1 files changed, 21 insertions, 0 deletions
diff --git a/src/internal/syscall/unix/nonblocking.go b/src/internal/syscall/unix/nonblocking.go
new file mode 100644
index 0000000..9e5f0fb
--- /dev/null
+++ b/src/internal/syscall/unix/nonblocking.go
@@ -0,0 +1,21 @@
+// Copyright 2018 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 dragonfly || freebsd || linux || netbsd || openbsd
+
+package unix
+
+import "syscall"
+
+// FcntlSyscall is the number for the fcntl system call. This is
+// usually SYS_FCNTL, but can be overridden to SYS_FCNTL64.
+var FcntlSyscall uintptr = syscall.SYS_FCNTL
+
+func IsNonblock(fd int) (nonblocking bool, err error) {
+	flag, _, e1 := syscall.Syscall(FcntlSyscall, uintptr(fd), uintptr(syscall.F_GETFL), 0)
+	if e1 != 0 {
+		return false, e1
+	}
+	return flag&syscall.O_NONBLOCK != 0, nil
+}