Implemented getpid(p::Process).

Closes # 4752.

Author: abalkin

base/process.jl

@@ -335,6 +335,20 @@ end
 pipe_reader(p::Process) = p.out
 pipe_writer(p::Process) = p.in
 
+"""
+    getpid(p::Process) -> Int32
+
+Get the process ID of a running process. Returns `-1` if the
+process is not running.
+"""
+function Base.getpid(p::Process)
+    if p.handle != C_NULL
+        ccall(:jl_uv_process_pid, Cint, (Ptr{Void},), p.handle)
+    else
+        Cint(-1)
+    end
+end
+
 struct ProcessChain <: AbstractPipe
     processes::Vector{Process}
     in::Redirectable

src/jl_uv.c

@@ -112,6 +112,7 @@ static void jl_uv_shutdownCallback(uv_shutdown_t *req, int status)
 }
 
 // getters and setters
+JL_DLLEXPORT int jl_uv_process_pid(uv_process_t *p) { return p->pid; }
 JL_DLLEXPORT void *jl_uv_process_data(uv_process_t *p) { return p->data; }
 JL_DLLEXPORT void *jl_uv_buf_base(const uv_buf_t *buf) { return buf->base; }
 JL_DLLEXPORT size_t jl_uv_buf_len(const uv_buf_t *buf) { return buf->len; }

test/spawn.jl

@@ -220,6 +220,16 @@ if valgrind_off
     @test success(proc)
 end
 
+# issue #4752
+let out = Pipe(), proc, pid
+    proc = spawn(pipeline(`$exename --startup-file=no -e 'println(STDERR,getpid())'`, stderr = out))
+    pid = getpid(proc)
+    close(out.in)
+    @test parse(Int32, read(out, String)) == pid
+    @test success(proc)
+    @test getpid(proc) == -1
+end
+
 # issue #6310
 @test read(pipeline(`$echocmd "2+2"`, `$exename --startup-file=no`), String) == "4\n"