mh-format(5mh)mh-format(5mh)Namemh-format - format file for MH message system
Description
Several MH commands utilize either a string or a file during their exe‐
cution. For example, uses a format string which specifies how should
generate the listing for each message; 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 string, but uses multi-letter escapes.
The rest of this reference page assumes a knowledge of the routine.
When specifying a string, the usual C backslash characters are honored:
and Continuation lines in format 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 will print at
most 4 digits of the value. Any overflow is marked by a in the first
position, for example A string escape, such as 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 the fill character is a zero.
The interpretation model is based on a simple machine with two regis‐
ters, and 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 or and, if it returns a value, it
writes either or
Escapes are of three types: and
Component Escapes
A component escape represents a header field in the message being pro‐
cessed. It is written where the name is the name of the header field.
For example, refers to the 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 is the string
Control Escapes
A control escape is one of: and These correspond to if-then-else con‐
structs.
There are two syntaxes allowed by these control escapes. The first is:
%<(function)Command-string%>
%<{component}Command-String%>
If the function or component is non-zero (for integer-valued escapes)
or non-empty (for string-valued escapes), everything up to the corre‐
sponding is interpreted. Otherwise, skip to the next and begin inter‐
preting 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 is inter‐
preted. Otherwise, skip to and interpret the Only one string is ever
interpreted; if the first string is interpreted, the system skips from
the control escape to the character.
Function Escapes
A function escape is specified as 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:
A literal number or string; for example,
takes the number 1234 as its argument.
Any header component; for example,
takes the contents of the From: header field as an argument.
An optional component, function or string, perhaps nested.
For example, takes the return value of the function as its
argument. If no argument is provided, the function will read
either the or the register, as appropriate.
Functions return three types of values: and, for those functions which
return a true or false status, In the tables that follow, and represent
the values stored in these registers. represents the value of the
argument supplied to the function.
The following table lists the function escapes:
───────────────────────────────────────────────────────────────────
Escape Argument Returns Interpretation
───────────────────────────────────────────────────────────────────
msg integer message number
cur integer message is current
size integer size of message
strlen integer length of str
width integer 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:
─────────────────────────────────────────────────────────────────────────
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 integer year of the century
zone date integer timezone in hours
tzone date string timezone as a string
szone date integer timezone explicit?
1 for explicit
0 for implicit
-1 for 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 epoch
rclock date integer 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).
────────────────────────────────────────────────────────────────────────
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)
nohost 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 integer the address appeared inside a group
(first only)
gname addr string name of the group (first only)
formataddr 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 and print their arguments as
specified by the field width arguments. So will print the message size
in six digits, filled with leading zeros; will print the From: header
field in 14 characters, with trailing spaces as required. With supply‐
ing a negative field width will cause the string to be right-justified
within the field. The functions and 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 display.
The function checks each of the addresses in the named header component
against the user's mailbox name, and against any other mailboxes listed
in the Alternate-Mailboxes entry in the user's It returns true if any
of the address matches. However, it also returns true if the named
header field is not present. If necessary, you can use the or func‐
tions to test explicitly for the presence of the field.
Examples
The default format string for follows. This has been divided into sev‐
eral 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:
%<(mymbox{from})To:%14(friendly{to})
If the message is from me, print To: followed by a user-friendly ren‐
dering 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
extract individual fields and print them in any format the user
desires.
If the -form formatfile switch is given with the command, it will treat
each line in the named file as a format string, and act accordingly.
This lets the user develop template listing formats. Some examples can
be found in and
See Alsoscan(1mh), ap(8mh), dp(8mh)mh-format(5mh)
