File Formats gnome-vfs-mime-magic.4(4)
NAME
gnome-vfs-mime-magic, gnome-vfs.mime, gnome-vfs.keys - GNOME
VFS MIME detection
DESCRIPTION
GnomeVFS is obsolete. Refer to the GNOME Desktop System
Administration Guide for information about how to register
MIME type information with the GNOME desktop. The GNOME
Desktop System Administration Guide can be viewed with
yelp(1).
On any modern desktop system, each document type or file
type must be given a unique identification name and icon. In
GNOME, this information is used extensively by the file
manager, nautilus(1). The primary underlying mechanism for
providing such definitions is achieved via gnome-vfs-mime-
magic. gnome-vfs-mime-magic contains the default file con-
tent sniffers for identifying MIME types. The concept of
MIME magic is similar to that of Solaris magic(4).
EXTENDED DESCRIPTION
gnome-vfs-mime-magic
Each line in the /etc/gnome/gnome-vfs-mime-magic file
describes a MIME type. The format of each line is as fol-
lows:
offsetstart[:offsetend] patterntype pattern [&patternmask] mime-type
Each line contains the following fields:
offsetstart Decimal number that, with
offsetend, specifies the bytes
offset within the file.
offsetend Decimal number that, with
offsetstart, specifies the bytes
offset within the file.
patterntype Can be one of the following types:
byte short long string date
beshort belong bedate
leshort lelong ledate
where be stands for Big Endian and
le stands for Little Endian.
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File Formats gnome-vfs-mime-magic.4(4)
pattern An ASCI string with non-printable
characters escaped as hex or octal
escape sequences, and spaces and
other important whitespace escaped
with a backslash (\).
patternmask A string of hex digits. The mask
must be the same specification as
the non-ambiguous patterns.
mime-type A valid MIME type.
The magic patterns are matched sequentially from the first
entry to the last entry of the list. Therefore, you should
put the non-ambiguous patterns at the start of the list. Any
pattern that requires a deep seek into the file should be
placed at the end of the list to reduce performance over-
head. When designing new document formats, include an
easily recognizable unique magic pattern near the start of
the file. A good pattern is is at least four bytes long and
contains one or two non-printable characters so that text
files are not misidentified.
gnome-vfs.mime
and gnome-vfs.keys"
Apart from file sniffing, GNOME also provide a secondary
mechanism to determine MIME types. If a file has been
sniffed and its type does not match any of the magic pat-
terns, GNOME looks for files called /usr/share/gnome/mime-
info/*.mime and processes these. The format of these files
is different to that of pattern magic. Instead of determin-
ing the MIME type by reading the content of the file, the
MIME type of the file is determined by its extension. The
mime info file has the following format:
mimetype
ext[,prio]: list of extensions for this mime-type
regex[,prio]: regular expression that matches the filename
More than one ext: and regex: field can be present for a
given MIME type. You can also associate a priority for each
field. The default priority (prio) is 1, a higher numerical
value indicates a higher priority. The indentation before
ext: and regex: must be a tab character (\t).
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File Formats gnome-vfs-mime-magic.4(4)
The searching sequence implies that the magic pattern file
has a higher precedence over the mime info files. As the
mime info files are read alphabetically, this also deter-
mines matching orders for the file extension.
For example, the file FirstFile.mime contains the following
definition:
application/foo
ext: foo
and the file SecondFile.mime contains the following defini-
tion:
application/mini
ext: foo
The definition in FirstFile.mime will be found first and
used.
For each MIME info file there must be an associated keys
file in the same directory. The key file provides human
readable text which can be localized into various languages.
The data in these keys files is used by the GNOME file
manager, nautilus(1).
EXAMPLES
Example 1: Magic pattern definition for PDF file
The following entry in the /etc/gnome/gnome-vfs-mime-magic
file describes the MIME type of application/pdf:
0 string %PDF- application/pdf
The first 5 characters of a PDF file are %PDF-. The symbols
% and - differentiate the PDF file from a text file.
Example 2: Magic pattern definition for BMP file
The following entry in the /etc/gnome/gnome-vfs-mime-magic
file describes the MIME type of application/bmp:
0 string BMxxxx 00 00 &0xffff00000000ffff image/bmp
The interpretation of this line is as follows:
]o The first two characters are BM and the seventh and
eighth characters are NUL.
]o The mask 0xffff00000000ffff allows the selction of the
first, second, seventh, and eighth characters to be
selected for comparison.
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File Formats gnome-vfs-mime-magic.4(4)
Example 3: MIME info file definition for application/x-
compress
The following entry in the /etc/gnome/gnome-vfs-mime-magic
file describes the MIME type of application/x-compress:
application/x-compress
ext: Z
This line indicates that the x-compress application searches
for files with a .Z extension.
The associated keys file entry in the
/usr/share/gnome/mime-info/gnome-vfs.mime file is as follows
(excluding all localized text):
application/x-compress
description=compress-compressed file
iconfilename=gnome-compressed
defaultactiontype=application
category=Packages
usecategorydefault=yes
Example 4: MIME info file definition for application/x-
compressed-tar
The following entry in the /etc/gnome/gnome-vfs-mime-magic
file describes the MIME type of application/x-compressed-
tar:
application/x-compressed-tar
regex,2: tar.gz$
ext: tgz
This example uses the priority flag to give regex a higher
priority than ext, which means that a file with an extension
of tar.gz should be matched first (to have a MIME type of
application/x-compressed-tar) before tgz.
FILES
The following files are used by this application:
/etc/gnome/gnome-vfs-mime-magic
/usr/share/gnome/mime-info/gnome-vfs.mime
/usr/share/gnome/mime-info/gnome-vfs.keys
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File Formats gnome-vfs-mime-magic.4(4)
/usr/share/gnome/mime-info/solaris-gnome2.0.mime
/usr/share/gnome/mime-info/solaris-gnome2.0.keys
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWgnome-vfs
Interface stability Obsolete Volatile
SEE ALSO
nautilus(1), gnome-vfs.applications(4), libgnomevfs-2(3),
gnome-interfaces(5)
Latest version of the GNOME Desktop System Administration
Guide for your platform.
Written by Ghee Teo, Sun Microsystems Inc., 2003.
SunOS 5.11 Last change: 14 May 2008 5
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