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MAILCAP(5)		  FreeBSD File Formats Manual		    MAILCAP(5)

NAME
     mailcap --	mail capabilities file

DESCRIPTION
     The mailcap file is read by the mutt(1) program to	determine how to dis-
     play non-text content.

     The syntax	of a mailcap file is quite simple.  Any	line that starts with
     "#" is a comment.	Blank lines are	ignored.  Otherwise, each line defines
     a single mailcap entry for	a single content type.	Long lines may be con-
     tinued by ending them with	a backslash character, \.

     Each individual mailcap entry consists of a content-type specification, a
     command to	execute, and (possibly)	a set of optional "flag" values.  For
     example, a	very simple mailcap entry would	look like this:

	 text/plain; cat %s

     The optional flags	can be used to specify additional information about
     the mail-handling command.	 For example:

	 text/plain; cat %s; copiousoutput

     can be used to indicate that the output of	the cat(1) command may be vo-
     luminous, requiring either	a scrolling window, a pager, or	some other ap-
     propriate coping mechanism.

     The type field ("text/plain", in the above	example) is simply any legal
     content type name,	as defined by RFC 822.	In practice, this is almost
     any string.  It is	the string that	will be	matched	against	the
     Content-type header to decide if this is the mailcap entry	that matches
     the current message.  Additionally, the type field	may specify a subtype
     (e.g. "text/ISO-8859-1") or a wildcard to match all subtypes (e.g.	"im-
     age/*").

     The command field is any UNIX command ("cat %s" in	the above example),
     and is used to specify the	interpreter for	the given type of message.
     Semicolons	and backslashes	within the command must	be quoted with back-
     slashes.  If the command contains "%s", those two characters will be re-
     placed by the name	of a file that contains	the body of the	message.  If
     it	contains "%t', those two characters will be replaced by	the content-
     type field, including the subtype,	if any.	 (That is, if the content-type
     was "image/pbm; opt1=something-else", then	"%t" would be replaced by "im-
     age/pbm".)	 If the	command	field contains "%{" followed by	a parameter
     name and a	closing	"}", then all those characters will be replaced	by the
     value of the named	parameter, if any, from	the Content-type header.
     Thus, in the previous example, "%{opt1}" will be replaced by "something-
     else".  Finally, if the command contains "", those	two characters will be
     replaced by a single % character.	(In fact, the backslash	can be used to
     quote any character, including itself.)

     If	no "%s"	appears	in the command field, then instead of placing the mes-
     sage body in a temporary file, mutt will pass the body to the command on
     the standard input.

     The test=xxx field	is a command that is executed to determine whether or
     not the mailcap line actually applies.  That is, if the content-type
     field matches the content-type on the message, but	a test=	field is
     present, then the test must succeed before	the mailcap line is considered
     to	"match"	the message being viewed.  The command may be any UNIX com-
     mand, using the same syntax and the same %-escapes	as for the viewing
     command, as described above.  A command is	considered to succeed if it
     exits with	a zero exit status, and	to fail	otherwise.

     The print=xxx field is a command that is executed to print	the data in-
     stead of display it interactively.

     The compose field may be used to specify a	program	that can be used to
     compose a new body	or body	part in	the given format.  Its intended	use is
     to	support	mail composing agents that support the composition of multiple
     types of mail using external composing agents.  As	with the view-command,
     the compose command will be executed after	replacing certain escape se-
     quences starting with "%".	 In particular,	%s should be replaced by the
     name of a file to which the composed data is to be	written	by the speci-
     fied composing program, thus allowing the calling program (mutt) to tell
     the called	program	where to store the composed data.  If %s does not ap-
     pear, then	the composed data will be assumed to be	written	by the compos-
     ing programs to standard output.  The result of the composing program may
     be	data that is NOT yet suitable for mail transport -- that is, a Con-
     tent-Transfer-Encoding may	still need to be applied to the	data.

     The composetyped field is similar to the compose field, but is to be used
     when the composing	program	needs to specify the Content-type header field
     to	be applied to the composed data.  The compose field is simpler,	and is
     preferred for use with existing (non-mail-oriented) programs for compos-
     ing data in a given format.  The composetyped field is necessary when the
     Content-type information must include auxilliary parameters, and the com-
     position program must then	know enough about mail formats to produce out-
     put that includes the mail	type information, and to apply any necessary
     Content-Transfer-Encoding.	 Conceptually, compose specifies a program
     that simply outputs the specified type of data in its raw form, while
     composetyped specifies a program that outputs the data as a MIME object,
     with all necessary	Content-* headers already in place.

     The edit field may	be used	to specify a program that can be used to edit
     a body or body part in the	given format.  In many cases, it may be	iden-
     tical in content to the compose field, and	shares the operating-system
     dependent semantics for program execution.

     The nametemplate field gives a file name format, in which %s will be re-
     placed by a short unique string to	give the name of the temporary file to
     be	passed to the viewing command.	This is	only expected to be relevant
     in	environments where filename extensions are meaningful, e.g., one
     coulld specify that a GIF file being passed to a gif viewer should	have a
     name eding	in ".gif" by using "nametemplate=%s.gif".

     needsterminal If this flag	is given, the named interpreter	needs to in-
     teract with the user on a terminal.  In some environments this will re-
     quire the creation	of a new terminal emulation window, while in most en-
     vironments	it will	not.

     copiousoutput This	flag should be given whenever the interpreter is capa-
     ble of producing more than	a few lines of output on stdout, and does no
     interaction with the user.	 If the	mailcap	entry specifies	copiousoutput
     then the output of	the command being executed will	be piped through the
     pagination	program	as specified in	the .muttrc file by the	pager vari-
     able.

SEE ALSO
     mutt(1), muttrc(5)

AUTHORS
     This mailcap(5) manpage is	based on the manpage provided by metamail(1)
     and the corresponding RFC 1524. Both were written by Nathaniel S. Boren-
     stein at Bell Communications Research, Inc. (Bellcore).

     mutt specific changes have	been applied by	Udo Schweigert.

				March 16, 2016

NAME | DESCRIPTION | SEE ALSO | AUTHORS

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