diff --git a/src/OSspecific/MSwindows/fileMonitor/fileMonitor.H b/src/OSspecific/MSwindows/fileMonitor/fileMonitor.H
index c3d90590e1..3b62cd7fea 100644
--- a/src/OSspecific/MSwindows/fileMonitor/fileMonitor.H
+++ b/src/OSspecific/MSwindows/fileMonitor/fileMonitor.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
-    Copyright (C) 2017-2018 OpenCFD Ltd.
+    Copyright (C) 2017-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -45,10 +45,11 @@ SourceFiles
 #ifndef fileMonitor_H
 #define fileMonitor_H
 
-#include <sys/types.h>
 #include "Enum.H"
 #include "className.H"
 #include "DynamicList.H"
+#include <memory>
+#include <sys/types.h>
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -67,7 +68,7 @@ class fileMonitor
 {
 public:
 
-    // Public data types
+    // Public Data Types
 
         //- Enumeration defining the file state.
         enum fileState
@@ -81,7 +82,7 @@ public:
 
 private:
 
-    // Private data
+    // Private Data
 
         //- Whether to use inotify (requires -DFOAM_USE_INOTIFY, see above)
         const bool useInotify_;
diff --git a/src/OSspecific/POSIX/fileMonitor/fileMonitor.H b/src/OSspecific/POSIX/fileMonitor/fileMonitor.H
index 4472bee15b..6dbeed8ac5 100644
--- a/src/OSspecific/POSIX/fileMonitor/fileMonitor.H
+++ b/src/OSspecific/POSIX/fileMonitor/fileMonitor.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
-    Copyright (C) 2017-2018 OpenCFD Ltd.
+    Copyright (C) 2017-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -45,10 +45,11 @@ SourceFiles
 #ifndef fileMonitor_H
 #define fileMonitor_H
 
-#include <sys/types.h>
 #include "Enum.H"
 #include "className.H"
 #include "DynamicList.H"
+#include <memory>
+#include <sys/types.h>
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -67,7 +68,7 @@ class fileMonitor
 {
 public:
 
-    // Public data types
+    // Public Data Types
 
         //- Enumeration defining the file state.
         enum fileState
@@ -81,7 +82,7 @@ public:
 
 private:
 
-    // Private data
+    // Private Data
 
         //- Whether to use inotify (requires -DFOAM_USE_INOTIFY, see above)
         const bool useInotify_;
@@ -99,7 +100,7 @@ private:
         DynamicList<label> freeWatchFds_;
 
         //- Watch mechanism (stat or inotify)
-        mutable autoPtr<fileMonitorWatcher> watcher_;
+        mutable std::unique_ptr<fileMonitorWatcher> watcher_;
 
 
     // Private Member Functions
diff --git a/src/fileFormats/stl/STLCore.C b/src/fileFormats/stl/STLCore.C
index bfcfc5d609..de43611e32 100644
--- a/src/fileFormats/stl/STLCore.C
+++ b/src/fileFormats/stl/STLCore.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2016-2017 OpenCFD Ltd.
+    Copyright (C) 2016-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -91,10 +91,10 @@ int Foam::fileFormats::STLCore::detectBinaryHeader
 )
 {
     bool compressed = false;
-    autoPtr<std::istream> streamPtr
-    (
+    std::unique_ptr<std::istream> streamPtr
+    {
         new std::ifstream(filename, std::ios::binary)
-    );
+    };
 
     // If the file is compressed, decompress it before further checking.
     if (!streamPtr->good() && isFile(filename + ".gz", false))
@@ -102,7 +102,7 @@ int Foam::fileFormats::STLCore::detectBinaryHeader
         compressed = true;
         streamPtr.reset(new igzstream((filename + ".gz").c_str()));
     }
-    std::istream& is = streamPtr();
+    auto& is = *streamPtr;
 
     if (!is.good())
     {
@@ -156,7 +156,7 @@ int Foam::fileFormats::STLCore::detectBinaryHeader
 }
 
 
-Foam::autoPtr<std::istream>
+std::unique_ptr<std::istream>
 Foam::fileFormats::STLCore::readBinaryHeader
 (
     const fileName& filename,
@@ -167,10 +167,10 @@ Foam::fileFormats::STLCore::readBinaryHeader
     bool compressed = false;
     nTrisEstimated = 0;
 
-    autoPtr<std::istream> streamPtr
-    (
+    std::unique_ptr<std::istream> streamPtr
+    {
         new std::ifstream(filename, std::ios::binary)
-    );
+    };
 
     // If the file is compressed, decompress it before reading.
     if (!streamPtr->good() && isFile(filename + ".gz", false))
@@ -178,12 +178,10 @@ Foam::fileFormats::STLCore::readBinaryHeader
         compressed = true;
         streamPtr.reset(new igzstream((filename + ".gz").c_str()));
     }
-    std::istream& is = streamPtr();
+    auto& is = *streamPtr;
 
     if (!is.good())
     {
-        streamPtr.clear();
-
         FatalErrorInFunction
             << "Cannot read file " << filename
             << " or file " << filename + ".gz"
@@ -198,8 +196,6 @@ Foam::fileFormats::STLCore::readBinaryHeader
     // Check that stream is OK, if not this may be an ASCII file
     if (!is.good()) // could check again: startsWithSolid(header)
     {
-        streamPtr.clear();
-
         FatalErrorInFunction
             << "problem reading header, perhaps file is not binary "
             << exit(FatalError);
@@ -235,8 +231,6 @@ Foam::fileFormats::STLCore::readBinaryHeader
 
     if (bad)
     {
-        streamPtr.clear();
-
         FatalErrorInFunction
             << "problem reading number of triangles, perhaps file is not binary"
             << exit(FatalError);
diff --git a/src/fileFormats/stl/STLCore.H b/src/fileFormats/stl/STLCore.H
index 4e194b768a..a7a013686a 100644
--- a/src/fileFormats/stl/STLCore.H
+++ b/src/fileFormats/stl/STLCore.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2017 OpenCFD Ltd.
+    Copyright (C) 2016-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -39,7 +39,7 @@ SourceFiles
 
 #include "STLpoint.H"
 #include "STLtriangle.H"
-#include "autoPtr.H"
+#include <memory>
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -56,7 +56,7 @@ class STLCore
 {
 public:
 
-    // Public data types
+    // Public Data Types
 
         //- Enumeration for the format of data in the stream
         enum STLFormat
@@ -88,7 +88,8 @@ protected:
         //- Read STL binary file header.
         //  Return the opened file stream and estimated number of triangles.
         //  The stream is invalid and number of triangles is 0 on error.
-        static autoPtr<std::istream> readBinaryHeader
+        static std::unique_ptr<std::istream>
+        readBinaryHeader
         (
             const fileName& filename,
             label& nTrisEstimated
@@ -100,9 +101,8 @@ protected:
 
     // Constructors
 
-        //- Construct null
+        //- Default construct
         STLCore() = default;
-
 };
 
 
diff --git a/src/fileFormats/stl/STLReader.C b/src/fileFormats/stl/STLReader.C
index 2d7f75418e..60cb4e84c1 100644
--- a/src/fileFormats/stl/STLReader.C
+++ b/src/fileFormats/stl/STLReader.C
@@ -90,17 +90,19 @@ bool Foam::fileFormats::STLReader::readBINARY
     format_ = STLFormat::UNKNOWN;
 
     label nTris = 0;
-    autoPtr<istream> streamPtr = readBinaryHeader(filename, nTris);
+    std::unique_ptr<std::istream> streamPtr
+    {
+        readBinaryHeader(filename, nTris)
+    };
 
-    if (!streamPtr.valid())
+    if (!streamPtr)
     {
         FatalErrorInFunction
             << "Error reading file " << filename
             << " or file " << filename + ".gz"
             << exit(FatalError);
     }
-
-    istream& is = streamPtr();
+    auto& is = *streamPtr;
 
 #ifdef DEBUG_STLBINARY
     Info<< "# " << nTris << " facets" << endl;
diff --git a/src/surfMesh/writers/vtk/vtkSurfaceWriter.C b/src/surfMesh/writers/vtk/vtkSurfaceWriter.C
index 0fade0f99f..df74db79e8 100644
--- a/src/surfMesh/writers/vtk/vtkSurfaceWriter.C
+++ b/src/surfMesh/writers/vtk/vtkSurfaceWriter.C
@@ -211,7 +211,7 @@ Foam::fileName Foam::surfaceWriters::vtkWriter::write()
 
     const meshedSurf& surf = surface();
 
-    if (writer_.empty() && (Pstream::master() || !parallel_))
+    if (!writer_ && (Pstream::master() || !parallel_))
     {
         writer_.reset
         (