1 files changed, 20 insertions, 0 deletions
diff --git a/src/os/exec/internal/fdtest/exists_plan9.go b/src/os/exec/internal/fdtest/exists_plan9.go
new file mode 100644
index 0000000..8886e06
--- /dev/null
+++ b/src/os/exec/internal/fdtest/exists_plan9.go
@@ -0,0 +1,20 @@
+// Copyright 2021 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.
+
+//go:build plan9
+
+package fdtest
+
+import (
+	"syscall"
+)
+
+const errBadFd = syscall.ErrorString("fd out of range or not open")
+
+// Exists returns true if fd is a valid file descriptor.
+func Exists(fd uintptr) bool {
+	var buf [1]byte
+	_, err := syscall.Fstat(int(fd), buf[:])
+	return err != errBadFd
+}