Add getresuid() and getresgid() to unistd

CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased] - ReleaseDate
+### Added
+- Added `getresuid` and `getresgid`
+  (#[1430](https://github.com/nix-rust/nix/pull/1430))
+
 ### Added
 - Added TIMESTAMPNS support for linux
   (#[1402](https://github.com/nix-rust/nix/pull/1402))

src/unistd.rs

@@ -29,6 +29,9 @@ pub use self::pivot_root::*;
           target_os = "linux", target_os = "openbsd"))]
 pub use self::setres::*;
 
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "openbsd"))]
+pub use self::getres::*;
+
 /// User identifier
 ///
 /// Newtype pattern around `uid_t` (which is just alias). It prevents bugs caused by accidentally
@@ -1078,7 +1081,7 @@ pub fn pipe() -> Result<(RawFd, RawFd)> {
 /// The following flags are supported, and will be set atomically as the pipe is
 /// created:
 ///
-/// `O_CLOEXEC`:    Set the close-on-exec flag for the new file descriptors.  
+/// `O_CLOEXEC`:    Set the close-on-exec flag for the new file descriptors.
 #[cfg_attr(target_os = "linux", doc = "`O_DIRECT`: Create a pipe that performs I/O in \"packet\" mode.  ")]
 #[cfg_attr(target_os = "netbsd", doc = "`O_NOSIGPIPE`: Return `EPIPE` instead of raising `SIGPIPE`.  ")]
 /// `O_NONBLOCK`:   Set the non-blocking flag for the ends of the pipe.
@@ -2524,6 +2527,51 @@ mod setres {
     }
 }
 
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "openbsd"))]
+mod getres {
+    use crate::Result;
+    use crate::errno::Errno;
+    use super::{Uid, Gid};
+
+    /// Gets the real, effective, and saved uid.
+    ///
+    /// ([see getresuid(2)](http://man7.org/linux/man-pages/man2/getresuid.2.html))
+    ///
+    /// #Returns
+    ///
+    /// - `Ok((Uid, Uid, Uid))`: tuple of real, effective and saved uids on success.
+    /// - `Err(x)`: libc error code on failure.
+    ///
+    #[inline]
+    pub fn getresuid() -> Result<(Uid, Uid, Uid)> {
+        let mut ruid = libc::uid_t::max_value();
+        let mut euid = libc::uid_t::max_value();
+        let mut suid = libc::uid_t::max_value();
+        let res = unsafe { libc::getresuid(&mut ruid, &mut euid, &mut suid) };
+
+        Errno::result(res).map(|_| (Uid(ruid), Uid(euid), Uid(suid)))
+    }
+
+    /// Gets the real, effective, and saved gid.
+    ///
+    /// ([see getresgid(2)](http://man7.org/linux/man-pages/man2/getresgid.2.html))
+    ///
+    /// #Returns
+    ///
+    /// - `Ok((Gid, Gid, Gid))`: tuple of real, effective and saved gids on success.
+    /// - `Err(x)`: libc error code on failure.
+    ///
+    #[inline]
+    pub fn getresgid() -> Result<(Gid, Gid, Gid)> {
+        let mut rgid = libc::gid_t::max_value();
+        let mut egid = libc::gid_t::max_value();
+        let mut sgid = libc::gid_t::max_value();
+        let res = unsafe { libc::getresgid(&mut rgid, &mut egid, &mut sgid) };
+
+        Errno::result(res).map(|_| (Gid(rgid), Gid(egid), Gid(sgid)))
+    }
+}
+
 libc_bitflags!{
     /// Options for access()
     pub struct AccessFlags : c_int {

test/test_unistd.rs

@@ -624,6 +624,25 @@ fn test_sysconf_unsupported() {
     assert!(open_max.expect("sysconf failed").is_none())
 }
 
+
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "openbsd"))]
+#[test]
+fn test_getresuid() {
+    let resuid = getresuid().unwrap();
+    assert!(resuid.0.as_raw() != libc::uid_t::max_value());
+    assert!(resuid.1.as_raw() != libc::uid_t::max_value());
+    assert!(resuid.2.as_raw() != libc::uid_t::max_value());
+}
+
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "openbsd"))]
+#[test]
+fn test_getresgid() {
+    let resgid = getresgid().unwrap();
+    assert!(resgid.0.as_raw() != libc::gid_t::max_value());
+    assert!(resgid.1.as_raw() != libc::gid_t::max_value());
+    assert!(resgid.2.as_raw() != libc::gid_t::max_value());
+}
+
 // Test that we can create a pair of pipes.  No need to verify that they pass
 // data; that's the domain of the OS, not nix.
 #[test]