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   1 .\"
   2 .\" %nmhwarning%
   3 .\"
   4 .TH MHL %manext1% "%nmhdate%" MH.6.8 [%nmhversion%]
   5 .SH NAME
   6 mhl \- produce formatted listings of nmh messages
   7 .SH SYNOPSIS
   8 .HP 5
   9 .na
  10 .B %libdir%/mhl
  11 .RB [ \-bell " | " \-nobell ]
  12 .RB [ \-clear " | " \-noclear ]
  13 .RB [ \-folder
  14 .IR +folder ]
  15 .RB [ \-form
  16 .IR formfile ]
  17 .RB [ \-length
  18 .IR lines ]
  19 .RB [ \-width
  20 .IR columns ]
  21 .RB [ \-moreproc
  22 .IR program ]
  23 .RB [ \-nomoreproc ]
  24 .RI [ files
  25 .IR \&... ]
  26 .RB [ \-version ]
  27 .RB [ \-help ]
  28 .ad
  29 .SH DESCRIPTION
  30 .B Mhl
  31 is an
  32 .B nmh
  33 command for filtering and/or displaying text
  34 messages.  It is the default method of displaying text messages for
  35 .B nmh
  36 (it is the default
  37 .IR showproc ).
  38 .PP
  39 As with
  40 .BR more ,
  41 each of the messages specified as arguments (or
  42 the standard input) will be output.  If more than one message file is
  43 specified, the user will be prompted prior to each one, and a <RETURN>
  44 or <EOT> will begin the output, with <RETURN> clearing the screen (if
  45 appropriate), and <EOT> (usually CTRL\-D) suppressing the screen clear.
  46 An <INTERRUPT> (usually CTRL\-C) will abort the current message output,
  47 prompting for the next message (if there is one), and a <QUIT> (usually
  48 CTRL-\\) will terminate the program (without core dump).
  49 .PP
  50 The
  51 .B \-bell
  52 option tells
  53 .B mhl
  54 to ring the terminal's bell at the
  55 end of each page, while the
  56 .B \-clear
  57 option tells
  58 .B mhl
  59 to clear the
  60 screen at the end of each page (or output a formfeed after each message).
  61 Both of these switches (and their inverse counterparts) take effect only
  62 if the profile entry
  63 .I moreproc
  64 is defined but empty, and
  65 .B mhl
  66 is outputting to a terminal.  If the
  67 .I moreproc
  68 entry is defined and
  69 non-empty, and
  70 .B mhl
  71 is outputting to a terminal, then
  72 .B mhl
  73 will
  74 cause the
  75 .I moreproc
  76 to be placed between the terminal and
  77 .B mhl
  78 and the switches are ignored.  Furthermore, if the
  79 .B \-clear
  80 switch is
  81 used and \fImhl's\fR output is directed to a terminal, then
  82 .B mhl
  83 will consult the
  84 .B $TERM
  85 and
  86 .B $TERMCAP
  87 environment variables
  88 to determine the user's terminal type in order to find out how to clear
  89 the screen.  If the
  90 .B \-clear
  91 switch is used and
  92 .BR mhl 's
  93 output is
  94 not directed to a terminal (e.g., a pipe or a file), then
  95 .B mhl
  96 will
  97 send a formfeed after each message.
  98 .PP
  99 To override the default
 100 .I moreproc
 101 and the profile entry, use the
 102 .B \-moreproc
 103 .I program
 104 switch.  Note that
 105 .B mhl
 106 will never start a
 107 .I moreproc
 108 if invoked on a hardcopy terminal.
 109 .PP
 110 The
 111 .B \-length
 112 .I length
 113 and
 114 .B \-width
 115 .I width
 116 switches set the screen
 117 length and width, respectively.  These default to the values indicated by
 118 .BR $TERMCAP ,
 119 if appropriate, otherwise they default to 40 and 80, respectively.
 120 .PP
 121 The default format file used by
 122 .B mhl
 123 is called
 124 .RI \*(lq mhl.format \*(rq.
 125 .B mhl
 126 will first search for this file in the user's
 127 .B nmh
 128 directory, and will then search in the directory
 129 .IR %etcdir% .
 130 This default
 131 can be changed by using the
 132 .B \-form
 133 .I formatfile
 134 switch.
 135 .PP
 136 Finally, the
 137 .B \-folder
 138 .I +folder
 139 switch sets the
 140 .B nmh
 141 folder name,
 142 which is used for the \*(lqmessagename:\*(rq field described below.  The
 143 environment variable
 144 .B $mhfolder
 145 is consulted for the default value,
 146 which
 147 .BR show ,
 148 .BR next ,
 149 and
 150 .B prev
 151 initialize appropriately.
 152 .PP
 153 .B Mhl
 154 operates in two phases: 1) read and parse the format file, and
 155 2) process each message (file).  During phase 1, an internal description
 156 of the format is produced as a structured list.  In phase 2, this list
 157 is walked for each message, outputting message information under the
 158 format constraints from the format file.
 159 .PP
 160 The format file can contain information controlling screen clearing,
 161 screen size, wrap\-around control, transparent text, component ordering,
 162 and component formatting.  Also, a list of components to ignore may be
 163 specified, and a couple of \*(lqspecial\*(rq components are defined
 164 to provide added functionality.  Message output will be in the order
 165 specified by the order in the format file.
 166 .PP
 167 Each line of a format file has one of the following forms:
 168 .PP
 169 .RS 5
 170 .nf
 171 ;comment
 172 :cleartext
 173 variable[,variable...]
 174 component:[variable,...]
 175 .fi
 176 .RE
 177 .PP
 178 .IP \(bu 4
 179 A line beginning with a `;' is a comment, and is ignored.
 180 .IP \(bu 4
 181 A line beginning with a `:' is clear text, and is output exactly as is.
 182 .IP \(bu 4
 183 A line containing only a `:' produces a blank line in the output.
 184 .IP \(bu 4
 185 A line beginning with \*(lqcomponent:\*(rq defines the format for the specified
 186 component,
 187 .IP \(bu 4
 188 Remaining lines define the global environment.
 189 .PP
 190 For example, the line:
 191 .PP
 192 .RS 5
 193 width=80,length=40,clearscreen,overflowtext="***",overflowoffset=5
 194 .RE
 195 .PP
 196 defines the screen size to be 80 columns by 40 rows, specifies that the
 197 screen should be cleared prior to each page, that the overflow indentation
 198 is 5, and that overflow text should be flagged with \*(lq***\*(rq.
 199 .PP
 200 Following are all of the current variables and their arguments.  If they
 201 follow a component, they apply only to that component, otherwise, their
 202 affect is global.  Since the whole format is parsed before any output
 203 processing, the last global switch setting for a variable applies to
 204 the whole message if that variable is used in a global context (i.e.,
 205 bell, clearscreen, width, length).
 206 .PP
 207 .RS 5
 208 .nf
 209 .ta \w'noclearscreen  'u +\w'integer/G  'u
 210 .I "variable    type    semantics"
 211 width   integer screen width or component width
 212 length  integer screen length or component length
 213 offset  integer positions to indent \*(lqcomponent: \*(rq
 214 overflowtext    string  text to use at the beginning of an
 215                 overflow line
 216 overflowoffset  integer positions to indent overflow lines
 217 compwidth       integer positions to indent component text
 218                 after the first line is output
 219 uppercase       flag    output text of this component in all
 220                 upper case
 221 nouppercase     flag    don't uppercase
 222 clearscreen     flag/G  clear the screen prior to each page
 223 noclearscreen   flag/G  don't clearscreen
 224 bell    flag/G  ring the bell at the end of each page
 225 nobell  flag/G  don't bell
 226 component       string/L        name to use instead of \*(lqcomponent\*(rq for
 227                 this component
 228 nocomponent     flag    don't output \*(lqcomponent: \*(rq for this
 229                 component
 230 center  flag    center component on line (works for
 231                 one\-line components only)
 232 nocenter        flag    don't center
 233 leftadjust      flag    strip off leading whitespace on each
 234                 line of text
 235 noleftadjust    flag    don't leftadjust
 236 compress        flag    change newlines in text to spaces
 237 nocompress      flag    don't compress
 238 wrap    flag    Wrap lines that exceed width (default)
 239 nowrap  flag    Do not perform line wrapping
 240 split   flag    don't combine multiple fields into
 241                 a single field
 242 nosplit flag    combine multiple fields into
 243                 a single field
 244 newline flag    print newline at end of components
 245                 (this is the default)
 246 nonewline       flag    don't print newline at end of components
 247 formatfield     string  format string for this component
 248                 (see below)
 249 decode  flag    decode text as RFC-2047 encoded
 250                 header field
 251 addrfield       flag    field contains addresses
 252 datefield       flag    field contains dates
 253 format  flag    Run component through formatproc filter
 254                 (body only)
 255 noformat        flag    Do not run component through
 256                 formatproc filter (default)
 257 .fi
 258 .RE
 259 .PP
 260 To specify the value of integer\-valued and string\-valued variables,
 261 follow their name with an equals\-sign and the value.  Integer\-valued
 262 variables are given decimal values, while string\-valued variables
 263 are given arbitrary text bracketed by double\-quotes.  If a value is
 264 suffixed by \*(lq/G\*(rq or \*(lq/L\*(rq, then its value is useful in
 265 a global\-only or local\-only context (respectively).
 266 .PP
 267 A line of the form:
 268 .PP
 269 .RS 5
 270 ignores=component,...
 271 .RE
 272 .PP
 273 specifies a list of components which are never output.
 274 .PP
 275 The component \*(lqMessageName\*(rq (case\-insensitive) will output the
 276 actual message name (file name) preceded by the folder name if one is
 277 specified or found in the environment.  The format is identical to that
 278 produced by the
 279 .B \-header
 280 option to
 281 .BR show .
 282 .PP
 283 The component \*(lqExtras\*(rq will output all of the components of the
 284 message which were not matched by explicit components, or included in
 285 the ignore list.  If this component is not specified, an ignore list is
 286 not needed since all non\-specified components will be ignored.
 287 .PP
 288 If \*(lqnocomponent\*(rq is NOT specified, then the component name will
 289 be output as it appears in the format file.
 290 .PP
 291 The default format file is:
 292 .PP
 293 .RS 5
 294 .nf
 295 %mhl_format%
 296 .fi
 297 .RE
 298 .PP
 299 The variable \*(lqformatfield\*(rq specifies a format string (see
 300 .BR mh\-format (5)).
 301 The flag variables \*(lqaddrfield\*(rq and
 302 \*(lqdatefield\*(rq (which are mutually exclusive), tell
 303 .B mhl
 304 to interpret the escapes in the format string as either addresses or
 305 dates, respectively.
 306 .PP
 307 By default,
 308 .B mhl
 309 does not apply any formatting string to fields
 310 containing address or dates (see
 311 .BR mh\-mail (5)
 312 for a list of these
 313 fields).  Note that this results in faster operation since
 314 .B mhl
 315 must parse both addresses and dates in order to apply a format string
 316 to them.  If desired,
 317 .B mhl
 318 can be given a default format string for
 319 either address or date fields (but not both).  To do this, on a global
 320 line specify: either the flag addrfield or datefield, along with the
 321 appropriate formatfield variable string.
 322 .PP
 323 The \*(lqformat\*(rq flag specifies that this component will be run through
 324 the filter program specified by the
 325 .IR formatproc
 326 profile entry.  This filter program is expected to read data on standard
 327 input and output data on standard output.  Currently the \*(lqformat\*(rq
 328 flag is only supported for the \(*lqbody\*(rq component.  The component
 329 name will be prefixed to the output
 330 .IR after
 331 the filter has been run.  The expected use of this is to filter a message
 332 body to create more pleasing text to use in a reply message.
 333 A suggested filter to use for
 334 .BR repl(1)
 335 is as follows:
 336 .PP
 337 .RS 5
 338 body:component=">",overflowtext=">",overflowoffset=0,format,nowrap
 339 .RE
 340 .SH FILES
 341 .fc ^ ~
 342 .nf
 343 .ta \w'%etcdir%/ExtraBigFileName  'u
 344 ^%etcdir%/mhl.format~^The message template
 345 ^or <mh\-dir>/mhl.format~^Rather than the standard template
 346 ^$HOME/\&.mh\(ruprofile~^The user profile
 347 .fi
 348
 349 .SH "PROFILE COMPONENTS"
 350 .fc ^ ~
 351 .nf
 352 .ta 2.4i
 353 .ta \w'ExtraBigProfileName  'u
 354 ^moreproc:~^Program to use as interactive front\-end
 355 ^formatproc:~^Program to use as a filter for components that
 356 ^^have the \*(lqformat\*(rq flag set.
 357 .fi
 358
 359 .SH "SEE ALSO"
 360 show(1), ap(8), dp(8)
 361
 362 .SH DEFAULTS
 363 .nf
 364 .RB ` \-bell '
 365 .RB ` \-noclear '
 366 .RB ` \-length\ 40 '
 367 .RB ` \-width\ 80 '
 368 .fi
 369
 370 .SH CONTEXT
 371 None
 372
 373 .SH BUGS
 374 There should be some way to pass `bell' and `clear' information to the
 375 front\-end.
 376 .PP
 377 The \*(lqnonewline\*(rq option interacts badly with \*(lqcompress\*(rq
 378 and \*(lqsplit\*(rq.