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# alookup

Lookup IPv4 and IPv6 addresses for a hostname. Only prints addresses on
`stdout` (one per line), errors to `stderr`, and hard errors can be
detected through inspecting the exit code.

It uses the [`resolv`] crate (specifically the [`query`] method), which
uses `libresolv.so` which is typically configured via `/etc/resolv.conf`
to do DNS resolution.

[`resolv`]: https://crates.io/crates/resolv
[`query`]: https://mikedilger.github.io/resolv-rs/resolv/struct.Resolver.html#method.query

## Install

Install from [`crates.io`](https://crates.io/crates/alookup) with
`cargo install alookup`.

## Using it

### Examples

	alookup mail.google.com


### Usage

	alookup [FLAGS] <NAME>

	FLAGS:

	    -4               Query only IPv4 records (A)
	    -6               Query only IPv6 records (AAAA)
	    -s, --sort       Sort (and deduplicate) addresses
	    -h, --help       Prints help information
	    -V, --version    Prints version information

	ARGS:

	    <NAME>    Name to lookup

### Exit codes

- `0`: success (or `NODATA`).  You might want to treat an empty address
  set (no output) as failure too (similar to `NXDOMAIN`).
- `1`: name not found (`NXDOMAIN`).  If an empty address set is ok for
  you, you might want to ignore this exit code.
- `2`: `SRVFAIL`, timeouts, failed parsing response, generic resolver failure...
- `3`: failed parsing a specific answer record (might have printed
  partial result, but breaks on first broken record)

Other exit codes should be treated as failures too; a non-zero exit code
always should show an error on `stderr`, and every time an error is
printed to `stderr` there should be a non-zero exit code.