Added documentation

Author: Kixunil

src/unistd.rs

@@ -24,18 +24,22 @@ pub use self::linux::*;
 pub struct Uid(uid_t);
 
 impl Uid {
+    /// Creates `Uid` from raw `uid_t`.
     pub fn from_raw(uid: uid_t) -> Self {
         Uid(uid)
     }
 
+    /// Returns Uid of calling process. This is practically a more Rusty alias for `getuid`.
     pub fn current() -> Self {
         getuid()
     }
 
+    /// Returns effective Uid of calling process. This is practically a more Rusty alias for `geteuid`.
     pub fn effective() -> Self {
         geteuid()
     }
 
+    /// Returns true if the `Uid` represents privileged user - root. (If it equals zero.)
     pub fn is_root(&self) -> bool {
         self.0 == 0
     }
@@ -64,14 +68,17 @@ pub const ROOT: Uid = Uid(0);
 pub struct Gid(gid_t);
 
 impl Gid {
+    /// Creates `Gid` from raw `gid_t`.
     pub fn from_raw(gid: gid_t) -> Self {
         Gid(gid)
     }
 
+    /// Returns Gid of calling process. This is practically a more Rusty alias for `getgid`.
     pub fn current() -> Self {
         getgid()
     }
 
+    /// Returns effective Gid of calling process. This is practically a more Rusty alias for `getgid`.
     pub fn effective() -> Self {
         getegid()
     }
@@ -97,14 +104,17 @@ impl fmt::Display for Gid {
 pub struct Pid(pid_t);
 
 impl Pid {
+    /// Creates `Pid` from raw `pid_t`.
     pub fn from_raw(pid: pid_t) -> Self {
         Pid(pid)
     }
 
+    /// Returns PID of calling process
     pub fn this() -> Self {
         getpid()
     }
 
+    /// Returns PID of parent of calling process
     pub fn parent() -> Self {
         getppid()
     }