1. 这些文件与gnome菜单条目及桌面文件的打开方式有关：
/usr/share/applications/* //这里存放所有菜单相关的应用程序配置
~/.local/share/applications/* //这里存放某用户已启动的应用程序缓存
/usr/share/applications/
mimeinfo.cache
~/.local/share/applications/
mimeinfo.cache
如果执行：sudo update-desktop-database
则生成 /usr/share/applications/
mimeinfo.cache
如果执行：update-desktop-database ~/.local/share/applications
则生成 ~/.local/share/applications/
mimeinfo.cache
2. 在'~/'中修改打开方式不对的文件类型：
比较对的打开程序的'~/.local/share/applications/打开程序名.desktop'和'/usr/share/applications/打开程序名.desktop'，将需要的'MimeType'复制到'~/...'文件中。
将错的打开程序的'~/.../xx.desktop'中的'MimeType'不该有的内容删除。
执行：update-desktop-database ~/.local/share/applications使改动生效。
这样用局部设置覆盖对应的全局设置。
3. 如果要删除gnome菜单的一个条目，直接删/usr/share/applications/或~/.local/share/applications/下对应的desktop文件即可。
* 如果desktop文件中有'NoDisplay=true'表示该条目不在GNOME菜单中出现，'=false'或没
有此行则会出现。
和Windows一样，在Gnome的文件管理器(nautilus)里，双击一个文件的时候，
系统会自动调用相应的程序去打开这个文件。前提是能打开这个文件的软件已经安装
并且配置完毕了。
在Nautilus里通过右键菜单固然可以修改默认的打开方式，但是缺乏灵活性和可
操作性，比如，不能删除一些候选的打开方式，不能批量增加一些打开方式等等。
经过反复的摸索，终于被我发现了GNMOE的打开方式的配置方式。
这里需要涉及到以下几个目录和文件
~/.local/share/applications
/etc/gnome/defaults.list
/usr/share/applications
/usr/share/applications/mimeinfo.cache
~/.local/share/applications/mimeinfo.cache
去这几个目录看一下，就会发现很多以 desktop 为后缀的文件。
这些文件是多功能的，第一，它们是组成GNMOE的“开始”菜单的一部分，即“开始”
菜单里的一些应用程序项，在这里都能找到。你可以运行 alacarte ， 这里会
列出整个菜单的结构，你可以编辑它，但是很多项你没法删除，因为没有权限，
你试着用root权限去运行 alacarte ，抱歉，你还是没有权限删除，要删除它们，
只有在/usr/share/applications下面找到对应的文件，直接删除这个文件即可。
从总体上讲
/etc/gnome/defaults.list 保存了全局的打开方式
~/.local/share/applications/defaults.list 保存了个人的打开方式
当两着不一致是，优先采用局部的个人设置。
~/.local/share/applications
/usr/share/applications
这两个分别是局部的desktop项和全局的desktop项
/usr/share/applications/mimeinfo.cache
~/.local/share/applications/mimeinfo.cache
这两个分别是全局的和局部的打开方式缓存
先看一下/etc/gnome/defaults.list的结构
[Default Applications]
application/csv=gnumeric.desktop
application/excel=ooo-calc.desktop
application/msexcel=ooo-calc.desktop
application/msword=ooo-writer.desktop
application/ogg=mplayer.desktop
application/pdf=evince.desktop
application/postscript=evince.desktop
.................
text/x-chdr=vim.desktop
text/x-csrc=vim.desktop
text/x-dtd=vim.desktop
text/x-java=vim.desktop
text/mathml=vim.desktop
text/x-python=vim.desktop
text/x-sql=vim.desktop
text/xml=firefox.desktop
video/dv=mplayer.desktop
video/mp4=mplayer.desktop
video/mpeg=mplayer.desktop
video/msvideo=mplayer.desktop
video/quicktime=mplayer.desktop
video/vnd.rn-realvideo=mplayer.desktop
video/x-anim=mplayer.desktop
video/x-avi=mplayer.desktop
video/x-flc=mplayer.desktop
......................
不难发现
是这样的一种形式
程序的类型/文件类型=打开这个文件的项[;项2]...[;项n]
候选打开方式可以有好几种
中间用;隔开，不留其余字符
要修改一个文件的打开方式，需要先确定这个文件的类型
以纯文本文件为例 类型是plain 打开方式默认为vim.desktop
候选的是firefox.desktop
text/plain=vim.desktop;firefox.desktop
可以直接编辑
~/.local/share/applications/defaults.list
/etc/gnome/defaults.list
编辑完之后，手工修改
/usr/share/applications/mimeinfo.cache
~/.local/share/applications/mimeinfo.cache
这两个cache文件。
这样就立即生效了
下面看一下desktop文件的结构
[Desktop Entry]
Encoding=UTF-8 //字符编码
Name=vim //现实的名字
MimeType=text/plain; //类型
Exec=vim %f //运行的程序 %f表示一个参数
Type=Application //类型
Terminal=true //是否使用终端
NoDisplay=true //是否显示在gnome菜单里
知道这些就可以很方便的定制“开始”菜单 和 文件的打开方式了
附录：Desktop项的结构
原文的ＵＲＬ是
Introduction
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.
Basic format of the file
These desktop entry files should have the extension
.desktop. 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 entries
which describe how a directory is to be formatted/displayed
should be simply called .directory.
The basic format of the desktop entry file requires that there be
a "group" header named [Desktop Entry]. This
"group" entry denotes that all {key,value}
pairs following it belong in the Desktop Entry group. 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 proceeding this group in
the desktop entry file but possibly one or more comments (see
below).
Group headers may not contain the characters [ and
] as those delimit the header.
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.
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.
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.
The escape sequences \s, \n,
\t, \r, and
\\ are supported, meaning ASCII space, newline,
tab, carriage return, and backslash, respectively.
Possible value types
The value types recognized are string, localestring, regexp,
boolean (encoded as the string true/false), and numeric.
Values of type string must contain only ASCII
characters excluding control characters. Values of type
localestring are user displayable, and are
encoded in UTF-8 unless the Legacy-Mixed
Encoding is specified (see
.)
Some keys can have multiple values; these should be separated by a
semicolon. Those keys which have several values should have a
semicolon as the trailing character. Semicolons in these values
need to be escaped using \;.
Recognized desktop entry 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
.ENCODING field is
used only when the value of the Encoding key
for the desktop entry file is Legacy-Mixed
(see
.)
The matching of 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 valuePossible keys in order of matchinglang_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.
Case is significant. The keys Name and NAME are not equivalent.
The same holds for group names. Key values are case sensitive as
well.
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. Additionally, keys either MUST or MAY be
supported by a particular implementation.
Some keys only make sense in the context when another particular key
is also present.
Some example keys: Name[C], Comment[it].
Table 2. Standard Keys
KeyDescriptionValue TypeREQ?MUST?TypeType
There are 4 types of desktop entries:
Application,
Link, FSDevice
and Directory.
stringYESYESVersion
Version of Desktop Entry Specification
(While the version field is not required to be present,
it should be in all newer implementations of the Desktop
Entry Specification. If the version number is not
present, a "pre-standard" desktop entry file is to be
assumed).
numericNOYES1-4Encoding
Encoding of the whole desktop entry file
(UTF-8 or
Legacy-Mixed).
stringYESYES1-4Name
Specific name of the application, for example "Mozilla".
localestringYESYES1-4GenericName
Generic name of the application, for example "Web Browser".
localestringNOYES1-4NoDisplay
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).
booleanNONO1-4Comment
Tooltip for the entry, for example "View sites on the
Internet", should not be redundant with Name or
GenericName.
localestringNOYES1-4Icon
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, an
implementation-dependent search algorithm will be used
to locate the icon. Icons may be localized with the
Icon[xx]= syntax.
stringNOYES1-4Hidden
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.
booleanNONO1-4FilePattern
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.
regexp(s)NONO1TryExec
File name of a binary on disk used to determine if the
program is actually installed. If not, entry may not
show in menus, etc.
stringNONO1Exec
Program to execute, possibly with arguments.
stringNOYES1Path
If entry is of type Application, the working directory to run the program in.
stringNOYES1Terminal
Whether the program runs in a terminal window.
booleanNOYES1SwallowTitle
If entry is swallowed onto the panel, this should be the title of the window.
localestringNONO1SwallowExec
Program to exec if swallowed app is clicked.
stringNONO1Actions
Additional actions possible, see MIME type discussion in
.
string(s)NOYES1MimeType
The MIME type(s) supported by this entry.
strings(s)NONO1SortOrder
This may specify the order in which to display files.
string(s)NONO4Dev
The device to mount.
stringNONO3FSType
The type of file system to try to mount.
stringNONO3MountPoint
The mount point of the device in question.
stringNONO3ReadOnly
Specifies whether or not the device is read only.
booleanNONO3UnmountIcon
Icon to display when device is not mounted. Mounted devices display icon from the Icon key.
UnmountIcons may be localized with the UnmountIcon[xx]= syntax.
stringNONO3URL
If entry is Link type, the URL to access.
stringNOYES2Categories
Categories in which the entry should be shown in a menu (for
possible values see the Desktop
Menu Specification).
string(s)NONO1OnlyShowIn, 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)NONO1-4StartupNotify
If true, it is KNOWN that the application will send a "remove"
message when started with the DESKTOP_LAUNCH_ID environment variable
set (see the
for more details).
booleanNONO1StartupWMClass
If true, 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
for more details).
stringNONO1Character set encoding of the file
Desktop entry files are encoded as lines of 8-bit characters separated
by LF characters.
Key names must contain only the characters A-Za-z0-9-
Group names may contain all ASCII characters except for
[ and ] and control characters.
Values of type string may contain all ASCII characters except
for control characters.
Values of type boolean must either be the string true or
false.
Numeric values must be a valid floating point number as recognized
by the %f specifier for scanf.
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.
The encoding for values of type localestring is determined by the
Encoding field.
List of valid Exec parameter variables
Each Exec field may take a number of arguments which will be
expanded by the file manager or program launcher and passed to the
program if necessary.
Literal % characters must be escaped as %%, and adding new
format characters is not allowed. It's a fatal error to have an
Exec field with a format character not given in the spec (exception
to this are the deprecated format characters which can be ignored,
that is expanded to no parameters, by the implementation).
Again for emphasis: nonstandard extensions are
not allowed here - you must add an X-Foo-Exec field if you have
nonstandard Exec lines.
The escaping of the exec parameters is done in the way the mailcap
specification describes. Take a look at
for more information.
Recognized fields are as follows:
%f
A single file name, even if multiple files are selected. The system
reading the desktop entry should recognize that the program in
question cannot handle multiple file arguments, and it should
should probably spawn and execute multiple copies of a program
for each selected file if the program is not able to handle
additional file arguments. If files are not on the local file system
(i.e. are on HTTP or FTP locations), the files will be copied to the local
file system and %f will be expanded to point at the temporary
file. Used for programs that do not understand the URL syntax.
%F
A list of files. Use for apps that can open several local
files at once.
%u
A single URL.
%U
A list of URLs.
%d
Directory containing the file that would be passed in a %f field.
%D
List of directories containing the files that would be
passed in to a %F field.
%n
A single filename (without path).
%N
A list of filenames (without paths).
%i
The Icon field of the desktop entry
expanded as two parameters, first
--icon and then the contents of the
Icon field. Should not expand as any
parameters if the Icon field is empty
or missing.
%c
The translated Name field associated with the desktop entry.
%k
The location of the desktop file as either a URI (if for
example gotten from the vfolder system) or a local
filename or empty if no location is known.
%v
The name of the Device entry in the desktop file.
Registering MIME Types
The MimeType key is used to indicate the MIME
Types that an application knows how to handle. Applications that
can handle multiple MIME Types would list all of the ones it can
handle in a ';' separated list, as normal. 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 keyword.
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.
Caching MIME Types
To make parsing of all the desktop files less costly, a
update-desktop-database program is provided
that will generate a cache file. The concept is identical to
that of the 'update-mime-database' program in that it lets
applications avoid reading in (potentially) hundreds of files.
It will need to be run after every desktop file is installed.
One cache file is created for every directory in
$XDG_DATA_DIRS/applications/, and will create a file called
$XDG_DATA_DIRS/applications/mimeinfo.cache.
The format of the cache is similar to that of the desktop file,
and is just a list mapping mime-types to desktop files. Here's
a quick example of what it would look like:
application/x-foo=foo.desktop;bar.desktop;
application/x-bar=bar.desktop;
Each MIME Type is listed only once per cache file, and the
desktop-id is expected to exist in that particular directory.
That is to say, if the cache file is located at
/usr/share/applications/mimeinfo.cache,
bar.desktop refers to the file
/usr/share/applications/bar.desktop.
Priority of MIME Types and desktop files
There is also a preference list to determine preferred
application of a given MIME Type. It defines the 'default'
application to handle a given MIME Type. It has the same format
as the cache list.
mime/type=desktop-id.desktop;
If a mime type is listed multiple times (either in the same
file, or in another file further down the search path), the
latter mention wins. If a listed file doesn't exist, or is
precluded through the OnlyShowIn or
NotShowIn files, they should be ignored.
This means that applications will have to keep a history of the
preferred applications that they run into, so that if the top
desktop file for a given MIME Type isn't available, the second
one can be tested, etc.
It is also worth noting who this mechanism is defined for. It
is primarily intended for use by distributors/sysadmins to
provide a sane set of defaults for their users. Additionally,
users themselves can use this mechanism to override the user
defaults. We intentionally don't provide a way for application
authors themselves to list themselves as the default for a given
type, as we felt that that cannot work.
Extending the format
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
Encoding=UTF-8
Name=Foo Viewer
Comment=The best viewer for Foo objects available!
TryExec=fooview
Exec=fooview %F
Icon=fooview.png
MimeType=image/x-foo
X-KDE-Library=libfooview
X-KDE-FactoryName=fooviewfactory
X-KDE-ServiceType=FooService
[Desktop Action Inverse]
Exec=fooview --inverse %f
Name=Foo Viewer (inverse image)
[Desktop Action Edit]
Exec=fooview --edit %f
Name=Foo Viewer (edit image)
Icon=fooview-edit.pngB. Currently reserved for use within KDE
During the time KDE added some extensions that are currently not
prefixed by the X- prefix, but should be in
future KDE releases.
Keys added by KDE: ServiceTypes,
DocPath, Keywords,
InitialPreference
Types added by KDE: ServiceType, Service
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.
Encoding=Legacy-Mixed, which allowed
localestrings in the encoding of the specified locale, is
deprecated.
Deprecated Exec parameters:
%m (the mini-icon associated with the
desktop entry, this should be expanded as two parameters,
--miniicon and the content of the
MiniIcon field, it can also be ignored by
expanding it to no parameters).
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.
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. 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 line, the implementation may choose
to autodetect the encoding of the file by using such factors
as:
The location of the file on the file system
Whether the contents of the file are valid UTF-8
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.
EncodingAliasesTagsARMSCII-8 (*) hyBIG5 zh_TWCP1251 be
bgEUC-CNGB2312zh_CNEUC-JP jaEUC-KR koGEORGIAN-ACADEMY (*) GEORGIAN-PS
(*) kaISO-8859-1 br ca da de en es eu fi fr gl it nl no pt sv
waISO-8859-2 cs hr hu pl ro sk sl sq srISO-8859-3 eoISO-8859-5 mk
spISO-8859-7 elISO-8859-9 trISO-8859-13 lt lv miISO-8859-14 cy
gaISO-8859-15 etKOI8-R ruKOI8-U ukTCVN-5712 (*)TCVNviTIS-620 thVISCII
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.
