line. The portion of a line following a hash character <samp>#</samp> is
taken as a comment and ignored. Each directive consists of a series
of tokens separated by linear whitespace (spaces and tabs); tokens may
-be words consisting of non-space characters, or, where a string is
-required, a string in double quotes. Double-quoted strings may
-contain the following backslash escapes:
+be words consisting of non-space characters (except backslash), or,
+where a string is required, a string in double quotes. Double-quoted
+strings may contain the following backslash escapes:
<dl compact>
<dt><samp>\n</samp><dd>newline
relative to the service user's home directory.
</p>
+<p>
+Logical lines may be continued by putting a backslash <samp>\</samp> at the
+end of a line; this counts as part of linear whitespace.
+</p>
+
<hr>
<h2>
the directory cannot be accessed.
A translation will be applied to values before they are used to
-construct a filename, so that the lookup cannot access dotfiles or
-files in other directories: values starting with full stops will have
-a colon prepended (making <samp>:.</samp>), colons will be doubled, and each
-slash will be replaced with a colon followed by a hyphen <samp>:-</samp>. A
-parameter value which is the empty string will be replaced with
+construct a filename, so that the lookup cannot access dotfiles,
+backup files, files in other directories and the like: each slash will
+be replaced with a colon followed by a hyphen <samp>:-</samp>, and all
+characters which are not lowercase alphanumerics, hyphens or
+underscores will have a colon prepended (so that colons are doubled).
+A parameter value which is the empty string will be replaced with
<samp>:empty</samp> (note that this is different from a parameter not having
any values).
<p><dt><samp>error <var>text ...</var></samp><dd>Causes an error whose message includes the descriptive string
<var>text</var>. <var>text</var> may consist of several tokens with intervening
-whitespace. The whitespace will be included in the message as found
-in the configuration file: all the characters until the end of the
-line will be included verbatim, unless they are part of a
-double-quoted string, in which case the usual meaning of the string
+linear whitespace. Each set of linear whitespace will appear in the
+message as a single space. The usual meaning of double-quoted strings
(i.e., after backslash escape processing) will be used. Comments and
linear whitespace at the end of the line (or just before the comment)
-will still be ignored.
+will still be ignored. Apart from those cases, each token's text will
+be included verbatim.
<p><dt><samp>message <var>text ...</var></samp><dd>Causes a message including the descriptive string <var>text</var> to be
delivered as if it were an error message, but does not actually cause