xprop [-display display] [-f atom format [dformat]]*
[-font font] [-frame] [-fs file] [-grammar]
[-help] [-id id] [-len n] [-name name]
[-notype] [-remove property-name] [-root] [-spy]
[format [dformat] atom]*
For each of these properties, a value on the selected window or font is printed using the supplied formatting information if there is 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 can be selected in one of four ways. First, if the desired window is the root window, the -root argument can be used. If the desired window is not the root window, it can be selected in two ways on the command line, either by id number, such as might be obtained from xwininfo(1), 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. If -font, -id, -name, or -root are not specified, a cross-hair cursor is displayed and the user can choose any visible window by pressing any pointer button in the desired window. 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 to specify 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.
Each property name is usually 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; 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 (that is, whether it is made up of words, bytes, longs?, and so on); the dformat specifies how the property should be displayed.
The following paragraphs describe how to construct formats and dformats. However, for the most users and uses, this should not be necessary because 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 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 that means 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. A value of 16 means 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 but the sequence of bytes will not be when read by a computer of the opposite byte order of the computer that originally wrote the property. or more information on how properties are formatted and stored, consult the Xlib manual.
After you have specified the size of the fields, you must specify the type of each field (for example, an integer, a string, or an atom). 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 meanings are as follows:
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 limitation on a dformat is that you cannot 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 $, ?, \, or (, precede it with a \. For example, to print out a $, use \$. Several special backslash sequences are provided as shortcuts. For example, \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. That is, if a cardinal is described by 'c', it will print in decimal; if it is described by an '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 and keep doing this up to 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 only if exp evaluates to non-zero. This is useful for two things. First, it allows fields to be displayed only if a flag is set. 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 returns 0 if they are 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 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, xpropr(1) needs both a format and a dformat. Before xpropr(1) 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 the following order:
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
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