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Registrable domain of a host

Source: R/query.R
registrable_domain.Rd

Returns the registrable domain (eTLD+1) of each host: its public suffix plus one host label to the left. It is NA when no such label exists (the host is itself a public suffix) or when the public suffix is NA.

Usage

registrable_domain(
  domain,
  section = c("all", "icann", "private"),
  output = c("ascii", "unicode"),
  unknown = c("default", "na"),
  invalid = c("na", "error")
)

Arguments

domain

Character vector of DNS hostnames (not URLs). Each element may be a mixed-case ASCII, Unicode, or A-label hostname, a single label, or a hostname with exactly one terminal root dot. See Input contract.

section

Which rule sections are eligible: "all" (default; ICANN and PRIVATE), "icann", or "private". Section filtering happens before prevailing-rule selection, so "private" does not silently add ICANN rules; a host matching no rule in the section falls through to the implicit default rule unless unknown = "na".

output

"ascii" (default) returns lowercase A-labels; "unicode" decodes them after matching. A terminal root dot is preserved either way.

unknown

"default" (default) applies the spec's implicit * rule, so an unlisted single label is its own public suffix; "na" returns NA when no explicit rule in the selected section matches.

invalid

"na" (default) returns NA for each invalid element without a warning; "error" aborts on the first invalid element, reporting its 1-based index.

Value

A character vector with length(domain), preserving the names of domain. Other attributes are dropped.

Input contract

NA is treated as missing (returns NA), not invalid. Invalid elements include empty or whitespace-only strings, leading or consecutive dots, URL syntax, IPv6 addresses, canonical dotted-decimal IPv4 literals, and labels that fail hostname/IDNA validation. Wrong argument types and non-scalar or unknown option values always abort regardless of invalid.

See also

public_suffix(), is_public_suffix(), suffix_extract()

Examples

registrable_domain("www.example.co.uk")
#> [1] "example.co.uk"
registrable_domain("com")
#> [1] NA
registrable_domain("foo.madeuptld", unknown = "na")
#> [1] NA