os: document that File.Seek works on directories, but not portably
Updates #36019
Change-Id: I9fea2c3c5138e2233290979e4724f6e7b91da652
Reviewed-on: https://go-review.googlesource.com/c/go/+/213439
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/src/os/file.go b/src/os/file.go
index 7995de7..9f8c827 100644
--- a/src/os/file.go
+++ b/src/os/file.go
@@ -204,6 +204,10 @@
// relative to the current offset, and 2 means relative to the end.
// It returns the new offset and an error, if any.
// The behavior of Seek on a file opened with O_APPEND is not specified.
+//
+// If f is a directory, the behavior of Seek varies by operating
+// system; you can seek to the beginning of the directory on Unix-like
+// operating systems, but not on Windows.
func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
if err := f.checkValid("seek"); err != nil {
return 0, err
