std: Add an unstable method Child::id

This commits adds a method to the `std::process` module to get the process
identifier of the child as a `u32`. On Windows the underlying identifier is
already a `u32`, and on Unix the type is typically defined as `c_int` (`i32` for
almost all our supported platforms), but the actually pid is normally a small
positive number.

Eventually we may add functions to load information about a process based on its
identifier or the ability to terminate a process based on its identifier, but
for now this function should enable this sort of functionality to exist outside
the standard library.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/libstd/sys/windows/process.rs b/src/libstd/sys/windows/process.rs
index 032a349b00e..bc4762c197e 100644
--- a/src/libstd/sys/windows/process.rs
+++ b/src/libstd/sys/windows/process.rs
@@ -193,6 +193,12 @@ impl Process {
         Ok(())
     }
 
+    pub fn id(&self) -> u32 {
+        unsafe {
+            c::GetProcessId(self.handle.raw()) as u32
+        }
+    }
+
     pub fn wait(&self) -> io::Result<ExitStatus> {
         use libc::{STILL_ACTIVE, INFINITE, WAIT_OBJECT_0};
         use libc::{GetExitCodeProcess, WaitForSingleObject};