「xprop」

  LINUX MANUAL PAGES

xprop,显示窗口的属性信息。

命令行语法格式(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]*

命令描述(SUMMARY)

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.

命令选项及含义(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.

-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.

命令描述(DESCRIPTION)

For each of these properties, its value on the selected window or font is printed using the supplied format‐
ting information if any. If no formatting information is supplied, internal defaults are used. If a prop‐
erty 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 dis‐
playing 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 dis‐
played. 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 neces‐
sary 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 repre‐

sent a string.

t This field and the next ones until either a 0 or the end of the property represent an international‐

ized 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 out‐

put.

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 dis‐
played 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 corre‐
sponding 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 val‐
ues 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.

简单示例(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

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

环境变量(ENVIRONMENT)

DISPLAY
To get default display.

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

相关文档(SEE ALSO)

X(7), xdpyinfo(1), xwininfo(1), xdriinfo(1), glxinfo(1), xvinfo(1)

参考文献

  • man 1 xprop, version 1.2.2