Hacker 2/HACKER2.mdf/internet/bd_ch9.txt

Text File | 1995-01-03 | 17KB | 357 lines

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Date: Thu, 3 Feb 1994 23:17:20 -0500 (EST)
From: Nancy Ammerman <emoryu1!phoenix.Princeton.EDU!nancyamm>
To: Jackie Ammerman <emory!emoryu1!awwe![e-mail]>
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Chapter 9: ADVANCED E-MAIL



9.1  THE FILE'S IN THE MAIL


     E-mail by itself is a powerful tool, and by now you may be
sending e-mail messages all over the place.  You might even be on a
mailing list or two. But there is a lot more to e-mail than just
sending messages.  If your host system does not have access to ftp,
or it doesn't have access to every ftp site on the Net, you can have
programs and files sent right to your mailbox.  And using some simple
techniques, you can use e-mail to send data files such as spreadsheets,
or even whole programs, to friends and colleagues around the world.
     A key to both is a set of programs known as encoders and
decoders.  For all its basic power, Net e-mail has a big problem: it
can't handle graphics characters or the control codes found in even
the simplest of computer programs. Encoders however, can translate
these into forms usable in e-mail, while decoders turn them back into
a form that you can actually use. If you are using a Unix-based host
system, chances are it already has an encoder and decoder online that
you can use. These programs will also let you use programs posted in
several Usenet newsgroups, such as comp.binaries.ibm.pc.
    If both you and the person with whom you want to exchange files use
Unix host systems, you're in luck because virtually all Unix
host systems have encoder/decoder programs online.  For now, let's
assume that's the case. First, upload the file you want to send to your
friend to your host site (ask your system administrator how to upload a
file to your name or "home" directory if you don't already know how).
Then type

                uuencode file file > file.uu

and hit enter. "File" is the name of the file you want to prepare for
mailing, and yes, you have to type the name twice!  The > is a Unix
command that tells the system to call the "encoded" file "file.uu"
(you could actually call it anything you want).
     Now to get it into a mail message.  The quick and dirty way is to
type

                mail friend

where "friend" is your friend's address.  At the subject line, tell
her the name of the enclosed file.  When you get the blank line, type

                ~r file.uu

or whatever you called the file, and hit enter. (on some systems, the ~
may not work; if so, ask your system administrator what to use).  This
inserts the file into your mail message.  Hit control-D, and your file
is on its way!
     On the other end, when your friend goes into her mailbox,  she
should transfer it to her home directory.  Then she should type

                uudecode file.name

and hit enter.  This creates a new file in her name directory with
whatever name you originally gave it.  She can then download it to her
own computer.  Before she can actually use it, though, she'll have to
open it up with a text processor and delete the mail header that has
been "stamped" on it.  If you use a mailer program that automatically
appends a "signature," tell her about that so she can delete that as
well.


9.2  RECEIVING FILES


    If somebody sends you a file through the mail, you'll have to go
through a couple of steps to get it into a form you can actually use.  If
you are using the simple mail program, go into mail and type

                w # file.name

where # is the number of the message you want to transfer and
file.name is what you want to call the resulting file.  In pine, call
up the message and hit your O key and then E.  You'll then be asked
for a file name. In elm, call up the message and hit your S key.
You'll get something that looks like this:

                =file.request

     Type a new file name and hit enter (if you hit enter without
typing a file name, the message will be saved to another mail folder,
not your home directory).
    In all three cases, exit the mail program to return to your host
system's command line. Because the file has been encoded for mail
delivery, you now have to run a decoder.  At the command line, type

                uudecode file.name

where file.name is the file you created while in mail. Uudecode will
create a new, uncompressed binary file.  In some cases, you may have to
run it through some other programs (for example, if it is in "tar" form),
but generally it should now be ready for you to download to your own
computer (on which you might then have to run a de-compressor program
such as PKXZIP).


9.3  FILES TO NON-INTERNET SITES


    What if your friend only connects with a non-Unix system, such as
CompuServe or MCIMail?  There are programs available for MS-DOS, Apple
and Amiga computers that will encode and decode files.  Of course, since
you can't send one of these programs to your friend via e-mail (how would
she un-encode it?), you'll have to mail (the old-fashioned way) or give
her a diskette with the program on it first.   Then, she can get the file
by e-mail and go through the above process (only on her own computer) to
get a usable file.  Remember to give her an encoder program as well, if
she wants to send you files in return.
     For MS-DOS machines, you'll want to get uunecode.com and
uudecode.com.  Both can be found through anonymous ftp at
wuarchive.wustl.edu in the /mirrors/msdos/starter directory. The MS-
DOS version is as easy to use as the Unix one: Just type

                uudecode filename.ext

and hit enter.
     Mac users should get a program called uutool, which can be found
in the info-mac/util directory on sumex-aim.stanford.edu.
     Think twice before sending somebody a giant file. Although large
sites connected directly to the Internet can probably handle mega-files,
many smaller systems cannot. Some commercial systems, such as CompuServe
and MCIMail, limit the size of mail messages their users can receive.
Fidonet doesn't even allow encoded messages.  In general, a file size of
30,000 or so bytes is a safe upper limit for non-Internet systems.


9.4  GETTING FTP FILES VIA E-MAIL


    To help people without ftp access, a number of ftp sites have set up
mail servers (also known as archive servers) that allow you to get files
via e-mail.  You send a request to one of these machines and they send
back the file you want.  As with ftp, you'll be able to find everything
from historical documents to software (but please note that if you do
have access to ftp, that method is always quicker and ties up fewer
resources than using e-mail).
      Some interesting or useful mail servers include:
      [e-mail]  Files of "frequently asked questions"
related to Usenet; state-by-state lists of U.S. representatives and
Senators and their addresses and office phone numbers.
      [e-mail]  Information about the Electronic Frontier
Foundation; documents about legal issues on the Net.
      [e-mail]  Back copies of the Computer
Underground Digest and every possible fact you could want to know about
"The Simpsons."
      [e-mail]  Programs for many types of personal computers;
archives of past postings from many Usenet newsgroups.
      [e-mail]  Space-related text and graphics
(GIF-format) files.
      [e-mail]  Detailed information about Internet.
      Most mail servers work pretty much the same -- you send an e-mail
message that tells them what file you want and how you want it sent to
you.  The most important command is "send," which tells the computer you
want it to send you a particular file.
     First, though, you'll need to know where the mail server stores
that file, because you have to tell it which directory or sub-
directory it's in.  There are a couple of ways to do this. You can
send an e-mail message to the archive-server that consists of one
line:

                index

     The server will then send you a directory listing of its main, or
root directory.  You'll then have to send a second message to the
archive server with one line:

                index directory/subdirectory

where that is the directory or directory path for which you want a
listing.  An alternative is to send an e-mail message to our old
friend archie, which should send you back the file's exact location on
the archive-server (along with similar listings for all the other
sites that may have the file, however)
     Once you have the file name and its directory path, compose a
message to the archive server like this:

                send directory/subdirectory/file

     Send off the message and, anywhere from a few minutes to a couple
of days later, you'll find a new message in your mailbox: a copy of the
file you requested.  The exact time it will take a file to get to you
depends on a variety of factors, including how many requests are in line
before yours (mail servers can only process so many requests at a time)
and the state of the connections between the server and you.
     Seems simple enough. It gets a little more complicated when you
request a program rather than a document.  Programs or other files that
contain unusual characters or lines longer than 130 characters (graphics
files, for example) require special processing by both the mail server
to ensure they are transmitted via e-mail.  Then you'll have to run them
through at least one converter program to put them in a form you can
actually use.  To ensure that a program or other "non-mailable" file
actually gets to you, include another line in your e-mail message to the
server:

                encoder

This converts the file into an encoded form.  To decode it, you'll
first have to transfer the file message into a file in your home
directory.
     One further complication comes when you request a particularly
long file.  Many Net sites can only handle so much mail at a time.  To
make sure you get the entire file, tell the mail server to break it up
into smaller pieces, with another line in your e-mail request like
this:

                size 100000

     This gives the mail server the maximum size, in bytes, of each
file segment.  This particular size is good for UUCP sites. Internet
and Bitnet sites can generally go up to 300000.  When you get all of
these files in mail, transfer them to your home directory.  Exit mail
and call up each file in your host system's text processor and delete
each one's entire header and footer (or "signature" at the end).  When
done with this, at your host system's command line, type

                cat file1 file2 > bigfile

where file1 is the first file, file2 the second file, and so on.  The >
tells your host system to combine them into a new megafile called
bigfile (or whatever you want to call it).  After you save the file to
your home directory (see section 9.2 above), you can then run uudecode,
tar, etc. One word of caution, though: if the file you want is long
enough that it has to be broken into pieces, think of how much time it's
going to take you to download the whole thing -- especially if you're
using a 2400-baud modem!
     There are a number of other mail servers.  To get a list, send an
e-mail message to [e-mail]:

send usenet/comp.sources.wanted/How_to_find_sources_(READ_THIS_BEFORE_POSTING)

     You'll have to spell it exactly as listed above.  Some mail
servers use different software, which will require slightly different
commands than the ones listed here.  In general, if you send a message
to a mail server that says only

                help

you should get back a file detailing all of its commands.
     But what if the file you want is not on one of these mail
servers?  That's where ftpmail comes in.  Run by Digital Equipment
Corp. in California, this service can connect to almost any ftp site
in the world, get the file you want and then mail it to you. Using it
is fairly simple -- you send an e-mail message to ftpmail that
includes a series of commands telling the system where to find the
file you want and how to format it to mail to you.
     Compose an e-mail message to

                [e-mail]

     Leave the "subject:" line blank.  Inside the message, there are
several commands you can give.  The first line should be

                reply address

where "address" is your e-mail address. The next line should be

                connect host

where "host" is the system that has the file you want (for example:
wuarchive.wustl.edu). Other commands you should consider using are
"binary" (required for program files); "compress" (reduces the file
size for quicker transmission) and "uuencode" (which encodes the file
so you can do something with it when it arrives).  The last line of
your message should be the word "quit".
     Let's say you want a copy of the U.S. constitution.  Using archie,
you've found a file called, surprise, constitution, at the ftp site
archive.cis.ohio-state.edu, in the /pub/firearms/politics/rkba
directory. You'd send a message to [e-mail] that looks
like this:

                reply [e-mail]
                connect archive.cis.ohio-state.edu
                binary
                compress
                uuencode
                get pub/firearms/politics/rkba/constitution
                quit

     When you get the file in your mailbox, use the above procedure
for copying it to a file.  Run it through uudecode.  Then type

                uncompress file.name

to make it usable.
     Since this was a text file, you could have changed the "binary" to
"ascii" and then eliminated the "uuencode" file.  For programs, though,
you'll want to keep these lines.  One caveat with ftpmail: it has become
such a popular service that it could take a week or more for your
requested files to arrive.


9.5  THE ALL KNOWING ORACLE


      One other thing you can do through e-mail is consult with the
Usenet Oracle.  You can ask the Oracle anything at all and get back an
answer (whether you like the answer is another question).
      First, you'll want to get instructions on how to address the Oracle
(he, or she, or it, is very particular about such things and likes being
addressed in august, solemn and particularly sycophantic tones).  Start
an e-mail message to

                [e-mail]

      In the "subject:" line, type

                help

and hit enter.  You don't actually have to say anything in the message
itself -- at least not yet.  Hit control-D to send off your request
for help.  Within a few hours, the Oracle will mail you back detailed
instructions.  It's a fairly long file, so before you start reading
it, turn on your communications software's logging function, to save
it to your computer (or save the message to a file on your host system's
home directory and then download the file).  After you've digested it,
you can compose your question to the Oracle.  Mail it to the above
address, only this time with a subject line that describes your
question.  Expect an answer within a couple of days. And don't be
surprised if you also find a question in your mailbox -- the Oracle
extracts payment by making seekers of knowledge answer questions as
well!






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