[WIP] add support for link|linkat

CHANGELOG.md

@@ -24,6 +24,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   ([#739](https://github.com/nix-rust/nix/pull/739))
 - Added nix::sys::ptrace::detach. 
   ([#749](https://github.com/nix-rust/nix/pull/749))
+- Added `nix::unistd::{link, linkat}`
+  ([#755](https://github.com/nix-rust/nix/pull/755))
 
 ### Changed
 - Renamed existing `ptrace` wrappers to encourage namespacing ([#692](https://github.com/nix-rust/nix/pull/692))

src/unistd.rs

@@ -2,7 +2,7 @@
 
 use errno;
 use {Errno, Error, Result, NixPath};
-use fcntl::{fcntl, OFlag, O_CLOEXEC, FD_CLOEXEC};
+use fcntl::{AtFlags, fcntl, OFlag, O_CLOEXEC, FD_CLOEXEC};
 use fcntl::FcntlArg::F_SETFD;
 use libc::{self, c_char, c_void, c_int, c_long, c_uint, size_t, pid_t, off_t,
            uid_t, gid_t, mode_t};
@@ -812,6 +812,36 @@ pub fn lseek64(fd: RawFd, offset: libc::off64_t, whence: Whence) -> Result<libc:
     Errno::result(res).map(|r| r as libc::off64_t)
 }
 
+/// Call the link function to create a link to a file
+/// ([posix specification](http://pubs.opengroup.org/onlinepubs/9699919799/functions/link.html)).
+pub fn link<P1: ?Sized + NixPath, P2: ?Sized + NixPath>(oldpath: &P1, newpath: &P2) -> Result<()> {
+    let res = try!(try!(oldpath.with_nix_path(|old|
+        newpath.with_nix_path(|new|
+            unsafe {
+                libc::link(old.as_ptr() as *const c_char, new.as_ptr() as *const c_char)
+            }
+        )
+    )));
+
+    Errno::result(res).map(drop)
+}
+
+/// Call the link function to create a link to a file
+/// ([posix specification](http://pubs.opengroup.org/onlinepubs/9699919799/functions/linkat.html)).
+pub fn linkat<P1: ?Sized + NixPath, P2: ?Sized + NixPath>(olddirfd: RawFd, oldpath: &P1,
+                                                          newdirfd: RawFd, newpath: &P2, flags: AtFlags) -> Result<()> {
+    let res = try!(try!(oldpath.with_nix_path(|old|
+        newpath.with_nix_path(|new|
+            unsafe {
+                libc::linkat(olddirfd, old.as_ptr() as *const c_char,
+                             newdirfd, new.as_ptr() as *const c_char, flags.bits())
+            }
+        )
+    )));
+
+    Errno::result(res).map(drop)
+}
+
 pub fn pipe() -> Result<(RawFd, RawFd)> {
     unsafe {
         let mut fds: [c_int; 2] = mem::uninitialized();

test/test_unistd.rs

@@ -1,5 +1,6 @@
 extern crate tempdir;
 
+use nix::fcntl;
 use nix::unistd::*;
 use nix::unistd::ForkResult::*;
 use nix::sys::wait::*;
@@ -250,6 +251,36 @@ fn test_fpathconf_limited() {
     assert!(path_max.expect("fpathconf failed").expect("PATH_MAX is unlimited") > 0);
 }
 
+#[test]
+fn test_linkat() {
+    let tempdir = TempDir::new("nix-test_linkat").unwrap();
+    let src = tempdir.path().join("foo");
+    let dst = tempdir.path().join("bar");
+    File::create(&src).unwrap();
+
+    let dirfd = fcntl::open(tempdir.path(),
+                            fcntl::OFlag::empty(),
+                            stat::Mode::empty());
+    linkat(dirfd.unwrap(),
+           &src.file_name(),
+           dirfd.unwrap(),
+           &dst.file_name(),
+           fcntl::AtFlags::empty()).unwrap();
+    assert!(dst.exists());
+}
+
+#[test]
+fn test_link() {
+    let tempdir = TempDir::new("nix-test_link").unwrap();
+    let src = tempdir.path().join("foo");
+    let dst = tempdir.path().join("bar");
+    File::create(&src).unwrap();
+
+    link(&src, &dst).unwrap();
+    assert!(dst.exists());
+}
+
+
 #[test]
 fn test_pathconf_limited() {
     // AFAIK, PATH_MAX is limited on all platforms, so it makes a good test