replace shellouts with libc calls where possible

[bookshelfdave]

You can test functionality via the test framework documented here.

Which reminds me, I'll have a PR "soonish" for the test stuff in Travis.

Signed-off-by: Dave Parfitt [email protected]

[thesentinels]

@metadave, thanks for your PR! By analyzing the annotation information on this pull request, we identified @fnichol, @adamhjk, @reset, @smith and @juliandunn to be potential reviewers

[reset]

[bookshelfdave]

I forgot to mention a few things here:

• as UDP is connectionless, you may be wondering why we call connect here:

  habitat/components/core/src/util/sys.rs

  Lines 26 to 31 in 00d0c8a

  	pub fn ip() -> Result<IpAddr> {
  	let socket = try!(UdpSocket::bind("0.0.0.0:0"));
  	let _ = try!(socket.connect(GOOGLE_DNS));
  	let addr =try!(socket.local_addr());
  	Ok(addr.ip())
  	}

After this call:

let socket = try!(UdpSocket::bind("0.0.0.0:0"));`

calling

socket.local_addr()

doesn't return a useful IP address.

However, calling

let _ = try!(socket.connect(GOOGLE_DNS));

performs some internal caching without making a network connection, and lets us use the result from:

let addr =try!(socket.local_addr());

See also:

• The Sockets Networking API: UNIX® Network Programming Volume 1, Third Edition
  • Chapter 8. Elementary UDP Sockets
• http://www.microhowto.info/howto/send_a_udp_datagram_in_c.html

@fnichol: anything else I should call out here?

---

• thanks to @markan for his original work to get rid of chown.
• thanks to @fnichol for a great pairing session.

Cheers!