Use system error codes

src/whoami/platform/unix.rs

@@ -7,6 +7,7 @@
  * file that was distributed with this source code.
  */
 
+use std::io::{Result, Error};
 use ::libc;
 use self::c_types::{c_passwd, getpwuid};
 
@@ -16,14 +17,14 @@ extern {
     pub fn geteuid() -> libc::uid_t;
 }
 
-pub unsafe fn getusername() -> Result<String, String> {
+pub unsafe fn getusername() -> Result<String> {
     // Get effective user id
     let uid = geteuid();
 
     // Try to find username for uid
     let passwd: *const c_passwd = getpwuid(uid);
     if passwd.is_null() {
-        return Err(format!("cannot find name for user ID {}", uid))
+        return Err(Error::last_os_error())
     }
 
     // Extract username from passwd struct

src/whoami/platform/windows.rs

@@ -10,6 +10,8 @@
 extern crate winapi;
 extern crate advapi32;
 
+use std::io::{Result, Error};
+
 #[path = "../../common/wide.rs"] #[macro_use] mod wide;
 
 use std::mem;
@@ -18,11 +20,11 @@ use std::ffi::OsString;
 use std::os::windows::ffi::OsStringExt;
 use self::wide::FromWide;
 
-pub unsafe fn getusername() -> Result<String, String> {
+pub unsafe fn getusername() -> Result<String> {
     let mut buffer: [winapi::WCHAR; winapi::UNLEN as usize + 1] = mem::uninitialized();
     let mut len = buffer.len() as winapi::DWORD;
     if advapi32::GetUserNameW(buffer.as_mut_ptr(), &mut len) == 0 {
-        return Err("failed to get username".to_string())
+        return Err(Error::last_os_error())
     }
     let username = String::from_wide(&buffer[..len as usize - 1]);
     Ok(username)

src/whoami/whoami.rs

@@ -56,7 +56,10 @@ pub fn exec() {
     unsafe {
         match platform::getusername() {
             Ok(username) => println!("{}", username),
-            Err(msg) => crash!(libc::EXIT_FAILURE, "{}", msg),
+            Err(err) => match err.raw_os_error() {
+                Some(0) | None => crash!(1, "failed to get username"),
+                Some(_) => crash!(1, "failed to get username: {}", err),
+            }
         }
     }
 }