Index: bolt/tools/merge-fdata/merge-fdata.cpp
===================================================================
--- bolt/tools/merge-fdata/merge-fdata.cpp
+++ bolt/tools/merge-fdata/merge-fdata.cpp
@@ -64,6 +64,12 @@
   cl::Optional,
   cl::cat(MergeFdataCategory));
 
+static cl::opt<std::string>
+OutputFilePath("o",
+  cl::value_desc("file"),
+  cl::desc("Write output to <file>"),
+  cl::cat(MergeFdataCategory));
+
 } // namespace opts
 
 namespace {
@@ -81,6 +87,18 @@
   exit(1);
 }
 
+static raw_fd_ostream &output() {
+  if (opts::OutputFilePath.empty() || opts::OutputFilePath == "-") {
+    return outs();
+  } else {
+    std::error_code EC;
+    static raw_fd_ostream output(opts::OutputFilePath, EC);
+    if (EC)
+      report_error(opts::OutputFilePath, EC);
+    return output;
+  }
+}
+
 void mergeProfileHeaders(BinaryProfileHeader &MergedHeader,
                          const BinaryProfileHeader &Header) {
   if (MergedHeader.FileName.empty())
@@ -283,9 +301,9 @@
   }
 
   if (BoltedCollection)
-    outs() << "boltedcollection\n";
+    output() << "boltedcollection\n";
   for (const auto &Entry : Entries)
-    outs() << Entry.getKey() << " " << Entry.getValue() << "\n";
+    output() << Entry.getKey() << " " << Entry.getValue() << "\n";
 
   errs() << "Profile from " << Filenames.size() << " files merged.\n";
 }
@@ -375,7 +393,7 @@
   }
 
   if (!opts::SuppressMergedDataOutput) {
-    yaml::Output YamlOut(outs());
+    yaml::Output YamlOut(output());
 
     BinaryProfile MergedProfile;
     MergedProfile.Header = MergedHeader;