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] [-set
property-name value] [-spy] [-version] [-f
atom
format [
dformat]]* [
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 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 information.
- -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 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
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.
- -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 property
change events.
- -version
- Print program version information and exit.
- -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 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 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 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 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
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 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 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 violation 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 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 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), <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. m
n 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.
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 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+\n" is assumed.
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
To set a simple string property:
xprop -root -format MY_ATOM_NAME 8s -set
MY_ATOM_NAME "my_value"
- DISPLAY
- To get default display.
- XPROPFORMATS
- Specifies the name of a file from which additional formats
are to be obtained.
X(7),
xdpyinfo(1),
xwininfo(1),
xdriinfo(1),
glxinfo(1),
xvinfo(1)
Mark Lillibridge, MIT Project Athena