R: Translate address to/from hostname

ip_to_hostname {ipaddress} | R Documentation

## Translate address to/from hostname

### Description

Perform reverse and forward DNS resolution.

Note: These functions are significantly slower than others in the ipaddress package.

### Usage

    ip_to_hostname(x, multiple = FALSE)

    hostname_to_ip(x, multiple = FALSE)

### Arguments

`x` | For `ip_to_hostname()`: An `ip_address` vector For `hostname_to_ip()`: A character vector of hostnames
`multiple` | A logical scalar indicating if all resolved endpoints are returned, or just the first endpoint (the default). This determines whether a vector or list of vectors is returned.

### Details

These functions require an internet connection. Before processing the input vector, we first check that a known hostname can be resolved. If this fails, an error is raised.

If DNS lookup cannot resolve an input, then `NA` is returned for that input. If an error occurs during DNS lookup, then a warning is emitted and `NA` is returned for that input.

DNS resolution performs a many-to-many mapping between IP addresses and hostnames. For this reason, these two functions can potentially return multiple values for each element of the input vector. The `multiple` argument control whether all values are returned (a vector for each input), or just the first value (a scalar for each input).

### Value

- For `ip_to_hostname()`: A character vector (`multiple = FALSE`) or a list of character vectors (`multiple = TRUE`)

- For `hostname_to_ip()`: A `ip_address` vector (`multiple = FALSE`) or a list of `ip_address` vectors (`multiple = TRUE`)

### See Also

The base function `nsl()` provides forward DNS resolution to IPv4 addresses, but only on Unix-like systems.

### Examples

    ## Not run:
    hostname_to_ip("r-project.org")

    ip_to_hostname(hostname_to_ip("r-project.org"))

    ## End(Not run)

[Package ipaddress version 0.5.2 Index]