of words will be byte
swapped while the sequence of bytes will not be when read
by a machine of the opposite byte order of the machine
that originally wrote the property. For more information
on how properties are formatted and stored, consult the
Xlib manual.

Once the size of the fields has been specified, it is nec-
essary to specify the type of each field (i.e., is it an
integer, a string, an atom, or what?) This is done using
one format character per field. If there are more fields
in the property than format characters supplied, the last
character will be repeated as many times as necessary for
the extra fields. The format characters and their meaning
are as follows:

a The field holds an atom number. A field of this
type should be of size 32.

b The field is an boolean. A 0 means false while
anything else means true.

c The field is an unsigned number, a cardinal.

i The field is a signed integer.

m The field is a set of bit flags, 1 meaning on.

s This field and the next ones until either a 0 or
the end of the property represent a sequence of
bytes. This format character is only usable with a
field size of 8 and is most often used to represent
a string.

x The field is a hex number (like ’c’ but displayed
in hex - most useful for displaying window ids and
the like)

An example format is 32ica which is the format for a prop-
erty of three fields of 32 bits each, the first holding a
signed integer, the second an unsigned integer, and the
third an atom.

The format of a dformat unlike that of a format is not so
rigid. The only limitations on a dformat is that one may
not start with a letter or a dash. This is so that it can
be distinguished from a property name or an argument. A
dformat is a text string containing special characters
instructing that various fields be printed at various
points in a manner similar to the formatting string used
by printf. For example, the dformat " is ( $0, $1 0
would render the POINT 3, -4 which has a format of 32ii as
" is ( 3, -4 )0.

Any character other than a $, ?, or a ( in a dformat
prints as itself. To print out one of $, ?, or ( pre-
cede it by a . For example, to print out a $, use
Several special backslash sequences are provided as short-
cuts. will cause a newline to be displayed while
will cause a tab to be displayed. o where o is an octal
number will display character number o.

A $ followed by a number n causes field number n to be
displayed. The format of the displayed field depends on
the formatting character used to describe it in the corre-
sponding format. I.e., if a cardinal is described by ’c’
it will print in decimal while if it is described by a ’x’
it is displayed in hex.

If the field is not present in the property (this is pos-
sible with some properties), <field not available> is dis-
played instead. $n+ will display field number n then a
comma then field number n+1 then another comma then ...
until the last field defined. If field n is not defined,
nothing is displayed. This is useful for a property that
is a list of values.

A ? is used to start a conditional expression, a kind of
if-then statement. ?exp(text) will display text if and
only if exp evaluates to non-zero. This is useful for two
things. First, it allows fields to be displayed if and
only if a flag is set. And second, it allows a value such
as a state number to be displayed as a name rather than as
just a number. The syntax of exp is as follows:

exp ::= term | term=exp | !exp

term ::= n | $n | mn

The ! operator is a logical ‘‘not’’, changing 0 to 1 and
any non-zero value to 0. = is an equality operator. Note
that internally all expressions are evaluated as 32 bit
numbers so -1 is not equal to 65535. = returns 1 if the
two values are equal and 0 if not. n represents the con-
stant value n while $n represents the value of field num-
ber n. mn is 1 if flag number n in the first field having
format character ’m’ in the corresponding format is 1, 0

Examples: ?m3(count: $30 displays field 3 with a label
of count if and only if flag number 3 (count starts at 0!)
is on. ?$2=0(True)?!$2=0(False) displays the inverted
value of field 2 as a boolean.

In order to display a property, xprop needs both a format
and a dformat. Before xprop uses its default values of a
format of 32x and a dformat of " = { $0+ }0, it searches
several places in an attempt to find more specific for-
mats. First, a search is made using the name of the prop-
erty. If this fails, a search is made using the type of
the property. This allows type STRING to be defined with
one set of formats while allowing property WM_NAME which
is of type STRING to be defined with a different format.
In this way, the display formats for a given type can be
overridden for specific properties.

The locations searched are in order: the format if any
specified with the property name (as in 8x WM_NAME), the
formats defined by -f options in last to first order, the
contents of the file specified by the -fs option if any,
the contents of the file specified by the environmental
variable XPROPFORMATS if any, and finally xprop’s built in
file of formats.

The format of the files referred to by the -fs argument
and the XPROPFORMATS variable is one or more lines of the
following form:

name format [dformat]

Where name is either the name of a property or the name of
a type, format is the format to be used with name and
dformat is the dformat to be used with name. If dformat
is not present, " = $0+0 is assumed.

To display the name of the root window: xprop -root

To display the window manager hints for the clock: xprop
-name xclock WM_HINTS

To display the start of the cut buffer: xprop -root -len

To display the point size of the fixed font: xprop -font

To display all the properties of window # 0x200007: xprop
-id 0x200007

DISPLAY To get default display.

Specifies the name of a file from which additional
formats are to be obtained.

X(1), xwininfo(1)

Mark Lillibridge, MIT Project Athena

X Version 11 Release 6 6