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\majorheading{MAILCAP(4)    Bellcore Prototype (Release 2)    MAILCAP(4)

}


}\indent1{\tempindentneg1{NAME 

}mailcap - metamail capabilities file 

\tempindentneg1{
DESCRIPTION 

}The \italic{mailcap }file is read by the \italic{metamail }program to 
determine how to display non-text at the local site. 


The syntax of a mailcap file is quite simple, at least compared to termcap 
files. 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 continued 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 (which is actually a built-in default 
behavior for metamail) 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' command may be 
voluminous, requiring either a scrolling window, a pager, or some other 
appropriate 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 (or the value passed in with -c) 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. "image/*"). 


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. It 
will be passed to the shell via the system(3) facility. Semicolons and 
backslashes within the command must be quoted with backslashes. If the 
command contains "%s", those two characters will be replaced 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 "image/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 % 
ch 




aracter. (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 
message body in a temporary file, metamail will pass the body to the 
command on the standard input. This is helpful in saving /tmp file space, 
but can be problematic for window-oriented applications under some window 
systems such as MGR. 


Two special codes can appear in the viewing command for objects of type 
multipart (any subtype). These are "%n" and "%F". %n will be replaced by 
the number of parts within the multipart object. %F will be replaced by a 
series of arguments, two for each part, giving first the content-type and 
then the name of the temporary file where the decoded part has been stored. 
In addition, for each file created by %F, a second file is created, with 
the same name followed by "H", which contains the header information for 
that body part. This will not be needed by most multipart handlers, but it 
is there if you ever need it. 


The "notes=xxx" field is an uninterpreted string that is used to specify 
the name of the person who installed this entry in the mailcap file. (The 
"xxx" may be replaced by any text string.) 


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 command, 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 "textualnewlines" field can be used in the rather obscure case where 
metamail's default rules for treating newlines in base64-encoded data are 
unsatisfactory. By default, metamail will translate CRLF to the local 
newline character in decoded base64 output if the content-type is "text" 
(any subtype), but will not do so otherwise. A mailcap entry with a field 
of "textualnewlines=1" will force such translation for the specified 
content-type, while "textualnewlines=0" will guarantee that the translation 
does not take place even for textual content-types. 



}\tempindentneg1{\indent2{\bold{needsterminal 

}}}\indent2{If this flag is given, the named interpreter needs to interact 
with the user on a terminal. In some environments (e.g. a window-oriented 
mail reader under X11) this will require the creation of a new terminal 
emulation window, while in most environments it will not. If the mailcap 
entry specifies "needsterminal" and metamail is not running on a terminal 
(as determined by isatty(3), the -x option, and the MM_NOTTTY environment 
variable) then metamail will try to run the command in a new terminal 
emulation window. Currently, metamail knows how to create new windows under 
the X11, SunTools, and WM window systems. 


}\tempindentneg1{\indent2{\bold{copiousoutput 

}}}\indent2{This flag should be given whenever the interpreter is capable 
of producing more than a few lines of output on stdout, and does no 
interaction with the user. If the mailcap entry specifies copiousoutput, 
and pagination has been requested via the "-p" command, then the output of 
the command being executed will be piped through a pagination program 
("more" by default, but this can be overridden with the METAMAIL_PAGER 
environment variable). 

}\indent1{\tempindentneg1{
BUILT-IN CONTENT-TYPE SUPPORT 

}The metamail program has built-in support for a few key content-types. In 
particular, it supports the text type, the multipart and 
multipart/alternative type, and the message/rfc822 types. This support is 
incomplete for many subtypes -- for example, it only supports US-ASCII text 
in general. This kind of built-in support can be OVERRIDDEN by an entry in 
any mailcap file on the user's search path. Metamail also has rudimentary 
built-in support for types that are totally unrecognized -- i.e. for which 
no mailcap entry or built-in handler exists. For such unrecognized types, 
metamail will write a file with a "clean" copy of the data -- i.e. a copy 
in which all mail headers have been removed, and in which any 7-bit 
transport encoding has been decoded. 

\tempindentneg1{
FILES 

}$HOME/.mailcap:/etc/mailcap:/usr/etc/mailcap:/usr/local/etc/mailcap -- 
default path for mailcap files. 

\tempindentneg1{
SEE ALSO 

}metamail(1) 

\tempindentneg1{
COPYRIGHT 

}Copyright (c) 1991 Bell Communications Research, Inc. (Bellcore) 


Permission to use, copy, modify, and distribute this material for any 
purpose and without fee is hereby granted, provided that the above 
copyright notice and this permission notice appear in all copies, and that 
the name of Bellcore not be used in advertising or publicity pertaining to 
this material without the specific, prior written permission of an 
authorized representative of Bellcore. BELLCORE MAKES NO REPRESENTATIONS 
ABOUT THE ACCURACY OR SUITABILITY OF THIS MATERIAL FOR ANY PURPOSE. IT IS 
PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES. 

\tempindentneg1{
AUTHOR 

}Nathaniel S. Borenstein 







































































































































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