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Table of Contents
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] [-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.
- -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.
- 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 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. 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.
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
- DISPLAY
- To get default
display.
- XPROPFORMATS
- Specifies the name of a file from which additional
formats are to be obtained.
X(7)
, xwininfo(1)
Mark Lillibridge,
MIT Project Athena
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