os: Implement few file and process functions.

os/os.py

@@ -1,4 +1,5 @@
 import ffi
+import array
 
 
 libc = ffi.open("libc.so.6")
@@ -7,6 +8,10 @@ errno = libc.var("i", "errno")
 mkdir_ = libc.func("i", "mkdir", "si")
 read_ = libc.func("i", "read", "ipi")
 write_ = libc.func("i", "write", "iPi")
+close_ = libc.func("i", "close", "i")
+fork_ = libc.func("i", "fork", "")
+pipe_ = libc.func("i", "pipe", "p")
+_exit_ = libc.func("v", "_exit", "i")
 
 
 def check_error(ret):
@@ -28,3 +33,23 @@ def write(fd, buf):
     r = write_(fd, buf, len(buf))
     check_error(r)
     return r
+
+def close(fd):
+    r = close_(fd)
+    check_error(r)
+    return r
+
+
+def fork():
+    r = fork_()
+    check_error(r)
+    return r
+
+def pipe():
+    a = array.array('i', [0, 0])
+    r = pipe_(a)
+    check_error(r)
+    return a[0], a[1]
+
+def _exit(n):
+    _exit_(n)

os/setup.py

@@ -1,7 +1,7 @@
 from distutils.core import setup
 
 setup(name='micropython-os',
-      version='0.0.2',
+      version='0.0.3',
       description='os module for MicroPython',
       url='https://github.com/micropython/micropython/issues/405',
       author='MicroPython Developers',