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\majorheading{METAMAIL(1)    Bellcore Prototype (Release 2)    METAMAIL(1)

}


}\indent1{\tempindentneg1{NAME 

}metamail - infrastructure for mailcap-based multimedia mail handling 

\tempindentneg1{
SYNOPSIS 

}\bold{metamail}	[-b] [-B] [-c \bold{contenttype} ...] [-d] [-e] [-E 
\bold{contentencoding}] [-f \bold{from-name}] [-h] [-m \bold{mailer-name}] 
[-p] [-P] [-r] [-s \bold{subject}] [-q] [-w] [-x] [-y] [-z] 
[\bold{file-name}] 

\tempindentneg1{
DESCRIPTION 

}The \italic{metamail }program reads a "mailcap" file to determine how to 
display non-text at the local site. Every mail-reading interface needs to 
call metamail whenever non-text mail is being viewed, unless the mail is of 
a type that is already understood by the mail-reading program. 
\italic{Metamail }consults the mailcap file(s) to determine what program to 
use to show the message to the user. 


At a site where all mail reading interfaces have been modified to call 
\italic{metamail }for non-text mail, extending the local email system to 
handle a new media type in the mail becomes a simple matter of adding a 
line to a mailcap file. (Although this manual page will discuss only mail, 
metamail is equally useful in adding multimedia support to news and 
bulletin board reading programs, assuming those programs preserve the 
"Content-type" header or some other indication of the content type of the 
messages.) 


In general, users will never run metamail directly. Instead, metamail will 
be invoked for the user automatically by the user's mail reading program, 
whenever a non-text message is to be viewed. This manual page, therefore, 
is directed not at end users, but at two categories of readers: those who 
are adding metamail support to a particular mail-reading program, and those 
who are adding lines to a mailcap file. The former need only to be 
concerned with the command line syntax of metamail. The latter may ignore 
the command line syntax, and need only be concerned with the mailcap file 
syntax, as described in a later section. 


Note: Metamail determines the type of a message using the "Content-type" 
header, as defined in RFC 1049 and RFC-1341 (MIME). However, using the -b 
and -c options, metamail can be made to work with mail that is not in 
Internet format, including X.400 messages. Note also that metamail 
automatically decodes mail that has been encoded for 7 bit transport if the 
mail includes a Content-Transfer-Encoding header as specified by RFC-1341. 
If data has been encoded via the "base64" encoding, it will map CRLF to 
local newlines for textual data, but not for other data, unless instructed 
otherwise by a "textualnewlines" field in a mailcap entry. 


\tempindentneg1{
OPTIONS 

}When called with no options or arguments, metamail expects to receive an 
RFC 822 format message on its standard input. The following options can 
alter that expectation: 


}\tempindentneg1{\indent2{\bold{-b 

}}}\indent2{This option tells metamail that the message is not in RFC 822 
format, but instead is only the body of the message (i.e. there are no 
message headers). The use of -b requires the use of -c. 


}\tempindentneg1{\indent2{\bold{-B 

}}}\indent2{This option tells metamail that the message is to be displayed 
in the background, if it is non-interactive (i.e. it doesn't have the 
"needsterminal" attribute in the mailcap file). It cannot be used with -p 
or -P. 


}\tempindentneg1{\indent2{\bold{-c <contenttype> 

}}}\indent2{This option tells metamail to use the specified content type 
rather than the one in the headers, if any. 


}\tempindentneg1{\indent2{\bold{-d 

}}}\indent2{This option tells metamail not to ask any questions before 
running an interpreter to view the message. (By default, metamail always 
asks before running almost any interpreter, if it is running in an 
interactive terminal and the MM_NOASK environment variable is not set. 
However, it does not ask about the content-type "text" -- that is, the 
default value for MM_NOASK is "text,text/plain") 


}\tempindentneg1{\indent2{\bold{-e 

}}}\indent2{This option tells metamail to "eat" leading newlines in message 
bodies. This is particularly useful for MH-format mail. 


}\tempindentneg1{\indent2{\bold{-f <address> 

}}}\indent2{This option specifies the name of the sender of the message. 
Otherwise, this is determined from the header, if possible. This 
information will be placed in the environment to make it available to any 
interpreters called by metamail. 


}\tempindentneg1{\indent2{\bold{-h 

}}}\indent2{This option specifies that metamail is being used for 
\italic{printing }a message. In particular, this means that the normal 
mailcap "command" field will not be executed, but instead the command 
specified in the "print" field will be executed. (If there is nothing in 
the print field, the mailcap entry will be ignored and the search will 
continue for a matching mailcap entry that does have a print field.) The -h 
option automatically turns on the -d option. 


}\tempindentneg1{\indent2{\bold{-m <mailername> 

}}}\indent2{This option specifies the name of the mail program that called 
metamail. This information will be placed in the environment to make it 
available to any interpreters called by metamail. 


}\tempindentneg1{\indent2{\bold{-p 

}}}\indent2{This option specifies that, if necessary, output should be 
shown to the user one page at a time. By default, this will cause such 
output to be piped through the "more" command, but the environment variable 
METAMAIL_PAGER can be used to specify an alternative command to use. Note 
that one should use -p rather than piping the output of metamail through a 
pager, because some interpreters called by metamail might be interactive 
rather than requiring pagination. Metamail can tell whether or not to use a 
pager from information in the mailcap file. This option cannot be used with 
-B. 


}\tempindentneg1{\indent2{\bold{-P 

}}}\indent2{This option is just like -p, except that it also causes 
metamail to print "Press RETURN to go on" and await a RETURN after it has 
finished with the message. This is intended for use only when metamail 
calls itself recursively in a new terminal window created only for that 
purpose. This option cannot be used with -B. 


}\tempindentneg1{\indent2{\bold{-q 

}}}\indent2{This option tells metamail to be quiet. By default, metamail 
prints a few key message headers (controllable with the KEYHEADS and 
KEYIGNHEADS environment variables) and some other informative information, 
on stdout before running the interpreter, but this behavior is suppressed 
with -q. 


}\tempindentneg1{\indent2{\bold{-r 

}}}\indent2{This option specifies that it is OK to run as root. By default, 
metamail refuses to run if the real or effective user id is root. You can 
get the same effect using the MM_RUNASROOT environment variable. 


}\tempindentneg1{\indent2{\bold{-R 

}}}\indent2{This option specifies that the /usr/ucb/reset should be 
executed to reset the terminal state, before any other I/O activity. 


}\tempindentneg1{\indent2{\bold{-s <subject> 

}}}\indent2{This option specifies the subject of the mail message. By 
default, this information is obtained from the headers. This information 
will be placed in the environment to make it available to any interpreters 
called by metamail. 


}\tempindentneg1{\indent2{\bold{-w 

}}}\indent2{This option tells metamail that instead of consulting a mailcap 
file to decide how to display the data, it should simply decode each part 
and write it to a file in its raw (possibly binary) format. Depending on 
the circumstances in which it is called, metamail may derive the file name 
to use from the message headers, by asking the user, or by generating a 
unique temporary file name. 


}\tempindentneg1{\indent2{\bold{-x 

}}}\indent2{This option tells metamail that it is definitely not running on 
a terminal, no matter what isatty() says. This is necessary when metamail 
is actually running on a pseudoterminal and isatty(3) returns TRUE but 
there's really no terminal on which to interact with the user. The same 
effect as -x can also be obtained with the environment variable MM_NOTTTY. 


}\tempindentneg1{\indent2{\bold{-y 

}}}\indent2{This option tells metamail to try to "yank" a MIME-format 
message from the body of the message. It is useful when a MIME-format has 
been rejected by a mail delivery system that does not now how to format the 
rejection in a MIME-compliant manner. (For the convenience of those who 
can't control how metamail is called from their mail reader, this can also 
be set with the MM_YANKMODE variable.) If you use yank mode on messages 
that really ARE in MIME format, or on messages that do not contain a MIME 
message in the body, the effects could be VERY strange. It won't hurt you, 
but you won't see anything very useful, either. 


}\tempindentneg1{\indent2{\bold{-z 

}}}\indent2{This option tells metamail to delete its input file when 
finished. The -z option requires that a file name was given as an argument 
to metamail, i.e. that it is not reading stdin. 


}\tempindentneg1{\indent2{\bold{-T 

}}}\indent2{This option is intended to be used by metamail recursively, to 
turn off the effect of the MM_TRANSPARENT environment variable. It should 
only be used when the metamail program restarts itself in a terminal 
emulator window. 


}\tempindentneg1{\indent2{\bold{File Name Arguments 

}}}\indent2{Any argument that does not start with "-" is interpreted as the 
name of a file to read instead of standard input. 

}\indent1{\tempindentneg1{
UNRECOGNIZED MAIL TYPES 

}From time to time, metamail may tell you something like 


**** Unrecognized mail type: 'smell-o-vision'. Writing to file 
/tmp/metamail.1234 **** 


What this means is that your are trying to read a message that contains 
data that is marked as being in "smell-o-vision" format, but that your site 
has not yet configured metamail to properly display that type of data. In 
the general case, such configuration is accomplished using the mailcap file 
mechanism, as described in the next section. 


For unrecognized types, metamail simply removes all header and encoding 
information from the data, and writes it out to a temporary file. (If 
running interactively, it will give you more alternatives -- writing it to 
a temporary file, viewing it as text, or jus skipping it.) It is up to the 
user to delete such files when he or she is through with them. 


\tempindentneg1{
THE MAILCAP FILE(S) 

}The primary purpose of the metamail program is to allow diverse mail 
reading programs to centralize their access to multimedia information. If 
all the mail reading programs call a single program to handle non-text 
mail, then only that program needs to know about the diverse types of 
non-text mail that might be received. 


The metamail program is made more flexible in this role through the 
mechanism of one or more "mailcap" files. The purpose of the mailcap files 
is to tell metamail what program to run in order to show the user mail in a 
given format. Thus it becomes possible to add a new media type to all of 
the mail reading programs at a site simply by adding a line to a mailcap 
file. 


Metamail uses a search path to find the mailcap file(s) to consult. Unlike 
many path searches, if necessary metamail will read \italic{all }the 
mailcap files on its path. That is, it will keep reading mailcap files 
until it runs out of them, or until it finds a line that tells it how to 
handle the piece of mail it is looking at. If it finds a matching line, it 
will execute the command that is specified in the mailcap file. 


The default search path is equivalent to 


$HOME/.mailcap:/usr/local/etc/mailcap:/usr/etc/mailcap:/etc/mailcap:/etc/mai\
l/mailcap:/usr/public/lib/mailcap" 


It can be overridden by setting the MAILCAPS environment variable. Note: 
Metamail does not actually interpret environment variables such as $HOME or 
the "~" syntax in this path search. 


The format of mailcap files is explained in the manual entry for 
mailcap(4). 


\tempindentneg1{
NON-ASCII HEADER FIELDS 

}Metamail has rudimentary built-in support for the emerging Internet 
standards for non-ASCII data in mail headers. What this means is that such 
data will be recognized, decoded, and sent to the terminal. This behavior 
may be more or less reasonable, depending on the character set in the 
header data and the capability of the user's terminal, but it will rarely 
be any worse than showing such data in its encoded form. 

\tempindentneg1{
ENVIRONMENT 

}}\tempindentneg1{\indent2{\bold{METAMAIL_TMPDIR 

}}}\indent2{If set, this variable overrides "/tmp" as the name of the 
directory in which metamail and associated programs will create temporary 
files on UNIX. 


}\tempindentneg1{\indent2{\bold{MM_NOASK 

}}}\indent2{If MM_NOASK is set to "1", metamail will never ask the user for 
confirmation before running an interpreter. Otherwise, MM_NOASK may be set 
to a comma-separated list of type names (without white space) for which the 
user does not desire confirmation. Thus, setting MM_NOASK to 
"magicmail,audio" will cause the user not to be asked before running 
interpreters for magicmail- or audio-format mail, but the user will still 
be asked for all other types. (If the -d command line option is given, 
MM_NOASK is set to 1 for spawned processes, allowing -d to work 
recursively.) 


}\tempindentneg1{\indent2{\bold{KEYHEADS 

}}}\indent2{The KEYHEADS variable may be set to a colon-separated list of 
header names, which are the only headers that metamail will print out. By 
default, the behavior is as if KEYHEADS were set to: 


Date:From:Subject:To:CC:Content-Description 


If KEYHEADS is set to the empty string, no header are printed out. If it is 
set to an asterisk ("*"), all headers are printed out. \bold{KEYIGNHEADS 
}The KEYIGNHEADS variable may be set to a colon-separated list of header 
names, which are the headers that metamail will not print out. This 
variable is only examined if KEYHEADS is not set. 


If KEYIGNHEADS is set to the empty string, all headers are printed out. If 
it is set to an asterisk ("*"), no headers will be printed out. 


}\tempindentneg1{\indent2{\bold{MM_NOTTTY 

}}}\indent2{If MM_NOTTTY is set to any nonzero value, metamail will assume 
that it is not running in a terminal window. MM_NOTTTY implies setting 
MM_NOASK to 1. If -z is given, MM_NOTTTY is set for spawned processes, 
allowing -z to work recursively. 


}\tempindentneg1{\indent2{\bold{MAILCAPS 

}}}\indent2{This variable can be used to override the default path search 
for mailcap files. 


}\tempindentneg1{\indent2{\bold{METAMAIL_PAGER 

}}}\indent2{If set, this variable overrides "more" as the name of the 
program to run to paginate output from an interpreter, when pagination has 
been requested. Note that the normal "PAGER" variable is not used because 
many pagers (notably the "less" pager) interfere with the workings of 
termcap-based mail viewers. 


}\tempindentneg1{\indent2{\bold{NOMETAMAIL 

}}}\indent2{This variable is not actually used by metamail, but is used by 
most metamail-compatible mail reading interfaces. If NOMETAMAIL is set to 
any value, most mail reading interfaces will never call the metamail 
program, effectively inhibiting all multimedia functionality. 


}\tempindentneg1{\indent2{\bold{MM_DEBUG 

}}}\indent2{If MM_DEBUG is set to any value, metamail will produce slightly 
more verbose output to tell what it is doing. 


}\tempindentneg1{\indent2{\bold{MM_QUIET 

}}}\indent2{If this variable is set to "1", metamail will produce even less 
output than usual. In particular, it will suppress the "Executing..." line 
unless MM_DEBUG is set. 


Otherwise, this variable can be set to a comma-separated list of short 
commands, and the "Executing..." line will be suppressed for those commands 
only. 


The default setting for MM_QUIET is "cat", which means that the 
"Executing..." line is printed for all commands executed except "cat". This 
makes text support look more natural without sacrificing an understanding 
of what is going on in more complex circumstances. 


}\tempindentneg1{\indent2{\bold{MM_YANKMODE 

}}}\indent2{Setting this variable to a non-zero value has the same effect 
as the -y switch. Be sure to read the caveats attached to the description 
of -y before you use it. Basically, the only time you would set MM_YANKMODE 
is in order to re-enter a mail reader in which you can't control the way 
metamail is called, just to read a single rejected MIME message that was 
rejected by a mail agent that does not understand MIME. In such cases, you 
should read that message, exit, and unset this variable. 


}\tempindentneg1{\indent2{\bold{MM_TRANSPARENT 

}}}\indent2{If this variable is set, metamail will reproduce the entire raw 
message on stdout, and will open up a new terminal emulator window in which 
to do something more intelligent. This option supports certain brain-dead 
mail readers, such as mailtool, that actually depend on the output of the 
UNIX "Mail" program being the same as the raw message in the database. 


}\tempindentneg1{\indent2{\bold{MM_CHARSET 

}}}\indent2{If this variable is set, it will suppress the printing of 
character set declarations when mail headers being printed contain text in 
this character set. For example, if you set MM_CHARSET to "iso-8859-8", it 
will suppress warnings when header output is produced in that character 
set. 


}\tempindentneg1{\indent2{\bold{DISPLAY 

}}}\indent2{Used to create a terminal window under the X11 window system. 


}\tempindentneg1{\indent2{\bold{WINDOW_PARENT 

}}}\indent2{Used to create a terminal window under the SunTools window 
system. 


}\tempindentneg1{\indent2{\bold{WMHOST 

}}}\indent2{Used to create a terminal window under the old Andrew WM window 
system. 

}\indent1{\tempindentneg1{
INTERPRETER ENVIRONMENT 

}When metamail calls an interpreter specified in a mailcap file, it sets 
several environment variables which can be used by the interpreter if 
desired: 


}\tempindentneg1{\indent2{\bold{MM_HEADERS 

}}}\indent2{This variable is set to the full set of RFC822 headers, if any. 


}\tempindentneg1{\indent2{\bold{MM_MAILER 

}}}\indent2{This variable is set to the name of the mailer that called 
metamail, if the -m option was used. 


}\tempindentneg1{\indent2{\bold{MM_CONTENTTYPE 

}}}\indent2{This variable is set to the content type, as named by the 
Content-type header or passed in via the -c option. If the content-type has 
a subtype and parameters, these are also included in MM_CONTENTTYPE, e.g. 
"multipart/mixed; boundary=foobar". 


}\tempindentneg1{\indent2{\bold{MM_SUMMARY 

}}}\indent2{This variable is set to an efficient one-line "caption" of the 
message, typically including its sender and subject. 


}\tempindentneg1{\indent2{\bold{MM_USEPAGER 

}}}\indent2{This variable is set to a non-zero if the use of a pager has 
been requested for long output (e.g. the -p switch was given.) If -p is 
given, MM_USEPAGER is set for spawned processes, allowing -p to work 
recursively. This option cannot be used with -B. 


}\tempindentneg1{\indent2{\bold{TERMINAL_CMD 

}}}\indent2{This variable may be set to a string that is used to start a 
new terminal window if necessary. The command to be executed in that window 
will be APPENDED to this command. By default, this is set to something like 
"xterm -e" if DISPLAY is set, or "shelltool" if WINDOW_PARENT is set. Users 
of Sun's OpenWindows may wish to set TERMINAL_CMD to "shelltool" if they 
prefer shelltool over xterm. 


}\tempindentneg1{\indent2{\bold{MM_RUNASROOT 

}}}\indent2{If set to a non-zero variable, this will allow the metamail 
program to be run by root, the same effect as the "-r" switch to metamail. 

}\indent1{\tempindentneg1{
FILES 

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

\tempindentneg1{
SEE ALSO 

}audiocompose(1), audiosend(1), ezview(1), getfilename(1), 
mailto-hebrew(1), mailto(1), metasend(1), mmencode(1), richtext(1), 
showaudio(1), showexternal(1), shownonascii(1), showpartial(1), 
showpicture(1), mailcap(4) 

\tempindentneg1{
BUGS 

}In a multipart/alternative body or body parts, some headers in the 
embedded part that should be displayed may not be displayed. This will 
rarely be a problem. Also, in a multipart/alternative, anything of type 
"multipart" or "message" is considered to be a recognized part, regardless 
of the recognizability of its contents. This might be a problem, only 
further experience will tell. 


The "textualnewlines" field in mailcap entries affects a global table of 
exceptions. This means that if there is more than one mailcap entry for a 
given content-type, and they have conflicting "textualnewlines" settings, 
the wrong value may be used. I have been unable to conceive of a situation 
where this would be a real problem, because it seems inconceivable that a 
single content-type would ever require newlines to be treated in two 
different ways, regardless of the environment. 

\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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