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Single field substitutions extract a single subdomain part from the host/domain specification being rewritten. The available single field substitutions are shown in Table 2-4.
Control Sequence | Usage |
---|---|
$&n | Substitute the nth element, n=0,1,2,..,9, in the host specification (the part that did not match or matched a wildcard of some kind). Elements are separated by dots; the first element on the left is element zero. The rewrite fails if the requested element does not exist. |
$!n | Substitute the nth element, n=0,1,2,..,9, in the host specification (the part that did not match or matched a wildcard of some kind). Elements are separated by dots; the first element on the right is element zero. The rewrite fails if the requested element does not exist. |
$*n | Substitute the nth element, n=0,1,2,...,9, in the domain specification (the part that did match explicit text in the pattern). Elements are separated by dots; the first element on the left is element zero. The rewrite fails if the requested element does not exist. |
$#n | Substitute the nth element, n=0,1,2,...,9, in the domain specification (the part that did match explicit text in the pattern). Elements are separated by dots; the first element on the right is element zero. The rewrite fails if the requested element does not exist. |
Suppose the address jdoe@vaxa.example.com matches the rewrite rule
*.EXAMPLE.COM $U%$&0.example.com@mailhub.example.com |
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