Both the KDE and GNOME desktop environments have adopted a similar
format for "desktop entries", or configuration files describing how a
particular program is to be launched, how it appears in menus, etc.
It is to the larger community's benefit that a unified standard be
agreed upon by all parties such that interoperation between the two
environments, and indeed any additional environments that implement
the specification, becomes simpler.
Desktop entry files should have the .desktop
extension, except for files of Type
Directory which should have the
.directory extension. Determining file type on basis
of extension makes determining the file type very easy and quick.
When no file extension is present, the desktop system should
fall back to recognition via "magic detection".
Desktop entry files are encoded in UTF-8. A file is interpreted as a
series of lines that are separated by linefeed characters. Case is
significant everywhere in the file.
Compliant implementations MUST not remove any fields from the file,
even if they don't support them. Such fields must be maintained in a
list somewhere, and if the file is "rewritten", they will be included.
This ensures that any desktop-specific extensions will be preserved
even if another system accesses and changes the file.
Lines beginning with a # and blank lines are
considered comments and will be ignored, however they should be
preserved across reads and writes of the desktop entry file.
Comment lines are uninterpreted and may contain any character
(except for LF). However, using UTF-8 for comment lines that
contain characters not in ASCII is encouraged.
A group header with name groupname is a line in the
format:
[groupname]
Group names may contain all ASCII characters except for
[ and ] and control characters.
Multiple groups may not have the same name.
All {key,value} pairs following a group header until
a new group header belong to the group.
The basic format of the desktop entry file requires that there be
a group header named Desktop Entry . There may
be other groups present in the file, but this is the most
important group which explicitly needs to be supported. This
group should also be used as the "magic key" for automatic MIME
type detection. There should be nothing preceding this group in
the desktop entry file but possibly one or more comments.
Entries in the file are {key,value} pairs in the
format:
Key=Value
Space before and after the equals sign should be ignored; the
= sign is the actual delimiter.
Only the characters A-Za-z0-9- may be used in
key names.
As the case is significant, the keys Name and
NAME are not equivalent.
Multiple keys in the same group may not have the same name. Keys in
different groups may have the same name.
The value types recognized are string ,
localestring ,
boolean , and
numeric .
-
Values of type string may contain all ASCII
characters except for control characters.
-
Values of type localestring are user displayable,
and are encoded in UTF-8.
-
Values of type boolean must either be the string
true or false .
-
Values of type numeric must be a valid floating
point number as recognized by the %f specifier for
scanf in the C locale.
The escape sequences \s , \n ,
\t , \r , and
\\ are supported for values of type
string and localestring , meaning
ASCII space, newline, tab, carriage return, and backslash, respectively.
Some keys can have multiple values. In such a case, the value of the key
is specified as a plural: for example, string(s) . The
multiple values should be separated by a semicolon, and the value of the
key should have a semicolon as trailing character. Semicolons in these
values need to be escaped using \; .
Localized values for keys
Keys with type localestring may be postfixed by
[LOCALE ],
where LOCALE is the locale type of the
entry. LOCALE must be of the form
lang _COUNTRY .ENCODING @MODIFIER ,
where
_COUNTRY ,
.ENCODING ,
and @MODIFIER
may be omitted. If a postfixed key occurs, the same
key must be also present without the postfix.
When reading in the desktop entry file, the value of the key is
selected by matching the current POSIX locale for the
LC_MESSAGES category against the
LOCALE postfixes of all occurrences
of the key, with the
.ENCODING part
stripped.
The matching is done as follows. If
LC_MESSAGES is of the form
lang _COUNTRY .ENCODING @MODIFIER ,
then it will match a key of the form
lang _COUNTRY @MODIFIER .
If such a key does not exist, it will attempt to match
lang _COUNTRY
followed by
lang @MODIFIER .
Then, a match against lang by itself
will be attempted. Finally, if no matching key is found the
required key without a locale specified is used. The encoding
from the LC_MESSAGES value is ignored
when matching.
If LC_MESSAGES does not have a MODIFIER
field, then no key with a modifier will be matched. Similarly, if
LC_MESSAGES does not have a COUNTRY
field, then no key with a country specified will be matched. If
LC_MESSAGES just has a lang field, then
it will do a straight match to a key with a similar value. The
following table lists possible matches of various LC_MESSAGES values in
the order in which they are matched. Note that the
ENCODING field isn't shown.
Table 1. Locale Matching
LC_MESSAGES value | Possible keys in order of matching |
lang _COUNTRY @MODIFIER
|
lang _COUNTRY @MODIFIER ,
lang _COUNTRY ,
lang @MODIFIER ,
lang ,
default value
|
lang _COUNTRY
|
lang _COUNTRY ,
lang ,
default value
|
lang @MODIFIER
|
lang @MODIFIER ,
lang ,
default value
|
lang |
lang ,
default value
|
For example, if the current value of the LC_MESSAGES category
is sr_YU@Latn and the desktop file includes:
Name=Foo
Name[sr_YU]=...
Name[sr@Latn]=...
Name[sr]=...
then the value of the Name keyed by sr_YU is used.
Recognized desktop entry keys
Keys are either OPTIONAL or REQUIRED. If a key is OPTIONAL it may or
may not be present in the file. However, if it isn't, the
implementation of the standard should not blow up, it must provide
some sane defaults.
Some keys only make sense in the context when another particular key
is also present and set to a specific value. Those keys should not be
used if the particular key is not present or not set to the specific
value. For example, the Terminal key can only be used
when the value of the Type key is
Application .
If a REQUIRED key is only valid in the context of another key set to a
specific value, then it has to be present only if the other key is set to
the specific value. For example, the URL key has to be
present when and only when when the value of the Type
key is Link .
Some example keys: Name[C] , Comment[it] .
Table 2. Standard Keys
Key | Description | Value Type | REQ? | Type |
Type |
This specification defines 3 types of desktop entries:
Application (type 1),
Link (type 2)
and Directory (type 3).
To allow the addition of new types in the future,
implementations should ignore desktop entries with an
unknown type.
|
string |
YES |
|
Version |
Version of the Desktop Entry Specification that the
desktop entry conforms with. Entries that confirm with this
version of the specification should use 1.0 .
Note that the version field is not required to be present.
|
string |
NO |
1-3 |
Name |
Specific name of the application, for example "Mozilla".
|
localestring |
YES |
1-3 |
GenericName |
Generic name of the application, for example "Web Browser".
|
localestring |
NO |
1-3 |
NoDisplay |
NoDisplay means "this application exists, but don't display it in the menus".
This can be useful to e.g. associate this application with MIME types, so that
it gets launched from a file manager (or other apps), without having a menu
entry for it (there are tons of good reasons for this, including e.g. the
netscape -remote , or kfmclient openURL kind of stuff).
|
boolean |
NO |
1-3 |
Comment |
Tooltip for the entry, for example "View sites on the
Internet". The value should not be redundant with the values of
Name and GenericName .
|
localestring |
NO |
1-3 |
Icon |
Icon to display in file manager, menus, etc. If the
name is an absolute path, the given file will be
used. If the name is not an absolute path, the algorithm described
in the Icon
Theme Specification will be used to locate the icon.
|
localestring |
NO |
1-3 |
Hidden |
Hidden should have been called Deleted .
It means the user deleted (at his level)
something that was present (at an upper level, e.g. in the system dirs). It's
strictly equivalent to the .desktop file not existing at all, as far as that user is
concerned. This can also be used to "uninstall" existing files (e.g. due to a renaming)
- by letting make install install a file with Hidden=true in it.
|
boolean |
NO |
1-3 |
OnlyShowIn , NotShowIn |
A list of strings identifying the environments that should
display/not display a given desktop entry. Only one of
these keys, either OnlyShowIn or
NotShowIn , may appear in a group (for
possible values see the Desktop
Menu Specification).
|
string(s) |
NO |
1-3 |
TryExec |
Path to an executable file on disk used to determine if the program
is actually installed. If the path is not an absolute path, the file
is looked up in the $PATH environment variable. If the file is not
present or if it is not executable, the entry may be ignored (not be
used in menus, for example).
|
string |
NO |
1 |
Exec |
Program to execute, possibly with arguments.
|
string |
YES |
1 |
Path |
If entry is of type Application , the working directory to run the program in.
|
string |
NO |
1 |
Terminal |
Whether the program runs in a terminal window.
|
boolean |
NO |
1 |
MimeType |
The MIME type(s) supported by this application.
|
string(s) |
NO |
1 |
Categories |
Categories in which the entry should be shown in a menu (for
possible values see the Desktop
Menu Specification).
|
string(s) |
NO |
1 |
StartupNotify |
If true, it is KNOWN that the application will send a "remove"
message when started with the DESKTOP_STARTUP_ID environment variable set.
If false, it is KNOWN that the application does not work
with startup notification at all (does not shown any window, breaks
even when using StartupWMClass, etc.).
If absent, a reasonable handling is up to implementations (assuming false,
using StartupWMClass, etc.). (See the Startup Notification Protocol Specification for more details).
|
boolean |
NO |
1 |
StartupWMClass |
If specified, it is known that the application will map at least one
window with the given string as its WM class or WM name hint (see the Startup Notification Protocol Specification for more details).
|
string |
NO |
1 |
URL |
If entry is Link type, the URL to access.
|
string |
YES |
2 |
The Exec key must contain a command line.
A command line consists of an executable program optionally followed
by one or more arguments.
The executable program can either be specified with its full path or
with the name of the executable only. If no full path is provided the
executable is looked up in the $PATH environment variable used by the
desktop environment.
The name or path of the executable program may not contain the equal
sign ("="). Arguments are separated by a space.
Arguments may be quoted in whole. If an argument contains a reserved
character the argument must be quoted. The rules for quoting of
arguments is also applicable to the executable name or path of the
executable program as provided.
Quoting must be done by enclosing the argument between double quotes
and escaping the double quote character, backtick character ("`"),
dollar sign ("$") and backslash character ("\") by preceding it with an
additional backslash character. Implementations must undo quoting before
expanding field codes and before passing the argument to the executable
program. Reserved characters are space (" "), tab, newline, double
quote, single quote ("'"), backslash character ("\"),
greater-than sign (">"), less-than sign ("<"),
tilde ("~"), vertical bar ("|"), ampersand ("&"), semicolon (";"),
dollar sign ("$"), asterisk ("*"), question mark ("?"), hash mark ("#"),
parenthesis ("(") and (")") and backtick character ("`").
Note that the general escape rule for values of type string states that
the backslash character can be escaped as ("\\") as well and that this
escape rule is applied before the quoting rule. As such, to
unambiguously represent a literal backslash character in a quoted
argument in a desktop entry file requires the use of four successive
backslash characters ("\\\\"). Likewise, a literal dollar sign in a
quoted argument in a desktop entry file is unambiguously represented
with ("\\$").
A number of special field codes have been defined which will be
expanded by the file manager or program launcher when encountered
in the command line.
Field codes consist of the percentage character ("%") followed by
an alpha character. Literal percentage characters must be escaped
as %% .
Deprecated field codes should be removed from the command line and
ignored.
Field codes are expanded only once, the string that is used to
replace the field code should not be checked for field codes itself.
Command lines that contain a field code that is not listed in this
specification are invalid and must not be processed, in particular
implementations may not introduce support for field codes not listed
in this specification. Extensions, if any, should be introduced by
means of a new key.
Implementations must take care not to expand field codes into multiple
arguments unless explicitly instructed by this specification.
This means that name fields, filenames and other replacements that
can contain spaces must be passed as a single argument
to the executable program after expansion.
Although the Exec key is defined to have a value
of the type string, which is limited to ASCII characters, field code
expansion may introduce non-ASCII characters in arguments.
Implementations must take care that all characters in arguments
passed to the executable program are properly encoded according to
the applicable locale setting.
Recognized field codes are as follows:
A command line may contain at most one %f, %u, %F or %U field code.
If the application should not open any
file the %f, %u, %F and %U field codes must be removed from the
command line and ignored.
Field codes must not be used inside a quoted argument, the result of
field code expansion inside a quoted argument is undefined. The %F and
%U field codes may only be used as an argument on their own.
The MimeType key is used to indicate the MIME
Types that an application knows how to handle. It is expected that
for some applications this list could become long. An application
is expected to be able to reasonably open files of these types
using the command listed in the Exec key.
There should be no priority for MIME Types in this field, or any
form of priority in the desktop file. Priority for applications
is handled external to the .desktop files.
If the standard is to be amended with a new {key,value} pair which
should be applicable to all supporting parties, a group discussion
will take place. This is the preferred method for introducing
changes. If one particular party wishes to add a field for personal
use, they should prefix the key with the string X-PRODUCT ,
e.g. X-NewDesktop-Foo , following the precedent set by other IETF and RFC
standards.
Alternatively, fields can be placed in their own group, where they may
then have arbitrary key names. If this is the case, the group should
follow the scheme outlined above,
i.e. [X-PRODUCT
GROUPNAME ] or
something similar. These steps will avoid namespace clashes between
different yet similar environments.
A. Example Desktop Entry File
[Desktop Entry]
Version=1.0
Type=Application
Name=Foo Viewer
Comment=The best viewer for Foo objects available!
TryExec=fooview
Exec=fooview %F
Icon=fooview
MimeType=image/x-foo;
X-KDE-Library=libfooview
X-KDE-FactoryName=fooviewfactory
X-KDE-ServiceType=FooService
B. Currently reserved for use within KDE
For historical reasons KDE is using some KDE-specific extensions
that are currently not prefixed by a X-KDE- prefix.
-
KDE specific keys: ServiceTypes ,
DocPath , Keywords ,
InitialPreference
-
KDE specific types: ServiceType ,
Service and FSDevice
KDE uses the following additional keys for desktop entries of the
FSDevice type.
Table B.1. FSDevice Specific Keys
Key | Description | Value Type |
Dev |
The device to mount.
|
string |
FSType |
The type of file system to try to mount.
|
string |
MountPoint |
The mount point of the device in question.
|
string |
ReadOnly |
Specifies whether or not the device is read only.
|
boolean |
UnmountIcon |
Icon to display when device is not mounted. Mounted devices display icon from the Icon key.
|
localestring |
C. Deprecated Items
As this standard is quite old there are some deprecated items that
may or may not be used by several implementations.
-
Type=MimeType is deprecated as there is a
new standard for this now, see the Shared
MIME-info Database specification for more
information. In consequence the Keys
Patterns (various file name extensions
associated with the MIME type) and
DefaultApp (the default application
associated with this MIME type) are also deprecated.
-
Using .kdelnk instead of
.desktop as the file extension is
deprecated.
-
Using [KDE Desktop Entry] instead of
[Desktop Entry] as header is deprecated.
-
The Encoding key is deprecated. It was used to
specify whether keys of type localestring were
encoded in UTF-8 or in the specified locale. Possible values are
UTF-8 and Legacy-Mixed . See
Appendix D, The Legacy-Mixed Encoding (Deprecated) for more details.
-
Deprecated Exec field codes:
%m (the mini-icon associated with the
desktop entry, this should be expanded as two arguments,
--miniicon and the content of the
MiniIcon key, it can also be ignored by
expanding it to no arguments), %v (the device as listed
in the Dev key in the desktop file),
%d (the directory of a file), %D (the directories of
files), %n (the base name of a file) and %N (the base names
of files).
-
Deprecated keys: MiniIcon (small icon for
menus, etc.), TerminalOptions (if the
program runs in a terminal, any options that should be
passed to the terminal emulator before actually executing
the program), Protocols ,
Extensions ,
BinaryPattern ,
MapNotify .
-
The SwallowTitle and
SwallowExec keys are deprecated.
The SwallowTitle key is of type
localestring and specifies the title of the window
if is swallowed onto the panel. The SwallowExec
key is of type string and specifies the
program to exec if swallowed app is clicked.
-
The SortOrder key is deprecated. It is of type
string(s) and may be used to specify the order in
which to display files. The Desktop
Menu Specification defines another mechanism for defining the
order of menu items.
-
The FilePattern key is deprecated.
The value is a list of regular
expressions to match against for a file manager to determine if this
entry's icon should be displayed. Usually simply the name of the main
executable and friends.
-
Historically some booleans have been represented by the numeric
entries 0 or 1 . With
this version of the standard they are now to be represented as a
boolean string. However, if an implementation is reading a pre-1.0
desktop entry, it should interpret 0 and
1 as false and
true , respectively.
-
Historically lists have been comma separated. This is
inconsistent with other lists which are separated by a semicolon. When
reading a pre-1.0 desktop entry, comma separated lists should continue
to be supported.
D. The Legacy-Mixed Encoding (Deprecated)
The Legacy-Mixed encoding corresponds to the
traditional encoding of desktop files in older versions of the GNOME and
KDE desktop files. In this encoding, the encoding of each
localestring key is determined by the locale tag for
that key, if any, instead of being UTF-8. For keys without a locale tag,
the value must contain only ASCII characters.
If the file specifies an unsupported encoding, the implementation
should either ignore the file, or, if the user has requested a direct
operation on the file (such as opening it for editing), display an
appropriate error indication to the user.
In the absence of an Encoding key, the implementation may choose
to autodetect the encoding of the file by using such factors
as:
If the implementation does not perform such auto-detection, it should
treat a file without an Encoding key in the same way as a file with an
unsupported Encoding key.
If the locale tag includes an .ENCODING part, then that determines
the encoding for the line. Otherwise, the encoding is determined
by the language, or
lang _COUNTRY
pair from the locale tag, according to the following table.
- Encoding
-
The name given here is listed here is typically the
canonical name for the encoding in the GNU C Library's
iconv facility. Encodings marked with (*) are not
currently supported by the GNU C Library; for this reason,
implementations may choose to ignore lines in desktop
files that resolve to this encoding. Desktop files with
these encodings are currently rare or non-existent.
- Aliases
-
Other names for the encoding found in existing desktop
files.
- Tags
-
Language tags for which this is the default encoding.
This table above covers all tags and encodings that are known to
be currently in use. Implementors may choose to support
encodings not in the above set. For tags without defaults listed
in the above table, desktop file creators must specify the
.ENCODING part of the locale tag.
Matching the .ENCODING part of the locale tag against a locale
name or alias should be done by stripping all punctuation
characters from both the tag and the name or alias, converting
both name and alias to lowercase, and comparing the result.
This is necessary because, for example, Big5 is frequently
found instead of BIG5 and georgianacademy instead of
GEORGIAN-ACADEMY . Desktop files creators should, however, use
the name as it appears in the "Encoding" column above.
|