meillo@58: .H0 "Discussion
meillo@0: .P
meillo@58: This main chapter discusses the practical work done in the mmh project.
meillo@104: It is structured along the goals to achieve.
meillo@104: The concrete work done
meillo@58: is described in the examples of how the general goals were achieved.
meillo@87: The discussion compares the current version of mmh with the state of
meillo@87: nmh just before the mmh project started, i.e. Fall 2011.
meillo@87: Current changes of nmh will be mentioned only as side notes.
meillo@87: .\" XXX where do I discuss the parallel development of nmh?
meillo@58: 
meillo@58: 
meillo@58: 
meillo@133: .\" --------------------------------------------------------------
meillo@125: .H1 "Streamlining
meillo@58: 
meillo@0: .P
meillo@58: MH had been considered an all-in-one system for mail handling.
meillo@58: The community around nmh has a similar understanding.
meillo@87: In fundamental difference, mmh shall be a MUA only.
meillo@87: I believe that the development of all-in-one mail systems is obsolete.
meillo@87: Today, email is too complex to be fully covered by single projects.
meillo@87: Such a project won't be able to excel in all aspects.
meillo@87: Instead, the aspects of email should be covered my multiple projects,
meillo@87: which then can be combined to form a complete system.
meillo@87: Excellent implementations for the various aspects of email exist already.
meillo@87: Just to name three examples: Postfix is a specialized MTA,
meillo@87: Procmail is a specialized MDA, and Fetchmail is a specialized MRA.
meillo@89: I believe that it is best to use such specialized tools instead of
meillo@87: providing the same function again as a side-component in the project.
meillo@58: .P
meillo@87: Doing something well, requires to focus on a small set of specific aspects.
meillo@87: Under the assumption that focused development produces better results
meillo@100: in the particular area, specialized projects will be superior
meillo@87: in their field of focus.
meillo@87: Hence, all-in-one mail system projects \(en no matter if monolithic
meillo@87: or modular \(en will never be the best choice in any of the fields.
meillo@87: Even in providing the best consistent all-in-one system they are likely
meillo@87: to be beaten by projects that focus only on integrating existing mail
meillo@89: components to a homogeneous system.
meillo@87: .P
meillo@87: The limiting resource in Free Software community development
meillo@87: is usually man power.
meillo@87: If the development power is spread over a large development area,
meillo@87: it becomes even more difficult to compete with the specialists in the
meillo@87: various fields.
meillo@87: The concrete situation for MH-based mail systems is even tougher,
meillo@87: given the small and aged community, including both developers and users,
meillo@87: it has.
meillo@87: .P
meillo@87: In consequence, I believe that the available development resources
meillo@100: should focus on the point where MH is most unique.
meillo@87: This is clearly the user interface \(en the MUA.
meillo@125: Peripheral parts should be removed to streamline mmh for the MUA task.
meillo@60: 
meillo@60: 
meillo@100: .H2 "Mail Transfer Facilities
meillo@60: .P
meillo@60: In contrast to nmh, which also provides mail submission and mail retrieval
meillo@87: agents, mmh is a MUA only.
meillo@100: This general difference initiated the development of mmh.
meillo@66: Removing the mail transfer facilities had been the first work task
meillo@76: in the mmh project.
meillo@60: .P
meillo@105: Focusing on one mail agent role only is motivated by Eric Allman's
meillo@105: experience with Sendmail.
meillo@105: He identified limiting Sendmail the MTA task had be one reason for
meillo@105: its success:
meillo@105: .[ [
meillo@105: costales sendmail
meillo@105: .], p. xviii]
meillo@105: .QS
meillo@105: Second, I limited myself to the routing function \(en
meillo@110: I wouldn't write user agents or delivery back-ends.
meillo@105: This was a departure of the dominant through of the time,
meillo@105: in which routing logic, local delivery, and often the network code
meillo@105: were incorporated directly into the user agents.
meillo@105: .QE
meillo@105: .P
meillo@105: In mmh, the Mail Submission Agent (MSA) is called
meillo@105: \fIMessage Transfer Service\fP (MTS).
meillo@105: This facility, implemented by the
meillo@105: .Pn post
meillo@105: command, established network connections and spoke SMTP to submit
meillo@60: messages for relay to the outside world.
meillo@105: The changes in email demanded changes in this part of nmh too.
meillo@89: Encryption and authentication for network connections
meillo@87: needed to be supported, hence TLS and SASL were introduced into nmh.
meillo@87: This added complexity to nmh without improving it in its core functions.
meillo@87: Also, keeping up with recent developments in the field of
meillo@87: mail transfer requires development power and specialists.
meillo@87: In mmh this whole facility was simply cut off.
meillo@76: .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@76: .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@76: .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@87: Instead, mmh depends on an external MSA.
meillo@60: The only outgoing interface available to mmh is the
meillo@60: .Pn sendmail
meillo@87: command, which almost any MSA provides.
meillo@87: If not, a wrapper program can be written.
meillo@87: It must read the message from the standard input, extract the
meillo@87: recipient addresses from the message header, and hand the message
meillo@87: over to the MSA.
meillo@87: For example, a wrapper script for qmail would be:
meillo@87: .VS
meillo@87: #!/bin/sh
meillo@138: exec qmail-inject  # ignore command line arguments
meillo@87: VE
meillo@87: The requirement to parse the recipient addresses out of the message header 
meillo@87: is likely to be removed in the future.
meillo@87: Then mmh would give the recipient addresses as command line arguments.
meillo@100: This appears to be the better interface.
meillo@87: .\" XXX implement it
meillo@60: .P
meillo@60: To retrieve mail, the
meillo@60: .Pn inc
meillo@100: command acted as Mail Retrieval Agent (MRA).
meillo@100: It established network connections
meillo@76: and spoke POP3 to retrieve mail from remote servers.
meillo@76: As with mail submission, the network connections required encryption and
meillo@87: authentication, thus TLS and SASL were added.
meillo@87: Support for message retrieval through IMAP will become necessary
meillo@100: to be added soon, too, and likewise for any other changes in mail transfer.
meillo@100: Not so for mmh because it has dropped the support for retrieving mail
meillo@100: from remote locations.
meillo@76: .Ci ab7b48411962d26439f92f35ed084d3d6275459c
meillo@76: Instead, it depends on an external tool to cover this task.
meillo@100: In mmh exist two paths for messages to enter mmh's mail storage:
meillo@100: (1) Mail can be incorporated with
meillo@60: .Pn inc
meillo@87: from the system maildrop, or (2) with
meillo@60: .Pn rcvstore
meillo@87: by reading them, one at a time, from the standard input.
meillo@60: .P
meillo@60: With the removal of the MSA and MRA, mmh converted from an all-in-one
meillo@87: mail system to being a MUA only.
meillo@60: Now, of course, mmh depends on third-party software.
meillo@87: An external MSA is required to transfer mail to the outside world;
meillo@60: an external MRA is required to retrieve mail from remote machines.
meillo@60: There exist excellent implementations of such software,
meillo@76: which do this specific task likely better than the internal
meillo@87: versions had done it.
meillo@87: Also, the best suiting programs can be freely chosen.
meillo@60: .P
meillo@60: As it had already been possible to use an external MSA or MRA,
meillo@60: why not keep the internal version for convenience?
meillo@76: The question whether there is sense in having a fall-back pager in all
meillo@76: the command line tools, for the cases when
meillo@60: .Pn more
meillo@60: or
meillo@60: .Pn less
meillo@76: aren't available, appears to be ridiculous.
meillo@100: Of course, MSAs and MRAs are more complex than text pagers
meillo@87: and not necessarily available but still the concept of orthogonal
meillo@87: design holds: ``Write programs that do one thing and do it well.''
meillo@87: .[
meillo@87: mcilroy unix phil
meillo@87: p. 53
meillo@87: .]
meillo@87: .[
meillo@87: mcilroy bstj foreword
meillo@87: .]
meillo@87: Here, this part of the Unix philosophy was applied not only
meillo@87: to the programs but to the project itself.
meillo@87: In other words:
meillo@87: ``Develop projects that focus on one thing and do it well.''
meillo@87: Projects grown complex should be split for the same reasons programs grown
meillo@87: complex should be split.
meillo@100: If it is conceptionally more elegant to have the MSA and MRA as
meillo@87: separate projects then they should be separated.
meillo@87: This is the case here, in my opinion.
meillo@87: The RFCs propose this separation by clearly distinguishing the different
meillo@87: mail handling tasks.
meillo@87: .[
meillo@87: rfc 821
meillo@87: .]
meillo@87: The small interfaces between the mail agents support the separation.
meillo@76: .P
meillo@87: In the beginning, email had been small and simple.
meillo@100: At that time,
meillo@60: .Pn /bin/mail
meillo@100: had covered anything there was to email and still had been small
meillo@100: and simple.
meillo@100: Later, the essential complexity of email increased.
meillo@87: (Essential complexity is the complexity defined by the problem itself.\0
meillo@87: .[[
meillo@87: brooks no silver bullet
meillo@87: .]])
meillo@87: Email systems reacted to this change: They grew.
meillo@100: RFCs started to introduce the concept of mail agents to separate the
meillo@100: various tasks because they became more extensive and new tasks appeared.
meillo@100: As the mail systems grew even more, parts were split off.
meillo@100: In nmh, for instance, the POP server, which was included in the original
meillo@100: MH, was removed.
meillo@100: Now is the time to go one step further and split the MSA and MRA off, too.
meillo@87: Not only does this decrease the code size of the project,
meillo@87: but, more important, it unburdens mmh of the whole field of
meillo@87: message transfer with all its implications for the project.
meillo@100: There is no more need to concern with changes in network transfer.
meillo@76: This independence is received by depending on an external program
meillo@76: that covers the field.
meillo@76: Today, this is a reasonable exchange.
meillo@60: .P
meillo@100: Functionality can be added in three different ways:
meillo@87: .BU
meillo@87: Implementing the function originally in the project.
meillo@87: .BU
meillo@87: Depending on a library that provides the function.
meillo@87: .BU
meillo@87: Depending on a program that provides the function.
meillo@87: .P
meillo@87: Whereas adding the function originally to the project increases the
meillo@76: code size most and requires most maintenance and development work,
meillo@87: it makes the project most independent of other software.
meillo@87: Using libraries or external programs require less maintenance work
meillo@87: but introduces dependencies on external software.
meillo@87: Programs have the smallest interfaces and provide the best separation
meillo@87: but possibly limit the information exchange.
meillo@87: External libraries are stronger connected than external programs,
meillo@87: thus information can be exchanged more flexible.
meillo@87: Adding code to a project increases maintenance work.
meillo@87: .\" XXX ref
meillo@100: Implementing complex functions originally in the project adds
meillo@87: a lot of code.
meillo@87: This should be avoided if possible.
meillo@66: Hence, the dependencies only change in kind, not in their existence.
meillo@66: In mmh, library dependencies on
meillo@66: .Pn libsasl2
meillo@66: and
meillo@66: .Pn libcrypto /\c
meillo@66: .Pn libssl
meillo@66: were treated against program dependencies on an MSA and an MRA.
meillo@87: This also meant treating build-time dependencies against run-time
meillo@87: dependencies.
meillo@66: Besides program dependencies providing the stronger separation
meillo@66: and being more flexible, they also allowed
meillo@66: over 6\|000 lines of code to be removed from mmh.
meillo@66: This made mmh's code base about 12\|% smaller.
meillo@87: Reducing the project's code size by such an amount without actually
meillo@87: losing functionality is a convincing argument.
meillo@87: Actually, as external MSAs and MRAs are likely superior to the
meillo@87: project's internal versions, the common user even gains functionality.
meillo@66: .P
meillo@76: Users of MH should not have problems to set up an external MSA and MRA.
meillo@60: Also, the popular MSAs and MRAs have large communities and a lot
meillo@60: of documentation available.
meillo@87: Choices for MSAs range from full-featured MTAs like
meillo@60: .I Postfix
meillo@87: over mid-size MTAs like
meillo@60: .I masqmail
meillo@60: and
meillo@60: .I dma
meillo@60: to small forwarders like
meillo@60: .I ssmtp
meillo@60: and
meillo@60: .I nullmailer .
meillo@60: Choices for MRAs include
meillo@60: .I fetchmail ,
meillo@60: .I getmail ,
meillo@60: .I mpop
meillo@60: and
meillo@60: .I fdm .
meillo@60: 
meillo@60: 
meillo@100: .H2 "Non-MUA Tools
meillo@60: .P
meillo@87: One goal of mmh is to remove the tools that are not part of the MUA's task.
meillo@89: Further more, any tools that don't improve the MUA's job significantly
meillo@87: should be removed.
meillo@87: Loosely related and rarely used tools distract from the lean appearance.
meillo@87: They require maintenance work without adding much to the core task.
meillo@125: By removing these tools, the project shall become more streamlined
meillo@87: and focused.
meillo@76: In mmh the following tools are not available anymore:
meillo@62: .BU
meillo@58: .Pn conflict
meillo@87: was removed
meillo@76: .Ci 8b235097cbd11d728c07b966cf131aa7133ce5a9
meillo@87: because it is a mail system maintenance tool that is not MUA-related.
meillo@87: It even checked
meillo@58: .Fn /etc/passwd
meillo@58: and
meillo@58: .Fn /etc/group
meillo@87: for consistency, which is completely unrelated to email.
meillo@87: A tool like
meillo@87: .Pn conflict
meillo@87: is surely useful, but it should not be shipped with mmh.
meillo@76: .\" XXX historic reasons?
meillo@62: .BU
meillo@58: .Pn rcvtty
meillo@87: was removed
meillo@87: .Ci 14767c94b3827be7c867196467ed7aea5f6f49b0
meillo@89: because its use case of writing to the user's terminal
meillo@76: on receiving of mail is obsolete.
meillo@87: If users like to be informed of new mail, the shell's
meillo@58: .Ev MAILPATH
meillo@87: variable or graphical notifications are technically more appealing.
meillo@100: Writing directly to terminals is hardly ever wanted today.
meillo@62: If though one wants to have it this way, the standard tool
meillo@58: .Pn write
meillo@58: can be used in a way similar to:
meillo@82: .VS
meillo@58: scan -file - | write `id -un`
meillo@82: VE
meillo@62: .BU
meillo@58: .Pn viamail
meillo@87: was removed
meillo@87: .Ci eda72d6a7a7c20ff123043fb7f19c509ea01f932
meillo@87: when the new attachment system was activated, because
meillo@58: .Pn forw
meillo@76: could then cover the task itself.
meillo@62: The program
meillo@58: .Pn sendfiles
meillo@62: was rewritten as a shell script wrapper around
meillo@58: .Pn forw .
meillo@76: .Ci 0e82199cf3c991a173e0ac8aa776efdb3ded61e6
meillo@62: .BU
meillo@58: .Pn msgchk
meillo@87: was removed
meillo@87: .Ci bb9360ead7eb7a3fedcce2eeedfc660014e41dbe ,
meillo@87: because it lost its use case when POP support was removed.
meillo@76: A call to
meillo@58: .Pn msgchk
meillo@87: provided hardly more information than:
meillo@82: .VS
meillo@58: ls -l /var/mail/meillo
meillo@82: VE
meillo@100: It did distinguish between old and new mail, but
meillo@100: this detail information can be retrieved with
meillo@76: .Pn stat (1),
meillo@62: too.
meillo@100: A small shell script could be written to print the information
meillo@76: in a similar way, if truly necessary.
meillo@76: As mmh's
meillo@76: .Pn inc
meillo@87: only incorporates mail from the user's local maildrop,
meillo@62: and thus no data transfers over slow networks are involved,
meillo@76: there's hardly any need to check for new mail before incorporating it.
meillo@62: .BU
meillo@58: .Pn msh
meillo@87: was removed
meillo@76: .Ci 916690191222433a6923a4be54b0d8f6ac01bd02
meillo@87: because the tool was in conflict with the philosophy of MH.
meillo@76: It provided an interactive shell to access the features of MH,
meillo@76: but it wasn't just a shell, tailored to the needs of mail handling.
meillo@76: Instead it was one large program that had several MH tools built in.
meillo@76: This conflicts with the major feature of MH of being a tool chest.
meillo@76: .Pn msh 's
meillo@76: main use case had been accessing Bulletin Boards, which have seized to
meillo@62: be popular.
meillo@62: .P
meillo@62: Removing
meillo@58: .Pn msh ,
meillo@76: together with the truly archaic code relicts
meillo@58: .Pn vmh
meillo@58: and
meillo@58: .Pn wmh ,
meillo@62: saved more than 7\|000 lines of C code \(en
meillo@66: about 15\|% of the project's original source code amount.
meillo@100: Having less code \(en with equal readability, of course \(en
meillo@76: for the same functionality is an advantage.
meillo@63: Less code means less bugs and less maintenance work.
meillo@76: As
meillo@63: .Pn rcvtty
meillo@63: and
meillo@63: .Pn msgchk
meillo@87: are assumed to be rarely used and can be implemented in different ways,
meillo@87: why should one keep them?
meillo@125: Removing them streamlines mmh.
meillo@63: .Pn viamail 's
meillo@63: use case is now partly obsolete and partly covered by
meillo@63: .Pn forw ,
meillo@76: hence there's no reason to still maintain it.
meillo@63: .Pn conflict
meillo@76: is not related to the mail client, and
meillo@63: .Pn msh
meillo@63: conflicts with the basic concept of MH.
meillo@76: Theses two tools might still be useful, but they should not be part of mmh.
meillo@63: .P
meillo@76: Finally, there's
meillo@76: .Pn slocal .
meillo@76: .Pn slocal
meillo@76: is an MDA and thus not directly MUA-related.
meillo@100: It should be removed from mmh, because including it conflicts with
meillo@100: the idea that mmh is a MUA only.
meillo@100: .Pn slocal
meillo@100: should rather become a separate project.
meillo@87: However,
meillo@76: .Pn slocal
meillo@76: provides rule-based processing of messages, like filing them into
meillo@76: different folders, which is otherwise not available in mmh.
meillo@87: Although
meillo@76: .Pn slocal
meillo@87: does neither pull in dependencies nor does it include a separate
meillo@100: technical area (cf. Sec. XXX), still,
meillo@100: it accounts for about 1\|000 lines of code that need to be maintained.
meillo@76: As
meillo@76: .Pn slocal
meillo@76: is almost self-standing, it should be split off into a separate project.
meillo@76: This would cut the strong connection between the MUA mmh and the MDA
meillo@76: .Pn slocal .
meillo@87: For anyone not using MH,
meillo@87: .Pn slocal
meillo@87: would become yet another independent MDA, like
meillo@87: .I procmail .
meillo@100: Then
meillo@87: .Pn slocal
meillo@100: could be installed without the complete MH system.
meillo@76: Likewise, mmh users could decide to use
meillo@76: .I procmail
meillo@87: without having a second, unused MDA,
meillo@87: .Pn slocal ,
meillo@76: installed.
meillo@100: That appears to be conceptionally the best solution.
meillo@76: Yet,
meillo@76: .Pn slocal
meillo@87: is not split off.
meillo@100: I defer the decision over
meillo@78: .Pn slocal
meillo@100: in need for deeper investigation.
meillo@100: In the meanwhile, it remains part of mmh.
meillo@100: That does not hurt because
meillo@100: .Pn slocal
meillo@100: is unrelated to the rest of the project.
meillo@0: 
meillo@58: 
meillo@133: 
meillo@134: .H2 "Displaying Messages
meillo@131: .P
meillo@133: Since the very beginning, already in the first concept paper,
meillo@58: .Pn show
meillo@62: had been MH's message display program.
meillo@58: .Pn show
meillo@76: mapped message numbers and sequences to files and invoked
meillo@58: .Pn mhl
meillo@89: to have the files formatted.
meillo@88: With MIME, this approach wasn't sufficient anymore.
meillo@100: MIME messages can consist of multiple parts. Some parts are not
meillo@100: directly displayable and text content might be encoded in
meillo@58: foreign charsets.
meillo@58: .Pn show 's
meillo@76: understanding of messages and
meillo@58: .Pn mhl 's
meillo@88: display capabilities couldn't cope with the task any longer.
meillo@62: .P
meillo@88: Instead of extending these tools, additional tools were written from
meillo@88: scratch and added to the MH tool chest.
meillo@88: Doing so is encouraged by the tool chest approach.
meillo@88: Modular design is a great advantage for extending a system,
meillo@88: as new tools can be added without interfering with existing ones.
meillo@62: First, the new MIME features were added in form of the single program
meillo@58: .Pn mhn .
meillo@58: The command
meillo@82: .Cl "mhn -show 42
meillo@58: would show the MIME message numbered 42.
meillo@58: With the 1.0 release of nmh in February 1999, Richard Coleman finished
meillo@58: the split of
meillo@58: .Pn mhn
meillo@88: into a set of specialized tools, which together covered the
meillo@88: multiple aspects of MIME.
meillo@88: One of them was
meillo@69: .Pn mhshow ,
meillo@88: which replaced
meillo@88: .Cl "mhn -show" .
meillo@88: It was capable of displaying MIME messages appropriately.
meillo@62: .P
meillo@88: From then on, two message display tools were part of nmh,
meillo@76: .Pn show
meillo@76: and
meillo@76: .Pn mhshow .
meillo@88: To ease the life of users,
meillo@69: .Pn show
meillo@69: was extended to automatically hand the job over to
meillo@69: .Pn mhshow
meillo@69: if displaying the message would be beyond
meillo@69: .Pn show 's
meillo@69: abilities.
meillo@88: In consequence, the user would simply invoke
meillo@69: .Pn show
meillo@69: (possibly through
meillo@69: .Pn next
meillo@69: or
meillo@69: .Pn prev )
meillo@69: and get the message printed with either
meillo@69: .Pn show
meillo@69: or
meillo@69: .Pn mhshow ,
meillo@69: whatever was more appropriate.
meillo@69: .P
meillo@69: Having two similar tools for essentially the same task is redundant.
meillo@88: Usually,
meillo@88: users wouldn't distinguish between
meillo@88: .Pn show
meillo@88: and
meillo@88: .Pn mhshow
meillo@88: in their daily mail reading.
meillo@88: Having two separate display programs was therefore mainly unnecessary
meillo@88: from a user's point of view.
meillo@88: Besides, the development of both programs needed to be in sync,
meillo@76: to ensure that the programs behaved in a similar way,
meillo@76: because they were used like a single tool.
meillo@76: Different behavior would have surprised the user.
meillo@69: .P
meillo@69: Today, non-MIME messages are rather seen to be a special case of
meillo@100: MIME messages, although it is the other way round.
meillo@69: As
meillo@69: .Pn mhshow
meillo@88: had already be able to display non-MIME messages, it appeared natural
meillo@69: to drop
meillo@69: .Pn show
meillo@69: in favor of using
meillo@69: .Pn mhshow
meillo@69: exclusively.
meillo@88: .Ci 4c1efddfd499300c7e74263e57d8aa137e84c853
meillo@88: Removing
meillo@88: .Pn show
meillo@88: is no loss in function, because functionally
meillo@88: .Pn mhshow
meillo@88: covers it completely.
meillo@88: The old behavior of
meillo@88: .Pn show
meillo@88: can still be emulated with the simple command line:
meillo@88: .VS
meillo@88: mhl `mhpath c`
meillo@88: VE
meillo@88: .P
meillo@76: For convenience,
meillo@76: .Pn mhshow
meillo@88: was renamed to
meillo@88: .Pn show
meillo@88: after
meillo@88: .Pn show
meillo@88: was gone.
meillo@88: It is clear that such a rename may confuse future developers when
meillo@88: trying to understand the history.
meillo@88: Nevertheless, I consider the convenience on the user's side,
meillo@88: to call
meillo@88: .Pn show
meillo@88: when they want a message to be displayed, to outweigh the inconvenience
meillo@88: on the developer's side when understanding the project history.
meillo@69: .P
meillo@88: To prepare for the transition,
meillo@69: .Pn mhshow
meillo@69: was reworked to behave more like
meillo@69: .Pn show
meillo@69: first.
meillo@88: (cf. Sec. XXX)
meillo@88: Once the tools behaved more alike, the replacing appeared to be
meillo@88: even more natural.
meillo@88: Today, mmh's new
meillo@69: .Pn show
meillo@88: became the one single message display program again, with the difference
meillo@88: that today it handles MIME messages as well as non-MIME messages.
meillo@88: The outcome of the transition is one program less to maintain,
meillo@88: no second display program for users to deal with,
meillo@88: and less system complexity.
meillo@69: .P
meillo@88: Still, removing the old
meillo@69: .Pn show
meillo@88: hurts in one regard: It had been such a simple program.
meillo@88: Its lean elegance is missing to the new
meillo@69: .Pn show .
meillo@88: But there is no chance;
meillo@88: supporting MIME demands for higher essential complexity.
meillo@58: 
meillo@134: .ig
meillo@134: XXX
meillo@134: Consider including text on scan listings here
meillo@58: 
meillo@134: Scan listings shall not contain body content. Hence, removed this feature.
meillo@134: Scan listings shall operator on message headers and non-message information
meillo@134: only. Displaying the beginning of the body complicates everything too much.
meillo@134: That's no surprise, because it's something completely different. If you
meillo@134: want to examine the body, then use show(1)/mhshow(1).
meillo@134: Changed the default scan formats accordingly.
meillo@134: .Ci 70b2643e0da8485174480c644ad9785c84f5bff4
meillo@134: ..
meillo@131: 
meillo@131: 
meillo@131: 
meillo@133: 
meillo@100: .H2 "Configure Options
meillo@58: .P
meillo@76: Customization is a double-edged sword.
meillo@76: It allows better suiting setups, but not for free.
meillo@76: There is the cost of code complexity to be able to customize.
meillo@76: There is the cost of less tested setups, because there are
meillo@72: more possible setups and especially corner-cases.
meillo@76: And, there is the cost of choice itself.
meillo@76: The code complexity directly affects the developers.
meillo@72: Less tested code affects both, users and developers.
meillo@76: The problem of choice affects the users, for once by having to
meillo@100: choose, but also by more complex interfaces that require more documentation.
meillo@72: Whenever options add little advantages, they should be considered for
meillo@72: removal.
meillo@72: I have reduced the number of project-specific configure options from 
meillo@72: fifteen to three.
meillo@74: 
meillo@76: .U3 "Mail Transfer Facilities
meillo@74: .P
meillo@85: With the removal of the mail transfer facilities five configure
meillo@85: options vanished:
meillo@85: .P
meillo@85: The switches
meillo@85: .Sw --with-tls
meillo@85: and
meillo@85: .Sw --with-cyrus-sasl
meillo@89: had activated the support for transfer encryption and authentication.
meillo@85: This is not needed anymore.
meillo@85: .Ci fecd5d34f65597a4dfa16aeabea7d74b191532c3
meillo@85: .Ci 156d35f6425bea4c1ed3c4c79783dc613379c65b
meillo@85: .P
meillo@85: The configure switch
meillo@85: .Sw --enable-pop
meillo@85: activated the message retrieval facility.
meillo@85: The code area that would be conditionally compiled in for TLS and SASL
meillo@85: support had been small.
meillo@85: The conditionally compiled code area for POP support had been much larger.
meillo@85: Whereas the code base changes would only slightly change on toggling
meillo@85: TLS or SASL support, it changed much on toggling POP support.
meillo@85: The changes in the code base could hardly be overviewed.
meillo@85: By having POP support togglable a second code base had been created,
meillo@85: one that needed to be tested.
meillo@85: This situation is basically similar for the conditional TLS and SASL  
meillo@85: code, but there the changes are minor and can yet be overviewed.
meillo@85: Still, conditional compilation of a code base creates variations
meillo@85: of the original program.
meillo@85: More variations require more testing and maintenance work.
meillo@85: .P
meillo@85: Two other options only specified default configuration values:
meillo@100: .Sw --with-mts
meillo@100: defined the default transport service, either
meillo@100: .Ar smtp
meillo@100: or
meillo@100: .Ar sendmail .
meillo@85: In mmh this fixed to
meillo@85: .Ar sendmail .
meillo@85: .Ci f6aa95b724fd8c791164abe7ee5468bf5c34f226
meillo@85: With
meillo@100: .Sw --with-smtpservers
meillo@85: default SMTP servers for the
meillo@85: .Ar smtp
meillo@85: transport service could be specified.
meillo@72: .Ci 128545e06224233b7e91fc4c83f8830252fe16c9
meillo@85: Both of them became irrelevant.
meillo@72: 
meillo@74: .U3 "Backup Prefix
meillo@74: .P
meillo@76: The backup prefix is the string that was prepended to message
meillo@76: filenames to tag them as deleted.
meillo@76: By default it had been the comma character `\f(CW,\fP'.
meillo@78: In July 2000, Kimmo Suominen introduced
meillo@78: the configure option
meillo@78: .Sw --with-hash-backup
meillo@78: to change the default to the hash symbol `\f(CW#\fP'.
meillo@78: The choice was probably personal preference, because first, the
meillo@78: option was named
meillo@78: .Sw --with-backup-prefix.
meillo@78: and had the prefix symbol as argument.
meillo@100: But giving the hash symbol as argument caused too many problems
meillo@100: for Autoconf,
meillo@100: thus the option was limited to use the hash symbol as the default prefix.
meillo@100: This supports the assumption, that the choice for the hash was
meillo@100: personal preference only.
meillo@100: Being related or not, words that start with the hash symbol
meillo@78: introduce a comment in the Unix shell.
meillo@72: Thus, the command line
meillo@72: .Cl "rm #13 #15
meillo@72: calls
meillo@72: .Pn rm
meillo@72: without arguments because the first hash symbol starts the comment
meillo@72: that reaches until the end of the line.
meillo@72: To delete the backup files,
meillo@72: .Cl "rm ./#13 ./#15"
meillo@72: needs to be used.
meillo@100: Using the hash as backup prefix can be seen as a precaution against
meillo@78: data loss.
meillo@78: .P
meillo@72: I removed the configure option but added the profile entry
meillo@72: .Pe backup-prefix ,
meillo@72: which allows to specify an arbitrary string as backup prefix.
meillo@72: .Ci 6c40d481d661d532dd527eaf34cebb6d3f8ed086
meillo@76: Profile entries are the common method to change mmh's behavior.
meillo@76: This change did not remove the choice but moved it to a location where
meillo@72: it suited better.
meillo@76: .P
meillo@78: Eventually, however, the new trash folder concept
meillo@78: .Cf "Sec. XXX
meillo@78: obsoleted the concept of the backup prefix completely.
meillo@78: .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@133: .Ci ca0b3e830b86700d9e5e31b1784de2bdcaf58fc5
meillo@133: 
meillo@76: 
meillo@76: .U3 "Editor and Pager
meillo@74: .P
meillo@74: The two configure options
meillo@74: .CW --with-editor=EDITOR
meillo@74: .CW --with-pager=PAGER
meillo@74: were used to specify the default editor and pager at configure time.
meillo@109: Doing so at configure time made sense in the eighties,
meillo@76: when the set of available editors and pagers varied much across
meillo@76: different systems.
meillo@89: Today, the situation is more homogeneous.
meillo@74: The programs
meillo@74: .Pn vi
meillo@74: and
meillo@74: .Pn more
meillo@76: can be expected to be available on every Unix system,
meillo@74: as they are specified by POSIX since two decades.
meillo@74: (The specifications for
meillo@74: .Pn vi
meillo@74: and
meillo@74: .Pn more
meillo@74: appeared in
meillo@74: .[
meillo@74: posix 1987
meillo@74: .]
meillo@74: and,
meillo@74: .[
meillo@74: posix 1992
meillo@74: .]
meillo@74: respectively.)
meillo@74: As a first step, these two tools were hard-coded as defaults.
meillo@74: .Ci 5d43a99db70c12a673028c7758c20cbe3e13ef5f
meillo@74: Not changed were the
meillo@74: .Pe editor
meillo@74: and
meillo@74: .Pe moreproc
meillo@76: profile entries, which allowed the user to override the system defaults.
meillo@74: Later, the concept was reworked to respect the standard environment
meillo@74: variables
meillo@74: .Ev VISUAL
meillo@74: and
meillo@74: .Ev PAGER
meillo@76: if they are set.
meillo@74: Today, mmh determines the editor to use in the following order,
meillo@74: taking the first available and non-empty item:
meillo@74: .IP (1)
meillo@74: Environment variable
meillo@74: .Ev MMHEDITOR
meillo@74: .IP (2)
meillo@74: Profile entry
meillo@74: .Pe Editor
meillo@74: .IP (3)
meillo@74: Environment variable
meillo@74: .Ev VISUAL
meillo@74: .IP (4)
meillo@74: Environment variable
meillo@74: .Ev EDITOR
meillo@74: .IP (5)
meillo@74: Command
meillo@74: .Pn vi .
meillo@74: .P
meillo@76: .Ci f85f4b7ae62e3d05a945dcd46ead51f0a2a89a9b
meillo@76: .P
meillo@89: The pager to use is determined in a similar order,
meillo@74: also taking the first available and non-empty item:
meillo@74: .IP (1)
meillo@74: Environment variable
meillo@74: .Ev MMHPAGER
meillo@74: .IP (2)
meillo@74: Profile entry
meillo@74: .Pe Pager
meillo@74: (replaces
meillo@74: .Pe moreproc )
meillo@74: .IP (3)
meillo@74: Environment variable
meillo@74: .Ev PAGER
meillo@74: .IP (4)
meillo@74: Command
meillo@74: .Pn more .
meillo@74: .P
meillo@74: .Ci 0c4214ea2aec6497d0d67b436bbee9bc1d225f1e
meillo@74: .P
meillo@76: By respecting the
meillo@74: .Ev VISUAL /\c
meillo@74: .Ev EDITOR
meillo@74: and
meillo@74: .Ev PAGER
meillo@76: environment variables,
meillo@76: the new behavior confirms better to the common style on Unix systems.
meillo@76: Additionally, the new approach is more uniform and clearer to users.
meillo@72: 
meillo@72: 
meillo@76: .U3 "ndbm
meillo@72: .P
meillo@74: .Pn slocal
meillo@78: used to depend on
meillo@74: .I ndbm ,
meillo@74: a database library.
meillo@76: The database is used to store the `\fLMessage-ID\fP's of all
meillo@76: messages delivered.
meillo@74: This enables
meillo@74: .Pn slocal
meillo@74: to suppress delivering the same message to the same user twice.
meillo@74: (This features was enabled by the
meillo@74: .Sw -suppressdup
meillo@74: switch.)
meillo@74: .P
meillo@100: A variety of versions of the database library exist.
meillo@78: .[
meillo@78: wolter unix incompat notes dbm
meillo@78: .]
meillo@74: Complicated autoconf code was needed to detect them correctly.
meillo@74: Further more, the configure switches
meillo@74: .Sw --with-ndbm=ARG
meillo@74: and
meillo@74: .Sw --with-ndbmheader=ARG
meillo@74: were added to help with difficult setups that would
meillo@78: not be detected automatically or correctly.
meillo@74: .P
meillo@74: By removing the suppress duplicates feature of
meillo@74: .Pn slocal ,
meillo@74: the dependency on
meillo@74: .I ndbm
meillo@78: vanished and 120 lines of complex autoconf code could be saved.
meillo@74: .Ci ecd6d6a20cb7a1507e3a20d6c4cb3a1cf14c6bbf
meillo@89: The change removed functionality too, but that is minor to the
meillo@78: improvement by dropping the dependency and the complex autoconf code.
meillo@72: 
meillo@74: .U3 "mh-e Support
meillo@72: .P
meillo@74: The configure option
meillo@74: .Sw --disable-mhe
meillo@74: was removed when the mh-e support was reworked. 
meillo@74: Mh-e is the Emacs front-end to MH.
meillo@76: It requires MH to provide minor additional functions.
meillo@76: The
meillo@76: .Sw --disable-mhe
meillo@76: configure option could switch these extensions off.
meillo@76: After removing the support for old versions of mh-e,
meillo@74: only the
meillo@74: .Sw -build
meillo@76: switches of
meillo@74: .Pn forw
meillo@74: and
meillo@74: .Pn repl
meillo@76: are left to be mh-e extensions.
meillo@76: They are now always built in because they add little code and complexity.
meillo@76: In consequence, the
meillo@74: .Sw --disable-mhe
meillo@76: configure option was removed
meillo@72: .Ci a7ce7b4a580d77b6c2c4d980812beb589aa4c643
meillo@74: Removing the option removed a second code setup that would have
meillo@74: needed to be tested.
meillo@76: This change was first done in nmh and thereafter merged into mmh.
meillo@76: .P
meillo@76: The interface changes in mmh require mh-e to be adjusted in order
meillo@76: to be able to use mmh as back-end.
meillo@76: This will require minor changes to mh-e, but removing the
meillo@76: .Sw -build
meillo@76: switches would require more rework.
meillo@72: 
meillo@74: .U3 "Masquerading
meillo@72: .P
meillo@74: The configure option
meillo@74: .Sw --enable-masquerade
meillo@76: could take up to three arguments:
meillo@76: `draft_from', `mmailid', and `username_extension'.
meillo@74: They activated different types of address masquerading.
meillo@74: All of them were implemented in the SMTP-speaking
meillo@74: .Pn post
meillo@76: command, which provided an MSA.
meillo@76: Address masquerading is an MTA's task and mmh does not cover
meillo@76: this field anymore.
meillo@76: Hence, true masquerading needs to be implemented in the external MTA.
meillo@74: .P
meillo@74: The
meillo@74: .I mmailid
meillo@74: masquerading type is the oldest one of the three and the only one
meillo@74: available in the original MH.
meillo@74: It provided a
meillo@74: .I username
meillo@74: to
meillo@74: .I fakeusername
meillo@76: mapping, based on the password file's GECOS field.
meillo@74: The man page
meillo@74: .Mp mh-tailor(5)
meillo@74: described the use case as being the following:
meillo@98: .QS
meillo@74: This is useful if you want the messages you send to always
meillo@74: appear to come from the name of an MTA alias rather than your
meillo@74: actual account name.  For instance, many organizations set up
meillo@74: `First.Last' sendmail aliases for all users.  If this is
meillo@74: the case, the GECOS field for each user should look like:
meillo@74: ``First [Middle] Last <First.Last>''
meillo@98: .QE
meillo@74: .P
meillo@74: As mmh sends outgoing mail via the local MTA only,
meillo@76: the best location to do such global rewrites is there.
meillo@74: Besides, the MTA is conceptionally the right location because it
meillo@74: does the reverse mapping for incoming mail (aliasing), too.
meillo@76: Further more, masquerading set up there is readily available for all
meillo@74: mail software on the system.
meillo@76: Hence, mmailid masquerading was removed.
meillo@74: .Ci 0836c8000ccb34b59410ef1c15b1b7feac70ce5f
meillo@74: .P
meillo@74: The
meillo@74: .I username_extension
meillo@76: masquerading type did not replace the username but would append a suffix,
meillo@76: specified by the
meillo@74: .Ev USERNAME_EXTENSION
meillo@76: environment variable, to it.
meillo@76: This provided support for the
meillo@74: .I user-extension
meillo@74: feature of qmail and the similar
meillo@74: .I "plussed user
meillo@74: processing of sendmail.
meillo@74: The decision to remove this username_extension masquerading was
meillo@74: motivated by the fact that
meillo@74: .Pn spost
meillo@76: hadn't supported it already.
meillo@76: .Ci 2abae0bfd0ad5bf898461e50aa4b466d641f23d9
meillo@76: Username extensions are possible in mmh, but less convenient to use.
meillo@76: .\" XXX format file %(getenv USERNAME_EXTENSION)
meillo@74: .P
meillo@74: The
meillo@74: .I draft_from
meillo@74: masquerading type instructed
meillo@74: .Pn post
meillo@84: to use the value of the
meillo@84: .Hd From
meillo@84: header field as SMTP envelope sender.
meillo@76: Sender addresses could be replaced completely.
meillo@74: .Ci b14ea6073f77b4359aaf3fddd0e105989db9
meillo@76: Mmh offers a kind of masquerading similar in effect, but
meillo@74: with technical differences.
meillo@76: As mmh does not transfer messages itself, the local MTA has final control
meillo@76: over the sender's address. Any masquerading mmh introduces may be reverted
meillo@76: by the MTA.
meillo@76: In times of pedantic spam checking, an MTA will take care to use
meillo@76: sensible envelope sender addresses to keep its own reputation up.
meillo@84: Nonetheless, the MUA can set the
meillo@84: .Hd From
meillo@84: header field and thereby propose
meillo@76: a sender address to the MTA.
meillo@74: The MTA may then decide to take that one or generate the canonical sender
meillo@74: address for use as envelope sender address.
meillo@74: .P
meillo@74: In mmh, the MTA will always extract the recipient and sender from the
meillo@84: message header (\c
meillo@74: .Pn sendmail 's
meillo@74: .Sw -t
meillo@74: switch).
meillo@84: The
meillo@84: .Hd From
meillo@84: header field of the draft may be set arbitrary by the user.
meillo@74: If it is missing, the canonical sender address will be generated by the MTA.
meillo@74: 
meillo@74: .U3 "Remaining Options
meillo@74: .P
meillo@74: Two configure options remain in mmh.
meillo@74: One is the locking method to use:
meillo@74: .Sw --with-locking=[dot|fcntl|flock|lockf] .
meillo@76: The idea of removing all methods except the portable dot locking
meillo@76: and having that one as the default is appealing, but this change
meillo@76: requires deeper technical investigation into the topic.
meillo@76: The other option,
meillo@74: .Sw --enable-debug ,
meillo@74: compiles the programs with debugging symbols and does not strip them.
meillo@74: This option is likely to stay.
meillo@72: 
meillo@72: 
meillo@58: 
meillo@63: 
meillo@100: .H2 "Command Line Switches
meillo@58: .P
meillo@93: The command line switches of MH tools follow the X Window style.
meillo@93: They are words, introduced by a single dash.
meillo@93: For example:
meillo@93: .Cl "-truncate" .
meillo@93: Every program in mmh has two generic switches:
meillo@93: .Sw -help ,
meillo@93: to print a short message on how to use the program, and 
meillo@93: .Sw -Version ,
meillo@93: to tell what version of mmh the program belongs to.
meillo@93: .P
meillo@93: Switches change the behavior of programs.
meillo@93: Programs that do one thing in one way require no switches.
meillo@93: In most cases, doing something in exactly one way is too limiting.
meillo@97: If there is basically one task to accomplish, but it should be done
meillo@93: in various ways, switches are a good approach to alter the behavior
meillo@93: of a program.
meillo@93: Changing the behavior of programs provides flexibility and customization
meillo@97: to users, but at the same time it complicates the code, documentation and
meillo@93: usage of the program.
meillo@97: .\" XXX: Ref
meillo@93: Therefore, the number of switches should be kept small.
meillo@93: A small set of well-chosen switches does no harm.
meillo@93: But usually, the number of switches increases over time.
meillo@93: Already in 1985, Rose and Romine have identified this as a major
meillo@93: problem of MH:
meillo@93: .[ [
meillo@93: rose romine real work
meillo@93: .], p. 12]
meillo@98: .QS
meillo@93: A complaint often heard about systems which undergo substantial development
meillo@93: by many people over a number of years, is that more and more options are
meillo@93: introduced which add little to the functionality but greatly increase the
meillo@93: amount of information a user needs to know in order to get useful work done.
meillo@93: This is usually referred to as creeping featurism.
meillo@93: .QP
meillo@93: Unfortunately MH, having undergone six years of off-and-on development by
meillo@93: ten or so well-meaning programmers (the present authors included),
meillo@93: suffers mightily from this.
meillo@98: .QE
meillo@93: .P
meillo@97: Being reluctant to adding new switches \(en or `options',
meillo@97: as Rose and Romine call them \(en is one part of a counter-action,
meillo@97: the other part is removing hardly used switches.
meillo@97: Nmh's tools had lots of switches already implemented,
meillo@97: hence, cleaning up by removing some of them was the more important part
meillo@97: of the counter-action.
meillo@93: Removing existing functionality is always difficult because it
meillo@93: breaks programs that use these functions.
meillo@93: Also, for every obsolete feature, there'll always be someone who still
meillo@93: uses it and thus opposes its removal.
meillo@93: This puts the developer into the position,
meillo@93: where sensible improvements to style are regarded as destructive acts.
meillo@97: Yet, living with the featurism is far worse, in my eyes, because
meillo@97: future needs will demand adding further features,
meillo@93: worsening the situation more and more.
meillo@93: Rose and Romine added in a footnote,
meillo@93: ``[...]
meillo@93: .Pn send
meillo@93: will no doubt acquire an endless number of switches in the years to come.''
meillo@97: Although clearly humorous, the comment points to the nature of the problem.
meillo@97: Refusing to add any new switches would encounter the problem at its root,
meillo@97: but this is not practical.
meillo@97: New needs will require new switches and it would be unwise to block
meillo@97: them strictly.
meillo@97: Nevertheless, removing obsolete switches still is an effective approach
meillo@97: to deal with the problem.
meillo@97: Working on an experimental branch without an established user base,
meillo@97: eased my work because I did not offend users when I removed existing
meillo@110: functions.
meillo@93: .P
meillo@93: Rose and Romine counted 24 visible and 9 more hidden switches for
meillo@93: .Pn send .
meillo@97: In nmh, they increased up to 32 visible and 12 hidden ones.
meillo@97: At the time of writing, no more than 7 visible switches and 1 hidden switch
meillo@97: have remained in mmh's
meillo@97: .Pn send .
meillo@97: (These numbers include two generic switches, help and version.)
meillo@93: .P
meillo@97: Fig. XXX
meillo@93: .\" XXX Ref
meillo@97: displays the number of switches for each of the tools that is available
meillo@97: in both, nmh and mmh.
meillo@100: The tools are sorted by the number of switches they had in nmh.
meillo@100: Visible and hidden switches were counted,
meillo@97: but not the generic help and version switches.
meillo@93: Whereas in the beginning of the project, the average tool had 11 switches,
meillo@93: now it has no more than 5 \(en only half as many.
meillo@93: If the `no' switches and similar inverse variant are folded onto
meillo@100: their counter-parts, the average tool had 8 switches in pre-mmh times and
meillo@100: has 4 now.
meillo@93: The total number of functional switches in mmh dropped from 465
meillo@93: to 234.
meillo@58: 
meillo@93: .KS
meillo@93: .in 1c
meillo@93: .so input/switches.grap
meillo@93: .KE
meillo@58: 
meillo@93: .P
meillo@93: A part of the switches vanished after functions were removed.
meillo@93: This was the case for network mail transfer, for instance.
meillo@97: Sometimes, however, the work flow was the other way:
meillo@97: I looked through the
meillo@97: .Mp mh-chart (7)
meillo@97: man page to identify the tools with apparently too many switches.
meillo@97: Then considering the value of each of the switches by examining
meillo@97: the tool's man page and source code, aided by recherche and testing.
meillo@97: This way, the removal of functions was suggested by the aim to reduce
meillo@97: the number of switches per command.
meillo@97: 
meillo@58: 
meillo@93: .U3 "Draft Folder Facility
meillo@93: .P
meillo@100: A change early in the project was the complete transition from
meillo@93: the single draft message to the draft folder facility.
meillo@97: .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@109: The draft folder facility was introduced in the mid-eighties, when
meillo@100: Rose and Romine called it a ``relatively new feature''.
meillo@93: .[
meillo@93: rose romine real work
meillo@93: .]
meillo@110: Since then, the facility had existed but was inactive by default.
meillo@93: The default activation and the related rework of the tools made it
meillo@93: possible to remove the
meillo@93: .Sw -[no]draftfolder ,
meillo@93: and
meillo@93: .Sw -draftmessage
meillo@93: switches from
meillo@93: .Pn comp ,
meillo@93: .Pn repl ,
meillo@93: .Pn forw ,
meillo@93: .Pn dist ,
meillo@93: .Pn whatnow ,
meillo@93: and
meillo@93: .Pn send .
meillo@97: .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@97: The only flexibility removed with this change is having multiple
meillo@97: draft folders within one profile.
meillo@97: I consider this a theoretical problem only.
meillo@93: In the same go, the
meillo@93: .Sw -draft
meillo@93: switch of
meillo@93: .Pn anno ,
meillo@93: .Pn refile ,
meillo@93: and
meillo@93: .Pn send
meillo@93: was removed.
meillo@93: The special-casing of `the' draft message became irrelevant after
meillo@93: the rework of the draft system.
meillo@93: (See Sec. XXX.)
meillo@95: Equally,
meillo@95: .Pn comp
meillo@95: lost its
meillo@95: .Sw -file
meillo@95: switch.
meillo@95: The draft folder facility, together with the
meillo@95: .Sw -form
meillo@95: switch, are sufficient.
meillo@93: 
meillo@95: 
meillo@102: .U3 "In Place Editing
meillo@93: .P
meillo@93: .Pn anno
meillo@93: had the switches
meillo@93: .Sw -[no]inplace
meillo@100: to either annotate the message in place and thus preserve hard links,
meillo@93: or annotate a copy to replace the original message, breaking hard links.
meillo@97: Following the assumption that linked messages should truly be the
meillo@97: same message, and annotating it should not break the link, the
meillo@93: .Sw -[no]inplace
meillo@93: switches were removed and the previous default
meillo@93: .Sw -inplace
meillo@93: was made the only behavior.
meillo@97: .Ci c8195849d2e366c569271abb0f5f60f4ebf0b4d0
meillo@93: The
meillo@93: .Sw -[no]inplace
meillo@93: switches of
meillo@93: .Pn repl ,
meillo@93: .Pn forw ,
meillo@93: and
meillo@93: .Pn dist
meillo@93: could be removed, too, as they were simply passed through to
meillo@93: .Pn anno .
meillo@93: .P
meillo@93: .Pn burst
meillo@93: also had
meillo@93: .Sw -[no]inplace
meillo@95: switches, but with different meaning.
meillo@95: With
meillo@95: .Sw -inplace ,
meillo@95: the digest had been replaced by the table of contents (i.e. the
meillo@110: introduction text) and the burst messages were placed right
meillo@95: after this message, renumbering all following messages.
meillo@95: Also, any trailing text of the digest was lost, though,
meillo@95: in practice, it usually consists of an end-of-digest marker only.
meillo@95: Nontheless, this behavior appeared less elegant than the
meillo@95: .Sw -noinplace
meillo@95: behavior, which already had been the default.
meillo@95: Nmh's
meillo@95: .Mp burst (1)
meillo@95: man page reads:
meillo@95: .sp \n(PDu
meillo@98: .QS
meillo@93: If -noinplace is given, each digest is preserved, no table
meillo@93: of contents is produced, and the messages contained within
meillo@93: the digest are placed at the end of the folder. Other messages
meillo@93: are not tampered with in any way.
meillo@98: .QE
meillo@95: .LP
meillo@93: The decision to drop the
meillo@93: .Sw -inplace
meillo@95: behavior was supported by the code complexity and the possible data loss
meillo@95: it caused.
meillo@93: .Sw -noinplace
meillo@95: was chosen to be the definitive behavior.
meillo@97: .Ci 68a686adeb39223a5e1ad35e4a24890ec053679d
meillo@93: 
meillo@95: 
meillo@95: .U3 "Forms and Format Strings
meillo@93: .P
meillo@95: Historically, the tools that had
meillo@95: .Sw -form
meillo@95: switches to supply a form file had
meillo@95: .Sw -format
meillo@95: switches as well to supply the contents of a form file as a string
meillo@95: on the command line directly.
meillo@95: In consequence, the following two lines equaled:
meillo@95: .VS
meillo@95: scan -form scan.mailx
meillo@95: scan -format "`cat .../scan.mailx`"
meillo@95: VE
meillo@95: The
meillo@95: .Sw -format
meillo@95: switches were dropped in favor for extending the
meillo@95: .Sw -form
meillo@95: switches.
meillo@97: .Ci f51956be123db66b00138f80464d06f030dbb88d
meillo@95: If their argument starts with an equal sign (`='),
meillo@95: then the rest of the argument is taken as a format string,
meillo@95: otherwise the arguments is treated as the name of a format file.
meillo@95: Thus, now the following two lines equal:
meillo@95: .VS
meillo@95: scan -form scan.mailx
meillo@95: scan -form "=`cat .../scan.mailx`"
meillo@95: VE
meillo@95: This rework removed the prefix collision between
meillo@95: .Sw -form
meillo@95: and
meillo@95: .Sw -format .
meillo@95: Now, typing
meillo@95: .Sw -fo
meillo@95: suffices to specify form or format string.
meillo@95: .P
meillo@95: The different meaning of
meillo@95: .Sw -format
meillo@95: for
meillo@95: .Pn repl
meillo@95: and
meillo@95: .Pn forw
meillo@95: was removed in mmh.
meillo@95: .Pn forw
meillo@95: was completely switched to MIME-type forwarding, thus removing the
meillo@95: .Sw -[no]format .
meillo@97: .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@95: For
meillo@95: .Pn repl ,
meillo@95: the
meillo@95: .Sw -[no]format
meillo@95: switches were reworked to
meillo@95: .Sw -[no]filter
meillo@95: switches.
meillo@97: .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@95: The
meillo@95: .Sw -format
meillo@95: switches of
meillo@95: .Pn send
meillo@95: and
meillo@95: .Pn post ,
meillo@95: which had a third meaning,
meillo@95: were removed likewise.
meillo@97: .Ci f3cb7cde0e6f10451b6848678d95860d512224b9
meillo@95: Eventually, the ambiguity of the
meillo@95: .Sw -format
meillo@95: switches was resolved by not anymore having any such switch in mmh.
meillo@95: 
meillo@95: 
meillo@95: .U3 "MIME Tools
meillo@95: .P
meillo@95: The MIME tools, which were once part of
meillo@100: .Pn mhn
meillo@100: [sic!],
meillo@95: had several switches that added little practical value to the programs.
meillo@95: The
meillo@95: .Sw -[no]realsize
meillo@95: switches of
meillo@95: .Pn mhbuild
meillo@95: and
meillo@95: .Pn mhlist
meillo@97: were removed, doing real size calculations always now
meillo@97: .Ci 8d8f1c3abc586c005c904e52c4adbfe694d2201c ,
meillo@97: as
meillo@95: ``This provides an accurate count at the expense of a small delay.''
meillo@95: This small delay is not noticable on modern systems.
meillo@95: .P
meillo@95: The
meillo@95: .Sw -[no]check
meillo@95: switches were removed together with the support for
meillo@95: .Hd Content-MD5
meillo@95: header fields.
meillo@95: .[
meillo@95: rfc 1864
meillo@95: .]
meillo@97: .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@95: (See Sec. XXX)
meillo@95: .P
meillo@95: The
meillo@95: .Sw -[no]ebcdicsafe
meillo@95: and
meillo@95: .Sw -[no]rfc934mode
meillo@95: switches of
meillo@95: .Pn mhbuild
meillo@95: were removed because they are considered obsolete.
meillo@97: .Ci 01a3480928da485b4d6109d36d751dfa71799d58
meillo@97: .Ci 3363e2624dce0eb8164cf8b3f1ab385c8ff72e88
meillo@95: .P
meillo@95: Content caching of external MIME parts, activated with the
meillo@95: .Sw -rcache
meillo@95: and
meillo@95: .Sw -wcache
meillo@95: switches was completely removed.
meillo@97: .Ci d1fefd9f614e4dc3cda16da6c69133c1b2005269
meillo@97: External MIME parts are rare today, having a caching facility
meillo@96: for them is appears to be unnecessary.
meillo@95: .P
meillo@95: In pre-MIME times,
meillo@95: .Pn mhl
meillo@95: had covered many tasks that are part of MIME handling today.
meillo@95: Therefore,
meillo@95: .Pn mhl
meillo@95: could be simplified to a large extend, reducing the number of its
meillo@95: switches from 21 to 6.
meillo@97: .Ci 350ad6d3542a07639213cf2a4fe524e829c1e7b6
meillo@97: .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@95: 
meillo@95: 
meillo@95: .U3 "Mail Transfer Switches
meillo@95: .P
meillo@95: With the removal of the mail transfer facilities, a lot of switches
meillo@95: vanished automatically.
meillo@95: .Pn inc
meillo@95: lost 9 switches, namely
meillo@95: .Sw -host ,
meillo@95: .Sw -port ,
meillo@95: .Sw -user ,
meillo@95: .Sw -proxy ,
meillo@95: .Sw -snoop ,
meillo@95: .Sw -[no]pack ,
meillo@95: as well as
meillo@95: .Sw -sasl
meillo@95: and
meillo@95: .Sw -saslmech .
meillo@95: .Pn send
meillo@95: and
meillo@95: .Pn post 
meillo@95: lost 11 switches each, namely
meillo@95: .Sw -server ,
meillo@95: .Sw -port ,
meillo@95: .Sw -client ,
meillo@95: .Sw -user ,
meillo@95: .Sw -mail ,
meillo@95: .Sw -saml ,
meillo@95: .Sw -send ,
meillo@95: .Sw -soml ,
meillo@95: .Sw -snoop ,
meillo@95: as well as
meillo@95: .Sw -sasl ,
meillo@95: .Sw -saslmech ,
meillo@95: and
meillo@95: .Sw -tls .
meillo@95: .Pn send
meillo@95: had the switches only to pass them further to
meillo@95: .Pn post ,
meillo@95: because the user would invoke
meillo@95: .Pn post
meillo@95: not directly, but through
meillo@95: .Pn send .
meillo@95: All these switches, except
meillo@95: .Sw -snoop
meillo@95: were usually defined as default switches in the user's profile,
meillo@95: but hardly given in interactive usage.
meillo@95: .P
meillo@95: Of course, those switches did not really ``vanish'', but the configuration
meillo@95: they did was handed over to external MSAs and MRAs.
meillo@95: Instead of setting up the mail transfer in mmh, it is set up in
meillo@95: external tools.
meillo@95: Yet, this simplifies mmh.
meillo@95: Specialized external tools will likely have simple configuration files.
meillo@95: Hence, instead of having one complicated central configuration file,
meillo@95: the configuration of each domain is separate.
meillo@95: Although the user needs to learn to configure each of the tools,
meillo@95: each configuration is likely much simpler.
meillo@95: 
meillo@95: 
meillo@95: .U3 "Maildrop Formats
meillo@95: .P
meillo@95: With the removal of MMDF maildrop format support,
meillo@95: .Pn packf
meillo@95: and
meillo@95: .Pn rcvpack
meillo@95: no longer needed their
meillo@95: .Sw -mbox
meillo@95: and
meillo@95: .Sw -mmdf
meillo@95: switches.
meillo@95: .Sw -mbox
meillo@95: is the sole  behavior now.
meillo@97: .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@95: In the same go,
meillo@95: .Pn packf
meillo@97: and
meillo@97: .Pn rcvpack
meillo@97: were reworked (see Sec. XXX) and their
meillo@95: .Sw -file
meillo@95: switch became unnecessary.
meillo@97: .Ci ca1023716d4c2ab890696f3e41fa0d94267a940e
meillo@95: 
meillo@95: 
meillo@95: .U3 "Terminal Magic
meillo@95: .P
meillo@95: Mmh's tools will no longer clear the screen (\c
meillo@95: .Pn scan 's
meillo@95: and
meillo@95: .Pn mhl 's
meillo@95: .Sw -[no]clear
meillo@97: switches
meillo@97: .Ci e57b17343dcb3ff373ef4dd089fbe778f0c7c270
meillo@97: .Ci 943765e7ac5693ae177fd8d2b5a2440e53ce816e ).
meillo@95: Neither will
meillo@95: .Pn mhl
meillo@95: ring the bell (\c
meillo@97: .Sw -[no]bell
meillo@97: .Ci e11983f44e59d8de236affa5b0d0d3067c192e24 )
meillo@95: nor page the output itself (\c
meillo@97: .Sw -length
meillo@97: .Ci 5b9d883db0318ed2b84bb82dee880d7381f99188 ).
meillo@95: .P
meillo@95: Generally, the pager to use is no longer specified with the
meillo@95: .Sw -[no]moreproc
meillo@95: command line switches for
meillo@95: .Pn mhl
meillo@95: and
meillo@95: .Pn show /\c
meillo@95: .Pn mhshow .
meillo@97: .Ci 39e87a75b5c2d3572ec72e717720b44af291e88a
meillo@95: .P
meillo@95: .Pn prompter
meillo@95: lost its
meillo@95: .Sw -erase
meillo@95: and
meillo@95: .Sw -kill
meillo@95: switches because today the terminal cares for the line editing keys.
meillo@95: 
meillo@95: 
meillo@95: .U3 "Header Printing
meillo@95: .P
meillo@95: .Pn folder 's
meillo@95: data output is self-explaining enough that
meillo@95: displaying the header line makes few sense.
meillo@95: Hence, the
meillo@95: .Sw -[no]header
meillo@95: switch was removed and headers are never printed.
meillo@97: .Ci 601cc73d1fa05ce96faa728f036d6c51b91701c7
meillo@95: .P
meillo@95: In
meillo@95: .Pn mhlist ,
meillo@95: the
meillo@95: .Sw -[no]header
meillo@95: switches were removed, too.
meillo@97: .Ci b24f96523aaf60e44e04a3ffb1d22e69a13a602f
meillo@95: But in this case headers are always printed,
meillo@95: because the output is not self-explaining.
meillo@95: .P
meillo@95: .Pn scan
meillo@95: also had
meillo@95: .Sw -[no]header
meillo@95: switches.
meillo@95: Printing the header had been sensible until the introduction of
meillo@95: format strings made it impossible to display the column headings.
meillo@95: Only the folder name and the current date remained to be printed.
meillo@95: As this information can be perfectly retrieved by
meillo@95: .Pn folder
meillo@95: and
meillo@95: .Pn date ,
meillo@95: consequently, the switches were removed.
meillo@97: .Ci c477dc5d1d03fa6d9a8ab3dd3508c63cbddc044e
meillo@95: .P
meillo@95: By removing all
meillo@95: .Sw -header
meillo@95: switches, the collision with
meillo@95: .Sw -help
meillo@95: on the first two letters was resolved.
meillo@95: Currently,
meillo@95: .Sw -h
meillo@95: evaluates to
meillo@95: .Sw -help
meillo@95: for all tools of mmh.
meillo@95: 
meillo@95: 
meillo@95: .U3 "Suppressing Edits or the WhatNow Shell
meillo@95: .P
meillo@95: The
meillo@95: .Sw -noedit
meillo@100: switch of
meillo@95: .Pn comp ,
meillo@95: .Pn repl ,
meillo@95: .Pn forw ,
meillo@95: .Pn dist ,
meillo@95: and
meillo@95: .Pn whatnow
meillo@95: was removed, but it can now be replaced by specifying
meillo@95: .Sw -editor
meillo@95: with an empty argument.
meillo@97: .Ci 75fca31a5b9d5c1a99c74ab14c94438d8852fba9
meillo@95: (Specifying
meillo@95: .Cl "-editor true
meillo@95: is nearly the same, only differing by the previous editor being set.)
meillo@95: .P
meillo@95: The more important change is the removal of the
meillo@95: .Sw -nowhatnowproc
meillo@95: switch.
meillo@97: .Ci ee4f43cf2ef0084ec698e4e87159a94c01940622
meillo@95: This switch had introduced an awkward behavior, as explained in nmh's
meillo@95: man page for
meillo@95: .Mp comp (1):
meillo@98: .QS
meillo@98: The \-editor editor switch indicates the editor to use for
meillo@98: the initial edit. Upon exiting from the editor, comp will
meillo@98: invoke the whatnow program. See whatnow(1) for a discussion
meillo@98: of available options. The invocation of this program can be
meillo@98: inhibited by using the \-nowhatnowproc switch. (In truth of
meillo@98: fact, it is the whatnow program which starts the initial
meillo@98: edit. Hence, \-nowhatnowproc will prevent any edit from
meillo@95: occurring.)
meillo@98: .QE
meillo@95: .P
meillo@95: Effectively, the
meillo@95: .Sw -nowhatnowproc
meillo@100: switch creates only a draft message.
meillo@95: As
meillo@95: .Cl "-whatnowproc true
meillo@95: causes the same behavior, the
meillo@95: .Sw -nowhatnowproc
meillo@95: switch was removed for being redundant.
meillo@100: Likely, the
meillo@95: .Sw -nowhatnowproc
meillo@100: switch was intended to be used by front-ends.
meillo@95: 
meillo@95: 
meillo@95: .U3 "Compatibility Switches
meillo@95: .BU
meillo@95: The hidden
meillo@95: .Sw -[no]total
meillo@95: switches of
meillo@95: .Pn flist .
meillo@95: They were simply the inverse of the visible
meillo@95: .Sw -[no]fast
meillo@95: switches:
meillo@95: .Sw -total
meillo@95: was
meillo@95: .Sw -nofast
meillo@95: and
meillo@95: .Sw -nototal
meillo@95: was
meillo@95: .Sw -fast .
meillo@95: I removed the
meillo@95: .Sw -[no]total
meillo@95: legacy.
meillo@97: .Ci ea21fe2c4bd23c639bef251398fae809875732ec
meillo@95: .BU
meillo@95: The
meillo@95: .Sw -subject
meillo@95: switch of
meillo@95: .Pn sortm
meillo@95: existed for compatibility only.
meillo@95: It can be fully replaced by
meillo@95: .Cl "-textfield subject
meillo@95: thus it was removed.
meillo@97: .Ci 00140a3c86e9def69d98ba2ffd4d6e50ef6326ea
meillo@95: 
meillo@95: 
meillo@95: .U3 "Various
meillo@95: .BU
meillo@96: In order to avoid prefix collisions among switch names, the
meillo@95: .Sw -version
meillo@95: switch was renamed to
meillo@95: .Sw -Version
meillo@95: (with capital `V').
meillo@97: .Ci 32b2354dbaf4bf934936eb5b102a4a3d2fdd209a
meillo@95: Every program has the
meillo@95: .Sw -version
meillo@95: switch but its first three letters collided with the
meillo@95: .Sw -verbose
meillo@95: switch, present in many programs.
meillo@95: The rename solved this problem once for all.
meillo@95: Although this rename breaks a basic interface, having the
meillo@95: .Sw -V
meillo@95: abbreviation to display the version information, isn't all too bad.
meillo@95: .BU
meillo@95: .Sw -[no]preserve
meillo@95: of
meillo@95: .Pn refile
meillo@95: was removed because what use was it anyway?
meillo@98: .QS
meillo@95: Normally when a message is refiled, for each destination
meillo@95: folder it is assigned the number which is one above the current
meillo@95: highest message number in that folder. Use of the
meillo@95: \-preserv [sic!] switch will override this message renaming, and try
meillo@95: to preserve the number of the message. If a conflict for a
meillo@95: particular folder occurs when using the \-preserve switch,
meillo@95: then refile will use the next available message number which
meillo@95: is above the message number you wish to preserve.
meillo@98: .QE
meillo@95: .BU
meillo@95: The removal of the
meillo@95: .Sw -[no]reverse
meillo@95: switches of
meillo@95: .Pn scan
meillo@97: .Ci 8edc5aaf86f9f77124664f6801bc6c6cdf258173
meillo@95: is a bug fix, supported by the comments
meillo@95: ``\-[no]reverse under #ifdef BERK (I really HATE this)''
meillo@95: by Rose and
meillo@95: ``Lists messages in reverse order with the `\-reverse' switch.
meillo@95: This should be considered a bug.'' by Romine in the documentation.
meillo@97: The question remains why neither Rose and Romine had fixed this
meillo@109: bug in the eighties when they wrote these comments nor has anyone
meillo@95: thereafter.
meillo@93: 
meillo@93: 
meillo@93: .ig
meillo@93: 
meillo@95: forw: [no]dashstuffing(mhl)
meillo@93: 
meillo@95: mhshow: [no]pause [no]serialonly
meillo@93: 
meillo@93: mhmail: resent queued
meillo@93: inc: snoop, (pop)
meillo@93: 
meillo@95: mhl: [no]faceproc folder sleep
meillo@95: 	[no]dashstuffing(forw) digest list volume number issue number
meillo@93: 
meillo@95: prompter: [no]doteof
meillo@93: 
meillo@93: refile: [no]preserve [no]unlink [no]rmmproc
meillo@93: 
meillo@95: send: [no]forward [no]mime [no]msgid
meillo@93: 	[no]push split [no]unique (sasl) width snoop [no]dashstuffing
meillo@93: 	attach attachformat
meillo@93: whatnow: (noedit) attach
meillo@93: 
meillo@93: slocal: [no]suppressdups
meillo@93: 
meillo@95: spost: [no]filter [no]backup width [no]push idanno
meillo@93: 	[no]check(whom) whom(whom)
meillo@93: 
meillo@93: whom: ???
meillo@93: 
meillo@95: ..
meillo@93: 
meillo@93: 
meillo@93: .ig
meillo@93: 
meillo@93: .P
meillo@93: In the best case, all switches are unambiguous on the first character,
meillo@93: or on the three-letter prefix for the `no' variants.
meillo@96: Reducing switch prefix collisions, shortens the necessary prefix length
meillo@93: the user must type.
meillo@93: Having less switches helps best.
meillo@93: 
meillo@93: ..
meillo@58: 
meillo@95: 
meillo@102: .\" XXX: whatnow prompt commands
meillo@102: 
meillo@102: 
meillo@95: 
meillo@95: 
meillo@133: .\" --------------------------------------------------------------
meillo@74: .H1 "Modernizing
meillo@102: .P
meillo@118: In the over thirty years of MH's existence, its code base was
meillo@118: extended more and more.
meillo@118: New features entered the project and became alternatives to the
meillo@118: existing behavior.
meillo@118: Relicts from several decades have gathered in the code base,
meillo@118: but seldom obsolete features were dropped.
meillo@118: This section describes the removing of old code
meillo@118: and the modernizing of the default setup.
meillo@118: It focuses on the functional aspect only;
meillo@118: the non-functional aspects of code style are discussed in
meillo@118: .\" FIXME REF
meillo@118: Sec. XXX.
meillo@58: 
meillo@58: 
meillo@100: .H2 "Code Relicts
meillo@0: .P
meillo@109: My position to drop obsolete functions of mmh, in order to remove old code,
meillo@104: is much more revolutional than the nmh community likes to have it.
meillo@104: Working on an experimental version, I was able to quickly drop
meillo@104: functionality I considered ancient.
meillo@104: The need for consensus with peers would have slowed this process down.
meillo@104: Without the need to justify my decisions, I was able to rush forward.
meillo@110: In December 2011, Paul Vixie motivated the nmh developers to just
meillo@104: do the work:
meillo@104: .[
meillo@104: paul vixie edginess nmh-workers
meillo@104: .]
meillo@104: .QS
meillo@104: let's stop walking on egg shells with this code base. there's no need to
meillo@104: discuss whether to keep using vfork, just note in [sic!] passing, [...]
meillo@104: we don't need a separate branch for removing vmh
meillo@104: or ridding ourselves of #ifdef's or removing posix replacement functions
meillo@104: or depending on pure ansi/posix "libc".
meillo@104: .QP
meillo@104: these things should each be a day or two of work and the "main branch"
meillo@104: should just be modern. [...]
meillo@104: let's push forward, aggressively.
meillo@104: .QE
meillo@104: .LP
meillo@104: I did so already in the months before.
meillo@104: I pushed forward.
meillo@104: I simply dropped the cruft.
meillo@104: .P
meillo@104: The decision to drop a feature was based on literature research and
meillo@104: careful thinking, but whether having had contact to this particular
meillo@104: feature within my own computer life served as a rule of thumb.
meillo@109: Always, I explained my reasons in the commit messages
meillo@109: in the version control system.
meillo@104: Hence, others can comprehend my view and argue for undoing the change
meillo@104: if I have missed an important aspect.
meillo@109: I was quick in dropping parts.
meillo@109: I rather re-included falsely dropped parts than going a slower pace.
meillo@109: Mmh is experimental work; it required tough decisions.
meillo@12: 
meillo@102: 
meillo@104: .U3 "Forking
meillo@12: .P
meillo@109: Being a tool chest, MH creates many processes.
meillo@104: In earlier times
meillo@104: .Fu fork()
meillo@104: had been an expensive system call, because the process's image needed
meillo@104: to be duplicated completely at once.
meillo@109: This was especially painful in the common case when the image gets
meillo@104: replaced by a call to
meillo@104: .Fu exec()
meillo@104: right after having forked the child process.
meillo@104: The
meillo@104: .Fu vfork()
meillo@104: system call was invented to speed up this particular case.
meillo@104: It completely omits the duplication of the image.
meillo@104: On old systems this resulted in significant speed ups.
meillo@104: Therefore MH used
meillo@104: .Fu vfork()
meillo@104: whenever possible.
meillo@12: .P
meillo@104: Modern memory management units support copy-on-write semantics, which make
meillo@104: .Fu fork()
meillo@104: almost as fast as
meillo@104: .Fu vfork() .
meillo@104: The man page of
meillo@104: .Mp vfork (2)
meillo@104: in FreeBSD 8.0 states:
meillo@104: .QS
meillo@104: This system call will be eliminated when proper system sharing mechanisms
meillo@104: are implemented. Users should not depend on the memory sharing semantics
meillo@104: of vfork() as it will, in that case, be made synonymous to fork(2).
meillo@104: .QE
meillo@104: .LP
meillo@104: Vixie supports the removal with the note that ``the last
meillo@104: system on which fork was so slow that an mh user would notice it, was
meillo@104: Eunice. that was 1987''.
meillo@104: .[
meillo@104: nmh-workers vixie edginess
meillo@104: .]
meillo@104: I replaced all calls to
meillo@104: .Fu vfork()
meillo@104: with calls to
meillo@104: .Fu fork() .
meillo@109: .Ci 40821f5c1316e9205a08375e7075909cc9968e7d
meillo@104: .P
meillo@104: Related to the costs of
meillo@104: .Fu fork()
meillo@104: is the probability of its success.
meillo@109: In the eighties, on heavy loaded systems, calls to
meillo@104: .Fu fork()
meillo@104: were prone to failure.
meillo@104: Hence, many of the
meillo@104: .Fu fork()
meillo@104: calls in the code were wrapped into loops to retry the
meillo@104: .Fu fork()
meillo@109: several times, to increase the changes to succeed, eventually.
meillo@109: On modern systems, a failing
meillo@104: .Fu fork()
meillo@109: call is unusual.
meillo@104: Hence, in the rare case when
meillo@104: .Fu fork()
meillo@104: fails, mmh programs simply abort.
meillo@109: .Ci 5fbf37ee68e018998ada61eeab73e035b26834b6
meillo@12: 
meillo@12: 
meillo@109: .U3 "Header Fields
meillo@104: .BU
meillo@84: The
meillo@84: .Hd Encrypted
meillo@104: header field was introduced by RFC\|822,
meillo@109: but already marked as legacy in RFC\|2822.
meillo@109: Today, OpenPGP provides the basis for standardized exchange of encrypted
meillo@104: messages [RFC\|4880, RFC\|3156].
meillo@109: Hence, the support for
meillo@104: .Hd Encrypted
meillo@104: header fields is removed in mmh.
meillo@109: .Ci 064527f7b57ab050e5af13e15ad99aeeab125857
meillo@104: .BU
meillo@84: Native support for
meillo@84: .Hd Face
meillo@104: header fields has been removed, as well.
meillo@109: .Ci 8e5be81f784682822f5e868c1bf3c8624682bd23
meillo@104: This feature is similar to the
meillo@84: .Hd X-Face
meillo@84: header field in its intent,
meillo@21: but takes a different approach to store the image.
meillo@84: Instead of encoding the image data directly into the header field,
meillo@109: it contains the hostname and UDP port where the image
meillo@109: date can be retrieved.
meillo@109: There exists even a third Face system,
meillo@109: which is the successor of
meillo@109: .Hd X-Face ,
meillo@109: although it re-uses the
meillo@104: .Hd Face
meillo@109: header field.
meillo@109: It was invented in 2005 and supports colored PNG images.
meillo@104: None of the Face systems described here is popular today.
meillo@104: Hence, mmh has no direct support for them.
meillo@104: .BU
meillo@104: The
meillo@104: .Hd Content-MD5
meillo@104: header field was introduced by RFC\|1864.
meillo@104: It provides detection of data corruption during the transfer.
meillo@104: But it can not ensure verbatim end-to-end delivery of the contents
meillo@104: [RFC\|1864].
meillo@104: The proper approach to verify content integrity in an
meillo@104: end-to-end relationship is the use of digital cryptography.
meillo@104: .\" XXX (RFCs FIXME).
meillo@104: On the other hand, transfer protocols should detect corruption during
meillo@109: the transmission.
meillo@109: The TCP includes a checksum field therefore.
meillo@104: These two approaches in combinations render the
meillo@104: .Hd Content-MD5
meillo@104: header field superfluous.
meillo@109: Not a single one out of 4\|200 messages from two decades
meillo@109: in an nmh-workers mailing list archive contains a
meillo@104: .Hd Content-MD5
meillo@104: header field.
meillo@104: Neither did any of the 60\|000 messages in my personal mail storage.
meillo@104: Removing the support for this header field,
meillo@104: removed the last place where MD5 computation was needed.
meillo@109: .Ci 31dc797eb5178970d68962ca8939da3fd9a8efda
meillo@104: Hence, the MD5 code could be removed as well.
meillo@104: Over 500 lines of code vanished by this one change.
meillo@104: 
meillo@104: 
meillo@104: .U3 "MMDF maildrop support
meillo@21: .P
meillo@104: This type of format is conceptionally similar to the mbox format,
meillo@104: but uses a different message delimiter (`\fL^A^A^A^A\fP' instead of
meillo@104: `\fLFrom\0\fP').
meillo@104: Mbox is the de-facto standard maildrop format on Unix,
meillo@109: whereas the MMDF maildrop format became forgotten.
meillo@104: I did drop MMDF maildrop format support.
meillo@109: Mbox is the only packed mailbox format supported in mmh.
meillo@104: .P
meillo@109: The simplifications within the code were moderate.
meillo@109: Mainly, the reading and writing of MMDF mailbox files was removed.
meillo@109: But also, switches of
meillo@109: .Pn packf
meillo@104: and
meillo@109: .Pn rcvpack
meillo@109: could be removed.
meillo@109: .Ci 3916ab66ad5d183705ac12357621ea8661afd3c0
meillo@109: In the message parsing function
meillo@109: .Fn sbr/m_getfld.c ,
meillo@109: knowledge of MMDF packed mail boxes was removed.
meillo@109: .Ci 684ec30d81e1223a282764452f4902ed4ad1c754
meillo@109: Further code structure simplifications may be possible there,
meillo@109: because only one single packed mailbox format is left to be supported.
meillo@104: I have not worked on them yet because
meillo@104: .Fu m_getfld()
meillo@104: is heavily optimized and thus dangerous to touch.
meillo@104: The risk of damaging the intricate workings of the optimized code is
meillo@104: too high.
meillo@104: .\" XXX: move somewhere else
meillo@104: This problem is know to the developers of nmh, too.
meillo@109: They also avoid touching this minefield.
meillo@104: 
meillo@12: 
meillo@101: .U3 "Prompter's Control Keys
meillo@20: .P
meillo@20: The program
meillo@20: .Pn prompter
meillo@104: queries the user to fill in a message form.
meillo@104: When used by
meillo@20: .Pn comp
meillo@104: as
meillo@104: .Cl "comp -editor prompter" ,
meillo@20: the resulting behavior is similar to
meillo@20: .Pn mailx .
meillo@51: Apparently,
meillo@20: .Pn prompter
meillo@104: hadn't been touched lately.
meillo@104: Otherwise it's hardly explainable why it
meillo@20: still offered the switches
meillo@84: .Sw -erase
meillo@84: .Ar chr
meillo@20: and
meillo@84: .Sw -kill
meillo@84: .Ar chr
meillo@20: to name the characters for command line editing.
meillo@21: The times when this had been necessary are long time gone.
meillo@20: Today these things work out-of-the-box, and if not, are configured
meillo@20: with the standard tool
meillo@20: .Pn stty .
meillo@104: The switches are removed now
meillo@104: .Ci 0bd9750710cdbab80cfb4036dd87af20afe1552f .
meillo@20: 
meillo@104: 
meillo@109: .U3 "Hardcopy Terminal Support
meillo@21: .P
meillo@109: More of a funny anecdote is a check for being connected to a
meillo@109: hardcopy terminal.
meillo@109: It remained in the code until Spring 2012, when I finally removed it
meillo@104: .Ci b7764c4a6b71d37918a97594d866258f154017ca .
meillo@109: I would be truly happy to see such a terminal in action today,
meillo@109: maybe even being able to work on it.
meillo@109: But I fear my chances are null.
meillo@21: .P
meillo@109: The check only prevented a pager to be placed between the printing
meillo@104: program (\c
meillo@104: .Pn mhl )
meillo@104: and the terminal.
meillo@109: In nmh, this could have been ensured statically with the
meillo@104: .Sw -nomoreproc
meillo@109: at the command line, too.
meillo@121: In mmh, setting the profile entry
meillo@104: .Pe Pager
meillo@104: or the environment variable
meillo@104: .Ev PAGER
meillo@104: to
meillo@109: .Pn cat
meillo@109: does the job.
meillo@104: 
meillo@104: 
meillo@21: 
meillo@12: 
meillo@58: .H2 "Attachments
meillo@22: .P
meillo@101: The mind model of email attachments is unrelated to MIME.
meillo@101: Although the MIME RFCs (2045 through 2049) define the technical
meillo@109: requirements for having attachments, they do not mention the word
meillo@101: ``attachment''.
meillo@101: Instead of attachments, MIME talks about ``multi-part message bodies''
meillo@101: [RFC\|2045], a more general concept.
meillo@101: Multi-part messages are messages
meillo@101: ``in which one or more different
meillo@101: sets of data are combined in a single body''
meillo@101: [RFC\|2046].
meillo@101: MIME keeps its descriptions generic;
meillo@101: it does not imply specific usage models.
meillo@109: One usage model became prevalent: attachments.
meillo@101: The idea is having a main text document with files of arbitrary kind
meillo@101: attached to it.
meillo@101: In MIME terms, this is a multi-part message having a text part first
meillo@110: and parts of arbitrary type following.
meillo@101: .P
meillo@101: MH's MIME support is a direct implementation of the RFCs.
meillo@101: The perception of the topic described in the RFCs is clearly visible
meillo@101: in MH's implementation.
meillo@109: In result, MH had all the MIME features but no idea of attachments.
meillo@109: But users don't need all the MIME features,
meillo@109: they want convenient attachment handling.
meillo@109: 
meillo@102: 
meillo@102: .U3 "Composing MIME Messages
meillo@102: .P
meillo@102: In order to improve the situation on the message composing side,
meillo@102: Jon Steinhart had added an attachment system to nmh in 2002.
meillo@101: .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@102: In the file
meillo@102: .Fn docs/README-ATTACHMENTS ,
meillo@102: he described his motivation to do so as such:
meillo@101: .QS
meillo@101: Although nmh contains the necessary functionality for MIME message handing,
meillo@101: the interface to this functionality is pretty obtuse.
meillo@101: There's no way that I'm ever going to convince my partner to write
meillo@101: .Pn mhbuild
meillo@101: composition files!
meillo@101: .QE
meillo@102: .LP
meillo@102: With this change, the mind model of attachments entered nmh.
meillo@102: In the same document:
meillo@101: .QS
meillo@101: These changes simplify the task of managing attachments on draft files.
meillo@101: They allow attachments to be added, listed, and deleted.
meillo@101: MIME messages are automatically created when drafts with attachments
meillo@101: are sent.
meillo@101: .QE
meillo@102: .LP
meillo@102: Unfortunately, the attachment system,
meillo@102: like any new facilities in nmh,
meillo@110: was inactive by default.
meillo@101: .P
meillo@101: During my work in Argentina, I tried to improve the attachment system.
meillo@102: But, because of great opposition in the nmh community,
meillo@102: my patch died as a proposal on the mailing list, after long discussions.
meillo@101: .[
meillo@101: nmh-workers attachment proposal
meillo@101: .]
meillo@110: In January 2012, I extended the patch and applied it to mmh.
meillo@101: .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@102: In mmh, the attachment system is active by default.
meillo@102: Instead of command line switches, the
meillo@102: .Pe Attachment-Header
meillo@102: profile entry is used to specify
meillo@102: the name of the attachment header field.
meillo@102: It is pre-defined to
meillo@102: .Hd Attach .
meillo@101: .P
meillo@101: To add an attachment to a draft, simply add an attachment header:
meillo@101: .VS
meillo@101: To: bob
meillo@101: Subject: The file you wanted
meillo@101: Attach: /path/to/the/file-bob-wanted
meillo@101: --------
meillo@101: Here it is.
meillo@101: VE
meillo@101: The header field can be added to the draft manually in the editor,
meillo@102: or by using the `attach' command at the WhatNow prompt, or
meillo@102: non-interactively with
meillo@101: .Pn anno :
meillo@101: .VS
meillo@102: anno -append -nodate -component Attach -text /path/to/attachment
meillo@101: VE
meillo@102: Drafts with attachment headers are converted to MIME automatically by
meillo@102: .Pn send .
meillo@102: The conversion to MIME is invisible to the user.
meillo@102: The draft stored in the draft folder is always in source form, with
meillo@101: attachment headers.
meillo@101: If the MIMEification fails, for instance because the file to attach
meillo@101: is not accessible, the original draft is not changed.
meillo@101: .P
meillo@102: The attachment system handles the forwarding of messages, too.
meillo@101: If the attachment header value starts with a plus character (`+'),
meillo@101: like in
meillo@101: .Cl "Attach: +bob 30 42" ,
meillo@101: The given messages in the specified folder will be attached.
meillo@101: This allowed to simplify
meillo@101: .Pn forw .
meillo@101: .Ci f41f04cf4ceca7355232cf7413e59afafccc9550
meillo@101: .P
meillo@101: Closely related to attachments is non-ASCII text content,
meillo@101: because it requires MIME too.
meillo@102: In nmh, the user needed to call `mime' at the WhatNow prompt
meillo@101: to have the draft converted to MIME.
meillo@102: This was necessary whenever the draft contained non-ASCII characters.
meillo@101: If the user did not call `mime', a broken message would be sent.
meillo@101: Therefore, the
meillo@101: .Pe automimeproc
meillo@101: profile entry could be specified to have the `mime' command invoked
meillo@102: automatically each time.
meillo@101: Unfortunately, this approach conflicted with with attachment system
meillo@101: because the draft would already be in MIME format at the time
meillo@101: when the attachment system wanted to MIMEify it.
meillo@102: To use nmh's attachment system, `mime' must not be called at the
meillo@102: WhatNow prompt and
meillo@101: .Pe automimeproc
meillo@102: must not be set in the profile.
meillo@101: But then the case of non-ASCII text without attachment headers was
meillo@101: not caught.
meillo@102: All in all, the solution was complex and irritating.
meillo@102: My patch from December 2010 would have simplified the situation.
meillo@102: .P
meillo@101: Mmh's current solution is even more elaborate.
meillo@101: Any necessary MIMEification is done automatically.
meillo@101: There is no `mime' command at the WhatNow prompt anymore.
meillo@102: The draft will be converted automatically to MIME when either an
meillo@102: attachment header or non-ASCII text is present.
meillo@101: Further more, the special meaning of the hash character (`#')
meillo@102: at line beginnings in the draft message is removed.
meillo@102: Users need not at all deal with the whole topic.
meillo@101: .P
meillo@102: Although the new approach does not anymore support arbitrary MIME
meillo@102: compositions directly, the full power of
meillo@101: .Pn mhbuild
meillo@101: can still be accessed.
meillo@102: Given no attachment headers are included, the user can create
meillo@101: .Pn mhbuild
meillo@102: composition drafts like in nmh.
meillo@101: Then, at the WhatNow prompt, he needs to invoke
meillo@101: .Cl "edit mhbuild
meillo@101: to convert it to MIME.
meillo@110: Because the resulting draft does neither contain non-ASCII characters
meillo@102: nor has it attachment headers, the attachment system will not touch it.
meillo@101: .P
meillo@121: The approach taken in mmh is tailored towards todays most common case:
meillo@101: a text part with possibly attachments.
meillo@102: This case is simplified a lot for users.
meillo@102: 
meillo@112: 
meillo@102: .U3 "MIME Type Guessing
meillo@102: .P
meillo@102: The use of
meillo@101: .Pn mhbuild
meillo@102: composition drafts had one notable advantage over attachment headers
meillo@102: from the programmer's point of view: The user provides the appropriate
meillo@102: MIME types for files to include.
meillo@102: The attachment system needs to find out the correct MIME type itself.
meillo@102: This is a difficult task, yet it spares the user irritating work.
meillo@102: Determining the correct MIME type of content is partly mechanical,
meillo@102: partly intelligent work.
meillo@102: Forcing the user to find out the correct MIME type,
meillo@102: forces him to do partly mechanical work.
meillo@102: Letting the computer do the work, can lead to bad choices for difficult
meillo@102: content.
meillo@102: For mmh, the latter option was chosen.
meillo@102: .P
meillo@102: Determining the MIME type by the suffix of the file name is a dumb
meillo@102: approach, yet it is simple to implement and provides good results
meillo@102: for the common cases.
meillo@102: Mmh implements this approach in the
meillo@102: .Pn print-mimetype
meillo@102: script.
meillo@112: .Ci 4b5944268ea0da7bb30598a27857304758ea9b44
meillo@102: Using it is the default choice.
meillo@102: .P
meillo@112: A far better, though less portable, approach is the use of
meillo@102: .Pn file .
meillo@102: This standard tool tries to determine the type of files.
meillo@102: Unfortunately, its capabilities and accuracy varies from system to system.
meillo@102: Additionally, its output was only intended for human beings,
meillo@102: but not to be used by programs.
meillo@102: It varies much.
meillo@102: Nevertheless, modern versions of GNU
meillo@102: .Pn file ,
meillo@102: which is prevalent on the popular GNU/Linux systems,
meillo@102: provides MIME type output in machine-readable form.
meillo@102: Although this solution is highly system-dependent,
meillo@102: it solves the difficult problem well.
meillo@102: On systems where GNU
meillo@102: .Pn file ,
meillo@102: version 5.04 or higher, is available it should be used.
meillo@102: One needs to specify the following profile entry to do so:
meillo@112: .Ci 3baec236a39c5c89a9bda8dbd988d643a21decc6
meillo@102: .VS
meillo@102: Mime-Type-Query: file -b --mime
meillo@102: VE
meillo@102: .LP
meillo@102: Other versions of
meillo@102: .Pn file
meillo@102: might possibly be usable with wrapper scripts to reformat the output.
meillo@102: The diversity among
meillo@102: .Pn file
meillo@102: implementations is great; one needs to check the local variant.
meillo@102: .P
meillo@102: If no MIME type can be determined, text content gets sent as
meillo@102: `text/plain' and anything else under the generic fall-back type
meillo@102: `application/octet-stream'.
meillo@102: It is not possible in mmh to override the automatic MIME type guessing
meillo@102: for a specific file.
meillo@102: To do so, the user would need to know in advance for which file
meillo@102: the automatic guessing does fail, or the system would require interaction.
meillo@102: I consider both cases impractical.
meillo@102: The existing solution should be sufficient.
meillo@102: If not, the user may always fall back to
meillo@102: .Pn mhbuild
meillo@102: composition drafts and ignore the attachment system.
meillo@101: 
meillo@102: 
meillo@102: .U3 "Storing Attachments
meillo@102: .P
meillo@108: Extracting MIME parts of a message and storing them to disk is done by
meillo@108: .Pn mhstore .
meillo@108: The program has two operation modes,
meillo@108: .Sw -auto
meillo@108: and
meillo@108: .Sw -noauto .
meillo@108: With the former one, each part is stored under the filename given in the
meillo@108: MIME part's meta information, if available.
meillo@108: This naming information is usually available for modern attachments.
meillo@108: If no filename is available, this MIME part is stored as if
meillo@108: .Sw -noauto
meillo@108: would have been specified.
meillo@108: In the
meillo@108: .Sw -noauto
meillo@108: mode, the parts are processed according to rules, defined by
meillo@108: .Pe mhstore-store-*
meillo@108: profile entries.
meillo@108: These rules define generic filename templates for storing
meillo@108: or commands to post-process the contents in arbitrary ways.
meillo@108: If no matching rule is available the part is stored under a generic
meillo@108: filename, built from message number, MIME part number, and MIME type.
meillo@108: .P
meillo@108: The
meillo@108: .Sw -noauto
meillo@108: mode had been the default in nmh because it was considered safe,
meillo@108: in contrast to the
meillo@108: .Sw -auto
meillo@108: mode.
meillo@108: In mmh,
meillo@108: .Sw -auto
meillo@108: is not dangerous anymore.
meillo@108: Two changes were necessary:
meillo@108: .BU
meillo@108: Any directory path is removed from the proposed filename.
meillo@108: Thus, the files are always stored in the expected directory.
meillo@108: .Ci 41b6eadbcecf63c9a66aa5e582011987494abefb
meillo@108: .BU
meillo@108: Tar files are not extracted automatically any more.
meillo@108: Thus, the rest of the file system will not be touched.
meillo@108: .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108: .LP
meillo@108: Now, the outcome of mmh's
meillo@108: .Cl "mhstore -auto
meillo@110: can be foreseen from the output of
meillo@108: .Cl "mhlist -verbose" .
meillo@108: .P
meillo@108: The
meillo@108: .Sw -noauto
meillo@108: mode is seen to be more powerful but less convenient.
meillo@108: On the other hand,
meillo@108: .Sw -auto
meillo@108: is safe now and
meillo@108: storing attachments under their original name is intuitive.
meillo@108: Hence,
meillo@108: .Sw -auto
meillo@108: serves better as the default option.
meillo@108: .Ci 3410b680416c49a7617491af38bc1929855a331d
meillo@108: .P
meillo@108: Files are stored into the directory given by the
meillo@108: .Pe Nmh-Storage
meillo@108: profile entry, if set, or
meillo@108: into the current working directory, otherwise.
meillo@108: Storing to different directories is only possible with
meillo@108: .Pe mhstore-store-*
meillo@108: profile entries.
meillo@108: .P
meillo@108: Still, in both modes, existing files get overwritten silently.
meillo@108: This can be considered a bug.
meillo@108: Yet, each other behavior has its draw-backs, too.
meillo@108: Refusing to replace files requires adding a
meillo@108: .Sw -force
meillo@108: option.
meillo@108: Users will likely need to invoke
meillo@108: .Pn mhstore
meillo@108: a second time with
meillo@108: .Sw -force
meillo@108: then.
meillo@108: Eventually, only the user can decide in the concrete case.
meillo@108: This requires interaction, which I like to avoid if possible.
meillo@108: Appending a unique suffix to the filename is another bad option.
meillo@108: For now, the behavior remains as it is.
meillo@108: .P
meillo@108: In mmh, only MIME parts of type message are special in
meillo@108: .Pn mhstore 's
meillo@108: .Sw -auto
meillo@108: mode.
meillo@108: Instead of storing message/rfc822 parts as files to disk,
meillo@108: they are stored as messages into the current mail folder.
meillo@108: The same applies to message/partial, only, the parts are reassembled
meillo@108: automatically before.
meillo@108: Parts of type message/external-body are not automatically retrieved
meillo@108: anymore. Instead, Information on how to retrieve them is output.
meillo@108: Not supporting this rare case saved nearly one thousand lines of code.
meillo@108: .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@108: .\" XXX mention somewhere else too: (The profile entry `nmh-access-ftp'
meillo@108: .\"     and sbr/ruserpass.c for reading ~/.netrc are gone now.)
meillo@108: Not special anymore is `application/octet-stream; type=tar'.
meillo@108: Automatically extracting such MIME parts had been the dangerous part
meillo@108: of the
meillo@108: .Sw -auto
meillo@108: mode.
meillo@108: .Ci 94c80042eae3383c812d9552089953f9846b1bb6
meillo@108: 
meillo@102: 
meillo@102: 
meillo@102: .U3 "Showing MIME Messages
meillo@102: .P
meillo@114: The program
meillo@114: .Pn mhshow
meillo@114: had been written to display MIME messages.
meillo@114: It implemented the conceptional view of the MIME RFCs.
meillo@114: Nmh's
meillo@114: .Pn mhshow
meillo@114: handled each MIME part independently, presenting them separately
meillo@114: to the user.
meillo@114: This does not match today's understanding of email attachments,
meillo@114: where displaying a message is seen to be a single, integrated operation.
meillo@114: Today, email messages are expected to consist of a main text part
meillo@114: plus possibly attachments.
meillo@114: They are not any more seen to be arbitrary MIME hierarchies with
meillo@114: information on how to display the individual parts.
meillo@114: I adjusted
meillo@114: .Pn mhshow 's
meillo@114: behavior to the modern view on the topic.
meillo@114: .P
meillo@114: Note that this section completely ignores the original
meillo@114: .Pn show
meillo@114: program, because it was not capable to display MIME messages
meillo@114: and is no longer part of mmh.
meillo@114: Although
meillo@114: .Pn mhshow
meillo@114: was renamed to
meillo@114: .Pn show
meillo@114: in mmh, this section uses the name
meillo@114: .Pn mhshow ,
meillo@114: in order to avoid confusion.
meillo@114: .P
meillo@114: In mmh, the basic idea is that
meillo@114: .Pn mhshow
meillo@114: should display a message in one single pager session.
meillo@114: Therefore,
meillo@114: .Pn mhshow
meillo@114: invokes a pager session for all its output,
meillo@114: whenever it prints to a terminal.
meillo@114: .Ci a4197ea6ffc5c1550e8b52d5a654bcaaaee04a4e
meillo@114: In consequence,
meillo@114: .Pn mhl
meillo@114: does no more invoke a pager.
meillo@114: .Ci 0e46503be3c855bddaeae3843e1b659279c35d70
meillo@114: With
meillo@114: .Pn mhshow
meillo@114: replacing the original
meillo@114: .Pn show ,
meillo@114: output from
meillo@114: .Pn mhl
meillo@114: does not go to the terminal directly, but through
meillo@114: .Pn mhshow .
meillo@114: Hence,
meillo@114: .Pn mhl
meillo@114: does not need to invoke a pager.
meillo@114: The one and only job of
meillo@114: .Pn mhl
meillo@114: is to format messages or parts of them.
meillo@114: The only place in mmh, where a pager is invoked is
meillo@114: .Pn mhshow .
meillo@114: .P
meillo@114: .Pe mhshow-show-*
meillo@114: profile entries can be used to display MIME parts in a specific way.
meillo@114: For instance, PDF and Postscript files could be converted to plain text
meillo@114: to display them in the terminal.
meillo@114: In mmh, the displaying of MIME parts will always be done serially.
meillo@114: The request to display the MIME type `multipart/parallel' in parallel
meillo@114: is ignored.
meillo@114: It is simply treated as `multipart/mixed'.
meillo@114: .Ci d0581ba306a7299113a346f9b4c46ce97bc4cef6
meillo@114: This could already be requested with the, now removed,
meillo@114: .Sw -serialonly
meillo@114: switch of
meillo@114: .Pn mhshow .
meillo@114: As MIME parts are always processed exclusively , i.e. serially,
meillo@114: the `%e' escape in
meillo@114: .Pe mhshow-show-*
meillo@114: profile entries became useless and was thus removed.
meillo@114: .Ci a20d405db09b7ccca74d3e8c57550883da49e1ae
meillo@114: .P
meillo@114: In the intended setup, only text content would be displayed.
meillo@114: Non-text content would be converted to text by appropriate
meillo@114: .Pe mhshow-show-*
meillo@114: profile entries before, if possible and wanted.
meillo@114: All output would be displayed in a single pager session.
meillo@114: Other kinds of attachments are ignored.
meillo@114: With
meillo@114: .Pe mhshow-show-*
meillo@114: profile entries for them, they can be displayed serially along
meillo@114: the message.
meillo@114: For parallel display, the attachments need to be stored to disk first.
meillo@114: .P
meillo@114: To display text content in foreign charsets, they need to be converted
meillo@114: to the native charset.
meillo@114: Therefore,
meillo@114: .Pe mhshow-charset-*
meillo@114: profile entries used to be needed.
meillo@121: In mmh, the conversion is done automatically by piping the text through
meillo@114: the
meillo@114: .Pn iconv
meillo@114: command, if necessary.
meillo@114: .Ci 2433122c20baccb10b70b49c04c6b0497b5b3b60
meillo@114: Custom
meillo@114: .Pe mhshow-show-*
meillo@114: rules for textual content might need a
meillo@114: .Cl "iconv -f %c %f |
meillo@114: prefix to have the text converted to the native charset.
meillo@114: .P
meillo@121: Although the conversion of foreign charsets to the native one
meillo@114: has improved, it is not consistent enough.
meillo@114: Further work needs to be done and
meillo@114: the basic concepts in this field need to be re-thought.
meillo@114: Though, the default setup of mmh displays message in foreign charsets
meillo@114: correctly without the need to configure anything.
meillo@114: 
meillo@114: 
meillo@114: .ig
meillo@114: 
meillo@114: .P
meillo@114: mhshow/mhstore: Removed support for retrieving message/external-body parts.
meillo@114: These tools won't download the contents automatically anymore. Instead,
meillo@114: they print the information needed to get the contents. If someone should
meillo@114: really receive one of those rare message/external-body messages, he can
meillo@114: do the job manually. We save nearly a thousand lines of code. That's worth
meillo@114: it!
meillo@114: (The profile entry `nmh-access-ftp' and sbr/ruserpass.c for reading
meillo@114: ~/.netrc are gone now.)
meillo@114: .Ci 55e1d8c654ee0f7c45b9361ce34617983b454c32
meillo@114: 
meillo@114: ..
meillo@102: 
meillo@58: 
meillo@58: 
meillo@58: .H2 "Digital Cryptography
meillo@22: .P
meillo@58: Signing and encryption.
meillo@112: .P
meillo@112: FIXME
meillo@58: 
meillo@58: 
meillo@102: 
meillo@133: .H2 "Draft and Trash Folder
meillo@131: .P
meillo@58: 
meillo@131: .U3 "Draft Folder
meillo@131: .P
meillo@131: In the beginning, MH had the concept of a draft message.
meillo@131: This is the file
meillo@131: .Fn draft
meillo@131: in the MH directory, which is treated special.
meillo@131: On composing a message, this draft file was used.
meillo@131: As the draft file was one particular file, only one draft could be
meillo@131: managed at any time.
meillo@131: When starting to compose another message before the former one was sent,
meillo@131: the user had to decide among:
meillo@131: .BU
meillo@131: Use the old draft to finish and send it before starting with a new one.
meillo@131: .BU
meillo@131: Discard the old draft, replacing it with the new one.
meillo@131: .BU
meillo@131: Preserve the old draft by refiling it to a folder.
meillo@131: .P
meillo@131: This was, it was only possible to work in alternation on multiple drafts.
meillo@131: Therefore, the current draft needed to be refiled to a folder and
meillo@131: another one re-using for editing.
meillo@131: Working on multiple drafts at the same time was impossible.
meillo@131: The usual approach of switching to a different MH context did not
meillo@131: change anything.
meillo@131: .P
meillo@131: The draft folder facility exists to
meillo@131: allow true parallel editing of drafts, in a straight forward way.
meillo@131: It was introduced by Marshall T. Rose, already in 1984.
meillo@131: Similar to other new features, the draft folder was inactive by default.
meillo@131: Even in nmh, the highly useful draft folder was not available
meillo@131: out-of-the-box.
meillo@131: At least, Richard Coleman added the man page
meillo@131: .Mp mh-draft (5)
meillo@131: to better document the feature.
meillo@131: .P
meillo@131: Not using the draft folder facility has the single advantage of having
meillo@131: the draft file at a static location.
meillo@131: This is simple in simple cases but the concept does not scale for more
meillo@131: complex cases.
meillo@131: The concept of the draft message is too limited for the problem.
meillo@131: Therefore the draft folder was introduced.
meillo@131: It is the more powerful and more natural concept.
meillo@131: The draft folder is a folder like any other folder in MH.
meillo@131: Its messages can be listed like any other messages.
meillo@131: A draft message is no longer a special case.
meillo@131: Tools do not need special switches to work on the draft message.
meillo@131: Hence corner-cases were removed.
meillo@131: .P
meillo@131: The trivial part of the work was activating the draft folder with a
meillo@131: default name.
meillo@131: I chose the name
meillo@131: .Fn +drafts
meillo@131: for obvious reasons.
meillo@131: In consequence, the command line switches
meillo@131: .Sw -draftfolder
meillo@131: and
meillo@131: .Sw -draftmessage
meillo@131: could be removed.
meillo@131: More difficult but also more improving was updating the tools to the
meillo@131: new concept.
meillo@131: For nearly three decades, the tools needed to support two draft handling
meillo@131: approaches.
meillo@131: By fully switching to the draft folder, the tools could be simplified
meillo@131: by dropping the awkward draft message handling code.
meillo@131: .Sw -draft
meillo@131: switches were removed because operating on a draft message is no longer
meillo@131: special.
meillo@131: It became indistinguishable to operating on any other message.
meillo@131: There is no more need to query the user for draft handling.
meillo@131: It is always possible to add another new draft.
meillo@131: Refiling drafts is without difference to refiling other messages.
meillo@131: All these special cases are gone.
meillo@131: Yet, one draft-related switch remained.
meillo@131: .Pn comp
meillo@131: still has
meillo@131: .Sw -[no]use
meillo@131: for switching between two modes:
meillo@131: .BU
meillo@131: .Sw -use :
meillo@131: Modify an existing draft.
meillo@131: .BU
meillo@131: .Sw -nouse :
meillo@131: Compose a new draft, possibly taking some existing message as a form.
meillo@131: .P
meillo@131: In either case, the behavior of
meillo@131: .Pn comp
meillo@131: is deterministic.
meillo@131: .P
meillo@131: .Pn send
meillo@131: now operates on the current message in the draft folder by default.
meillo@131: As message and folder can both be overridden by specifying them on
meillo@131: the command line, it is possible to send any message in the mail storage
meillo@131: by simply specifying its number and folder.
meillo@131: In contrast to the other tools,
meillo@131: .Pn send
meillo@131: takes the draft folder as its default folder.
meillo@131: .P
meillo@131: Dropping the draft message concept in favor for the draft folder concept,
meillo@131: removed special cases with regular cases.
meillo@131: This simplified the source code of the tools, as well as the concepts.
meillo@131: In mmh, draft management does not break with the MH concepts
meillo@131: but applies them.
meillo@133: .Cl "scan +drafts" ,
meillo@133: for instance, is a truly natural request.
meillo@131: Most of the work was already done by Rose in the eighties.
meillo@133: The original improvement of mmh is dropping the old draft message approach
meillo@133: and thus simplifying the tools, the documentation and the system as a whole.
meillo@131: Although my part in the draft handling improvement was small,
meillo@133: it was an important one.
meillo@131: 
meillo@131: 
meillo@131: .U3 "Trash Folder
meillo@131: .P
meillo@131: Similar to the situation for drafts is the situation for removed messages.
meillo@131: Historically, a message was ``deleted'' by prepending a specific
meillo@131: \fIbackup prefix\fP, usually the comma character,
meillo@131: to the file name.
meillo@131: The specific message would vanish from MH because only files with
meillo@131: non-digit characters in their name are not treated as messages.
meillo@131: Although files remained in the file system,
meillo@131: the messages were no more visible in MH.
meillo@131: To truly delete them, a maintenance job is needed.
meillo@131: Usually a cron job is installed to delete them after a grace time.
meillo@131: For instance:
meillo@131: .VS
meillo@131: find $HOME/Mail -type f -name ',*' -ctime +7 -delete
meillo@131: VE
meillo@131: In such a setup, the original message can be restored
meillo@131: within the grace time interval by stripping the
meillo@131: the backup prefix from the file name.
meillo@131: But one can not rely on this statement.
meillo@131: If the last message of a folder with six messages (1-6) is removed,
meillo@131: message
meillo@131: .Fn 6 ,
meillo@131: becomes file
meillo@131: .Fn ,6 .
meillo@131: If then a new message enters the same folder, it will be given
meillo@131: the number one higher than the highest existing message.
meillo@131: In this case the message is named
meillo@131: .Fn 6
meillo@131: then.
meillo@131: If this message is removed as well,
meillo@131: then the backup of the former message gets overwritten.
meillo@131: Hence, the ability to restore removed messages does not only depend on
meillo@131: the ``sweeping cron job'' but also on the removing of further messages.
meillo@131: It is undesirable to have such obscure and complex mechanisms.
meillo@131: The user should be given a small set of clear assertions.
meillo@131: ``Removed files are restorable within a seven-day grace time.''
meillo@131: is such a clear assertion.
meillo@131: With the addition ``... unless a message with the same name in the
meillo@131: same folder is removed before.'' the statement becomes complex.
meillo@131: A user will hardly be able to keep track of any removal to know
meillo@131: if the assertion still holds true for a specific file.
meillo@131: The the real mechanism is practically obscure to the user.
meillo@131: The consequences of further removals are not obvious.
meillo@131: .P
meillo@131: Further more, the backup files are scattered within the whole mail storage.
meillo@131: This complicates managing them.
meillo@131: It is possible, with help of
meillo@131: .Pn find ,
meillo@131: but everything would be more convenient
meillo@131: if the deleted messages would be collected in one place.
meillo@131: .P
meillo@131: The profile entry
meillo@131: .Pe rmmproc
meillo@131: (previously named
meillo@131: .Pe Delete-Prog )
meillo@131: was introduced very early to improve the situation.
meillo@131: It could be set to any command, which would be executed to removed
meillo@131: the specified messages.
meillo@131: This would override the default action, described above.
meillo@131: Refiling the to-be-removed files to a garbage folder is the usual example.
meillo@131: Nmh's man page
meillo@131: .Mp rmm (1)
meillo@131: proposes to set the
meillo@131: .Pe rmmproc
meillo@131: to
meillo@131: .Cl "refile +d
meillo@131: to move messages to the garbage folder,
meillo@131: .Fn +d ,
meillo@131: instead of renaming them with the backup prefix.
meillo@131: The man page proposes additionally the expunge command
meillo@131: .Cl "rm `mhpath +d all`
meillo@131: to empty the garbage folder.
meillo@131: .P
meillo@131: Removing messages in such a way has advantages.
meillo@131: The mail storage is prevented from being cluttered with removed messages
meillo@131: because they are all collected in one place.
meillo@131: Existing and removed messages are thus separated more strictly.
meillo@131: No backup files are silently overwritten.
meillo@131: Most important is the ability to keep removed messages in the MH domain.
meillo@131: Messages in the trash folder can be listed like those in any other folder.
meillo@131: Deleted messages can be displayed like any other messages.
meillo@131: Restoring a deleted messages can be done with
meillo@131: .Pn refile .
meillo@131: All operations on deleted files are still covered by the MH tools.
meillo@131: The trash folder is just like any other folder in the mail storage.
meillo@131: .P
meillo@131: Similar to the draft folder case, I dropped the old backup prefix approach
meillo@131: in favor for replacing it by the better suiting trash folder system.
meillo@131: Hence,
meillo@131: .Pn rmm
meillo@131: calls
meillo@131: .Pn refile
meillo@131: to move the to-be-removed message to the trash folder,
meillo@131: .Fn +trash
meillo@131: by default.
meillo@131: To sweep it clean, one can use
meillo@131: .Cl "rmm -unlink +trash a" ,
meillo@131: where the
meillo@131: .Sw -unlink
meillo@131: switch causes the files to be unlinked.
meillo@131: .P
meillo@131: Dropping the legacy approach and completely converting to the new approach
meillo@131: simplified the code base.
meillo@131: The relationship between
meillo@131: .Pn rmm
meillo@131: and
meillo@131: .Pn refile
meillo@131: was inverted.
meillo@131: In mmh,
meillo@131: .Pn rmm
meillo@131: invokes
meillo@131: .Pn refile ,
meillo@131: which used to be the other way round.
meillo@131: Yet, the relationship is simpler now.
meillo@131: No more can loops, like described in nmh's man page for
meillo@131: .Mp refile (1),
meillo@131: occur:
meillo@131: .QS
meillo@131: Since
meillo@131: .Pn refile
meillo@131: uses your
meillo@131: .Pe rmmproc
meillo@131: to delete the message, the
meillo@131: .Pe rmmproc
meillo@131: must NOT call
meillo@131: .Pn refile
meillo@131: without specifying
meillo@131: .Sw -normmproc
meillo@131: or you will create an infinite loop.
meillo@131: .QE
meillo@131: .LP
meillo@131: .Pn rmm
meillo@131: either unlinks a message with
meillo@131: .Fu unlink()
meillo@131: or invokes
meillo@131: .Pn refile
meillo@131: to move it to the trash folder.
meillo@131: .Pn refile
meillo@131: does not invoke any tools.
meillo@131: .P
meillo@136: By generalizing the message removal in the way that it became covered
meillo@136: by the MH concepts made the whole system more powerful.
meillo@131: 
meillo@131: 
meillo@131: 
meillo@131: 
meillo@131: 
meillo@133: .H2 "Modern Defaults
meillo@133: .P
meillo@133: Nmh has a bunch of convenience-improving features inactive by default,
meillo@133: although one can expect every new user wanting to have them active.
meillo@133: The reason they are inactive by default is the wish to stay compatible
meillo@133: with old versions.
meillo@136: But what is the definition for old versions?
meillo@136: Still, the highly useful draft folder facility has not been activated
meillo@136: by default although it was introduced over twenty-five years ago.
meillo@133: .[
meillo@133: rose romine real work
meillo@133: .]
meillo@136: The community seems not to care.
meillo@136: This is one of several examples that require new users to first build up
meillo@136: a profile before they can access the modern features of nmh.
meillo@136: Without an extensive profile, the setup is hardly usable
meillo@133: for modern emailing.
meillo@133: The point is not the customization of the setup,
meillo@136: but the need to activate generally useful facilities.
meillo@133: .P
meillo@133: Yet, the real problem lies less in enabling the features, as this is
meillo@133: straight forward as soon as one knows what he wants.
meillo@133: The real problem is that new users need deep insights into the project
meillo@133: before they find out what they are missing and that nmh actually
meillo@133: provides it already, it just was not activated.
meillo@133: To give an example, I needed one year of using nmh
meillo@133: before I became aware of the existence of the attachment system.
meillo@133: One could argue that this fact disqualifies my reading of the
meillo@133: documentation.
meillo@133: If I would have installed nmh from source back then, I could agree.
meillo@133: Yet, I had used a prepackaged version and had expected that it would
meillo@133: just work.
meillo@133: Nevertheless, I had been convinced by the concepts of MH already
meillo@133: and I am a software developer,
meillo@133: still I required a lot of time to discover the cool features.
meillo@133: How can we expect users to be even more advanced than me,
meillo@133: just to allow them use MH in a convenient and modern way?
meillo@133: Unless they are strongly convinced of the concepts, they will fail.
meillo@133: I have seen friends of me giving up disappointed
meillo@133: before they truly used the system,
meillo@133: although they had been motivated in the beginning.
meillo@133: They suffer hard enough to get used to the toolchest approach,
meillo@133: we should spare them further inconveniences.
meillo@133: .P
meillo@136: Maintaining compatibility for its own sake is bad,
meillo@136: because the code base collects more and more compatibility code.
meillo@136: Sticking to the compatiblity code means remaining limited;
meillo@136: not using it renders it unnecessary.
meillo@136: Keeping unused alternative in the code is a bad choice as they likely
meillo@136: gather bugs, by not being well tested.
meillo@136: Also, the increased code size and the greater number of conditions
meillo@136: increase the maintenance costs.
meillo@133: If any MH implementation would be the back-end of widespread
meillo@133: email clients with large user bases, compatibility would be more
meillo@133: important.
meillo@133: Yet, it appears as if this is not the case.
meillo@133: Hence, compatibility is hardly important for technical reasons.
meillo@133: Its importance originates rather from personal reasons.
meillo@133: Nmh's user base is small and old.
meillo@133: Changing the interfaces would cause inconvenience to long-term users of MH.
meillo@133: It would force them to change their many years old MH configurations.
meillo@133: I do understand this aspect, but it keeps new users from using MH.
meillo@133: By sticking to the old users, new users are kept away.
meillo@133: Yet, the future lies in new users.
meillo@133: Hence, mmh invites new users by providing a convenient and modern setup,
meillo@133: readily usable out-of-the-box.
meillo@133: .P
meillo@136: In mmh, all modern features are active by default and many previous
meillo@136: approaches are removed or only accessible in manual ways.
meillo@136: New default features include:
meillo@133: .BU
meillo@133: The attachment system (\c
meillo@133: .Hd Attach ).
meillo@133: .Ci 8ff284ff9167eff8f5349481529332d59ed913b1
meillo@133: .BU
meillo@133: The draft folder facility (\c
meillo@133: .Fn +drafts ).
meillo@133: .Ci 337338b404931f06f0db2119c9e145e8ca5a9860
meillo@133: .BU
meillo@133: The unseen sequence (`u')
meillo@133: .Ci c2360569e1d8d3678e294eb7c1354cb8bf7501c1
meillo@133: and the sequence negation prefix (`!').
meillo@133: .Ci db74c2bd004b2dc9bf8086a6d8bf773ac051f3cc
meillo@133: .BU
meillo@133: Quoting the original message in the reply.
meillo@133: .Ci 67411b1f95d6ec987b4c732459e1ba8a8ac192c6
meillo@133: .BU
meillo@133: Forwarding messages using MIME.
meillo@133: .Ci 6e271608b7b9c23771523f88d23a4d3593010cf1
meillo@136: .P
meillo@136: In consequence, a setup with a profile that defines only the path to the
meillo@136: mail storage, is already convenient to use.
meillo@136: Again, Paul Vixie's ``edginess'' appeal supports the direction I took:
meillo@136: ``the `main branch' should just be modern''.
meillo@136: .[
meillo@136: paul vixie edginess nmh-workers
meillo@136: .]
meillo@131: 
meillo@133: 
meillo@133: 
meillo@133: 
meillo@133: 
meillo@133: .\" --------------------------------------------------------------
meillo@131: .H1 "Styling
meillo@22: .P
meillo@118: Kernighan and Pike have emphasized the importance of style in the
meillo@118: preface of their book:
meillo@118: .[ [
meillo@118: kernighan pike practice of programming
meillo@118: .], p. x]
meillo@118: .QS
meillo@118: Chapter 1 discusses programming style.
meillo@118: Good style is so important to good programming that we have chose
meillo@118: to cover it first.
meillo@118: .QE
meillo@118: This section covers changes in mmh that were motivated by the desire
meillo@118: to improve on style.
meillo@118: Many of them follow the rules given in the quoted book.
meillo@118: .[
meillo@118: kernighan pike practice of programming
meillo@118: .]
meillo@118: 
meillo@118: 
meillo@127: 
meillo@127: 
meillo@127: .H2 "Code Style
meillo@118: .P
meillo@118: .U3 "Indentation Style
meillo@118: .P
meillo@118: Indentation styles are the holy cow of programmers.
meillo@118: Again Kernighan and Pike:
meillo@118: .[ [
meillo@118: kernighan pike practice of programming
meillo@118: .], p. 10]
meillo@118: .QS
meillo@118: Programmers have always argued about the layout of programs,
meillo@118: but the specific style is much less important than its consistent
meillo@118: application.
meillo@121: Pick one style, preferably ours, use it consistently, and don't waste
meillo@118: time arguing.
meillo@118: .QE
meillo@118: .P
meillo@118: I agree that the constant application is most important,
meillo@118: but I believe that some styles have advantages over others.
meillo@118: For instance the indentation with tab characters only.
meillo@118: Tab characters directly map to the nesting level \(en
meillo@118: one tab, one level.
meillo@118: Tab characters are flexible because developers can adjust them to
meillo@118: whatever width they like to have.
meillo@118: There is no more need to run
meillo@118: .Pn unexpand
meillo@118: or
meillo@118: .Pn entab
meillo@118: programs to ensure the correct mixture of leading tabs and spaces.
meillo@118: The simple rules are: (1) Leading whitespace must consist of tabs only.
meillo@118: (2) Any other whitespace should consist of spaces.
meillo@121: These two rules ensure the integrity of the visual appearance.
meillo@121: Although reformatting existing code should be avoided, I did it.
meillo@136: I did not waste time arguing; I just reformated the code.
meillo@118: .Ci a485ed478abbd599d8c9aab48934e7a26733ecb1
meillo@118: 
meillo@118: .U3 "Comments
meillo@118: .P
meillo@118: Section 1.6 of
meillo@118: .[ [
meillo@118: kernighan pike practice of programming
meillo@118: .], p. 23]
meillo@118: demands: ``Don't belabor the obvious.''
meillo@122: Hence, I simply removed all the comments in the following code excerpt:
meillo@118: .VS
meillo@120: context_replace(curfolder, folder);  /* update current folder  */
meillo@120: seq_setcur(mp, mp->lowsel);  /* update current message */
meillo@120: seq_save(mp);  /* synchronize message sequences */
meillo@120: folder_free(mp);  /* free folder/message structure */
meillo@120: context_save();  /* save the context file */
meillo@120: 
meillo@120: [...]
meillo@120: 
meillo@120: int c;  /* current character */
meillo@120: char *cp;  /* miscellaneous character pointer */
meillo@120: 
meillo@120: [...]
meillo@120: 
meillo@120: /* NUL-terminate the field */
meillo@120: *cp = '\0';
meillo@118: VE
meillo@120: .Ci 426543622b377fc5d091455cba685e114b6df674
meillo@118: .P
meillo@136: The program code explains enough itself, already.
meillo@136: 
meillo@118: 
meillo@118: .U3 "Names
meillo@118: .P
meillo@118: Kernighan and Pike suggest:
meillo@118: ``Use active names for functions''.
meillo@118: .[ [
meillo@118: kernighan pike practice of programming
meillo@118: .], p. 4]
meillo@118: One application of this rule was the rename of
meillo@118: .Fu check_charset()
meillo@118: to
meillo@118: .Fu is_native_charset() .
meillo@118: .Ci 8d77b48284c58c135a6b2787e721597346ab056d
meillo@118: The same change fixed a violation of ``Be accurate'' as well.
meillo@118: The code did not match the expectation the function suggested,
meillo@118: as it, for whatever reason, only compared the first ten characters
meillo@118: of the charset name.
meillo@118: .P
meillo@118: More important than using active names is using descriptive names.
meillo@118: Renaming the obscure function
meillo@118: .Fu m_unknown()
meillo@118: was a delightful event.
meillo@118: .Ci 611d68d19204d7cbf5bd585391249cb5bafca846
meillo@118: .P
meillo@118: Magic numbers are generally considered bad style.
meillo@118: Obviously, Kernighan and Pike agree:
meillo@118: ``Give names to magic numbers''.
meillo@118: .[ [
meillo@118: kernighan pike practice of programming
meillo@118: .], p. 19]
meillo@118: One such change was naming the type of input \(en mbox or mail folder \(en
meillo@118: to be scanned:
meillo@118: .VS
meillo@118: #define SCN_MBOX (-1)
meillo@118: #define SCN_FOLD 0
meillo@118: VE
meillo@118: .Ci 7ffb36d28e517a6f3a10272056fc127592ab1c19
meillo@118: .P
meillo@118: The argument
meillo@118: .Ar outnum
meillo@118: of the function
meillo@118: .Fu scan()
meillo@118: in
meillo@118: .Fn uip/scansbr.c
meillo@118: defines the number of the message to be created.
meillo@118: If no message is to be created, the argument is misused to transport
meillo@118: program logic.
meillo@118: This lead to obscure code.
meillo@118: I improved the clarity of the code by introducing two variables:
meillo@118: .VS
meillo@118: int incing = (outnum > 0);
meillo@118: int ismbox = (outnum != 0);
meillo@118: VE
meillo@118: They cover the magic values and are used for conditions.
meillo@118: The variable
meillo@118: .Ar outnum
meillo@118: is only used when it holds an ordinary message number.
meillo@118: .Ci b8b075c77be7794f3ae9ff0e8cedb12b48fd139f
meillo@118: The clarity improvement of the change showed detours in the program logic
meillo@118: of related code parts.
meillo@118: Having the new variables with descriptive names, a more
meillo@121: straight forward implementation became apparent.
meillo@118: Before the clarification was done,
meillo@118: the possibility to improve had not be seen.
meillo@118: .Ci aa60b0ab5e804f8befa890c0a6df0e3143ce0723
meillo@118: 
meillo@133: 
meillo@133: 
meillo@133: .H2 "Structural Rework
meillo@133: .P
meillo@136: Although the stylistic changes described up to here improve the
meillo@136: readability of the source code, all of them are changes ``in the small''.
meillo@136: Structural changes affect a much larger area.
meillo@136: They are more difficult to do but lead to larger improvements,
meillo@136: especially as they influence the outer shape of the tools as well.
meillo@118: .P
meillo@118: At the end of their chapter on style,
meillo@118: Kernighan and Pike ask: ``But why worry about style?''
meillo@136: Following are two examples of structural rework that show
meillo@136: why style is important in the first place.
meillo@136: 
meillo@136: 
meillo@136: .U3 "Rework of \f(CWanno\fP
meillo@118: .P
meillo@120: Until 2002,
meillo@120: .Pn anno
meillo@120: had six functional command line switches,
meillo@120: .Sw -component
meillo@120: and
meillo@120: .Sw -text ,
meillo@120: which took an argument each,
meillo@120: and the two pairs of flags,
meillo@120: .Sw -[no]date
meillo@120: and
meillo@120: .Sw -[no]inplace.,
meillo@120: .Sw -component
meillo@120: and
meillo@120: .Sw -text ,
meillo@120: which took an argument each,
meillo@120: and the two pairs of flags,
meillo@120: .Sw -[no]date
meillo@120: and
meillo@120: .Sw -[no]inplace .
meillo@120: Then Jon Steinhart introduced his attachment system.
meillo@120: In need for more advanced annotation handling, he extended
meillo@120: .Pn anno .
meillo@120: He added five more switches:
meillo@120: .Sw -draft ,
meillo@120: .Sw -list ,
meillo@120: .Sw -delete ,
meillo@120: .Sw -append ,
meillo@120: and
meillo@120: .Sw -number ,
meillo@120: the last one taking an argument.
meillo@121: .Ci 7480dbc14bc90f2d872d434205c0784704213252
meillo@120: Later,
meillo@120: .Sw -[no]preserve
meillo@120: was added.
meillo@121: .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@120: Then, the Synopsis section of the man page
meillo@120: .Mp anno (1)
meillo@120: read:
meillo@120: .VS
meillo@120: anno [+folder] [msgs] [-component field] [-inplace | -noinplace]
meillo@120: 	[-date | -nodate] [-draft] [-append] [-list] [-delete]
meillo@120: 	[-number [num|all]] [-preserve | -nopreserve] [-version]
meillo@120: 	[-help] [-text body]
meillo@120: VE
meillo@120: .LP
meillo@120: The implementation followed the same structure.
meillo@120: Problems became visible when
meillo@120: .Cl "anno -list -number 42
meillo@120: worked on the current message instead on message number 42,
meillo@120: and
meillo@120: .Cl "anno -list -number l:5
meillo@124: did not work on the last five messages but failed with the mysterious
meillo@120: error message: ``anno: missing argument to -list''.
meillo@121: Yet, the invocation matched the specification in the man page.
meillo@120: There, the correct use of
meillo@120: .Sw -number
meillo@120: was defined as being
meillo@120: .Cl "[-number [num|all]]
meillo@120: and the textual description for the combination with
meillo@120: .Sw -list
meillo@120: read:
meillo@120: .QS
meillo@120: The -list option produces a listing of the field bodies for
meillo@120: header fields with names matching the specified component,
meillo@120: one per line. The listing is numbered, starting at 1, if
meillo@120: the -number option is also used.
meillo@120: .QE
meillo@120: .LP
meillo@120: The problem was manifold.
meillo@120: The code required a numeric argument to the
meillo@120: .Sw -number
meillo@120: switch.
meillo@120: If it was missing or non-numeric,
meillo@120: .Pn anno
meillo@120: aborted with an error message that had an off-by-one error,
meillo@120: printing the switch one before the failing one.
meillo@120: Semantically, the argument to the
meillo@120: .Sw -number
meillo@120: switch is only necessary in combination with
meillo@120: .Sw -delete ,
meillo@120: but not with
meillo@120: .Sw -list .
meillo@120: In the former case it is even necessary.
meillo@120: .P
meillo@120: Trying to fix these problems on the surface would not have solved it truly.
meillo@120: The problems discovered originate from a discrepance between the semantic
meillo@120: structure of the problem and the structure implemented in the program.
meillo@120: Such structural differences can not be cured on the surface.
meillo@120: They need to be solved by adjusting the structure of the implementation
meillo@120: to the structure of the problem.
meillo@120: .P
meillo@120: In 2002, the new switches
meillo@120: .Sw -list
meillo@120: and
meillo@120: .Sw -delete
meillo@120: were added in the same way, the
meillo@120: .Sw -number
meillo@120: switch for instance had been added.
meillo@120: Yet, they are of structural different type.
meillo@120: Semantically,
meillo@120: .Sw -list
meillo@120: and
meillo@120: .Sw -delete
meillo@120: introduce modes of operation.
meillo@120: Historically,
meillo@120: .Pn anno
meillo@120: had only one operation mode: adding header fields.
meillo@120: With the extension, it got two moder modes:
meillo@120: listing and deleting header fields.
meillo@120: The structure of the code changes did not pay respect to this
meillo@120: fundamental change to
meillo@120: .Pn anno 's
meillo@120: behavior.
meillo@120: Neither the implementation nor the documentation did clearly
meillo@120: define them as being exclusive modes of operation.
meillo@120: Having identified the problem, I solved it by putting structure into
meillo@120: .Pn anno
meillo@120: and its documentation.
meillo@120: .Ci d54c8db8bdf01e8381890f7729bc0ef4a055ea11
meillo@120: .P
meillo@120: The difference is visible in both, the code and the documentation.
meillo@121: The following code excerpt:
meillo@120: .VS
meillo@120: int delete = -2;  /* delete header element if set */
meillo@120: int list = 0;  /* list header elements if set */
meillo@120: [...]
meillo@121: 	case DELETESW:  /* delete annotations */
meillo@121: 		delete = 0;
meillo@121: 		continue;
meillo@121: 	case LISTSW:  /* produce a listing */
meillo@121: 		list = 1;
meillo@121: 		continue;
meillo@120: VE
meillo@121: .LP
meillo@121: was replaced by:
meillo@120: .VS
meillo@120: static enum { MODE_ADD, MODE_DEL, MODE_LIST } mode = MODE_ADD;
meillo@120: [...]
meillo@121: 	case DELETESW:  /* delete annotations */
meillo@121: 		mode = MODE_DEL;
meillo@121: 		continue;
meillo@121: 	case LISTSW:  /* produce a listing */
meillo@121: 		mode = MODE_LIST;
meillo@121: 		continue;
meillo@120: VE
meillo@120: .LP
meillo@121: The replacement code does not only reflect the problem's structure better,
meillo@121: it is easier to understand as well.
meillo@121: The same applies to the documentation.
meillo@120: The man page was completely reorganized to propagate the same structure.
meillo@121: This is visible in the Synopsis section:
meillo@120: .VS
meillo@120: anno [+folder] [msgs] [-component field] [-text body]
meillo@120: 	[-append] [-date | -nodate] [-preserve | -nopreserve]
meillo@120: 	[-Version] [-help]
meillo@120: 
meillo@120: anno -delete [+folder] [msgs] [-component field] [-text
meillo@120: 	body] [-number num | all ] [-preserve | -nopreserve]
meillo@120: 	[-Version] [-help]
meillo@120: 
meillo@120: anno -list [+folder] [msgs] [-component field] [-number]
meillo@120: 	[-Version] [-help]
meillo@120: VE
meillo@121: .\" XXX think about explaining the -preserve rework?
meillo@118: 
meillo@58: 
meillo@58: 
meillo@133: .U3 "Path Conversion
meillo@133: .P
meillo@134: Four kinds of path names can appear in MH:
meillo@134: .IP (1)
meillo@134: Absolute Unix directory paths, like
meillo@134: .Fn /etc/passwd .
meillo@134: .IP (2)
meillo@134: Relative Unix directory paths, like
meillo@134: .Fn ./foo/bar .
meillo@134: .IP (3)
meillo@134: Absolute MH folder paths, like
meillo@134: .Fn +friends/phil .
meillo@134: .IP (4)
meillo@134: Relative MH folder paths, like
meillo@134: .Fn @subfolder .
meillo@134: .P
meillo@134: The last type, relative MH folder paths, are hardly documented.
meillo@134: Nonetheless, they are useful for large mail storages.
meillo@134: The current mail folder is specified as `\c
meillo@134: .Fn @ ',
meillo@134: just like the current directory is specified as `\c
meillo@134: .Fn . '.
meillo@134: .P
meillo@134: To allow MH tools to understand all four notations,
meillo@134: they need to convert between them.
meillo@134: In nmh, these path name conversion functions were located in the files
meillo@134: .Fn sbr/path.c
meillo@134: (``return a pathname'') and
meillo@134: .Fn sbr/m_maildir.c
meillo@134: (``get the path for the mail directory'').
meillo@134: The seven functions in the two files were documented with no more
meillo@134: than two comments, which described obvious information.
meillo@134: The function signatures were neither explaining:
meillo@134: .VS
meillo@134: char *path(char *, int);
meillo@134: char *pluspath(char *);
meillo@134: char *m_mailpath(char *);
meillo@134: char *m_maildir(char *);
meillo@134: VE
meillo@134: .P
meillo@134: My investigation provides the following description:
meillo@134: .BU
meillo@134: The second parameter of
meillo@134: .Fu path()
meillo@134: defines the type of path given as first parameter.
meillo@134: Directory paths are converted to absolute directory paths.
meillo@134: Folder paths are converted to absolute folder paths.
meillo@134: Folder paths must not include a leading `@' character.
meillo@134: Leading plus characters are preserved.
meillo@134: The result is a pointer to newly allocated memory.
meillo@134: .BU
meillo@134: .Fu pluspath()
meillo@134: is a convenience-wrapper to
meillo@134: .Fu path() ,
meillo@134: to convert folder paths only.
meillo@134: This function can not be used for directory paths.
meillo@134: An empty string parameter causes a buffer overflow.
meillo@134: .BU
meillo@134: .Fu m_mailpath()
meillo@134: converts directory paths to absolute directory paths.
meillo@134: The characters `+' or `@' at the beginning of the path name are
meillo@134: treated literal, i.e. as the first character of a relative directory path.
meillo@134: Hence, this function can not be used for folder paths.
meillo@134: In any case, the result is an absolute directory path.
meillo@134: The result is a pointer to newly allocated memory.
meillo@134: .BU
meillo@134: .Fu m_maildir()
meillo@134: returns the parameter unchanged if it is an absolute directory path
meillo@134: or begins with the entry `.' or `..'.
meillo@134: All other strings are prepended with the current working directory.
meillo@134: Hence, this functions can not be used for folder paths.
meillo@134: The result is either an absolute directory path or a relative
meillo@134: directory path, starting with a dot.
meillo@134: In contrast to the other functions, the result is a pointer to
meillo@134: static memory.
meillo@134: .P
meillo@134: The situation was obscure, irritating, error-prone, and non-orthogonal.
meillo@134: No clear terminology was used to name the different kinds of path names.
meillo@134: The first argument of
meillo@134: .Fu m_mailpath() ,
meillo@134: for instance, was named
meillo@134: .Ar folder ,
meillo@134: though
meillo@134: .Fu m_mailpath()
meillo@134: can not be used for MH folders.
meillo@134: .P
meillo@134: I reworked the path name conversion completely, introducing clarity.
meillo@134: First of all, the terminology needed to be defined.
meillo@134: A path name is either in the Unix domain, then it is called
meillo@134: \fIdirectory path\fP, `dirpath' for short, or it is in the MH domain,
meillo@134: then it is called \fIfolder path\fP, `folpath' for short.
meillo@134: The two terms need to be used with strict distinction.
meillo@134: Having a clear terminology is often an indicator of having understood
meillo@134: the problem itself.
meillo@134: Second, I exploited the concept of path type indicators.
meillo@134: By requesting every path name to start with a clear type identifier,
meillo@134: conversion between the types can be fully automated.
meillo@134: Thus the tools can accept paths of any type from the user.
meillo@134: Therefore, it was necessary to require relative directory paths to be
meillo@134: prefixed with a dot character.
meillo@134: In consequence, the dot character could no longer be an alias for the
meillo@134: current message.
meillo@134: .Ci cff0e16925e7edbd25b8b9d6d4fbdf03e0e60c01
meillo@134: Third, I created three new functions to replace the previous mess:
meillo@134: .BU
meillo@134: .Fu expandfol()
meillo@134: converts folder paths to absolute folder paths,
meillo@134: without the leading plus character.
meillo@134: Directory paths are simply passed through.
meillo@134: This function is to be used for folder paths only, thus the name.
meillo@134: The result is a pointer to static memory.
meillo@134: .BU
meillo@134: .Fu expanddir()
meillo@134: converts directory paths to absolute directory paths.
meillo@134: Folder paths are treated as relative directory paths.
meillo@134: This function is to be used for directory paths only, thus the name.
meillo@134: The result is a pointer to static memory.
meillo@134: .BU
meillo@134: .Fu toabsdir()
meillo@134: converts any type of path to an absolute directory path.
meillo@134: This is the function of choice for path conversion.
meillo@134: Absolute directory paths are the most general representation of a
meillo@134: path name.
meillo@134: The result is a pointer to static memory.
meillo@134: .P
meillo@134: The new functions have names that indicate their use.
meillo@134: Two of the functions convert relative to absolute path names of the
meillo@134: same type.
meillo@134: The third function converts any path name type to the most general one,
meillo@134: the absolute directory path.
meillo@134: All of the functions return pointers to static memory.
meillo@134: All three functions are implemented in
meillo@134: .Fn sbr/path.c .
meillo@134: .Fn sbr/m_maildir.c
meillo@134: is removed.
meillo@134: .P
meillo@134: Along with the path conversion rework, I also replaced
meillo@134: .Fu getfolder(FDEF)
meillo@134: with
meillo@134: .Fu getdeffol()
meillo@134: and
meillo@134: .Fu getfolder(FCUR)
meillo@134: with
meillo@134: .Fu getcurfol() ,
meillo@134: which is only a convenience wrapper for
meillo@134: .Fu expandfol("@") .
meillo@134: This code was moved from
meillo@134: .Fn sbr/getfolder.c
meillo@134: to
meillo@134: .Fn sbr/path.c .
meillo@134: .P
meillo@134: The related function
meillo@134: .Fu etcpath()
meillo@134: was moved to
meillo@134: .Fn sbr/path.c ,
meillo@134: too.
meillo@134: Previously, it had been located in
meillo@134: .Fn config/config.c ,
meillo@134: for whatever reasons.
meillo@134: .P
meillo@134: .Fn sbr/path.c
meillo@134: now contains all path handling code.
meillo@134: Only 173 lines of code were needed to replace the previous 252 lines.
meillo@134: The readability of the code is highly improved.
meillo@134: Additionally, each of the six exported and one static functions
meillo@134: is introduced by an explaining comment.
meillo@134: .Ci d39e2c447b0d163a5a63f480b23d06edb7a73aa0
meillo@133: 
meillo@133: 
meillo@133: 
meillo@133: 
meillo@133: .H2 "Profile Reading
meillo@133: .P
meillo@138: The MH profile contains the configuration for the user-specific MH setup.
meillo@138: MH tools read the profile right after starting up,
meillo@138: as it contains the location of the user's mail storage
meillo@138: and similar settings that influence the whole setup.
meillo@138: Further more, the profile contains the default switches for the tools,
meillo@138: hence, it must be read before the command line switches are processed.
meillo@138: .P
meillo@138: For historic reasons, some MH tools did not read the profile and context.
meillo@138: Among them were
meillo@138: .Pn post /\c
meillo@138: .Pn spost ,
meillo@138: .Pn mhmail ,
meillo@138: and
meillo@138: .Pn slocal .
meillo@138: The reason why these tools ignored the profile were not clearly stated.
meillo@138: During the discussion on the nmh-workers mailing list,
meillo@138: .[
meillo@138: nmh-workers levine post profile
meillo@138: .]
meillo@138: David Levine posted an explanation, quoting John Romine:
meillo@138: .QS
meillo@138: I asked John Romine and here's what he had to say, which
meillo@138: agrees and provides an example that convinces me:
meillo@138: .QS
meillo@138: My take on this is that post should not be called by
meillo@138: users directly, and it doesn't read the .mh_profile
meillo@138: (only front-end UI programs read the profile).
meillo@138: .QP
meillo@138: For example, there can be contexts where post is called
meillo@138: by a helper program (like 'mhmail') which may be run by
meillo@138: a non-MH user.  We don't want this to prompt the user
meillo@138: to create an MH profile, etc.
meillo@138: .QP
meillo@138: My suggestion would be to have send pass a (hidden)
meillo@138: `\-fileproc proc' option to post if needed.  You could also
meillo@138: use an environment variable (I think send/whatnow do
meillo@138: this).
meillo@138: .QE
meillo@138: I think that's the way to go.  My personal preference is to use a command line option, not an environment variable.
meillo@138: .QE
meillo@138: .P
meillo@138: To solve the problem of
meillo@138: .Pn post
meillo@138: not honoring the
meillo@138: .Pe fileproc
meillo@138: profile entry,
meillo@138: the community roughly agreed that a switch
meillo@138: .Sw -fileproc
meillo@138: should be added to
meillo@138: .Pn post
meillo@138: to be able to pass a different fileproc.
meillo@138: I strongly disagree with this approach because it does not solve
meillo@138: the problem; it only removes a single symptom.
meillo@138: The problem is that
meillo@138: .Pn post
meillo@138: does not behave as expected.
meillo@138: But all programs should behave as expected.
meillo@138: Clear and simple concepts are a precondition for this.
meillo@138: Hence, the real solution is having all MH tools read the profile.
meillo@138: .P
meillo@138: Yet, the problem has a further aspect.
meillo@138: It mainly originates in
meillo@138: .Pn mhmail .
meillo@138: .Pn mhmail
meillo@138: was intended to be a replacement for
meillo@138: .Pn mailx
meillo@138: on systems with MH installations.
meillo@138: .Pn mhmail
meillo@138: should have been able to use just like
meillo@138: .Pn mailx ,
meillo@138: but sending the message via MH's
meillo@138: .Pn post
meillo@138: instead of
meillo@138: .Pn sendmail .
meillo@138: Using
meillo@138: .Pn mhmail
meillo@138: should not be influenced by the question whether the user had
meillo@138: MH set up for himself or not.
meillo@138: .Pn mhmail
meillo@138: did not read the profile as this requests the user to set up MH
meillo@138: if not done yet.
meillo@138: As
meillo@138: .Pn mhmail
meillo@138: used
meillo@138: .Pn post ,
meillo@138: .Pn post
meillo@138: could not read the profile neither.
meillo@138: This is the reason why
meillo@138: .Pn post
meillo@138: does not read the profile.
meillo@138: This is the reason for the actual problem.
meillo@138: It was not much of a problem because
meillo@138: .Pn post
meillo@138: was not intended to be used by users directly.
meillo@138: .Pn send
meillo@138: is the interactive front-end to
meillo@138: .Pn post .
meillo@138: .Pn send
meillo@138: read the profile and passed all relevant values on the command line to
meillo@138: .Pn post
meillo@138: \(en an awkward solution.
meillo@138: .P
meillo@138: The important insight is that
meillo@138: .Pn mhmail
meillo@138: is no true MH tool.
meillo@138: The concepts broke because this outlandish tool was treated as any other
meillo@138: MH tool.
meillo@138: Instead it should have been treated accordingly to its foreign style.
meillo@138: The solution is not to prevent the tools reading the profile but
meillo@138: to instruct them reading a different profile.
meillo@138: .Pn mhmail
meillo@138: could have set up a well-defined profile and caused all MH tools
meillo@138: in the session use it by exporting an environment variable.
meillo@138: With this approach, no special cases would have been introduced,
meillo@138: no surprises would have been caused.
meillo@138: By writing a clean-profile-wrapper, the concept could have been
meillo@138: generalized orthogonally to the whole MH toolchest.
meillo@138: Then Rose's motivation behind the decision that
meillo@138: .Pn post
meillo@138: ignores the profile, as quoted by Jeffrey Honig,
meillo@138: .[
meillo@138: nmh-workers post profile
meillo@138: .]
meillo@138: would have become possible:
meillo@138: .QS
meillo@138: when you run mh commands in a script, you want all the defaults to be
meillo@138: what the man page says.
meillo@138: when you run a command by hand, then you want your own defaults...
meillo@138: .QE
meillo@138: .LP
meillo@138: Yet, I consider this explanation short-sighted.
meillo@138: We should rather regard theses two cases as just two different MH setups,
meillo@138: based on two different profiles.
meillo@138: Mapping such problems on the concepts of switching between different
meillo@138: profiles, solves them once for all.
meillo@138: .P
meillo@138: In mmh, the wish to have
meillo@138: .Pn mhmail
meillo@138: as as replacement for
meillo@138: .Pn mailx
meillo@138: is considered obsolete.
meillo@138: Mmh's
meillo@138: .Pn mhmail
meillo@138: does no longer cover this use-case.
meillo@138: Currently,
meillo@138: .Pn mhmail
meillo@138: is in a transition state.
meillo@138: .Ci 32d4f9daaa70519be3072479232ff7be0500d009
meillo@138: It may become a front-end to
meillo@138: .Pn comp ,
meillo@138: which provides an interface more convenient in some cases.
meillo@138: In this case,
meillo@138: .Pn mhmail
meillo@138: will become an ordinary MH tool, reading the profile.
meillo@138: If, however, this idea will not convince, then
meillo@138: .Pn mhmail
meillo@138: will be removed.
meillo@138: .P
meillo@138: Every program in the mmh toolchest reads the profile.
meillo@138: The only exception is
meillo@138: .Pn slocal ,
meillo@138: which is not considered part of the mmh toolchest.
meillo@138: This MDA is only distributed with mmh, currently.
meillo@138: Mmh has no
meillo@138: .Pn post
meillo@138: program, but
meillo@138: .Pn spost ,
meillo@138: which now reads the profile.
meillo@138: .Ci 3e017a7abbdf69bf0dff7a4073275961eda1ded8
meillo@138: With this change,
meillo@138: .Pn send
meillo@138: and
meillo@138: .Pn spost
meillo@138: can be considered to be merged.
meillo@138: Direct invocations of
meillo@138: .Pn spost
meillo@138: are only done by the to-be-changed
meillo@138: .Pn mhmail
meillo@138: implementation and by
meillo@138: .Pn rcvdist ,
meillo@138: which will require rework.
meillo@138: .P
meillo@138: The
meillo@138: .Fu context_foil()
meillo@138: function to pretend to have read an empty profile was removed.
meillo@138: .Ci 68af8da96bea87a5541988870130b6209ce396f6
meillo@138: All mmh tools read the profile.
meillo@133: 
meillo@133: 
meillo@127: 
meillo@121: .H2 "Standard Libraries
meillo@22: .P
meillo@121: MH is one decade older than the POSIX and ANSI C standards.
meillo@121: Hence, MH included own implementations of functions
meillo@121: that are standardized and thus widely available today,
meillo@121: but were not back then.
meillo@121: Today, twenty years after the POSIX and ANSI C were published,
meillo@121: developers can expect system to comply with these standards.
meillo@121: In consequence, MH-specific replacements for standard functions
meillo@121: can and should be dropped.
meillo@121: Kernighan and Pike advise: ``Use standard libraries.''
meillo@121: .[ [
meillo@121: kernighan pike practice of programming
meillo@121: .], p. 196]
meillo@121: Actually, MH had followed this advice in history,
meillo@121: but it had not adjusted to the changes in this field.
meillo@121: The
meillo@121: .Fu snprintf()
meillo@121: function, for instance, was standardized with C99 and is available
meillo@121: almost everywhere because of its high usefulness.
meillo@123: In project's own implementation of
meillo@121: .Fu snprintf()
meillo@123: was dropped in March 2012 in favor for using the one of the
meillo@123: standard library.
meillo@123: .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32
meillo@123: Such decisions limit the portability of mmh
meillo@121: if systems don't support these standardized and widespread functions.
meillo@123: This compromise is made because mmh focuses on the future.
meillo@121: .P
meillo@123: I am not yet thirty years old and my C and Unix experience comprises
meillo@123: only half a dozen years.
meillo@121: Hence, I need to learn about the history in retrospective.
meillo@121: I have not used those ancient constructs myself.
meillo@121: I have not suffered from their incompatibilities.
meillo@121: I have not longed for standardization.
meillo@121: All my programming experience is from a time when ANSI C and POSIX
meillo@121: were well established already.
meillo@121: I have only read a lot of books about the (good) old times.
meillo@121: This puts me in a difficult positions when working with old code.
meillo@123: I need to freshly acquire knowledge about old code constructs and ancient
meillo@123: programming styles, whereas older programmers know these things by
meillo@123: heart from their own experience.
meillo@121: .P
meillo@123: Being aware of the situation, I rather let people with more historic
meillo@123: experience replace ancient code constructs with standardized ones.
meillo@121: Lyndon Nerenberg covered large parts of this task for the nmh project.
meillo@121: He converted project-specific functions to POSIX replacements,
meillo@121: also removing the conditionals compilation of now standardized features.
meillo@123: Ken Hornstein and David Levine had their part in the work, too.
meillo@121: Often, I only needed to pull over changes from nmh into mmh.
meillo@121: These changes include many commits; these are among them:
meillo@121: .Ci 768b5edd9623b7238e12ec8dfc409b82a1ed9e2d
meillo@121: .Ci 0052f1024deb0a0a2fc2e5bacf93d45a5a9c9b32 .
meillo@102: .P
meillo@123: During my own work, I tidied up the \fIMH standard library\fP,
meillo@123: .Fn libmh.a ,
meillo@123: which is located in the
meillo@123: .Fn sbr
meillo@123: (``subroutines'') directory in the source tree.
meillo@123: The MH library includes functions that mmh tools usually need.
meillo@123: Among them are MH-specific functions for profile, context, sequence,
meillo@123: and folder handling, but as well
meillo@123: MH-independent functions, such as auxiliary string functions,
meillo@123: portability interfaces and error-checking wrappers for critical
meillo@123: functions of the standard library.
meillo@123: .P
meillo@123: I have replaced the
meillo@121: .Fu atooi()
meillo@121: function with calls to
meillo@123: .Fu strtoul()
meillo@121: with the third parameter \(en the base \(en set to eight.
meillo@121: .Fu strtoul()
meillo@123: is part of C89 and thus considered safe to use.
meillo@121: .Ci c490c51b3c0f8871b6953bd0c74551404f840a74
meillo@102: .P
meillo@121: I did remove project-included fallback implementations of
meillo@121: .Fu memmove()
meillo@121: and
meillo@121: .Fu strerror() ,
meillo@121: although Peter Maydell had re-included them into nmh in 2008
meillo@121: to support SunOS 4.
meillo@121: Nevertheless, these functions are part of ANSI C.
meillo@121: Systems that do not even provide full ANSI C support should not
meillo@121: put a load on mmh.
meillo@121: .Ci b067ff5c465a5d243ce5a19e562085a9a1a97215
meillo@121: .P
meillo@121: The
meillo@121: .Fu copy()
meillo@121: function copies the string in argument one to the location in two.
meillo@121: In contrast to
meillo@121: .Fu strcpy() ,
meillo@121: it returns a pointer to the terminating null-byte in the destination area.
meillo@123: The code was adjusted to replace
meillo@121: .Fu copy()
meillo@123: with
meillo@121: .Fu strcpy() ,
meillo@121: except within
meillo@121: .Fu concat() ,
meillo@121: where
meillo@121: .Fu copy()
meillo@123: was more convenient.
meillo@123: Therefore, the definition of
meillo@121: .Fu copy()
meillo@123: was moved into the source file of
meillo@121: .Fu concat()
meillo@123: and its visibility is now limited to it.
meillo@121: .Ci 552fd7253e5ee9e554c5c7a8248a6322aa4363bb
meillo@121: .P
meillo@121: The function
meillo@121: .Fu r1bindex()
meillo@121: had been a generalized version of
meillo@121: .Fu basename()
meillo@121: with minor differences.
meillo@121: As all calls to
meillo@121: .Fu r1bindex()
meillo@121: had the slash (`/') as delimiter anyway,
meillo@121: replacing
meillo@121: .Fu r1bindex()
meillo@121: with the more specific and better-named function
meillo@121: .Fu basename()
meillo@121: became desirable.
meillo@121: Unfortunately, many of the 54 calls to
meillo@121: .Fu r1bindex()
meillo@123: depended on a special behavior,
meillo@121: which differed from the POSIX specification for
meillo@121: .Fu basename() .
meillo@121: Hence,
meillo@121: .Fu r1bindex()
meillo@121: was kept but renamed to
meillo@123: .Fu mhbasename() ,
meillo@123: fixing the delimiter to the slash.
meillo@121: .Ci 240013872c392fe644bd4f79382d9f5314b4ea60
meillo@121: For possible uses of
meillo@121: .Fu r1bindex()
meillo@121: with a different delimiter,
meillo@121: the ANSI C function
meillo@121: .Fu strrchr()
meillo@121: provides the core functionality.
meillo@121: .P
meillo@121: The
meillo@121: .Fu ssequal()
meillo@121: function \(en apparently for ``substring equal'' \(en
meillo@121: was renamed to
meillo@121: .Fu isprefix() ,
meillo@121: because this is what it actually checks.
meillo@121: .Ci c20b4fa14515c7ab388ce35411d89a7a92300711
meillo@121: Its source file had included the following comments, no joke.
meillo@121: .VS
meillo@121: /*
meillo@121:  * THIS CODE DOES NOT WORK AS ADVERTISED.
meillo@121:  * It is actually checking if s1 is a PREFIX of s2.
meillo@121:  * All calls to this function need to be checked to see
meillo@121:  * if that needs to be changed. Prefix checking is cheaper, so
meillo@121:  * should be kept if it's sufficient.
meillo@121:  */
meillo@121: 
meillo@121: /*
meillo@121:  * Check if s1 is a substring of s2.
meillo@121:  * If yes, then return 1, else return 0.
meillo@121:  */
meillo@121: VE
meillo@123: Two months later, it was completely removed by replacing it with
meillo@123: .Fu strncmp() .
meillo@123: .Ci b0b1dd37ff515578cf7cba51625189eb34a196cb
meillo@121: 
meillo@102: 
meillo@102: 
meillo@102: 
meillo@133: 
meillo@133: .H2 "User Data Locations
meillo@133: .P
meillo@133: In nmh, a personal setup consists of the MH profile and the MH directory.
meillo@133: The profile is a file named
meillo@133: .Fn \&.mh_profile
meillo@133: in the user's home directory.
meillo@133: It contains the static configuration.
meillo@133: It also contains the location of the MH directory in the profile entry
meillo@133: .Pe Path .
meillo@133: The MH directory contains the mail storage and is the first
meillo@133: place to search for personal forms, scan formats, and similar
meillo@133: configuration files.
meillo@133: The location of the MH directory can be chosen freely by the user.
meillo@133: The default and usual name is a directory named
meillo@133: .Fn Mail
meillo@133: in the home directory.
meillo@133: .P
meillo@133: The way MH data is splitted between profile and MH directory is a legacy.
meillo@133: It is only sensible in a situation where the profile is the only
meillo@133: configuration file.
meillo@133: Why else should the mail storage and the configuration files be intermixed?
meillo@133: They are different kinds of data:
meillo@133: The data to be operated on and the configuration to change how
meillo@133: tools operate.
meillo@133: Splitting the configuration between the profile and the MH directory
meillo@133: is bad.
meillo@133: Merging the mail storage and the configuration in one directory is bad
meillo@133: as well.
meillo@133: As the mail storage and the configuration were not separated sensibly
meillo@133: in the first place, I did it now.
meillo@133: .P
meillo@133: Personal mmh data is grouped by type, resulting in two distinct parts:
meillo@133: The mail storage and the configuration.
meillo@133: In mmh, the mail storage directory still contains all the messages,
meillo@133: but, in exception of public sequences files, nothing else.
meillo@133: In difference to nmh, the auxiliary configuration files are no longer
meillo@133: located there.
meillo@133: Therefore, the directory is no longer called the user's \fIMH directory\fP
meillo@133: but his \fImail storage\fP.
meillo@133: Its location is still user-chosen, with the default name
meillo@133: .Fn Mail ,
meillo@133: in the user's home directory.
meillo@133: In mmh, the configuration is grouped together in
meillo@133: the hidden directory
meillo@133: .Fn \&.mmh
meillo@133: in the user's home directory.
meillo@133: This \fImmh directory\fP contains the context file, personal forms,
meillo@133: scan formats, and the like, but also the user's profile, now named
meillo@133: .Fn profile .
meillo@133: The location of the profile is no longer fixed to
meillo@133: .Fn $HOME/.mh_profile
meillo@133: but to
meillo@133: .Fn $HOME/.mmh/profile .
meillo@133: Having both, the file
meillo@133: .Fn $HOME/.mh_profile
meillo@133: and the configuration directory
meillo@133: .Fn $HOME/.mmh
meillo@133: appeared to be inconsistent.
meillo@133: The approach chosen for mmh is consistent, simple, and familiar to
meillo@133: Unix users.
meillo@133: .P
meillo@133: MH allows users to have multiiple MH setups.
meillo@133: Therefore, it is necessary to select a different profile.
meillo@133: The profile is the single entry point to access the rest of a
meillo@133: personal MH setup.
meillo@133: In nmh, the environment variable
meillo@133: .Ev MH
meillo@133: could be used to specifiy a different profile.
meillo@133: To operate in the same MH setup with a separate context,
meillo@133: the
meillo@133: .Ev MHCONTEXT
meillo@133: environment variable could be used.
meillo@133: This allows having own current folders and current messages in
meillo@133: each terminal, for instance.
meillo@133: In mmh, three environment variables are used.
meillo@133: .Ev MMH
meillo@133: overrides the default location of the mmh directory (\c
meillo@133: .Fn .mmh ).
meillo@133: .Ev MMHP
meillo@133: and
meillo@133: .Ev MMHC
meillo@133: override the paths to the profile and context files, respectively.
meillo@133: This approach allows the set of personal configuration files to be chosen
meillo@133: independently from the profile, context, and mail storage.
meillo@133: .P
meillo@133: The separation of the files by type is sensible and convenient.
meillo@133: The new approach has no functional disadvantages,
meillo@133: as every setup I can imagine can be implemented with both approaches,
meillo@133: possibly even easier with the new approach.
meillo@133: The main achievement of the change is the clear and sensible split
meillo@133: between mail storage and configuration.
meillo@133: 
meillo@133: 
meillo@133: 
meillo@133: 
meillo@133: 
meillo@118: .H2 "Modularization
meillo@118: .P
meillo@123: The source code of the mmh tools is located in the
meillo@122: .Fn uip
meillo@123: (``user interface programs'') directory.
meillo@123: Each tools has a source file with the same name.
meillo@122: For example,
meillo@122: .Pn rmm
meillo@122: is built from
meillo@122: .Fn uip/rmm.c .
meillo@123: Some source files are used for multiple programs.
meillo@122: For example
meillo@122: .Fn uip/scansbr.c
meillo@123: is used for both,
meillo@122: .Pn scan
meillo@122: and
meillo@122: .Pn inc .
meillo@122: In nmh, 49 tools were built from 76 source files.
meillo@123: This is a ratio of 1.6 source files per program.
meillo@123: 32 programs depended on multiple source files;
meillo@123: 17 programs depended on one source file only.
meillo@122: In mmh, 39 tools are built from 51 source files.
meillo@123: This is a ratio of 1.3 source files per program.
meillo@123: 18 programs depend on multiple source files;
meillo@123: 21 programs depend on one source file only.
meillo@123: (These numbers and the ones in the following text ignore the MH library
meillo@123: as well as shell scripts and multiple names for the same program.)
meillo@122: .P
meillo@123: Splitting the source code of a large program into multiple files can
meillo@122: increase the readability of its source code.
meillo@124: Most of the mmh tools, however, are simple and straight-forward programs.
meillo@122: With the exception of the MIME handling tools,
meillo@122: .Pn pick
meillo@122: is the largest tools.
meillo@122: It contains 1\|037 lines of source code (measured with
meillo@122: .Pn sloccount ), excluding the MH library.
meillo@122: Only the MIME handling tools (\c
meillo@122: .Pn mhbuild ,
meillo@122: .Pn mhstore ,
meillo@122: .Pn show ,
meillo@122: etc.)
meillo@122: are larger.
meillo@122: Splitting programs with less than 1\|000 lines of code into multiple
meillo@123: source files seldom leads to better readability.
meillo@123: For such tools, splitting makes sense
meillo@122: when parts of the code are reused in other programs,
meillo@122: and the reused code fragment is not general enough
meillo@122: for including it in the MH library,
meillo@124: or, if the code has dependencies on a library that only few programs need.
meillo@122: .Fn uip/packsbr.c ,
meillo@122: for instance, provides the core program logic for the
meillo@122: .Pn packf
meillo@122: and
meillo@122: .Pn rcvpack
meillo@122: programs.
meillo@122: .Fn uip/packf.c
meillo@122: and
meillo@122: .Fn uip/rcvpack.c
meillo@122: mainly wrap the core function appropriately.
meillo@122: No other tools use the folder packing functions.
meillo@123: As another example,
meillo@123: .Fn uip/termsbr.c
meillo@123: provides termcap support, which requires linking with a termcap or
meillo@123: curses library.
meillo@123: Including
meillo@123: .Fn uip/termsbr.c
meillo@123: into the MH library would require every program to be linked with
meillo@123: termcap or curses, although only few of the programs require it.
meillo@122: .P
meillo@122: The task of MIME handling is complex enough that splitting its code
meillo@122: into multiple source files improves the readability.
meillo@122: The program
meillo@122: .Pn mhstore ,
meillo@122: for instance, is compiled out of seven source files with 2\|500
meillo@122: lines of code in summary.
meillo@122: The main code file
meillo@122: .Fn uip/mhstore.c
meillo@123: consists of 800 lines; the other 1\|700 lines of code are reused in
meillo@123: other MIME handling tools.
meillo@123: It seems to be worthwhile to bundle the generic MIME handling code into
meillo@123: a MH-MIME library, as a companion to the MH standard library.
meillo@122: This is left open for the future.
meillo@122: .P
meillo@123: The work already done, focussed on the non-MIME tools.
meillo@122: The amount of code compiled into each program was reduced.
meillo@123: This eases the understanding of the code base.
meillo@122: In nmh,
meillo@122: .Pn comp
meillo@122: was built from six source files:
meillo@122: .Fn comp.c ,
meillo@122: .Fn whatnowproc.c ,
meillo@122: .Fn whatnowsbr.c ,
meillo@122: .Fn sendsbr.c ,
meillo@122: .Fn annosbr.c ,
meillo@122: and
meillo@122: .Fn distsbr.c .
meillo@122: In mmh, it builds from only two:
meillo@122: .Fn comp.c
meillo@122: and
meillo@122: .Fn whatnowproc.c .
meillo@123: In nmh's
meillo@123: .Pn comp ,
meillo@123: the core function of
meillo@122: .Pn whatnow ,
meillo@122: .Pn send ,
meillo@122: and
meillo@122: .Pn anno
meillo@123: were compiled into
meillo@122: .Pn comp .
meillo@123: This saved the need to execute these programs with
meillo@122: .Fu fork()
meillo@122: and
meillo@122: .Fu exec() ,
meillo@122: two expensive system calls.
meillo@122: Whereis this approach improved the time performance,
meillo@122: it interweaved the source code.
meillo@122: Core functionalities were not encapsulated into programs but into
meillo@122: function, which were then wrapped by programs.
meillo@122: For example,
meillo@122: .Fn uip/annosbr.c
meillo@122: included the function
meillo@122: .Fu annotate() .
meillo@122: Each program that wanted to annotate messages, included the source file
meillo@123: .Fn uip/annosbr.c
meillo@123: and called
meillo@123: .Fu annotate() .
meillo@123: Because the function
meillo@123: .Fu annotate()
meillo@123: was used like the tool
meillo@123: .Pn anno ,
meillo@123: it had seven parameters, reflecting the command line switches of the tool.
meillo@122: When another pair of command line switches was added to
meillo@122: .Pn anno ,
meillo@122: a rather ugly hack was implemented to avoid adding another parameter
meillo@122: to the function.
meillo@122: .Ci d9b1d57351d104d7ec1a5621f090657dcce8cb7f
meillo@122: .P
meillo@122: Separation simplifies the understanding of program code
meillo@122: because the area influenced by any particular statement is smaller.
meillo@122: The separating on the program-level is more strict than the separation
meillo@122: on the function level.
meillo@122: In mmh, the relevant code of
meillo@122: .Pn comp
meillo@122: comprises the two files
meillo@122: .Fn uip/comp.c
meillo@122: and
meillo@122: .Fn uip/whatnowproc.c ,
meillo@123: together 210 lines of code.
meillo@122: In nmh,
meillo@122: .Pn comp
meillo@122: comprises six files with 2\|450 lines.
meillo@123: Not all of the code in these six files was actually used by
meillo@122: .Pn comp ,
meillo@123: but the code reader needed to read all of the code first to know which
meillo@123: parts were used.
meillo@122: .P
meillo@123: As I have read a lot in the code base during the last two years,
meillo@123: I learned about the easy and the difficult parts.
meillo@123: Code is easy to understand if:
meillo@123: .BU
meillo@123: The influenced code area is small
meillo@123: .BU
meillo@124: The boundaries are strictly defined
meillo@123: .BU
meillo@123: The code is written straight-forward
meillo@123: .P
meillo@123: .\" XXX move this paragraph somewhere else?
meillo@123: Reading
meillo@122: .Pn rmm 's
meillo@122: source code in
meillo@122: .Fn uip/rmm.c
meillo@122: is my recommendation for a beginner's entry point into the code base of nmh.
meillo@122: The reasons are that the task of
meillo@122: .Pn rmm
meillo@122: is straight forward and it consists of one small source code file only,
meillo@122: yet its source includes code constructs typical for MH tools.
meillo@122: With the introduction of the trash folder in mmh,
meillo@122: .Pn rmm
meillo@122: became a bit more complex, because it invokes
meillo@122: .Pn refile .
meillo@122: Still, it is a good example for a simple tool with clear sources.
meillo@122: .P
meillo@122: Understanding
meillo@122: .Pn comp
meillo@122: requires to read 210 lines of code in mmh, but ten times as much in nmh.
meillo@123: Due to the aforementioned hack in
meillo@122: .Pn anno
meillo@122: to save the additional parameter, information passed through the program's
meillo@122: source base in obscure ways.
meillo@123: Thus, understanding
meillo@122: .Pn comp ,
meillo@123: required understanding the inner workings of
meillo@122: .Fn uip/annosbr.c
meillo@122: first.
meillo@123: To be sure to fully understand a program, its whole source code needs
meillo@122: to be examined.
meillo@123: Not doing so is a leap of faith, assuming that the developers
meillo@122: have avoided obscure programming techniques.
meillo@122: By separating the tools on the program-level, the boundaries are
meillo@122: clearly visible and technically enforced.
meillo@122: The interfaces are calls to
meillo@122: .Fu exec()
meillo@122: rather than arbitrary function calls.
meillo@123: .P
meillo@123: But the real problem is another:
meillo@123: Nmh violates the golden ``one tool, one job'' rule of the Unix philosophy.
meillo@123: Understanding
meillo@122: .Pn comp
meillo@123: requires understanding
meillo@123: .Fn uip/annosbr.c
meillo@123: and
meillo@123: .Fn uip/sendsbr.c
meillo@123: because
meillo@123: .Pn comp
meillo@123: does annotate and send messages.
meillo@123: In nmh, there surely exists the tool
meillo@122: .Pn send ,
meillo@123: which does (almost) only send messages.
meillo@123: But
meillo@122: .Pn comp
meillo@123: and
meillo@122: .Pn repl
meillo@122: and
meillo@122: .Pn forw
meillo@122: and
meillo@122: .Pn dist
meillo@122: and
meillo@122: .Pn whatnow
meillo@122: and
meillo@123: .Pn viamail ,
meillo@123: they all (!) have the same message sending function included, too.
meillo@123: In result,
meillo@123: .Pn comp
meillo@123: sends messages without using
meillo@123: .Pn send .
meillo@123: The situation is the same as if
meillo@123: .Pn grep
meillo@123: would page without
meillo@123: .Pn more
meillo@123: just because both programs are part of the same code base.
meillo@123: .P
meillo@122: The clear separation on the surface \(en the toolchest approach \(en
meillo@123: is violated on the level below.
meillo@122: This violation is for the sake of time performance.
meillo@122: On systems where
meillo@122: .Fu fork()
meillo@122: and
meillo@122: .Fu exec()
meillo@122: are expensive, the quicker response might be noticable.
meillo@124: In the old times, sacrificing readability and conceptional beauty for
meillo@124: speed might even have been a must to prevent MH from being unusably slow.
meillo@122: Whatever the reasons had been, today they are gone.
meillo@123: No longer should we sacrifice readability or conceptional beauty.
meillo@122: No longer should we violate the Unix philosophy's ``one tool, one job''
meillo@122: guideline.
meillo@123: No longer should we keep speed improvements that became unnecessary.
meillo@122: .P
meillo@123: Therefore, mmh's
meillo@123: .Pn comp
meillo@123: does no longer send messages.
meillo@123: In mmh, different jobs are divided among separate programs that
meillo@122: invoke each other as needed.
meillo@123: In consequence,
meillo@123: .Pn comp
meillo@123: invokes
meillo@123: .Pn whatnow
meillo@123: which thereafter invokes
meillo@123: .Pn send .
meillo@123: The clear separation on the surface is maintained on the level below.
meillo@123: Human users and the tools use the same interface \(en
meillo@123: annotations, for example, are made by invoking
meillo@123: .Pn anno ,
meillo@123: no matter if requested by programs or by human beings.
meillo@123: The decrease of tools built from multiple source files and thus
meillo@123: the decrease of
meillo@123: .Fn uip/*sbr.c
meillo@123: files confirm the improvement.
meillo@123: .P
meillo@123: One disadvantage needs to be taken with this change:
meillo@123: The compiler can no longer check the integrity of the interfaces.
meillo@123: By changing the command line interfaces of tools, it is
meillo@123: the developer's job to adjust the invocations of these tools as well.
meillo@123: As this is a manual task and regression tests, which could detect such
meillo@124: problems, are not available yet, it is prone to errors.
meillo@123: These errors will not be detected at compile time but at run time.
meillo@123: Installing regression tests is a task left to do.
meillo@123: In the best case, a uniform way of invoking tools from other tools
meillo@123: can be developed to allow automated testing at compile time.