xprop Man page

XPROP(1) General Commands 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 prop‐
erty-name] [-set property-name value] [-spy] [-f atom format [dfor‐
mat]]* [format [dformat] atom]*

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


-help Print out a summary of command line options.

Print out a detailed grammar for all command line options.

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

-name name
This argument allows the user to specify that the window named
name is the target window on the command 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 win‐
dow. 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(7).

-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 dis‐

-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 indi‐
cated window.

-set property-name value
Specifies the name of a property and a property value, to be
set on the indicated window.

-spy Examine window properties forever, looking for property change

-f name format [dformat] Specifies that the format for name should be format and that
the dformat for name should be dformat. If dformat is missing,
” = $0+\n” is assumed.


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 supplied, 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

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 window, it may be selected in two ways
on the command line, either by id number such as might be obtained from
xwininfo, 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 command 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 win‐
dow, the -font argument must be used.

Other than the above four arguments and the -help argument for obtain‐
ing help, and the -grammar argument for listing the full grammar for
the command line, all the other command 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 full.

Normally each property name is displayed by printing first the property
name then its type (if it has one) in parentheses followed by its
value. The -notype argument specifies 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 consists of two
parts, a format and a dformat. The format specifies the actual format‐
ting 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 dfor‐
mats. However, for the vast majority of users and uses, this should
not be necessary as the built in defaults contain the formats and dfor‐
mats necessary to display all the standard properties. It should only
be necessary to specify formats and dformats if a new property 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 mean‐
ing use the field size information associated with the property itself.
(This is only needed for special cases like type INTEGER which is actu‐
ally three different types depending on the size of the fields of the

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 origi‐
nally 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 necessary 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.

o The field is an array of icons, packed as a sequence of 32 bit
numbers consisting of the width, height and ARGB pixel values,
as defined for the _NET_WM_ICON property in the Extended Window
Manager Hints specification. A field of this type must be of
size 32.

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.

t This field and the next ones until either a 0 or the end of the
property represent an internationalized text string. This format
character is only usable with a field size of 8. The string is
assumed to be in an ICCCM compliant encoding and is converted to
the current locale encoding before being output.

u This field and the next ones until either a 0 or the end of the
property represent an UTF-8 encoded unicode string. This format
character is only usable with a field size of 8. If the string
is found to be an invalid character, the type of encoding viola‐
tion is printed instead, followed by the string formatted using
‘s’. When in an environment not capable of displaying UTF-8
encoded string, behaviour is identical to ‘s’.

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 property 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 exam‐
ple, the dformat ” is ( $0, $1 \)\n” would render the POINT 3, -4 which
has a format of 32ii as ” is ( 3, -4 )\n”.

Any character other than a $, ?, \, or a ( in a dformat prints as
itself. To print out one of $, ?, \, or ( precede it by a \. For
example, to print out a $, use \$. Several special backslash sequences
are provided as shortcuts. \n will cause a newline to be displayed
while \t will cause a tab to be displayed. \o where o is an octal num‐
ber 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 corresponding 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 possible with some
properties), is displayed instead. $n+ will dis‐
play 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 state‐
ment. ?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 repre‐
sents the constant 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 char‐
acter ‘m’ in the corresponding format is 1, 0 otherwise.

Examples: ?m3(count: $3\n) 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

In order to display a property, xprop needs both a format and a dfor‐
mat. Before xprop uses its default values of a format of 32x and a
dformat of ” = { $0+ }\n”, it searches several places in an attempt to
find more specific formats. First, a search is made using the name of
the property. If this fails, a search is made using the type of the
property. This allows type STRING to be defined with one set of for‐
mats 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 for‐

The format of the files referred to by the -fs argument and the XPROP‐
FORMATS 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, for‐
mat is the format to be used with name and dformat is the dformat to be
used with name. If dformat is not present, ” = $0+\n” is assumed.

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


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

To display the start of the cut buffer: xprop -root -len 100 CUT_BUF‐

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

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

To set a simple string property: xprop -root -format MY_ATOM_NAME 8s
-set MY_ATOM_NAME “my_value”

DISPLAY To get default display.

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


X(7), xdpyinfo, xwininfo, xdriinfo, glxinfo, xvinfo


Mark Lillibridge, MIT Project Athena

X Version 11 xprop 1.2.2 XPROP(1)

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