.\" @(MHWARNING) .\" @(#)$Id: mh-format.rf,v 1.47 1995/12/06 23:33:39 jromine Exp $ .SC MH-FORMAT 5 .NA mh-format \- format file for MH message system .SY some \fIMH\fR commands .DE Several \fIMH\fR commands utilize either a \fIformat\fR string or a \fIformat\fR file during their execution. For example, \fIscan\fR\0(1) uses a format string which directs it how to generate the scan listing for each message; \fIrepl\fR\0(1) uses a format file which directs it how to generate the reply to a message, and so on. Format strings are designed to be efficiently parsed by \fIMH\fR which means they are not necessarily simple to write and understand. This means that novice, casual, or even advanced users of \fIMH\fR should not have to deal with them. Some canned scan listing formats are in @(MHETCPATH)/scan.time, @(MHETCPATH)/scan.size, and @(MHETCPATH)/scan.timely. Look in @(MHETCPATH) for other \fIscan\fR and \fIrepl\fR format files which may have been written at your site. It suffices to have your local \fIMH\fR expert actually write new format commands or modify existing ones. This manual section explains how to do that. Note: familiarity with the C \fIprintf\fR routine is assumed. A format string consists of ordinary text, and special multi-character \fIescape\fR 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 `\\' followed by the newline character. To put a literal `%' or `\\' in a format string, use two of them: `%%' and `\\\\'. .\" talk about syntax first, then semantics There are three types of \fIescape\fR sequences: header \fIcomponents\fR, built-in \fIfunctions\fR, and flow \fIcontrol\fR. A \fIcomponent\fR escape is specified as `%{\fIcomponent\fR\^}', and exists for each header found in the message being processed. For example `%{date}' refers to the \*(lqDate:\*(rq field of the appropriate message. All component escapes have a string value. Normally, component values are compressed by converting 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 \fIfunction\fR escape is specified as `%(\fIfunction\fR\^)'. All functions are built-in, and most have a string or numeric value. .ne 12 .Uh "Control-flow escapes" A \fIcontrol\fR escape is one of: `%<', `%?', `%|', or `%>'. .\" `%[', or `%]'. These are combined into the conditional execution construct: .sp .nf % .fi .sp Extra white space is shown here only for clarity. These constructs may be nested without ambiguity. They form a general \fBif\-elseif\-else\-endif\fP block where only one of the \fIformat text\fP segments is interpreted. The `%<' and `%?' control escapes causes a condition to be evaluated. This condition may be either a \fIcomponent\fP or a \fIfunction\fP. The four constructs have the following syntax: .sp 1 .nf %<{component} %<(function) %?{component} %?(function) .fi .sp These control escapes test whether the 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 text up to the next corresponding control escape (one of `%|', `%?', or `%>') is interpreted normally. Next, all format text (if any) up to the corresponding `%>' control escape is skipped. The `%>' control escape is not interpreted; normal interpretation 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 is evaluated, and interpretation proceeds after that test as described in the previous paragraph. If the control escape encountered was `%|', then the format text up to the corresponding `%>' escape is interpreted normally. As above, the `%>' escape is not interpreted and normal interpretation resumes after the `%>' escape. The `%?' control escape and its following format text is optional, and may be included zero or more times. The `%|' control escape and its following format text is also optional, and may be included zero or one times. .\" The '%[' and '%]' escapes form a loop construct. .\" For format strings which are executed repeatedly .\" (as with \fIscan\fP), these escapes delimit the main .\" body of execution. Format text which occurs .\" before the '%[' escape is executed once only, prior .\" to processing the first message; format text occuring .\" after the '%]' escape is ignored. .\" (These escapes may not be nested). .\" .Uh "Function escapes" .ne 10 Most functions expect an argument of a particular type: .sp 1 .nf .ta +\w'Argument 'u +\w'An optional component, 'u \fIArgument\fR \fIDescription\fR \fIExample Syntax\fR literal A literal number, %(\fIfunc\fR 1234) or string %(\fIfunc\fR text string) comp Any header component %(\fIfunc\fR\^{\fIin-reply-to\fR\^}) date A date component %(\fIfunc\fR\^{\fIdate\fR\^}) addr An address component %(\fIfunc\fR\^{\fIfrom\fR\^}) expr An optional component, %(\fIfunc\fR\^(\fIfunc2\fR\^)) function or control, %(\fIfunc\fR %<{\fIreply-to\fR\^}%|%{\fIfrom\fR\^}%>) perhaps nested %(\fIfunc\fR\^(\fIfunc2\fR\^{\fIcomp\fR\^})) .re .fi The types \fIdate\fR and \fIaddr\fR have the same syntax as \fIcomp\fR, but require that the header component be a date string, or address string, respectively. All arguments except those of type \fIexpr\fR are required. For the \fIexpr\fR 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 strings is based on a simple machine with an integer register \fInum\fR, and a text string register \fIstr\fR. When a function escape is processed, if it accepts an optional \fIexpr\fR argument which is not present, it reads the current value of either \fInum\fR or \fIstr\fR as appropriate. .\" return values .Uh "Return values" Component escapes write the value of their message header in \fIstr\fR. Function escapes write their return value in \fInum\fR for functions returning \fIinteger\fR or \fIboolean\fR values, and in \fIstr\fR for functions returning string values. (The \fIboolean\fR type is a subset of integers with usual values 0=false and 1=true.) Control escapes return a \fIboolean\fP value, and set \fInum\fP. All component escapes, and those function escapes which return an \fIinteger\fR or \fIstring\fR value, pass this value back to their caller in addition to setting \fIstr\fR or \fInum\fR. These escapes will print out this value unless called as part of an argument to another escape sequence. Escapes which return a \fIboolean\fR value do pass this value back to their caller in \fInum\fP, but will never print out the value. .nf .ta \w'Formataddr 'u +\w'Argument 'u +\w'Rboolean 'u \fIFunction\fR \fIArgument\fR \fIReturn\fR \fIDescription\fR msg integer message number cur integer message is current .\" unseen integer message is unseen size integer size of message strlen integer length of \fIstr\fR width integer output buffer size in bytes charleft integer bytes left in output buffer timenow integer seconds since the UNIX epoch me string the user's mailbox eq literal boolean \fInum\fR == \fIarg\fR ne literal boolean \fInum\fR != \fIarg\fR gt literal boolean \fInum\fR > \fIarg\fR match literal boolean \fIstr\fR contains \fIarg\fR amatch literal boolean \fIstr\fR starts with \fIarg\fR plus literal integer \fIarg\fR plus \fInum\fR minus literal integer \fIarg\fR minus \fInum\fR divide literal integer \fInum\fR divided by \fIarg\fR modulo literal integer \fInum\fR modulo \fIarg\fR num literal integer Set \fInum\fR to \fIarg\fR lit literal string Set \fIstr\fR to \fIarg\fR getenv literal string Set \fIstr\fR to environment value of \fIarg\fR profile literal string Set \fIstr\fR to profile component \fIarg\fR value .\" dat literal int return value of dat[arg] nonzero expr boolean \fInum\fR is non-zero zero expr boolean \fInum\fR is zero null expr boolean \fIstr\fR is empty nonnull expr boolean \fIstr\fR is non-empty void expr Set \fIstr\fR or \fInum\fR comp comp string Set \fIstr\fR to component text compval comp integer \fInum\fR set to \*(lq\fBatoi\fR(\fIcomp\fR\^)\*(rq .\" compflag comp integer Set \fInum\fR to component flags bits (internal) trim expr trim trailing white-space from \fIstr\fR putstr expr print \fIstr\fR putstrf expr print \fIstr\fR in a fixed width putnum expr print \fInum\fR putnumf expr print \fInum\fR in a fixed width .\" addtoseq literal add msg to sequence (LBL option) .re .fi These functions require a date component as an argument: .sp 1 .nf .ta \w'Formataddr 'u +\w'Argument 'u +\w'Rboolean 'u \fIFunction\fR \fIArgument\fR \fIReturn\fR \fIDescription\fR sec date integer seconds of the minute min date integer minutes of the hour hour 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 week sday date integer day of the week known? (0=implicit,\-1=unknown) mday date integer day of the month yday date integer day of the year mon date integer month of the year month date string month of the year (abbrev.) lmonth date string month of the year year date integer year (may be > 100) zone date integer timezone in hours tzone date string timezone string szone date integer timezone explicit? (0=implicit,\-1=unknown) date2local date coerce date to local timezone date2gmt date coerce date to GMT dst date integer daylight savings in effect? clock date integer seconds since the UNIX epoch rclock date integer seconds prior to current time tws date string official 822 rendering pretty date string user-friendly rendering nodate date integer \fIstr\fR not a date string .re .fi .ne 12 These functions require an address component as an argument. The return value of functions noted with `*' pertain only to the first address present in the header component. .sp 1 .nf .ta \w'Formataddr 'u +\w'Argument 'u +\w'Rboolean 'u \fIFunction\fR \fIArgument\fR \fIReturn\fR \fIDescription\fR proper addr string official 822 rendering friendly addr string user-friendly rendering addr addr string mbox@host 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 \fIarg\fR to \fIstr\fR as a (comma separated) address list putaddr literal print \fIstr\fR address list with \fIarg\fR as optional label; get line width from \fInum\fR .re .fi 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, .ti +.5i %<(mymbox{from}) To: %{to}%> writes the value of the header component \*(lqFrom:\*(rq to \fIstr\fR\^; then (\fImymbox\fR\^) reads \fIstr\fR and writes its result to \fInum\fR; then the control escape evaluates \fInum\fR. If \fInum\fR is non-zero, the string \*(lqTo: \*(rq is printed followed by the value of the header component \*(lqTo:\*(rq. A minor explanation of (\fImymbox\fR\^{\fIcomp\fR\^}) is in order. In general, it checks each of the addresses in the header component \*(lq\fIcomp\fR\*(rq against the user's mailbox name and any \fIAlternate-Mailboxes\fR. It returns true if any address matches, however, it also returns true if the \*(lq\fIcomp\fR\*(rq header is not present in the message. If needed, the (\fInull\fR\^) function can be used to explicitly test for this condition. When a function or component escape is interpreted and the result will be immediately printed, an optional field width can be specified to print the field in exactly a given number of characters. For example, a numeric escape like %4(\fIsize\fR\^) will print at most 4 digits of the message size; overflow will be indicated by a `?' in the first position (like `?234'). A string escape like %4(\fIme\fR\^) will print the first 4 characters and truncate 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 (\fIputnumf\fR\^) and (\fIputstrf\fR\^) print their result in exactly the number of characters specified by their leading field width argument. For example, %06(\fIputnumf\fR\^(\fIsize\fR\^)) will print the message size in a field six characters wide filled with leading zeros; %14(\fIputstrf\^\fR{\fIfrom\^\fR}) will print the \*(lqFrom:\*(rq header component in fourteen characters with trailing spaces added as needed. For \fIputstrf\fR, using a negative value for the field width causes right-justification of the string within the field, with padding on the left up to the field width. The functions (\fIputnum\fR\^) and (\fIputstr\fR\^) print their result in the minimum number of characters required, and ignore any leading field width argument. The available output width is kept in an internal register; any output past this width will be truncated. Comments may be inserted in most places where a function argument is not expected. A comment begins with `%;' and ends with a (non-escaped) newline. With all this in mind, here's the default format string for \fIscan\fR. It's been divided into several pieces for readability. The first part is: .ti +.5i %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 be printed, and if a \*(lqReplied:\*(rq field is present then a `\-' else if an \*(lqEncrypted:\*(rq field is present then an `E' otherwise a space should be printed. Next: .ti +.5i %02(mon{date})/%02(mday{date}) the month and date are printed in two digits (zero filled) separated by a slash. Next, .ti +.5i %<{date} %|*> If a \*(lqDate:\*(rq field was present, then a space is printed, otherwise a `*'. Next, .ti +.5i %<(mymbox{from})%<{to}To:%14(friendly{to})%>%> if the message is from me, and there is a \*(lqTo:\*(rq header, print `To:' followed by a \*(lquser-friendly\*(rq rendering of the first address in the \*(lqTo:\*(rq field. Continuing, .ti +.5i %<(zero)%17(friendly{from})%> if either of the above two tests failed, then the \*(lqFrom:\*(rq address is printed in a \*(lquser-friendly\*(rq format. And finally, .ti +.5i %{subject}%<{body}<<%{body}%> the subject and initial body (if any) are printed. For a more complicated example, next consider the default \fIreplcomps\fR format file. .ti +.5i %(lit)%(formataddr %<{reply-to} This clears \fIstr\fR and formats the \*(lqReply-To:\*(rq header if present. If not present, the else-if clause is executed. .ti +.5i %?{from}%?{sender}%?{return-path}%>)\\ This formats the \*(lqFrom:\*(rq, \*(lqSender:\*(rq and \*(lqReturn-Path:\*(rq headers, stopping as soon as one of them is present. Next: .ti +.5i %<(nonnull)%(void(width))%(putaddr To: )\\n%>\\ If the \fIformataddr\fR result is non-null, it is printed as an address (with line folding if needed) in a field \fIwidth\fR wide with a leading label of \*(lqTo: \*(rq. .ti +.5i %(lit)%(formataddr{to})%(formataddr{cc})%(formataddr(me))\\ \fIstr\fR is cleared, and the \*(lqTo:\*(rq and \*(lqCc:\*(rq headers, along with the user's address (depending on what was specified with the \*(lq\-cc\*(rq switch to \fIrepl\fR\^) are formatted. .ti +.5i %<(nonnull)%(void(width))%(putaddr cc: )\\n%>\\ If the result is non-null, it is printed as above with a leading label of \*(lqcc: \*(rq. .ti +.5i %<{fcc}Fcc: %{fcc}\\n%>\\ If a \*(lq\-fcc\ folder\*(rq switch was given to \fIrepl\fR (see \fIrepl\fR\0(1) for more details about %{\fIfcc\fR\^}), an \*(lqFcc:\*(rq header is output. .ti +.5i %<{subject}Subject: Re: %{subject}\\n%>\\ If a subject component was present, a suitable reply subject is output. .nf .ti +.5i %<{date}In-reply-to: Your message of "\\ .ti +.5i %<(nodate{date})%{date}%|%(pretty{date})%>."%<{message-id} .ti +.5i %{message-id}%>\\n%>\\ .ti +.5i \-\-\-\-\-\-\-\- .fi If a date component was present, an \*(lqIn-Reply-To:\*(rq header is output with the preface \*(lqYour message of \*(rq. If the date was parseable, it is output 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: .sp 1 .nf .in +.5i .ta .5i 1i 1.5i 2i if (comp_exists(date)) then print (\*(lqIn-reply-to: Your message of \\\*(lq\*(rq) if (not_date_string(date.value) then print (date.value) else print (pretty(date.value)) endif print (\*(lq\\\*(rq\*(rq) if (comp_exists(message-id)) then print (\*(lq\\n\\t\*(rq) print (message-id.value) endif print (\*(lq\\n\*(rq) endif .re .in -.5i .fi .sp 1 Although this seems complicated, in point of fact, this method is flexible enough to extract individual fields and print them in any format the user desires. .Fi None .Pr None .Sa scan(1), repl(1), ap(8), dp(8) .De None .Co None .Hi This software was contributed for MH 6.3. Prior to this, output format specifications were much easier to write, but considerably less flexible. .Bu On hosts where \fIMH\fR was configured with the BERK option, address parsing is not enabled. .En