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1 .H0 "Discussion
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2 .P
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3 This main chapter discusses the practical work done in the mmh project.
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4 It is structured along the goals to achieve. The concrete work done
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5 is described in the examples of how the general goals were achieved.
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6
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7
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8
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9
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10 .H1 "Stream-lining
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11
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12 .P
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13 MH had been considered an all-in-one system for mail handling.
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14 The community around nmh has a similar understanding.
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15 In fundamental difference, I believe that mmh should be a MUA but
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16 nothing more. I believe that all-in-one mail systems are not the way
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17 to go. There are excellent specialized MTAs, like Postfix;
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18 there are specialized MDAs, like Procmail; there are specialized
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19 MRAs, like Fetchmail. I believe it's best to use them instead of
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20 providing the same function ourselves. Doing something well requires to
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21 focus on this particular aspect or a small set of aspects. The more
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22 it is possible to focus, the better the result in this particular
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23 area will be. The limiting resource in Free Software community development
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24 usually is human power. If the low development power is even parted
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25 into multiple development areas, it will hardly be possible to
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26 compete with the specialists in the various fields. This is even
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27 increased, given the small community \(en developers and users \(en
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28 that MH-based mail systems have. In consequence, I believe that the
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29 available resources should be concentrated at the point where MH is
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30 most unique. This is clearly the MUA part.
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31 .P
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32 The goal for mmh was to remove peripheral parts and stream-line
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33 it for the MUA task.
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34
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35
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36 .H2 "Removal of Mail Transfer Facilities
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37 .P
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38 In contrast to nmh, which also provides mail submission and mail retrieval
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39 facilities, mmh is a MUA only.
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40 This general difference in the view on the character of nmh
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41 strongly supported the development of mmh.
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42 Removing the mail transfer facilities had been the first work task
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43 for the mmh project.
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44 .P
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45 The MSA is called \fIMessage Transfer Service\fP (MTS) in nmh.
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46 The facility establishes TCP/IP connections and speaks SMTP to submit
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47 messages for relay to the outside world.
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48 This part is implemented in the
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49 .Pn post
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50 command.
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51 Demanded by the changes in
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52 emailing, this part of nmh required changes in the last years.
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53 Encrypted connections needed to be supported, hence SASL was introduced
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54 into nmh. This added complexity to the nmh without improving it in
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55 its core functions. Also, keeping up with recent developments in
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56 this field needs requires development power and specialists.
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57 Mmh cuts this whole facility off and depends on an external MTA instead.
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58 The only outgoing interface available to mmh is the
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59 .Pn sendmail
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60 command.
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61 Almost any MTA provides a
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62 .Pn sendmail
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63 command.
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64 It not, any program can be substituted if it reads the
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65 message from the standard input, extracts the recipient addresses
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66 from the message header and does not conflict
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67 with sendmail-specific command line arguments.
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68 .P
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69 To retrieve mail, the
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70 .Pn inc
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71 command in nmh has the ability to establish TCP/IP connections
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72 and speaks POP3 to retrieve mail from remote servers.
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73 As with mail submission, here encrypted connections are required
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74 today, thus SASL support was added.
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75 As POP3 is superseded by IMAP more and more, support for message
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76 retrieval through IMAP will become necessary to be added soon.
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77 Mmh has no support for retrieving mail from remote locations.
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78 It depends on an external tool to cover this task.
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79 There are two ways for messages to enter mmh's mail storage:
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80 Incorporate them with
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81 .Pn inc
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82 from the system maildrop, or with
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83 .Pn rcvstore
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84 from the standard input.
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85 In consequence, mmh has not any longer networking code
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86 and thus does no more need to do transfer encryption and authentication.
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87 Two large functional units are removed.
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88 .P
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89 With the removal of the MSA and MRA, mmh converted from an all-in-one
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90 mail system to being only a MUA.
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91 Following the Unix philosophy, it focuses on one job and to do that well.
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92 Now, of course, mmh depends on third-party software.
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93 An external MTA/MSA is required to transfer mail to the outside world;
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94 an external MRA is required to retrieve mail from remote machines.
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95 There exist excellent implementations of such software,
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96 which do this specific task likely much better than the internal
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97 versions of nmh do it. Also, this provides the choice for the best
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98 suiting one of the available implementation.
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99 .P
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100 As it had already been possible to use an external MSA or MRA,
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101 why not keep the internal version for convenience?
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102 If this would question the sense in having a fall-back pager in all
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103 the command line tools, in case
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104 .Pn more
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105 or
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106 .Pn less
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107 wouldn't be available, the answer is intuitively seen.
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108 Now, an MSA or MRA is clearly more complex than a text pager, but
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109 still the concept holds: If programs become complex, split them;
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110 if projects become complex, split them.
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111 Complexity is demanded by the problem to solve. Decades ago,
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112 emailing had been small and simple.
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113 (Remember,
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114 .Pn /bin/mail
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115 had once covered anything there was to email and still had been small.)
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116 As the complexity in emailing increased, MH remainded mostly unchanged.
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117 Nontheless, in nmh the POP server, which the original MH had included,
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118 was removed. Now is the time to take one step further and remove
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119 the MSA and MRA.
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120 Not only does it decrease the code amount of the project,
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121 but more important, it removes the whole field of message transfer
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122 with all its implications from the project.
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123 .P
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124 If a project needs some kind of function, there's always the choice
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125 between implementing the the function in the project directly or
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126 depending on a library that provides the function or depending on
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127 a program that provides the function.
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128 Whereas adding the function directly to the project increases the
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129 code size most, it makes the project most independent.
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130 On the other end, interfacing external programs keeps the interface
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131 smallest, but the depencency highest.
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132 Using a library is in the middle.
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133 Adding the function directly to the project is a bad choice for
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134 any function of higher complexity, unless it's not available in other ways.
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135 Hence, the dependencies only change in kind, not in their existence.
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136 In mmh, library dependencies on
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137 .Pn libsasl2
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138 and
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139 .Pn libcrypto /\c
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140 .Pn libssl
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141 were treated against program dependencies on an MSA and an MRA.
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142 Besides program dependencies providing the stronger separation
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143 and being more flexible, they also allowed
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144 over 6\|000 lines of code to be removed from mmh.
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145 This made mmh's code base about 12\|% smaller.
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146 Reducing the projects code size by such an amount without actually
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147 losing function is a convincing argument.
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148 .P
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149 Users of MH should have not problem to set up an external MSA and MRA.
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150 Also, the popular MSAs and MRAs have large communities and a lot
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151 of documentation available.
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152 .P
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153 Choices for MSAs range from the full-featured
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154 .I Postfix
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155 over mid-size solutions like
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156 .I masqmail
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157 and
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158 .I dma
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159 to small forwarders like
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160 .I ssmtp
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161 and
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162 .I nullmailer .
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163 Choices for MRAs include
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164 .I fetchmail ,
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165 .I getmail ,
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166 .I mpop
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167 and
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168 .I fdm .
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169
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170
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171 .H2 "Removal of non-MUA Tools
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172 .P
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173 Some of nmh's tools were removed from mmh because they didn't
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174 match the main focus of adding to the MUA's task.
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175 .BU
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176 .Pn conflict
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177 was removed because it is a mail system maintenance tool.
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178 Besides, it even checks
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179 .Fn /etc/passwd
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180 and
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181 .Fn /etc/group
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182 for consistency, which has nothing at all to do with emailing.
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183 The tool might be useful, but it should not be shipped with mmh.
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184 .BU
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185 .Pn rcvtty
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186 was removed because its usecase of writing to the user's terminal
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187 on receiving of mail is hardly wanted today. If users like to be
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188 informed of new mail, then using the shell's
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189 .Ev MAILPATH
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190 variable or graphical notifications are likely more
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191 appealing.
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192 Writing directly to a terminals is hardly ever wanted today.
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193 If though one wants to have it this way, the standard tool
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194 .Pn write
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195 can be used in a way similar to:
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196 .DS
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197 scan -file - | write `id -un`
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198 .DE
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199 .BU
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200 .Pn viamail
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201 was removed when the new attachment system was introduced, because
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202 .Pn forw
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203 could can now the task itself.
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204 The program
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205 .Pn sendfiles
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206 was rewritten as a shell script wrapper around
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207 .Pn forw .
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208 .BU
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209 .Pn msgchk
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210 was removed, because it lost its usefulness when POP support was removed.
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211 .Pn msgchk
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212 provides hardly more information than:
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213 .DS
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214 ls -l /var/mail/meillo
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215 .DE
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216 It does separate between old and new mail, but that's merely a detail
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217 and can be done with
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218 .Pn stat (1)
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219 too.
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220 A very small shell script could be written to output the information
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221 in a convenient way, if truly necessary.
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222 As mmh's inc only incorporates mail from the user's local maildrop
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223 and thus no data transfers over slow networks are involved,
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224 there's hardly need to check for new mail before incorporating it.
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225 .BU
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226 .Pn msh
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227 was removed because the tool was in conflict with the
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228 philosophy of MH. It provided an interactive shell to access the
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229 features of MH. One major feature of MH is being a tool chest.
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230 .Pn msh
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231 wouldn't be just another shell, tailored to the needs of mail
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232 handling, but one large program to have the MH tools built in.
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233 It's main use was for accessing Bulletin Boards, which have seized to
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234 be popular.
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235 .P
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236 Removing
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237 .Pn msh ,
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238 together with the truly obsolete code relicts
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239 .Pn vmh
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240 and
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241 .Pn wmh ,
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242 saved more than 7\|000 lines of C code \(en
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243 about 15\|% of the project's original source code amount.
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244 Having the same functionality in less code (with equal readability,
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245 of course) is an advantage.
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246 Less code means less bugs and less maintenance work.
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247 If
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248 .Pn rcvtty
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249 and
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250 .Pn msgchk
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251 are rarely used and can be implemented in different ways,
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252 then why should one keep them?
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253 .Pn viamail 's
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254 use case is now partly obsolete and partly covered by
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255 .Pn forw ,
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256 hence there's no reason to still have
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257 .Pn viamail
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258 around.
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259 .Pn conflict
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260 is not related with the mail client, and
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261 .Pn msh
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262 conflicts with the basic concept of MH.
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263 Both tools could still be useful, but not as part of mmh.
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264 .P
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265 It is a design goal of mmh to remove those parts that are rarely used.
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266 The project shall become more stream-lined.
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267 Rarely used and loosely related tools distract from the lean appearance.
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268 They require maintenance cost without adding to the core task.
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269 Therefore they were removed.
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270
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271
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272 .H2 "Merge of \f(CWshow\fP and \f(CWmhshow\fP
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273 .P
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274 Since the very beginning, already in the first concept paper,
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275 .Pn show
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276 had been MH's message display program.
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277 .Pn show
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278 found out which pathnames the relevant messages had and invoked
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279 .Pn mhl
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280 then to have the content formated.
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281 With the advent of MIME, this approach wasn't sufficient anymore.
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282 MIME messages can consist of multiple parts, some of which aren't
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283 directly displayable, and text content might be encoded in
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284 foreign charsets.
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285 .Pn show 's
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286 simple approach and
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287 .Pn mhl 's
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288 limited display facilities couldn't cope with the task any longer.
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289 .P
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290 Instead of extending these tools, new ones were written from scratch
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291 and then added to the MH tool chest. Doing so is encouraged by the
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292 tool chest approach. The new tools could be added without interfering
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293 with the existing ones. This is great. The ease of adding new tools
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294 even made MH the first MUA to implement MIME.
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295 .P
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296 First, the new MIME features were added in form of the single program
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297 .Pn mhn .
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298 The command
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299 .Cl "mhn \-show 42
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300 would show the MIME message numbered 42.
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301 With the 1.0 release of nmh in February 1999, Richard Coleman finished
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302 the split of
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303 .Pn mhn
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304 into a set of specialized programs, which together covered the
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305 multiple aspects of MIME. One of these resulting tools was
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306 .Pn mhshow .
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307 .Pn mhshow
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308 resembled the
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309 .Cl "mhn \-show
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310 call.
|
|
meillo@62
|
311 .P
|
|
meillo@58
|
312
|
|
meillo@58
|
313
|
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meillo@58
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314 .H2 "Removal of Configure Options
|
|
meillo@58
|
315 .P
|
|
meillo@58
|
316
|
|
meillo@63
|
317
|
|
meillo@58
|
318 .H2 "Removal of switches
|
|
meillo@58
|
319 .P
|
|
meillo@58
|
320
|
|
meillo@58
|
321
|
|
meillo@58
|
322
|
|
meillo@58
|
323
|
|
meillo@58
|
324 .H1 "Moderizing
|
|
meillo@58
|
325
|
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meillo@58
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326
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meillo@58
|
327 .H2 "Removal of Code Relicts
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meillo@0
|
328 .P
|
|
meillo@51
|
329 The code base of mmh originates from the late Seventies,
|
|
meillo@51
|
330 had been extensively
|
|
meillo@51
|
331 worked on in the mid Eighties, and had been partly reorganized and extended
|
|
meillo@51
|
332 in the Nineties. Relicts of all those times had gathered in the code base.
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|
meillo@12
|
333 My goal was to remove any ancient code parts. One part of the task was
|
|
meillo@12
|
334 converting obsolete code constructs to standard constructs, the other part
|
|
meillo@12
|
335 was dropping obsolete functions.
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|
meillo@12
|
336 .P
|
|
meillo@12
|
337 As I'm not even thirty years old and have no more than seven years of
|
|
meillo@51
|
338 Unix experience, I needed to learn about the history in retrospective.
|
|
meillo@51
|
339 Older people likely have used those ancient constructs themselves
|
|
meillo@51
|
340 and have suffered from their incompatibilities and have longed for
|
|
meillo@12
|
341 standardization. Unfortunately, I have only read that others had done so.
|
|
meillo@12
|
342 This put me in a much more difficult positions when working on the old
|
|
meillo@12
|
343 code. I needed to recherche what other would have known by heart from
|
|
meillo@12
|
344 experience. All my programming experience comes from a time past ANSI C
|
|
meillo@12
|
345 and past POSIX. Although I knew about the times before, I took the
|
|
meillo@51
|
346 current state implicitly for granted most of the time.
|
|
meillo@12
|
347 .P
|
|
meillo@12
|
348 Being aware of
|
|
meillo@12
|
349 these facts, I rather let people with more historic experience solve the
|
|
meillo@12
|
350 task of converting the ancient code constructs to standardized ones.
|
|
meillo@12
|
351 Luckily, Lyndon Nerenberg focused on this task at the nmh project.
|
|
meillo@12
|
352 He converted large parts of the code to POSIX constructs, removing
|
|
meillo@12
|
353 the conditionals compilation for now standardized features.
|
|
meillo@12
|
354 I'm thankful for this task being solved. I only pulled the changes into
|
|
meillo@12
|
355 mmh.
|
|
meillo@12
|
356 .P
|
|
meillo@20
|
357 The other task \(en dropping ancient functionality to remove old code \(en
|
|
meillo@12
|
358 I did myself, though. My position to strip mmh to the bare minimum of
|
|
meillo@12
|
359 frequently used features is much more revolutional than the nmh community
|
|
meillo@20
|
360 likes it. Without the need to justify my decisions, I was able to quickly
|
|
meillo@20
|
361 remove functionality I considered ancient.
|
|
meillo@20
|
362 The need to discuss my decisions with
|
|
meillo@20
|
363 peers likely would have slowed this process down. Of course, I researched
|
|
meillo@12
|
364 if a particular feature really should be dropped. Having not had any
|
|
meillo@12
|
365 contact to this feature within my computer life was a first indicator to
|
|
meillo@12
|
366 drop it, but I also asked others and searched the literature for modern
|
|
meillo@12
|
367 usage of the feature. If it appeared to be truly ancient, I dropped it.
|
|
meillo@12
|
368 The reason for dropping is always part of the commit message in the
|
|
meillo@12
|
369 version control system. Thus, it is easy for others to check their
|
|
meillo@12
|
370 view on the topic with mine and possibly to argue for reinclusion.
|
|
meillo@12
|
371
|
|
meillo@12
|
372 .U2 "MMDF maildrop support
|
|
meillo@12
|
373 .P
|
|
meillo@12
|
374 I did drop any support for the MMDF maildrop format. This type of format
|
|
meillo@12
|
375 is conceptionally similar to the mbox format, but uses four bytes with
|
|
meillo@12
|
376 value 1 (\fL^A^A^A^A\fP) as message delimiter,
|
|
meillo@18
|
377 instead of the string ``\fLFrom\ \fP''.
|
|
meillo@12
|
378 Due to the similarity and mbox being the de-facto standard maildrop
|
|
meillo@12
|
379 format on Unix, but also due to the larger influence of Sendmail than MMDF,
|
|
meillo@12
|
380 the MMDF maildrop format had vanished.
|
|
meillo@12
|
381 .P
|
|
meillo@12
|
382 The simplifications within the code were only moderate. Switches could
|
|
meillo@12
|
383 be removed from tools like
|
|
meillo@12
|
384 .L packf ,
|
|
meillo@12
|
385 which generate packed mailboxes. Only one packed mailbox format remained:
|
|
meillo@12
|
386 mbox.
|
|
meillo@12
|
387 The most important changes affect the equally named mail parsing routine in
|
|
meillo@12
|
388 .L sbr/m_getfld.c .
|
|
meillo@12
|
389 The direct MMDF code had been removed, but as now only one packed mailbox
|
|
meillo@12
|
390 format is left, code structure simplifications are likely possible.
|
|
meillo@12
|
391 The reason why they are still outstanding is the heavily optimized code
|
|
meillo@18
|
392 of
|
|
meillo@18
|
393 .Fu m_getfld() .
|
|
meillo@18
|
394 Changes beyond a small local scope \(en
|
|
meillo@12
|
395 which restructuring in its core is \(en cause a high risk of damaging
|
|
meillo@12
|
396 the intricate workings of the optimized code. This problem is know
|
|
meillo@12
|
397 to the developers of nmh, too. They also avoid touching this minefield
|
|
meillo@12
|
398 if possible.
|
|
meillo@12
|
399
|
|
meillo@12
|
400 .U2 "UUCP Bang Paths
|
|
meillo@12
|
401 .P
|
|
meillo@12
|
402 More questionably than the former topic is the removal of support for the
|
|
meillo@12
|
403 UUCP bang path address style. However, the user may translate the bang
|
|
meillo@12
|
404 paths on retrieval to Internet addresses and the other way on posting
|
|
meillo@12
|
405 messages. The former can be done my an MDA like procmail; the latter
|
|
meillo@12
|
406 by a sendmail wrapper. This would ensure that any address handling would
|
|
meillo@12
|
407 work as expected. However, it might just work well without any
|
|
meillo@12
|
408 such modifications, as mmh does not touch addresses much, in general.
|
|
meillo@12
|
409 But I can't ensure as I have never used an environment with bang paths.
|
|
meillo@12
|
410 Also, the behavior might break at any point in further development.
|
|
meillo@12
|
411
|
|
meillo@12
|
412 .U2 "Hardcopy terminal support
|
|
meillo@12
|
413 .P
|
|
meillo@12
|
414 More of a funny anecdote is the remaining of a check for printing to a
|
|
meillo@12
|
415 hardcopy terminal until Spring 2012, when I finally removed it.
|
|
meillo@12
|
416 I surely would be very happy to see such a terminal in action, maybe
|
|
meillo@12
|
417 actually being able to work on it, but I fear my chances are null.
|
|
meillo@12
|
418 .P
|
|
meillo@12
|
419 The check only prevented a pager to be placed between the outputting
|
|
meillo@18
|
420 program (\c
|
|
meillo@18
|
421 .Pn mhl )
|
|
meillo@18
|
422 and the terminal. This could have been ensured with
|
|
meillo@18
|
423 the
|
|
meillo@18
|
424 .Sw \-nomoreproc
|
|
meillo@18
|
425 at the command line statically, too.
|
|
meillo@12
|
426
|
|
meillo@12
|
427 .U2 "Removed support for header fields
|
|
meillo@12
|
428 .P
|
|
meillo@12
|
429 The `Encrypted' header had been introduced by RFC\^822, but already
|
|
meillo@12
|
430 marked legacy in RFC 2822. It was superseded by FIXME.
|
|
meillo@12
|
431 Mmh does no more support this header.
|
|
meillo@12
|
432 .P
|
|
meillo@21
|
433 Native support for `Face' headers
|
|
meillo@21
|
434 had been removed, as well.
|
|
meillo@21
|
435 The feature is similar to the `X-Face' header in its intent,
|
|
meillo@21
|
436 but takes a different approach to store the image.
|
|
meillo@21
|
437 Instead of encoding the image data directly into the header,
|
|
meillo@21
|
438 the the header contains the hostname and UDP port where the image
|
|
meillo@21
|
439 date could be retrieved.
|
|
meillo@21
|
440 Neither `X-Face' nor the here described `Face' system
|
|
meillo@21
|
441 \**
|
|
meillo@21
|
442 .FS
|
|
meillo@21
|
443 There is also a newer but different system, invented 2005,
|
|
meillo@21
|
444 using `Face' headers.
|
|
meillo@21
|
445 It is the successor of `X-Face' providing colored PNG images.
|
|
meillo@21
|
446 .FE
|
|
meillo@21
|
447 became well used in the large scale.
|
|
meillo@21
|
448 It's still possible to use a Face systems,
|
|
meillo@21
|
449 although mmh does not provide support for any of the different systems
|
|
meillo@21
|
450 anymore. It's fairly easy to write a small shell script to
|
|
meillo@21
|
451 extract the embedded or fetch the external Face data and display the image.
|
|
meillo@21
|
452 Own Face headers can be added into the draft template files.
|
|
meillo@21
|
453 .P
|
|
meillo@12
|
454 `Content-MD5' headers were introduced by RFC\^1864. They provide only
|
|
meillo@12
|
455 a verification of data corruption during the transfer. By no means can
|
|
meillo@12
|
456 they ensure verbatim end-to-end delivery of the contents. This is clearly
|
|
meillo@12
|
457 stated in the RFC. The proper approach to provide verificationability
|
|
meillo@12
|
458 of content in an end-to-end relationship is the use of digital cryptography
|
|
meillo@12
|
459 (RFCs FIXME). On the other hand, transfer protocols should ensure the
|
|
meillo@12
|
460 integrity of the transmission. In combinations these two approaches
|
|
meillo@12
|
461 make the `Content-MD5' header field useless. In consequence, I removed
|
|
meillo@12
|
462 the support for it. By this removal, MD5 computation is not needed
|
|
meillo@12
|
463 anywhere in mmh. Hence, over 500 lines of code were removed by this one
|
|
meillo@12
|
464 change. Even if the `Content-MD5' header field is useful sometimes,
|
|
meillo@12
|
465 I value its usefulnes less than the improvement in maintainability, caused
|
|
meillo@12
|
466 by the removal.
|
|
meillo@12
|
467
|
|
meillo@20
|
468 .U2 "Prompter's Control Keys
|
|
meillo@20
|
469 .P
|
|
meillo@20
|
470 The program
|
|
meillo@20
|
471 .Pn prompter
|
|
meillo@20
|
472 queries the user to fill in a message form. When used by
|
|
meillo@20
|
473 .Pn comp
|
|
meillo@20
|
474 as:
|
|
meillo@20
|
475 .DS
|
|
meillo@20
|
476 comp \-editor prompter
|
|
meillo@20
|
477 .DE
|
|
meillo@20
|
478 the resulting behavior is similar to
|
|
meillo@20
|
479 .Pn mailx .
|
|
meillo@51
|
480 Apparently,
|
|
meillo@20
|
481 .Pn prompter
|
|
meillo@20
|
482 hadn't been touched lately. Otherwise it's hardly explainable why it
|
|
meillo@20
|
483 still offered the switches
|
|
meillo@20
|
484 .Sn \-erase \fUchr\fP
|
|
meillo@20
|
485 and
|
|
meillo@20
|
486 .Sn \-kill \fUchr\fP
|
|
meillo@20
|
487 to name the characters for command line editing.
|
|
meillo@21
|
488 The times when this had been necessary are long time gone.
|
|
meillo@20
|
489 Today these things work out-of-the-box, and if not, are configured
|
|
meillo@20
|
490 with the standard tool
|
|
meillo@20
|
491 .Pn stty .
|
|
meillo@20
|
492
|
|
meillo@21
|
493 .U2 "Vfork and Retry Loops
|
|
meillo@21
|
494 .P
|
|
meillo@51
|
495 MH creates many processes, which is a consequence of the tool chest approach.
|
|
meillo@21
|
496 In earlier times
|
|
meillo@21
|
497 .Fu fork()
|
|
meillo@21
|
498 had been an expensive system call, as the process's whole image needed
|
|
meillo@21
|
499 to be duplicated. One common case is replacing the image with
|
|
meillo@21
|
500 .Fu exec()
|
|
meillo@21
|
501 right after having forked the child process.
|
|
meillo@21
|
502 To speed up this case, the
|
|
meillo@21
|
503 .Fu vfork()
|
|
meillo@21
|
504 system call was invented at Berkeley. It completely omits copying the
|
|
meillo@21
|
505 image. If the image gets replaced right afterwards then unnecessary
|
|
meillo@21
|
506 work is omited. On old systems this results in large speed ups.
|
|
meillo@21
|
507 MH uses
|
|
meillo@21
|
508 .Fu vfork()
|
|
meillo@21
|
509 whenever possible.
|
|
meillo@21
|
510 .P
|
|
meillo@21
|
511 Memory management units that support copy-on-write semantics make
|
|
meillo@21
|
512 .Fu fork()
|
|
meillo@21
|
513 almost as fast as
|
|
meillo@21
|
514 .Fu vfork()
|
|
meillo@21
|
515 in the cases when they can be exchanged.
|
|
meillo@21
|
516 With
|
|
meillo@21
|
517 .Fu vfork()
|
|
meillo@51
|
518 being more error-prone and hardly faster, it's preferable to simply
|
|
meillo@21
|
519 use
|
|
meillo@21
|
520 .Fu fork()
|
|
meillo@21
|
521 instead.
|
|
meillo@21
|
522 .P
|
|
meillo@21
|
523 Related to the costs of
|
|
meillo@21
|
524 .Fu fork()
|
|
meillo@21
|
525 is the probability of its success.
|
|
meillo@21
|
526 Today on modern systems, the system call will succeed almost always.
|
|
meillo@51
|
527 In the Eighties on heavy loaded systems, as they were common at
|
|
meillo@21
|
528 universities, this had been different. Thus, many of the
|
|
meillo@21
|
529 .Fu fork()
|
|
meillo@21
|
530 calls were wrapped into loops to retry to fork several times in
|
|
meillo@21
|
531 short intervals, in case of previous failure.
|
|
meillo@21
|
532 In mmh, the program aborts at once if the fork failed.
|
|
meillo@21
|
533 The user can reexecute the command then. This is expected to be a
|
|
meillo@21
|
534 very rare case on modern systems, especially personal ones, which are
|
|
meillo@21
|
535 common today.
|
|
meillo@21
|
536
|
|
meillo@12
|
537
|
|
meillo@58
|
538 .H2 "Attachments
|
|
meillo@22
|
539 .P
|
|
meillo@58
|
540 MIME
|
|
meillo@58
|
541
|
|
meillo@58
|
542
|
|
meillo@58
|
543 .H2 "Digital Cryptography
|
|
meillo@22
|
544 .P
|
|
meillo@58
|
545 Signing and encryption.
|
|
meillo@58
|
546
|
|
meillo@58
|
547
|
|
meillo@58
|
548 .H2 "Good Defaults
|
|
meillo@22
|
549 .P
|
|
meillo@58
|
550 foo
|
|
meillo@58
|
551
|
|
meillo@58
|
552
|
|
meillo@58
|
553
|
|
meillo@58
|
554
|
|
meillo@58
|
555 .H1 "Code style
|
|
meillo@22
|
556 .P
|
|
meillo@58
|
557 foo
|
|
meillo@58
|
558
|
|
meillo@58
|
559
|
|
meillo@58
|
560 .H2 "Standard Code
|
|
meillo@22
|
561 .P
|
|
meillo@58
|
562 POSIX
|
|
meillo@22
|
563
|
|
meillo@22
|
564
|
|
meillo@58
|
565 .H2 "Separation
|
|
meillo@14
|
566
|
|
meillo@58
|
567 .U2 "MH Directory Split
|
|
meillo@0
|
568 .P
|
|
meillo@19
|
569 In MH and nmh, a personal setup had consisted of two parts:
|
|
meillo@19
|
570 The MH profile, named
|
|
meillo@19
|
571 .Fn \&.mh_profile
|
|
meillo@19
|
572 and being located directly in the user's home directory.
|
|
meillo@19
|
573 And the MH directory, where all his mail messages and also his personal
|
|
meillo@19
|
574 forms, scan formats, other configuration files are stored. The location
|
|
meillo@19
|
575 of this directory could be user-chosen. The default was to name it
|
|
meillo@19
|
576 .Fn Mail
|
|
meillo@19
|
577 and have it directly in the home directory.
|
|
meillo@19
|
578 .P
|
|
meillo@19
|
579 I've never liked the data storage and the configuration to be intermixed.
|
|
meillo@19
|
580 They are different kinds of data. One part, are the messages,
|
|
meillo@19
|
581 which are the data to operate on. The other part, are the personal
|
|
meillo@19
|
582 configuration files, which are able to change the behavior of the operations.
|
|
meillo@19
|
583 The actual operations are defined in the profile, however.
|
|
meillo@19
|
584 .P
|
|
meillo@19
|
585 When storing data, one should try to group data by its type.
|
|
meillo@19
|
586 There's sense in the Unix file system hierarchy, where configuration
|
|
meillo@19
|
587 file are stored separate (\c
|
|
meillo@19
|
588 .Fn /etc )
|
|
meillo@19
|
589 to the programs (\c
|
|
meillo@19
|
590 .Fn /bin
|
|
meillo@19
|
591 and
|
|
meillo@19
|
592 .Fn /usr/bin )
|
|
meillo@19
|
593 to their sources (\c
|
|
meillo@19
|
594 .Fn /usr/src ).
|
|
meillo@19
|
595 Such separation eases the backup management, for instance.
|
|
meillo@19
|
596 .P
|
|
meillo@19
|
597 In mmh, I've reorganized the file locations.
|
|
meillo@19
|
598 Still there are two places:
|
|
meillo@19
|
599 There's the mail storage directory, which, like in MH, contains all the
|
|
meillo@19
|
600 messages, but, unlike in MH, nothing else.
|
|
meillo@19
|
601 Its location still is user-chosen, with the default name
|
|
meillo@19
|
602 .Fn Mail ,
|
|
meillo@19
|
603 in the user's home directory. This is much similar to the case in nmh.
|
|
meillo@19
|
604 The configuration files, however, are grouped together in the new directory
|
|
meillo@19
|
605 .Fn \&.mmh
|
|
meillo@19
|
606 in the user's home directory.
|
|
meillo@19
|
607 The user's profile now is a file, named
|
|
meillo@19
|
608 .Fn profile ,
|
|
meillo@19
|
609 in this mmh directory.
|
|
meillo@19
|
610 Consistently, the context file and all the personal forms, scan formats,
|
|
meillo@19
|
611 and the like, are also there.
|
|
meillo@19
|
612 .P
|
|
meillo@19
|
613 The naming changed with the relocation.
|
|
meillo@19
|
614 The directory where everything, except the profile, had been stored (\c
|
|
meillo@19
|
615 .Fn $HOME/Mail ),
|
|
meillo@19
|
616 used to be called \fIMH directory\fP. Now, this directory is called the
|
|
meillo@19
|
617 user's \fImail storage\fP. The name \fImmh directory\fP is now given to
|
|
meillo@19
|
618 the new directory
|
|
meillo@19
|
619 (\c
|
|
meillo@19
|
620 .Fn $HOME/.mmh ),
|
|
meillo@19
|
621 containing all the personal configuration files.
|
|
meillo@19
|
622 .P
|
|
meillo@19
|
623 The separation of the files by type of content is logical and convenient.
|
|
meillo@19
|
624 There are no functional differences as any possible setup known to me
|
|
meillo@19
|
625 can be implemented with both approaches, although likely a bit easier
|
|
meillo@19
|
626 with the new approach. The main goal of the change had been to provide
|
|
meillo@19
|
627 sensible storage locations for any type of personal mmh file.
|
|
meillo@19
|
628 .P
|
|
meillo@19
|
629 In order for one user to have multiple MH setups, he can use the
|
|
meillo@19
|
630 environment variable
|
|
meillo@19
|
631 .Ev MH
|
|
meillo@19
|
632 the point to a different profile file.
|
|
meillo@19
|
633 The MH directory (mail storage plus personal configuration files) is
|
|
meillo@19
|
634 defined by the
|
|
meillo@19
|
635 .Pe Path
|
|
meillo@19
|
636 profile entry.
|
|
meillo@19
|
637 The context file could be defined by the
|
|
meillo@19
|
638 .Pe context
|
|
meillo@19
|
639 profile entry or by the
|
|
meillo@19
|
640 .Ev MHCONTEXT
|
|
meillo@19
|
641 environment variable.
|
|
meillo@19
|
642 The latter is useful to have a distinct context (e.g. current folders)
|
|
meillo@19
|
643 in each terminal window, for instance.
|
|
meillo@19
|
644 In mmh, there are three environment variables now.
|
|
meillo@19
|
645 .Ev MMH
|
|
meillo@19
|
646 may be used to change the location of the mmh directory.
|
|
meillo@19
|
647 .Ev MMHP
|
|
meillo@19
|
648 and
|
|
meillo@19
|
649 .Ev MMHC
|
|
meillo@19
|
650 change the profile and context files, respectively.
|
|
meillo@19
|
651 Besides providing a more consistent feel (which simply is the result
|
|
meillo@19
|
652 of being designed anew), the set of personal configuration files can
|
|
meillo@19
|
653 be chosen independently from the profile (including mail storage location)
|
|
meillo@19
|
654 and context, now. Being it relevant for practical use or not, it
|
|
meillo@19
|
655 de-facto is an improvement. However, the main achievement is the
|
|
meillo@19
|
656 split between mail storage and personal configuration files.
|
|
meillo@17
|
657
|
|
meillo@0
|
658
|
|
meillo@58
|
659 .H2 "Modularization
|
|
meillo@0
|
660 .P
|
|
meillo@58
|
661 whatnowproc
|
|
meillo@0
|
662 .P
|
|
meillo@49
|
663 The \fIMH library\fP
|
|
meillo@49
|
664 .Fn libmh.a
|
|
meillo@49
|
665 collects a bunch of standard functions that many of the MH tools need,
|
|
meillo@49
|
666 like reading the profile or context files.
|
|
meillo@49
|
667 This doesn't hurt the separation.
|
|
meillo@49
|
668
|
|
meillo@58
|
669
|
|
meillo@58
|
670 .H2 "Style
|
|
meillo@58
|
671 .P
|
|
meillo@58
|
672 Code layout, goto, ...
|
|
meillo@58
|
673
|
|
meillo@58
|
674
|
|
meillo@58
|
675
|
|
meillo@58
|
676
|
|
meillo@58
|
677 .H1 "Concept Exploitation/Homogeniety
|
|
meillo@58
|
678
|
|
meillo@58
|
679
|
|
meillo@58
|
680 .H2 "Draft Folder
|
|
meillo@58
|
681 .P
|
|
meillo@58
|
682 Historically, MH provided exactly one draft message, named
|
|
meillo@58
|
683 .Fn draft
|
|
meillo@58
|
684 and
|
|
meillo@58
|
685 being located in the MH directory. When starting to compose another message
|
|
meillo@58
|
686 before the former one was sent, the user had been questioned whether to use,
|
|
meillo@58
|
687 refile or replace the old draft. Working on multiple drafts at the same time
|
|
meillo@58
|
688 was impossible. One could only work on them in alteration by refiling the
|
|
meillo@58
|
689 previous one to some directory and fetching some other one for reediting.
|
|
meillo@58
|
690 This manual draft management needed to be done each time the user wanted
|
|
meillo@58
|
691 to switch between editing one draft to editing another.
|
|
meillo@58
|
692 .P
|
|
meillo@58
|
693 To allow true parallel editing of drafts, in a straight forward way, the
|
|
meillo@58
|
694 draft folder facility exists. It had been introduced already in July 1984
|
|
meillo@58
|
695 by Marshall T. Rose. The facility was deactivated by default.
|
|
meillo@58
|
696 Even in nmh, the draft folder facility remained deactivated by default.
|
|
meillo@58
|
697 At least, Richard Coleman added the man page
|
|
meillo@58
|
698 .Mp mh-draft(5)
|
|
meillo@58
|
699 to document
|
|
meillo@58
|
700 the feature well.
|
|
meillo@58
|
701 .P
|
|
meillo@58
|
702 The only advantage of not using the draft folder facility is the static
|
|
meillo@58
|
703 name of the draft file. This could be an issue for MH frontends like mh-e.
|
|
meillo@58
|
704 But as they likely want to provide working on multiple drafts in parallel,
|
|
meillo@58
|
705 the issue is only concerning compatibility. The aim of nmh to stay compatible
|
|
meillo@58
|
706 prevented the default activation of the draft folder facility.
|
|
meillo@58
|
707 .P
|
|
meillo@58
|
708 On the other hand, a draft folder is the much more natural concept than
|
|
meillo@58
|
709 a draft message. MH's mail storage consists of folders and messages,
|
|
meillo@58
|
710 the messages named with ascending numbers. A draft message breaks with this
|
|
meillo@58
|
711 concept by introducing a message in a file named
|
|
meillo@58
|
712 .Fn draft .
|
|
meillo@58
|
713 This draft
|
|
meillo@58
|
714 message is special. It can not be simply listed with the available tools,
|
|
meillo@58
|
715 but instead requires special switches. I.e. corner-cases were
|
|
meillo@58
|
716 introduced. A draft folder, in contrast, does not introduce such
|
|
meillo@58
|
717 corner-cases. The available tools can operate on the messages within that
|
|
meillo@58
|
718 folder like on any messages within any mail folders. The only difference
|
|
meillo@58
|
719 is the fact that the default folder for
|
|
meillo@58
|
720 .Pn send
|
|
meillo@58
|
721 is the draft folder,
|
|
meillo@58
|
722 instead of the current folder, like for all other tools.
|
|
meillo@58
|
723 .P
|
|
meillo@58
|
724 The trivial part of the change was activating the draft folder facility
|
|
meillo@58
|
725 by default and setting a default name for this folder. Obviously, I chose
|
|
meillo@58
|
726 the name
|
|
meillo@58
|
727 .Fn +drafts .
|
|
meillo@58
|
728 This made the
|
|
meillo@58
|
729 .Sw \-draftfolder
|
|
meillo@58
|
730 and
|
|
meillo@58
|
731 .Sw \-draftmessage
|
|
meillo@58
|
732 switches useless, and I could remove them.
|
|
meillo@58
|
733 The more difficult but also the part that showed the real improvement,
|
|
meillo@58
|
734 was updating the tools to the new concept.
|
|
meillo@58
|
735 .Sw \-draft
|
|
meillo@58
|
736 switches could
|
|
meillo@58
|
737 be dropped, as operating on a draft message became indistinguishable to
|
|
meillo@58
|
738 operating on any other message for the tools.
|
|
meillo@58
|
739 .Pn comp
|
|
meillo@58
|
740 still has its
|
|
meillo@58
|
741 .Sw \-use
|
|
meillo@58
|
742 switch for switching between its two modes: (1) Compose a new
|
|
meillo@58
|
743 draft, possibly by taking some existing message as a form. (2) Modify
|
|
meillo@58
|
744 an existing draft. In either case, the behavior of
|
|
meillo@58
|
745 .Pn comp is
|
|
meillo@58
|
746 deterministic. There is no more need to query the user. I consider this
|
|
meillo@58
|
747 a major improvement. By making
|
|
meillo@58
|
748 .Pn send
|
|
meillo@58
|
749 simply operate on the current
|
|
meillo@58
|
750 message in the draft folder by default, with message and folder both
|
|
meillo@58
|
751 overridable by specifying them on the command line, it is now possible
|
|
meillo@58
|
752 to send a draft anywhere within the storage by simply specifying its folder
|
|
meillo@58
|
753 and name.
|
|
meillo@58
|
754 .P
|
|
meillo@58
|
755 All theses changes converted special cases to regular cases, thus
|
|
meillo@58
|
756 simplifying the tools and increasing the flexibility.
|
|
meillo@58
|
757
|
|
meillo@58
|
758
|
|
meillo@58
|
759 .H2 "Trash Folder
|
|
meillo@58
|
760 .P
|
|
meillo@58
|
761 Similar to the situation for drafts is the situation for removed messages.
|
|
meillo@58
|
762 Historically, a message was deleted by renaming. A specific
|
|
meillo@58
|
763 \fIbackup prefix\fP, often comma (\c
|
|
meillo@58
|
764 .Fn , )
|
|
meillo@58
|
765 or hash (\c
|
|
meillo@58
|
766 .Fn # ),
|
|
meillo@58
|
767 being prepended to the file name. Thus, MH wouldn't recognize the file
|
|
meillo@58
|
768 as a message anymore, as only files whose name consists of digits only
|
|
meillo@58
|
769 are treated as messages. The removed messages remained as files in the
|
|
meillo@58
|
770 same directory and needed some maintenance job to truly delete them after
|
|
meillo@58
|
771 some grace time. Usually, by running a command similar to
|
|
meillo@58
|
772 .DS
|
|
meillo@58
|
773 find /home/user/Mail \-ctime +7 \-name ',*' | xargs rm
|
|
meillo@58
|
774 .DE
|
|
meillo@58
|
775 in a cron job. Within the grace time interval
|
|
meillo@58
|
776 the original message could be restored by stripping the
|
|
meillo@58
|
777 the backup prefix from the file name. If however, the last message of
|
|
meillo@58
|
778 a folder is been removed \(en say message
|
|
meillo@58
|
779 .Fn 6
|
|
meillo@58
|
780 becomes file
|
|
meillo@58
|
781 .Fn ,6
|
|
meillo@58
|
782 \(en and a new message enters the same folder, thus the same
|
|
meillo@58
|
783 numbered being given again \(en in our case
|
|
meillo@58
|
784 .Fn 6
|
|
meillo@58
|
785 \(en, if that one
|
|
meillo@58
|
786 is removed too, then the backup of the former message gets overwritten.
|
|
meillo@58
|
787 Thus, the ability to restore removed messages does not only depend on
|
|
meillo@58
|
788 the ``sweeping cron job'' but also on the removing of further messages.
|
|
meillo@58
|
789 This is undesirable, because the real mechanism is hidden from the user
|
|
meillo@58
|
790 and the consequences of further removals are not always obvious.
|
|
meillo@58
|
791 Further more, the backup files are scattered within the whole mail
|
|
meillo@58
|
792 storage, instead of being collected at one place.
|
|
meillo@58
|
793 .P
|
|
meillo@58
|
794 To improve the situation, the profile entry
|
|
meillo@58
|
795 .Pe rmmproc
|
|
meillo@58
|
796 (previously named
|
|
meillo@58
|
797 .Pe Delete-Prog )
|
|
meillo@58
|
798 was introduced, very early.
|
|
meillo@58
|
799 It could be set to any command, which would care for the mail removal
|
|
meillo@58
|
800 instead of taking the default action, described above.
|
|
meillo@58
|
801 Refiling the to-be-removed files to some garbage folder was a common
|
|
meillo@58
|
802 example. Nmh's man page
|
|
meillo@58
|
803 .Mp rmm(1)
|
|
meillo@58
|
804 proposes
|
|
meillo@58
|
805 .Cl "refile +d
|
|
meillo@58
|
806 to move messages to the garbage folder and
|
|
meillo@58
|
807 .Cl "rm `mhpath +d all`
|
|
meillo@58
|
808 the empty the garbage folder.
|
|
meillo@58
|
809 Managing the message removal this way is a sane approach. It keeps
|
|
meillo@58
|
810 the removed messages in one place, makes it easy to remove the backup
|
|
meillo@58
|
811 files, and, most important, enables the user to use the tools of MH
|
|
meillo@58
|
812 itself to operate on the removed messages. One can
|
|
meillo@58
|
813 .Pn scan
|
|
meillo@58
|
814 them,
|
|
meillo@58
|
815 .Pn show
|
|
meillo@58
|
816 them, and restore them with
|
|
meillo@58
|
817 .Pn refile .
|
|
meillo@58
|
818 There's no more
|
|
meillo@58
|
819 need to use
|
|
meillo@58
|
820 .Pn mhpath
|
|
meillo@58
|
821 to switch over from MH tools to Unix tools \(en MH can do it all itself.
|
|
meillo@58
|
822 .P
|
|
meillo@58
|
823 This approach matches perfect with the concepts of MH, thus making
|
|
meillo@58
|
824 it powerful. Hence, I made it the default. And even more, I also
|
|
meillo@58
|
825 removed the old backup prefix approach, as it is clearly less powerful.
|
|
meillo@58
|
826 Keeping unused alternative in the code is a bad choice as they likely
|
|
meillo@58
|
827 gather bugs, by not being constantly tested. Also, the increased code
|
|
meillo@58
|
828 size and more conditions crease the maintenance costs. By strictly
|
|
meillo@58
|
829 converting to the trash folder approach, I simplified the code base.
|
|
meillo@58
|
830 .Pn rmm
|
|
meillo@58
|
831 calls
|
|
meillo@58
|
832 .Pn refile
|
|
meillo@58
|
833 internally to move the to-be-removed
|
|
meillo@58
|
834 message to the trash folder (\c
|
|
meillo@58
|
835 .Fn +trash
|
|
meillo@58
|
836 by default). Messages
|
|
meillo@58
|
837 there can be operated on like on any other message in the storage.
|
|
meillo@58
|
838 The sweep clean, one can use
|
|
meillo@58
|
839 .Cl "rmm \-unlink +trash a" ,
|
|
meillo@58
|
840 where the
|
|
meillo@58
|
841 .Sw \-unlink
|
|
meillo@58
|
842 switch causes the files to be truly unliked instead
|
|
meillo@58
|
843 of moved to the trash folder.
|
|
meillo@58
|
844
|
|
meillo@58
|
845
|
|
meillo@58
|
846 .H2 "Path Notations
|
|
meillo@58
|
847 .P
|
|
meillo@58
|
848 foo
|
|
meillo@58
|
849
|
|
meillo@58
|
850
|
|
meillo@58
|
851 .H2 "MIME Integration
|
|
meillo@58
|
852 .P
|
|
meillo@58
|
853 user-visible access to whole messages and MIME parts are inherently
|
|
meillo@58
|
854 different
|
|
meillo@58
|
855
|
|
meillo@58
|
856
|
|
meillo@58
|
857 .H2 "Of One Cast
|
|
meillo@58
|
858 .P
|
