os: add example for OpenFile

New beginners are not familiar with open(2)-style masking of the
flags. Add an example demonstrates the flag or'ing.

Change-Id: Ifa8009c55173ba0dc6642c1d3b3124c766b1ebbb
Reviewed-on: https://go-review.googlesource.com/27996
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/os/example_test.go b/src/os/example_test.go
new file mode 100644 (file)
index 0000000..e82ee3e
--- /dev/null
+++ b/src/os/example_test.go
@@ -0,0 +1,20 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os_test
+
+import (
+       "log"
+       "os"
+)
+
+func ExampleOpenFile() {
+       f, err := os.OpenFile("notes.txt", os.O_RDWR|os.O_CREATE, 0755)
+       if err != nil {
+               log.Fatal(err)
+       }
+       if err := f.Close(); err != nil {
+               log.Fatal(err)
+       }
+}