Default applications

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Programs sometimes need to open a file or a URI in the user's preferred application. To open a file in the user's preferred application the filetype needs to be detected (usually using filename extensions or magic numbers mapped to MIME types) and there needs to be an application associated with the filetype.

• Some programs (particularly command-line programs) detect default programs using environment variables, see Environment variables#Default programs.
• Some programs (particularly heirloom UNIX programs) use mime.types for MIME type detection and mailcap for application association.
• Many programs outsource the task completely to a #Resource opener.

Freedesktop.org has standardized filetype detection with the Shared MIME database specification and application association with the XDG MIME Applications specification.

Some desktop environments also provide a GUI or a file-manager which can interactively configure default applications. If you do not use a desktop environment, you may need to install additional software in order to conveniently manage default applications.

Resource openers

• XDG MIME Apps: implements the XDG MIME Applications specification
• RegEx rules: allows MIME types to be associated with applications using regular expressions
• URI support: allows arbitrary URI schemes to be associated with applications

Name	Package	XDG MIME Apps	RegEx rules	URI support
xdg-open	xdg-utils	是	否	是
mimeopen(1p)	perl-file-mimeinfo包	是	否	否
mimeo	mimeoAUR	是	是	是
whippet	whippetAUR[損壞的連結：package not found]	是	否	是
linopen	linopenAUR	否	是	是
mimi	mimi-gitAUR	否	否	partly
busking	busking-gitAUR	否	是	是
sx-open	sx-openAUR[損壞的連結：package not found]	否	是	是
rifle(1)	ranger	否	是	否

xdg-open

xdg-open (part of xdg-utils) implements XDG MIME Applications and is used by many programs.

Because of the complexity of the xdg-utils version of xdg-open, it can be difficult to debug when the wrong default application is being opened. Because of this, there are many alternatives that attempt to improve upon it. Several of these alternatives replace the /usr/bin/xdg-open executable, thus changing the default application behavior of most applications. Others simply provide an alternative method of choosing default applications.

perl-file-mimeinfo

perl-file-mimeinfo^包 provides the tools mimeopen(1p) and mimetype(1p). These have a slightly nicer interface than their xdg-utils^包 equivalents:

# determine a file's MIME type
$ mimetype photo.jpeg
photo.jpeg: image/jpeg

# choose the default application for this file
$ mimeopen -d photo.jpeg
Please choose an application

    1) Feh (feh)
    2) GNU Image Manipulation Program (gimp)
    3) Pinta (pinta)

use application #

# open a file with its default application
$ mimeopen -n photo.jpeg

Most importantly, xdg-utils programs will actually call mimetype instead of file for MIME type detection, if it does not detect your desktop environment. This is important because file does not follow the XDG standard.

注意： perl-file-mimeinfo^包 before 0.28-1 does not entirely follow the XDG standard. For example it does not read distribution-wide defaults and it saves its config in deprecated locations.

mimeo

mimeo^AUR provides the tool mimeo, which unifies the functionality of xdg-open and xdg-mime.

# determine a file's MIME type
$ mimeo -m photo.jpeg
photo.jpeg
  image/jpeg

# choose the default application for this MIME type
$ mimeo --add image/jpeg feh.desktop

# open a file with its default application
$ mimeo photo.jpeg

However a big difference with xdg-utils is that mimeo also supports custom "association files" that allow for more complex associations. For example, passing specific command line arguments based on a regular expression match:

# open youtube links in VLC without opening a new instance
vlc --one-instance --playlist-enqueue %U
  ^https?://(www.)?youtube.com/watch\?.*v=

xdg-utils-mimeo^AUR patches xdg-utils so that xdg-open falls back to mimeo if no desktop environment is detected.

whippet

whippet^{AUR[損壞的連結：package not found]} provides the tool whippet, which is similar to xdg-open. It has X11 integration by using libnotify^包 to display errors and dmenu^包 to display choices between applications to open.

# open a file with its default application
$ whippet -M photo.jpeg

# choose from all possible applications for opening a file (without setting a default)
$ whippet -m photo.jpeg

In addition to implementing XDG MIME Applications, whippet can also use a SQlite database of weighted application/MIME type/regex associations to determine which app to use.

Minimalist replacements

The following packages conflict with and provide xdg-utils^包 because they provide their own /usr/bin/xdg-open script.

If you want to use one of these resource openers while still being able to use xdg-utils^包, install them manually in a PATH directory before /usr/bin.

• linopen^AUR - 170-line Bash script, supports regex rules
• mimi-git^AUR - 130-line Bash script, can change command arguments for each MIME type
• busking-git^AUR - 80-line Perl script similar to mimi but also supports regex rules
• sx-open^{AUR[損壞的連結：package not found]} - 60-line Bash script, uses a simple shell-based config file

run-mailcap

警告： If you use run-mailcap^AUR, it is possible for xdg-open to delegate to it. This will cause an infinite loop if you are using the /etc/mailcap from mailcap^包, because it also delegates to xdg-open.