XPROP(1) UNIX Programmer's Manual XPROP(1)
NAME
xprop - property displayer for X
SYNOPSIS
xprop [-help] [-grammar] [-id id] [-root] [-name name] [-
frame] [-font font] [-display display] [-len n] [-notype]
[-fs file] [-remove property-name] [-set property-name
value] [-spy] [-f atom format [dformat]]* [format [dformat]
atom]*
SUMMARY
The xprop utility is for displaying window and font proper-
ties in an X server. One window or font is selected using
the command line arguments or possibly in the case of a win-
dow, by clicking on the desired window. A list of proper-
ties is then given, possibly with formatting information.
OPTIONS
-help Print out a summary of command line options.
-grammar
Print out a detailed grammar for all command line
options.
-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 window 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(7).
-len n Specifies that at most n bytes of any property
should be read or displayed.
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-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.
-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 pro-
perty change events.
-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.
DESCRIPTION
For each of these properties, its value on the selected win-
dow or font is printed using the supplied formatting infor-
mation 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
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 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
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properties of a font as opposed to a window, the -font argu-
ment 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 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 formatting of the property (i.e., is it made up
of words, bytes, or longs?, etc.) while the dformat speci-
fies 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 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 pro-
perty. 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 ori-
ginally wrote the property. For more information on how
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properties are formatted and stored, consult the Xlib
manual.
Once the size of the fields has been specified, it is neces-
sary 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 fol-
lows:
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 any-
thing 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.
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.
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 pro-
perty 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 dfor-
mat is a text string containing special characters instruct-
ing that various fields be printed at various points in a
manner similar to the formatting string used by printf. For
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example, 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 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 correspond-
ing 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 possi-
ble with some properties), <field not available> is
displayed 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 constant value n
while $n represents the value of field number n. mn is 1 if
flag number n in the first field having format character '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 boolean.
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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+ }\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
formats.
The format of the files referred to by the -fs argument and
the XPROPFORMATS variable is one or more lines of the fol-
lowing 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+\n" is assumed.
EXAMPLES
To display the name of the root window: xprop -root WM_NAME
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 100
CUT_BUFFER0
To display the point size of the fixed font: xprop -font
fixed POINT_SIZE
To display all the properties of window # 0x200007: xprop
-id 0x200007
ENVIRONMENT
DISPLAY To get default display.
XPROPFORMATS
Specifies the name of a file from which additional
formats are to be obtained.
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SEE ALSO
X(7), xwininfo(1)
AUTHOR
Mark Lillibridge, MIT Project Athena
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