docs/unix-phil: unix-phil.ms comparison

comparison unix-phil.ms @ 19:d8f428cee0d1

about mh (ch04)

author	meillo@marmaro.de
date	Thu, 25 Feb 2010 15:06:34 +0100
parents	e2240a387a84
children	578d5c84e5c0

comparison

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 .I "``Use software leverage!''
 .NH 1
-Case study: nmh
+Case study: \s-1MH\s0
 .LP
 The last chapter introduced and explained the Unix Philosophy
 from a general point of view.
 The driving force were the guidelines and references to
 existing software were given only sparsely.
 In this and the next chapter, concrete software will be
 the driving force in the discussion.
 .PP
 This first case study is about the mail user agents \s-1MH\s0
 (``mail handler'') and its descendent \fInmh\fP (``new mail handler'').
+In this document, the name \s-1MH\s0 will be used for both of them.
+A distinction will only be made if differences between
-.NH 2
+them are described.
-History of \s-1MH\s0
-.LP
-In 1977, Stockton Gaines and Norman Shapiro of the \s-1RAND\s0 Corporation
+.NH 2
-came up with a concept for a new electronic mail system.
+Historical background
-Till then, \s-1RAND\s0 had used \s-1MS\s0 (``mail system''),
+.LP
-which was monolithic.
+Electronic mail was available in Unix very early.
-In 1978 and 1989, Bruce Borden implemented the concept \(en
+It is out of matter that in the beginning mail was only
-this was the birth of \s-1MH\s0.
+transferred within one machine.
+This chapter is about a mail user agent (\s-1MUA\s0),
+which provides functions to read, compose, and organize mail,
+but (ideally) not to transfer.
+.PP
+The first \s-1MUA\s0 on Unix was \f(CWmail\fP.
+It was a small program that either prints the own mailbox file
+or appends text to someone elses mailbox file,
+depending on the command line arguments.
+.[
+%O http://cm.bell-labs.com/cm/cs/who/dmr/pdfs/man12.pdf
+.]
+It was a program that did one job well.
+This job was emailing, which then was very simple.
+.PP
+Later, emailing became more powerfull, and thus more complex.
+The simple \f(CWmail\fP, which knew nothing of subjects,
+independent handling of single messages,
+and long-time storage of them, was not powerful enough anymore.
+At Berkeley, Kurt Shoens wrote \fIMail\fP (with capital `M')
+in 1978 to provide additional functions for emailing.
+Mail was still one program, but now it was large and did
+several jobs.
+Its user interface is modeled after the one of ed.
+It is designed for humans, but is still scriptable.
+\fImailx\fP is the adaption of Berkeley Mail into System V.
+.[
+%A Gunnar Ritter
+%O http://heirloom.sourceforge.net/mailx_history.html
+.]
+Elm, pine, mutt, and today a whole bunch of graphical \s-1MUA\s0s
+followed Mail's direction.
+They are large, monolithic programs which include all emailing functions.
+.PP
+A different way took the people of \s-1RAND\s0 Corporation.
+In the beginning, they also had used a monolitic mail system,
+simply called \s-1MS\s0 for ``mail system''.
+But in 1977, Stockton Gaines and Norman Shapiro
+came up with a proposal of a new email system concept \(en
+one that honors the Unix Philosophy.
+The concept was implemented by Bruce Borden in 1978 and 1979.
+This was the birth of \s-1MH\s0 \(en the ``mail handler''.
 .PP
 Since then, \s-1RAND\s0, the University of California at Irvine and
-at Berkeley, and several others have contributet to the software.
+at Berkeley, and several others have contributed to the software.
 However, it's core concepts remained the same.
-In the 90s, the development of \s-1MH\s0 slowed down.
+In the 90s, when development of \s-1MH\s0 slowed down,
-Richard Coleman started with \fInmh\fP, the new mail handler,
+Richard Coleman started with \fInmh\fP, the new mail handler.
-in 1997 to improve \s-1MH\s0, especially in regard of modern emailing.
+This was in 1997.
-Today, nmh is developed by various people on the internet.
+His goal was to improve \s-1MH\s0, especially in regard of
+the requirements of modern email.
+Today, nmh is developed by various people on the Internet.
 .[
 %T RAND and the Information Evolution: A History in Essays and Vignettes
 %A Willis H. Ware
 %D 2008
 %I The RAND Corporation
 %P Appendix B
 %O Also available online: \f(CW\s-2http://rand-mh.sourceforge.net/book/\fP
 .]
 .NH 2
-Contrasts to similar sw
+Contrasts to similar software
 .LP
-vs. Thunderbird, mutt, mailx, pine
+All \s-1MUA\s0s are monolithic, except \s-1MH\s0.
-.LP
+This might not be completely true,
+but it reflects the general situation pretty well.
+.PP
+While monolithic \s-1MUA\s0s gather all function in one program,
+\s-1MH\s0 is a toolchest of many small tools \(en one for each job.
+Following is a list of important programs of \s-1MH\s0's toolchest:
+.IP \(bu
+.CW inc :
+incorporate new mail
+.IP \(bu
+.CW scan :
+list messages in folder
+.IP \(bu
+.CW show :
+show message
+.IP \(bu
+.CW next\fR/\fPprev :
+show next/previous message
+.IP \(bu
+.CW folder :
+change current folder
+.IP \(bu
+.CW refile :
+refile message into folder
+.IP \(bu
+.CW rmm :
+remove message
+.IP \(bu
+.CW comp :
+compose a new message
+.IP \(bu
+.CW repl :
+reply to a message
+.IP \(bu
+.CW forw :
+forward a message
+.IP \(bu
+.CW send :
+send a prepared message
+.LP
+\s-1MH\s0 has no special user interface like monolithic \s-1MUA\s0s have.
+The user does not leave the shell to run \s-1MH\s0,
+but he uses \s-1MH\s0 within the shell.
+\s-1MH\s0's mail storage is (only little more than) a directory tree
+where directories are mail folders and files are mail messages.
+Working with \s-1MH\s0's toolchest is much like working
+with Unix' toolchest:
+\f(CWscan\fP is like \f(CWls\fP,
+\f(CWshow\fP is like \f(CWcat\fP,
+\f(CWfolder\fP is like \f(CWcd\fP,
+\f(CWrefile\fP is like \f(CWmv\fP,
+and \f(CWrmm\fP is like \f(CWrm\fP.
+.PP
+The most important difference to Unix' toolchest is,
+that \s-1MH\s0's tools have an own context.
+The context of the Unix tools is mainly the current working directory,
+the user identification, and the environment variables.
+\s-1MH\s0 extends this context by two more items:
+A current mail folder, similar to the current working directory,
+is maintained; \f(CWfolder\fP provides the functionality
+of \f(CWpwd\fP and \f(CWcd\fP for it.
+A current message, relative to the current folder, is maintained.
+This enables commands like \f(CWnext\fP and \f(CWprev\fP.
+In contrast to Unix' context, which is chained to the shell session,
+\s-1MH\s0's context is meant to be chained to a mail account.
+Actually, the current message is a property of the mail folder.
+This is without problem as long as a mail folder belongs to one user.
+But when multiple users want to work on one mail folder simultaneously,
+it will cause problems.
+This is a legacy from a time when emailing was different.
+.PP
+Using a monolithic program with a captive user interface
+means ``entering'' the program, using it, and ``leaving'' the program.
+Using a toolchest like \s-1MH\s0 means running programs,
+alone or in combinition with others, even from other toolchests,
+without leaving the shell.
+.NH 2
+Gains of the design
+.LP
+\s-1MH\s0 is perfectly suited for non-interactive use.
+It offers all functions directly and without captive user interfaces.
+If users want a graphical user interface, anyhow,
+they can have it with \fIxmh\fP or \fIexmh\fP.
+These are graphical frontends for the \s-1MH\s0 toolchest.
+This means, all email-related work is still done by \s-1MH\s0 tools,
+but xmh issues the calls when the user clicks a button.
+Providing easy-to-use user interfaces as frontends is a good
+approach, because it does not limit the power of the backend itself.
+The frontend will anyways only be able to make a part of the
+backend's power and flexibility available.
+If it is separate, then the missing parts can still be accessed
+at the backend directly.
+If it is integrated, then this will hardly be possible.
+.PP
 flexibility, no redundancy, use the shell
-.NH 2
+.PP
-Gains of the design
+easy to write: see ksh-book
-.LP
 .NH 2
 Problems
 .LP

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