os: add basic OS functionality

src/os/file_unix.go

@@ -0,0 +1,24 @@
+// +build linux
+
+package os
+
+import (
+	"syscall"
+)
+
+// Read reads up to len(b) bytes from the File. It returns the number of bytes
+// read and any error encountered. At end of file, Read returns 0, io.EOF.
+func (f *File) Read(b []byte) (n int, err error) {
+	return syscall.Read(int(f.fd), b)
+}
+
+// Write writes len(b) bytes to the File. It returns the number of bytes written
+// and an error, if any. Write returns a non-nil error when n != len(b).
+func (f *File) Write(b []byte) (n int, err error) {
+	return syscall.Write(int(f.fd), b)
+}
+
+// Close closes the File, rendering it unusable for I/O.
+func (f *File) Close() error {
+	return syscall.Close(int(f.fd))
+}