Miguel Marquina IT/User Support
Nowadays, access to remote computers is, in general, no longer a problem.
The classical and recommended
file exchange is made using net protocols like
ftp, or using modern interfaces through WWW (see the article
"Anonymous ftp access using WWW"
in CNL 223).
However there may be occasions when you wish to send or receive files at your ordinary electronic mailbox. This article is intended to give you some hints on how to do that.
The first thing to remember is that e-mail only enables you to transmit properly ASCII text (the one you can produce from an International keyboard, composed by so-called "quoted-printable" characters), and this is guaranteed to work and be readable across computers. If you want to transmit binary files (images, drawings, etc.) you need to convert them to ASCII first. There are several methods to achieve this and we will present you the two most common ones:
Mail Agents may use different standards for encoding and decoding
attachments, but today the world is converging on the Internet standard
called MIME (Multipurpose Internet Mail Extensions) which is used, for
Netscape, Quickmail and the CERN
As for natural languages, the mail agents at both
sides must be using the same standard to understand each other. It is
not enough to know that "you got an attachment". Useful information
that you or your correspondant should include when transmitting a
pine, Netscape) and from where (Mac, PC, UNIX station, etc.)
If your mail client is properly configured and it uses the same standard as the one of your correspondent, it will automatically identify the type of the received file and launch the appropriate file browser for it (if available at your system).
Details of usage vary from client to client, but for example, using pine, an incoming mail with an attachment looks like this:
Parts/attachments: 1 Shown 2 lines Text 2 17 KB Application ---------------------------------------- Hi John, please find here the paper I am preparing for the next conference, as MIME attachment. [Part 2, Application/MSWORD 23KB] [Cannot display this part. Press "V" then "S" to save in a file] MS-Word document received as an attachmentTo send a file as an attachment, position the cursor in the header of the mail and use the Attach (ctrl-J) command.
For systems that don't yet have MIME support, the most common format used in file exchange via e-mail is "uuencoding". You recognize it immediately because the incoming e-mail looks like this:
Hi John, please find here the paper I am preparing for the next conference, in "uuencode" format... begin 644 myfile M)2$*)254:71L93H@+W1M<"]X9FEG+69I9S`Q-C$V-`HE)4-R96%T;W(Z(&9I M9S)D978*)25#CF5A=&EO;D1A=&4Z(%1U92!/8W0@,C0@,#4Z-30Z,SD@,3DY ... M9F]N="!S971F;VYT"C(R-"`R,3D@;2`*9W,@,2`M,2!S8V%L92`@-"XP(')O M=&%T92`H5&\@1V5X*2!C;VPM,2!S:&]W(&=R"G-H;W=P86=E"B1&,G!S16YD ""@IT ` end File "myfile" encoded with the "uuencode" program
Simply extract the text of your mail as a file (using the corresponding "Export" feature of your Mail Agent) and then execute the "uudecode" program on it (if available on your system); e.g. on UNIX:
uudecode mailtextIt is very easy to send uuencoded files. On UNIX, one would encode "myfile" with the command:
uuencode myfile myfile >mailtextand then incorporate the generated file "mailtext" into your outgoing mail.