diff --git a/llvm/include/llvm/Support/FileSystem.h b/llvm/include/llvm/Support/FileSystem.h
--- a/llvm/include/llvm/Support/FileSystem.h
+++ b/llvm/include/llvm/Support/FileSystem.h
@@ -634,6 +634,12 @@
 ///          platform-specific error_code.
 std::error_code is_other(const Twine &path, bool &result);
 
+/// Does FD refer to a terminal?
+///
+/// @param FD Input file descriptor.
+/// @returns true if the file descriptor refers to a terminal.
+bool is_tty(int FD);
+
 /// Get file status as if by POSIX stat().
 ///
 /// @param path Input path.
diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -694,6 +694,10 @@
   return fillStatus(StatRet, Status, Result);
 }
 
+bool is_tty(int FD) {
+  return isatty(FD);
+}
+
 std::error_code setPermissions(const Twine &Path, perms Permissions) {
   SmallString<128> PathStorage;
   StringRef P = Path.toNullTerminatedStringRef(PathStorage);
diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -734,6 +734,10 @@
   return getStatus(FileHandle, Result);
 }
 
+bool is_tty(int FD) {
+  return _isatty(FD);
+}
+
 std::error_code setPermissions(const Twine &Path, perms Permissions) {
   SmallVector<wchar_t, 128> PathUTF16;
   if (std::error_code EC = widenPath(Path, PathUTF16))