gnome-vfs-mime-magic.4(4)					   File Formats 					 gnome-vfs-mime-magic.4(4)

NAME

       gnome-vfs-mime-magic, gnome-vfs.mime, gnome-vfs.keys - GNOME VFS MIME detection

DESCRIPTION

       On  any modern desktop system, each document type or file type must be given a unique identification name and icon. In GNOME, this informa-
       tion 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 content 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 follows:

       offset_start[:offset_end] pattern_type pattern  [&pattern_mask] mime-type

       Each line contains the following fields:

       offset_start	       Decimal number that, with offset_end, specifies the bytes offset within the file.

       offset_end	       Decimal number that, with offset_start, specifies the bytes offset within the file.

       pattern_type	       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.

       pattern		       An ASCII string with non-printable characters escaped as hex or octal escape sequences, and spaces and other impor-
			       tant whitespace escaped with a backslash ().

       pattern_mask	       A string of hex digits. The mask must be the same specification as the non-ambigous 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-ambigous
       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 overhead.  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 patterns, 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 determining 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:

       mime_type
	   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
       (	).

       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 determines 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 definition:

       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 NULL.

	 o  The mask 0xffff00000000ffff allows the selction of the first, second, seventh, and eighth characters to be selected for comparison.

       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
		 icon_filename=gnome-compressed
		 default_action_type=application
		 category=Packages
		 use_category_default=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

       /usr/share/gnome/mime-info/solaris-gnome2.0.mime

       /usr/share/gnome/mime-info/solaris-gnome2.0.keys

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWgnome-vfs		   |
       +-----------------------------+-----------------------------+
       |Interface stability	     |External			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       nautilus(1), gnome-vfs.applications(4), libgnomevfs-2(3)

       Latest version of the GNOME Desktop User Guide for your platform.

       Written by Ghee Teo, Sun Microsystems  Inc., 2003.

SunOS 5.10							    13 Jan 2003 					 gnome-vfs-mime-magic.4(4)