-a
Append tag on successful match V8.1 and later
When a key is looked up in a database (from inside the
$(
and $)
operators of the RHS
of rules) a successfully found key is replaced by
its data. If the -a
switch is given, the text following
that switch, up to the first delimiting whitespace
character, is appended to the replacement data. For
example:
-a appends nothing -a. appends . -a,MAGICTOKEN appends ,MAGICTOKEN
The text to be appended is taken literally. Quotation
marks and backslashed characters are included
without interpretation, so whitespace cannot be
included in that text. Because the rewritten RHS is
normalized as an address, special address
expressions (such as parentheses) should be avoided.
The use of appended text is one of two methods used
for recognizing a successful lookup in rules. We’ll
discuss the other, $
:, in Specify a Default with $: on
page 893.
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