MAN page from Old RedHat 5.X mh-6.8.4-6.i386.rpm
MH-FORMAT
Section: File Formats (5)
Updated: MH.6.8
Index NAME
mh-format - format file for MH message system
SYNOPSIS
some
MH commands
DESCRIPTION
Several
MH commands utilize either a
format string or a
format file during their execution.For example,
scan (1) uses a format string which directs it how to generate thescan listing for each message;
repl (1) uses a format file which directs it how to generate thereply to a message, and so on.
Format strings are designed to be efficiently parsed by MH whichmeans they are not necessarily simple to write and understand.This means that novice, casual, or even advanced users of MH shouldnot have to deal with them.Some canned scan listing formats are in/usr/lib/mh/scan.time, /usr/lib/mh/scan.size, and /usr/lib/mh/scan.timely.Look in /usr/lib/mh for other scan and repl format fileswhich may have been written at your site.
It suffices to have your local MH expert actually write new formatcommands or modify existing ones.This manual section explains how to do that.Note: familiarity with the C printf routine is assumed.
A format string consists of ordinary text, and specialmulti-character escape sequences which begin with `%'.When specifying a format string,the usual C backslash characters are honored:`\b', `\f', `\n', `\r', and `\t'.Continuation lines in format files end with `\' followedby the newline character.To put a literal `%' or `\' in a format string, use two of them:`%%' and `\\'.There are three types of escape sequences:header components, built-in functions, and flow control.
A component escape is specified as `%{component}',and exists for each header found in the message being processed.For example `%{date}' refers to the ``Date:'' field of the appropriatemessage.All component escapes have a string value.Normally, component values are compressed byconverting any control characters (tab and newline included) to spaces,then eliding any leading or multiple spaces.However,commands may give different interpretations to some component escapes; be sure to refer to each command's manual entry for complete details.
A function escape is specified as `%(function)'.All functions are built-in, and most have a string or numeric value.
A control escape is one of: `%<', `%?', `%|', or `%>'. These are combined into the conditional execution construct:
%<condition format text 1 %?condition2 format text 2 %?condition3 format text 3 ... %| format text N %>
Extra white space is shown here only for clarity.These constructs may be nested without ambiguity.They form a general if-elseif-else-endif block whereonly one of the format text segments is interpreted.
The `%<' and `%?' control escapes causes a condition to be evaluated. This conditionmay be either a component or a function.The four constructs have the following syntax:
%<{component} %<(function) %?{component} %?(function)These control escapes test whetherthe function or component value is non-zero (for integer-valued escapes),or non-empty (for string-valued escapes).
If this test evaulates true,then the format textup to the next corresponding control escape (one of `%|', `%?', or `%>')is interpreted normally.Next,all format text (if any) up to the corresponding `%>' controlescape is skipped.The `%>' control escape is not interpreted;normalinterpretation resumes after the `%>' escape.
If the test evaluates false, however,then the format text up to the next corresponding control escape(again, one of `%|', `%?', or `%>')is skipped, instead of being interpreted.If the control escape encountered was `%?',then the condition associated with that control escape isevaluated, and interpretationproceeds after that testas described in the previous paragraph.If the control escape encountered was `%|',then the format textup to the corresponding `%>' escapeis interpreted normally.As above, the `%>' escape is not interpreted and normalinterpretation resumes after the `%>' escape.
The `%?' control escape and its following format textis optional, and may be included zero or more times.The `%|' control escape and its following format textis also optional, and may be included zero or one times.
Most functions expect an argument of a particular type:
Argument Description Example Syntaxliteral A literal number, %(func 1234) or string %(func text string)comp Any header component %(func{in-reply-to})date A date component %(func{date})addr An address component %(func{from})expr An optional component, %(func(func2)) function or control, %(func %<{reply-to}%|%{from}%>) perhaps nested %(func(func2{comp}))The types date and addr have the same syntaxas comp, but require that the header component be a date string, or address string, respectively.
All arguments except those of type expr are required.For the expr argument type, the leading `%' must be omitted for component and function escape arguments,and must be present (with a leading space) for control escape arguments.
The evaluation of format stringsis based on a simple machine with aninteger register num, and a text string register str.When a function escape is processed,if it accepts an optional expr argument which is not present, it reads the current value of either num or str as appropriate.
Component escapes write the value of their message header in str.Function escapes write their return value innum for functions returning integer or boolean values,and in str for functions returning string values.(The boolean type is a subset of integers with usualvalues 0=false and 1=true.)Control escapes return a boolean value, and set num.
All component escapes, and thosefunction escapes which return an integer or string value,pass this value back to their callerin addition to setting str or num.These escapes will print out this valueunless called as part of an argument to another escape sequence.Escapes which return a boolean value do pass this valueback to their caller in num, but will never print out the value.
Function Argument Return Descriptionmsg integer message numbercur integer message is currentsize integer size of messagestrlen integer length of strwidth integer output buffer size in bytescharleft integer bytes left in output buffertimenow integer seconds since the UNIX epochme string the user's mailboxeq literal boolean num == argne literal boolean num != arggt literal boolean num > argmatch literal boolean str contains argamatch literal boolean str starts with argplus literal integer arg plus numminus literal integer arg minus numdivide literal integer num divided by argmodulo literal integer num modulo argnum literal integer Set num to arglit literal string Set str to arggetenv literal string Set str to environment value of argprofile literal string Set str to profile component arg valuenonzero expr boolean num is non-zerozero expr boolean num is zeronull expr boolean str is emptynonnull expr boolean str is non-emptyvoid expr Set str or numcomp comp string Set str to component textcompval comp integer num set to ``atoi(comp)''trim expr trim trailing white-space from strputstr expr print strputstrf expr print str in a fixed widthputnum expr print numputnumf expr print num in a fixed width
These functions require a date component as an argument:
Function Argument Return Descriptionsec date integer seconds of the minutemin date integer minutes of the hourhour date integer hours of the day (0-23)wday date integer day of the week (Sun=0)day date string day of the week (abbrev.)weekday date string day of the weeksday date integer day of the week known? (0=implicit,-1=unknown)mday date integer day of the monthyday date integer day of the yearmon date integer month of the yearmonth date string month of the year (abbrev.)lmonth date string month of the yearyear date integer year (may be > 100)zone date integer timezone in hourstzone date string timezone stringszone date integer timezone explicit? (0=implicit,-1=unknown)date2local date coerce date to local timezonedate2gmt date coerce date to GMTdst date integer daylight savings in effect?clock date integer seconds since the UNIX epochrclock date integer seconds prior to current timetws date string official 822 renderingpretty date string user-friendly renderingnodate date integer str not a date string
These functions require an address component as an argument. The return value of functions noted with `*' pertain only tothe first address present in the header component.
Function Argument Return Descriptionproper addr string official 822 renderingfriendly addr string user-friendly renderingaddr addr string mboxAATThost or host!mbox rendering*pers addr string the personal name*note addr string commentary text*mbox addr string the local mailbox*mymbox addr integer the user's addresses? (0=no,1=yes)host addr string the host domain*nohost addr integer no host was present*type addr integer host type* (0=local,1=network, -1=uucp,2=unknown)path addr string any leading host route*ingrp addr integer address was inside a group*gname addr string name of group*formataddr expr append arg to str as a (comma separated) address listputaddr literal print str address list with arg as optional label; get line width from num
When escapes are nested, evaluation is done from inner-most to outer-most.The outer-most escape must begin with `%'; the inner escapes must not.For example,
%<(mymbox{from}) To: %{to}%>
writes the value of the header component ``From:'' to str;then (mymbox) reads str and writes its result to num;then the control escape evaluates num. If num isnon-zero, the string ``To: '' is printed followed bythe value of the header component ``To:''.
A minor explanation of (mymbox{comp}) is in order.In general, it checks each of the addresses in the header component``comp''against the user's mailbox name and any Alternate-Mailboxes.It returns true if any address matches, however, italso returns true if the ``comp'' header is not presentin the message. If needed, the (null) function can beused to explicitly test for this condition.
When a function or component escape is interpreted and the resultwill be immediately printed,an optional field width can bespecified to print the field in exactly a given number of characters.For example, a numeric escape like %4(size) will print at most 4digits of the message size; overflow will be indicated by a `?' in thefirst position (like `?234').A string escape like %4(me) will print the first 4 characters andtruncate at the end. Short fields are padded at the right with the fill character (normally,a blank). If the field width argument begins with a leading zero,then the fill character is set to a zero.
As above,the functions (putnumf) and (putstrf) print their result inexactly the number of characters specified by their leading field widthargument. For example,%06(putnumf(size)) will print the message size in a field six characters wide filled with leading zeros;%14(putstrf{from}) will printthe ``From:'' header component in fourteen characters withtrailing spaces added as needed.For putstrf,using a negative value for the field width causes right-justificationof the string within the field,with padding on the left up to the field width.The functions (putnum) and (putstr) print their result inthe minimum number of characters required, and ignore any leading field width argument.
The available output width is kept in an internal register; any output pastthis width will be truncated.
Comments may be inserted in most places where a function argumentis not expected. A comment begins with `%;' and ends witha (non-escaped) newline.
With all this in mind,here's the default format string for scan.It's been divided into several pieces for readability.The first part is:
%4(msg)%<(cur)+%| %>%<{replied}-%?{encrypted}E%| %>
which says that the message number should be printed in four digits,if the message is the current message then a `+' else a space should beprinted,and if a ``Replied:'' field is present then a `-' else if an ``Encrypted:'' field is present then an `E' otherwisea space should be printed.Next:
%02(mon{date})/%02(mday{date})
the month and date are printed in two digits (zero filled) separated bya slash.Next,
%<{date} %|*>
If a ``Date:'' field was present,then a space is printed, otherwise a `*'.Next,
%<(mymbox{from})%<{to}To:%14(friendly{to})%>%>
if the message is from me,and there is a ``To:'' header,print `To:' followed by a ``user-friendly'' rendering of the first address in the ``To:'' field.Continuing,
%<(zero)%17(friendly{from})%>
if either of the above two tests failed,then the ``From:'' address is printedin a ``user-friendly'' format.And finally,
%{subject}%<{body}<<%{body}%>
the subject and initial body (if any) are printed.
For a more complicated example, next considerthe default replcomps format file.
%(lit)%(formataddr %<{reply-to}
This clears str and formats the ``Reply-To:'' header if present. If not present, the else-if clause is executed.
%?{from}%?{sender}%?{return-path}%>)\
This formats the ``From:'', ``Sender:'' and ``Return-Path:''headers, stopping as soon as one of them is present. Next:
%<(nonnull)%(void(width))%(putaddr To: )\n%>\
If the formataddr result is non-null, it is printed asan address (with line folding if needed) in a field widthwide with a leading label of ``To: ''.
%(lit)%(formataddr{to})%(formataddr{cc})%(formataddr(me))\
str is cleared, and the ``To:'' and ``Cc:'' headers, along with the user'saddress (depending on what was specified withthe ``-cc'' switch to repl) are formatted.
%<(nonnull)%(void(width))%(putaddr cc: )\n%>\
If the result is non-null, it is printed as above with aleading label of ``cc: ''.
%<{fcc}Fcc: %{fcc}\n%>\
If a ``-fcc folder'' switch was given to repl(see repl (1) for more details about %{fcc}),an ``Fcc:'' header is output.
%<{subject}Subject: Re: %{subject}\n%>\
If a subject component was present,a suitable reply subject is output.
%<{date}In-reply-to: Your message of "\
%<(nodate{date})%{date}%|%(pretty{date})%>."%<{message-id}
%{message-id}%>\n%>\
--------
If a date component was present,an ``In-Reply-To:'' header is output with the preface``Your message of ''. If the date was parseable, it isoutput in a user-friendly format, otherwise it is output as-is.The message-id is included if present.As with all plain-text,the row of dashes are output as-is.
This last part is a good example for a little more elaboration.Here's that part again in pseudo-code:
if (comp_exists(date)) then print (``In-reply-to: Your message of \``'') if (not_date_string(date.value) then print (date.value) else print (pretty(date.value)) endif print (``\'''') if (comp_exists(message-id)) then print (``\n\t'') print (message-id.value) endif print (``\n'')endif
Although this seems complicated,in point of fact,this method is flexible enough to extract individual fields and print them inany format the user desires.NoneNonescan(1), repl(1), ap(8), dp(8)NoneNoneThis software was contributed for MH 6.3. Prior to this, outputformat specifications were much easier to write, but considerablyless flexible.On hosts where MH was configured with the BERK option,address parsing is not enabled.
Index
- NAME
- SYNOPSIS
- DESCRIPTION
This document was created byman2html,using the manual pages.
