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mh-format(4) Kernel Interfaces Manual mh-format(4) NAME mh-format - Format file for the MH message system 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 specifies how scan should generate the scan listing for each mes- sage; repl(1) uses a format file which directs it how to generate the reply to a message, and so on. This reference page describes how to write new format commands or mod- ify existing ones. You should not attempt this unless you are an expe- rienced MH user. A format string is similar to a printf string, but uses multi-letter escapes. The rest of this reference page assumes a knowledge of the printf routine. When specifying a string, the usual C backslash char- acters are honored: \b, \f, \n, \r and \t. Continuation lines in for- mat files end with \ followed by the newline character. When an escape is interpreted and the result is immediately printed, you can specify an optional field width to print the field in exactly a given number of characters. A numeric escape, such as "%4(size)", will print at most 4 digits of the value. Any overflow is marked by a ? in the first position, for example ?123. A string escape, such as "%4(me)", will print the first four characters of the string. In both cases, short fields are padded at the right, usually with a blank. If the field width argument begins with a zero, for example "%04(size)", the fill character is a zero. The interpretation model is based on a simple machine with two regis- ters, num and str. The former contains an integer value, the latter a string value. When an escape is processed, if it requires an argument, it reads the current value of either num or str; and, if it returns a value, it writes either num or str. Escapes are of three types: components, functions, and control. Component Escapes A component escape represents a header field in the message being processed. It is written {name}, where the name is the name of the header field. For example, {date} refers to the Date: field of the message. The value of a component escape is the content of the named field. This is always a string. For example, the header of an unsent message might look as follows: To: smith@local cc: davis Subject: tomorrow's meeting In this example, the value of the component escape {subject} is the string "tomorrow's meeting". Control Escapes A control escape is one of: %<, %| and %>. These correspond to if- then-else constructs. There are two syntaxes allowed by these control escapes. The first is: %<(function)Command-string%> %<{component}Command-String%> If the func- tion or component is non-zero (for integer-valued escapes) or non-empty (for string-valued escapes), everything up to the corresponding %> is interpreted. Otherwise, skip to the next %> and begin interpreting again. The second form of syntax is as follows: %<(function)Then-Command- String%|Else-Command-String%> %<{component}Then-Command-String%|Else- Command-String%> If the function or component is non-zero or non-null, the Then-Command-String is interpreted. Otherwise, skip to %| and in- terpret the Else-Command-String. Only one string is ever interpreted; if the first string is interpreted, the system skips from the %| con- trol escape to the %> character. Function Escapes A function escape is specified as %(name), and is statically defined. Most functions expect an argument of a particular type. In the tables of functions that follow, these types are referred to: literal A literal number or string; for example, %(func 1234) takes the number 1234 as its argument. comp Any header component; for example, %(func{from}) takes the contents of the From: header field as an argument. expr An optional component, function or string, perhaps nested. For example, %(func (func2{comp})) takes the return value of the function (func2{comp}) as its argument. If no argument is provided, the function will read either the num or the str register, as appropriate. Functions return three types of values: string, integer, and, for those functions which return a true or false status, boolean. In the tables that follow, str and num represent the values stored in these regis- ters. arg represents the value of the argument supplied to the func- tion. The following table lists the function escapes: tab(+); lfHB lfHB lfHB lfHB l l l l. _ Escape+Argument+Returns+Interpretation _ msg+ +integer+message number cur+ +integer+message is current size+ +integer+size of message strlen+ +integer+length of str width+ +inte- ger+output buffer size in bytes charleft+integer+integer+space left in output buffer timenow+ +integer+seconds since the epoch me+ +string+the user's mailbox eq+literal+integer+num == arg ne+literal+integer+num != arg gt+literal+integer+num > arg match+literal+boolean+str contains arg amatch+literal+boolean+str starts with arg plus+ +integer+arg plus num minus+ +integer+arg minus num divide+literal+integer+num divided by arg num+literal+integer+Set num to arg lit+literal+integer+Set str to arg nonzero+expr+integer+num is non-zero zero+expr+integer+num is zero null+expr+integer+str is empty nonnull+expr+integer+str is non-empty void+expr+ +Set str or num comp+comp+string+Set str to component text compval+comp+integer+num set to atoi(str) trim+expr+ +trim trailing white space from str putstr+expr+ +print str putstrf+expr+ +print str in a fixed width putnum+expr+ +print num putnum+expr+ +print num in a fixed width _ The following functions require a date component as an argument: lfHB lfHB lfHB lfHB l l l l. _ Escape Argument Returns Interpretation _ sec date integer seconds of the minute min date integer minutes of the day hour date integer hours of the day (24 hour clock) wday date integer day of the week (Sunday=0) day date string day of the week weekday date string day of the week (long) sday date integer day of the week known 1 for explicit in date 0 for implicit -1 for 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 (abbreviated) lmonth date string month of the year (long form) year date inte- ger year of the century zone date integer timezone in hours tzone date string timezone as a string szone date inte- ger timezone explicit? 1 for explicit 0 for implicit -1 for unknown date2lo- cal date coerce date to local timezone date2gmt date co- erce date to GMT dst date integer daylight savings in effect? clock date integer seconds since the epoch rclock date inte- ger seconds prior to current time tws date string official RFC 822 rendering of the date pretty date string a more user-friendly rendering nodate date str could not be parsed as a date _ The following functions require an address component as an argument. Some functions return a value based on the first address in the field only. These are indicated by the note (first only). lfHB lfHB lfHB lfHB l l l l. _ Escape Argument Returns Interpretation _ proper addr string official RFC 822 rendering of the address friendly string string a more user-friendly rendering pers addr string the personal name (first only) note addr string commentary text (first only) mbox addr string the local part of the address (first only) mymbox addr does the address refer to the user's mailbox? (0=no, 1=yes) host addr string the domain part of the address (first only) no- host addr integer no host was present in the address (first only) type addr integer the type of host -1 for uucp 0 for local 1 for network 2 for unknown path addr string the route part of the address (first only) ingrp addr inte- ger the address appeared inside a group (first only) gname addr string name of the group (first only) for- mataddr expr append arg to str as an address list putaddr literal print str address list with arg as an optional label; get line width from num _ Some functions that print their arguments can be controlled by giving field width arguments. The functions (putnumf) and (putstrf) print their arguments as specified by the field width arguments. So %06(put- numf(size)) will print the message size in six digits, filled with leading zeros; %14(putsrtf{from}) will print the From: header field in 14 characters, with trailing spaces as required. With (putstrf), sup- plying a negative field width will cause the string to be right-justi- fied within the field. The functions (putnum) and (putstr) ignore any field width arguments, and print their arguments in the minimum number of characters required. RESTRICTIONS When the friendly format for addresses is used, addresses longer than about 180 characters are truncated to an empty string. This means that such addresses will not appear in the scan display. The function (mymbox{comp}) checks each of the addresses in the named header component {comp} against the user's mailbox name, and against any other mailboxes listed in the Alternate-Mailboxes entry in the user's .mh_profile. It returns true if any of the address matches. However, it also returns true if the named {comp} header field is not present. If necessary, you can use the (null) or (nonnull) functions to test explicitly for the presence of the field. EXAMPLES The default format string for scan follows. This has been divided into several pieces for readability. The first part is: %4(msg)%<(cur)+%| %>%<{replied}-%| %> This means that the message number should be printed in four digits; if the message is the current message then a + is printed. If the message is not the current message, then a space is printed. If a Replied: field is present, a - is printed. If no Replied: field is present, then a space is printed. Next: %02(mon{date})/%02(mday{date}) The month and date are printed in two digits (zero filled). Next: %<{date} %|*> If no Date: field is present, then a * is printed, otherwise a space. Next: %<(mym- box{from})To:%14(friendly{to}) If the message is from me, print To: followed by a user-friendly rendering of the first address in the To: field. %|%17(friendly{from})%> If the message is not from me, then the From: address is printed. And finally: %{subject}%<{body}<<%{body}%> The subject and initial body are printed preceded by the string <<. Although this seems complicated, this method is flexible enough to ex- tract individual fields and print them in any format the user desires. If the -form formatfile switch is given with the scan command, it will treat each line in the named file as a format string, and act accord- ingly. This lets the user develop template scan listing formats. Some examples can be found in /usr/lib/mh/scan.time, /usr/lib/mh/scan.size, and /usr/lib/mh/scan.timely. RELATED INFORMATION scan(1), ap(8), dp(8) delim off mh-format(4)