diff --git a/applications/test/cstring/Test-cstring.C b/applications/test/cstring/Test-cstring.C
index fc4605cfa4..fadc7a4755 100644
--- a/applications/test/cstring/Test-cstring.C
+++ b/applications/test/cstring/Test-cstring.C
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2016 OpenCFD Ltd.
+    \\  /    A nd           | Copyright (C) 2016-2017 OpenCFD Ltd.
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -30,8 +30,10 @@ Description
 #include "DynamicList.H"
 #include "IOstreams.H"
 #include "fileNameList.H"
+#include "stringOps.H"
 #include "stringList.H"
 #include "wordList.H"
+#include "SubStrings.H"
 
 using namespace Foam;
 
@@ -53,6 +55,26 @@ int print(const CStringList& cstrLst)
 }
 
 
+// Using nullptr termination
+int print(char *argv[])
+{
+    if (!argv)
+    {
+        Info<< "argv=null" << endl;
+        return 0;
+    }
+
+    int i=0;
+    while (argv[i])
+    {
+        Info<< "  argv[" << i << "] = \"" << argv[i] << "\"" << endl;
+        ++i;
+    }
+
+    return i;
+}
+
+
 // Main program:
 
 int main(int argc, char *argv[])
@@ -62,18 +84,49 @@ int main(int argc, char *argv[])
 
     dynlst.append("string1 with content");
     dynlst.append("string2 other content");
-    dynlst.append("string3 done");
+    dynlst.append("string3 more");
+    dynlst.append("string4 done");
 
     {
         CStringList inC(dynlst);
 
-        Info<< "input: " << dynlst << endl;
+        Info<< "input: " << dynlst << nl;
         print(inC);
+
+        Info<< "null-terminated string list" << nl;
+        print(inC.strings());
+
+        Info<< "sublist: starting at " << inC.size()/2 << nl;
+        print(inC.strings(inC.size()/2));
+
+        Info<< nl;
+    }
+
+    {
+        string testInput
+        (
+            " A   test   input   line with various spacing  "
+            "  and  text to be split on whitespace  "
+        );
+
+        Info<< testInput << nl;
+        SubStrings<string> args = stringOps::splitSpace(testInput);
+        Info<< "split into " << args.size() << " args" << nl;
+
+        CStringList inC(args);
+        print(inC);
+
+        Info<< "sublist: starting at " << inC.size()/2 << nl;
+        print(inC.strings(inC.size()/2));
+
+        Info<< nl;
     }
 
     Info<<"command-line with " << CStringList::count(argv) << " items"<< endl;
 
     print(argc, argv);
+
+    Info<< nl;
     {
         dynlst.clear();
         for (int i=0; i<argc; ++i)
diff --git a/src/OpenFOAM/Make/files b/src/OpenFOAM/Make/files
index ff43bb7750..29d6eee577 100644
--- a/src/OpenFOAM/Make/files
+++ b/src/OpenFOAM/Make/files
@@ -112,6 +112,7 @@ $(strings)/fileName/fileNameIO.C
 $(strings)/keyType/keyType.C
 $(strings)/wordRe/wordRe.C
 $(strings)/wordRes/wordRes.C
+$(strings)/lists/CStringList.C
 $(strings)/lists/hashedWordList.C
 $(strings)/stringOps/stringOps.C
 $(strings)/stringOps/stringOpsSort.C
diff --git a/src/OpenFOAM/primitives/ints/int32/int32.H b/src/OpenFOAM/primitives/ints/int32/int32.H
index 3e883827fb..d58f017cec 100644
--- a/src/OpenFOAM/primitives/ints/int32/int32.H
+++ b/src/OpenFOAM/primitives/ints/int32/int32.H
@@ -69,7 +69,7 @@ word name(const char* fmt, const int32_t val);
 
 //- Return a word representation of an int32, using printf-style formatter.
 //  The representation is not checked for valid word characters.
-word name(const std::string&, const int32_t val);
+word name(const std::string& fmt, const int32_t val);
 
 
 // * * * * * * * * * * * * * * * IOstream Operators  * * * * * * * * * * * * //
diff --git a/src/OpenFOAM/primitives/strings/lists/CStringList.C b/src/OpenFOAM/primitives/strings/lists/CStringList.C
new file mode 100644
index 0000000000..f6e05e6998
--- /dev/null
+++ b/src/OpenFOAM/primitives/strings/lists/CStringList.C
@@ -0,0 +1,45 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2017 OpenCFD Ltd.
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "CStringList.H"
+#include "Ostream.H"
+
+// * * * * * * * * * * * * * * * IOstream Operators  * * * * * * * * * * * * //
+
+Foam::Ostream& Foam::operator<<(Ostream& os, const CStringList& list)
+{
+    const int n = list.size();
+
+    for (int i = 0; i<n; ++i)
+    {
+        if (i) os << ' ';
+        if (list[i]) os << list[i];
+    }
+
+    return os;
+}
+
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/primitives/strings/lists/CStringList.H b/src/OpenFOAM/primitives/strings/lists/CStringList.H
index 30a21a4fcb..8ff6377589 100644
--- a/src/OpenFOAM/primitives/strings/lists/CStringList.H
+++ b/src/OpenFOAM/primitives/strings/lists/CStringList.H
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2016 OpenCFD Ltd.
+    \\  /    A nd           | Copyright (C) 2016-2017 OpenCFD Ltd.
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -58,6 +58,13 @@ Description
 namespace Foam
 {
 
+// Forward declarations
+class Ostream;
+class CStringList;
+template<class String> class SubStrings;
+
+Ostream& operator<<(Ostream& os, const CStringList& list);
+
 /*---------------------------------------------------------------------------*\
                          Class CStringList Declaration
 \*---------------------------------------------------------------------------*/
@@ -82,6 +89,19 @@ class CStringList
 
     // Private Member Functions
 
+        //- Copy string characters into dest as NUL-terminated string.
+        //  Forces conversion of std::sub_match to string form
+        //
+        //  \return the location one-past the end of dest, which is used
+        //      for the next destination
+        static inline char* stringCopy(char *dest, const std::string& str);
+
+        //- Copy the input list of strings.
+        //  \return number of arguments (argc)
+        template<class ListType>
+        int resetContent(const ListType& input);
+
+
         //- Disallow default bitwise copy construct
         CStringList(const CStringList&) = delete;
 
@@ -96,11 +116,15 @@ public:
         //- Construct empty, adding content later (via reset).
         inline CStringList();
 
-
-        //- Construct from a list of strings
+        //- Copy construct from a list of strings
         //  Copies the input characters.
         template<class StringType>
-        CStringList(const UList<StringType>& input);
+        inline explicit CStringList(const UList<StringType>& input);
+
+        //- Copy construct from a list of sub-string references
+        //  Copies the input characters.
+        template<class StringType>
+        inline explicit CStringList(const SubStrings<StringType>& input);
 
 
     //- Destructor
@@ -123,6 +147,11 @@ public:
         //  The position at argc is a nullptr
         inline char** strings() const;
 
+        //- Return the sublist of C-strings (ie, argv) starting at the
+        //- specified offset.
+        //  \param start the offset, must be less than argc
+        inline char** strings(int start) const;
+
 
         //- Overall length of the flattened character (data) content
         inline size_t length() const;
@@ -130,15 +159,20 @@ public:
         //- The flattened character content, with interspersed nul-chars
         inline const char* data() const;
 
-
     // Edit
 
         //- Clear contents and free memory
         inline void clear();
 
         //- Copy the input list of strings.
+        //  \return number of arguments (argc)
         template<class StringType>
-        void reset(const UList<StringType>& input);
+        inline int reset(const UList<StringType>& input);
+
+        //- Copy the input list of strings.
+        //  \return number of arguments (argc)
+        template<class StringType>
+        inline int reset(const SubStrings<StringType>& input);
 
 
     // Other
@@ -153,6 +187,17 @@ public:
         template<class StringType>
         static inline List<StringType> asList(const char * const argv[]);
 
+
+    // Member operators
+
+        //- Return element at the given index. No bounds checking.
+        inline const char* operator[](int i) const;
+
+
+    // IOstream Operators
+
+        friend Ostream& operator<<(Ostream& os, const CStringList& list);
+
 };
 
 
diff --git a/src/OpenFOAM/primitives/strings/lists/CStringListI.H b/src/OpenFOAM/primitives/strings/lists/CStringListI.H
index 197633691e..6b9efee13a 100644
--- a/src/OpenFOAM/primitives/strings/lists/CStringListI.H
+++ b/src/OpenFOAM/primitives/strings/lists/CStringListI.H
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2016 OpenCFD Ltd.
+    \\  /    A nd           | Copyright (C) 2016-2017 OpenCFD Ltd.
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -23,20 +23,34 @@ License
 
 \*---------------------------------------------------------------------------*/
 
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+inline char* Foam::CStringList::stringCopy(char *dest, const std::string& str)
+{
+    for (auto iter = str.cbegin(); iter != str.cend(); ++iter)
+    {
+        *dest = *iter;
+        ++dest;
+    }
+    *(dest++) = '\0';
+
+    return dest;
+}
+
+
 // * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * * //
 
 inline int Foam::CStringList::count(const char * const argv[])
 {
-    int nElem = 0;
+    int n = 0;
     if (argv)
     {
-        while (argv[nElem])
+        while (argv[n])
         {
-            ++nElem;
+            ++n;
         }
     }
-
-    return nElem;
+    return n;
 }
 
 
@@ -51,6 +65,24 @@ inline Foam::CStringList::CStringList()
 {}
 
 
+template<class StringType>
+inline Foam::CStringList::CStringList(const UList<StringType>& input)
+:
+    CStringList()
+{
+    reset(input);
+}
+
+
+template<class StringType>
+inline Foam::CStringList::CStringList(const SubStrings<StringType>& input)
+:
+    CStringList()
+{
+    reset(input);
+}
+
+
 // * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
 
 inline Foam::CStringList::~CStringList()
@@ -97,10 +129,38 @@ inline char** Foam::CStringList::strings() const
 }
 
 
+inline char** Foam::CStringList::strings(int start) const
+{
+    return &(argv_[start]);
+}
+
+
 inline const char* Foam::CStringList::data() const
 {
     return data_;
 }
 
 
+template<class StringType>
+inline int Foam::CStringList::reset(const UList<StringType>& input)
+{
+    return resetContent(input);
+}
+
+
+template<class StringType>
+inline int Foam::CStringList::reset(const SubStrings<StringType>& input)
+{
+    return resetContent(input);
+}
+
+
+// * * * * * * * * * * * * * * * Member Operators  * * * * * * * * * * * * * //
+
+inline const char* Foam::CStringList::operator[](int i) const
+{
+    return argv_[i];
+}
+
+
 // ************************************************************************* //
diff --git a/src/OpenFOAM/primitives/strings/lists/CStringListTemplates.C b/src/OpenFOAM/primitives/strings/lists/CStringListTemplates.C
index 8c2fad816e..b656d32d93 100644
--- a/src/OpenFOAM/primitives/strings/lists/CStringListTemplates.C
+++ b/src/OpenFOAM/primitives/strings/lists/CStringListTemplates.C
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2016 OpenCFD Ltd.
+    \\  /    A nd           | Copyright (C) 2016-2017 OpenCFD Ltd.
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -23,26 +23,14 @@ License
 
 \*---------------------------------------------------------------------------*/
 
-// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+#include "SubStrings.H"
 
-template<class StringType>
-Foam::CStringList::CStringList
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+template<class ListType>
+int Foam::CStringList::resetContent
 (
-    const UList<StringType>& input
-)
-:
-    CStringList()
-{
-    reset(input);
-}
-
-
-// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
-
-template<class StringType>
-void Foam::CStringList::reset
-(
-    const UList<StringType>& input
+    const ListType& input
 )
 {
     clear();
@@ -52,36 +40,35 @@ void Foam::CStringList::reset
         // Special handling of an empty list
         argv_ = new char*[1];
         argv_[0] = nullptr;     // Final nullptr terminator
-        return;
+        return 0;
     }
 
     // Count overall required string length, including each trailing nul char
     for (const auto& str : input)
     {
-        len_ += str.size() + 1;
+        len_ += str.length() + 1;
     }
     --len_; // No final nul in overall count
 
     argv_ = new char*[input.size()+1];  // Extra +1 for terminating nullptr
     data_ = new char[len_+1];           // Extra +1 for terminating nul char
 
-    // Copy contents
-    char* ptr = data_;
+    argv_[0] = data_;   // Starts here
+
     for (const auto& str : input)
     {
-        argv_[argc_++] = ptr;   // The start of this string
-
-        for (auto iter = str.cbegin(); iter != str.cend(); ++iter)
-        {
-            *(ptr++) = *iter;
-        }
-        *(ptr++) = '\0';
+        char *next = stringCopy(argv_[argc_], str);
+        argv_[++argc_] = next;   // The start of next string
     }
 
     argv_[argc_] = nullptr;     // Final nullptr terminator
+
+    return argc_;
 }
 
 
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
 template<class StringType>
 Foam::List<StringType>
 Foam::CStringList::asList(int argc, const char * const argv[])
diff --git a/src/OpenFOAM/primitives/strings/stringOps/stringOps.C b/src/OpenFOAM/primitives/strings/stringOps/stringOps.C
index 8646523b68..5bbc041ba5 100644
--- a/src/OpenFOAM/primitives/strings/stringOps/stringOps.C
+++ b/src/OpenFOAM/primitives/strings/stringOps/stringOps.C
@@ -28,13 +28,14 @@ License
 #include "OSspecific.H"
 #include "etcFiles.H"
 #include "StringStream.H"
+#include <cctype>
 
 // * * * * * * * * * * * * * * * Local Functions * * * * * * * * * * * * * * //
 
 namespace Foam
 {
 // Standard handling of "~/", "./" etc.
-static void standardExpansions(Foam::string& s)
+static void standardExpansions(std::string& s)
 {
     if (s.empty())
     {
@@ -181,52 +182,53 @@ Foam::string Foam::stringOps::expand
 )
 {
     string s(original);
-    return inplaceExpand(s, mapping);
+    inplaceExpand(s, mapping);
+    return s;
 }
 
 
-Foam::string& Foam::stringOps::inplaceExpand
+void Foam::stringOps::inplaceExpand
 (
-    string& s,
+    std::string& s,
     const HashTable<string, word, string::hash>& mapping,
     const char sigil
 )
 {
-    string::size_type begVar = 0;
+    std::string::size_type varBeg = 0;
 
     // Expand $VAR or ${VAR}
     // Repeat until nothing more is found
     while
     (
-        (begVar = s.find(sigil, begVar)) != string::npos
-     && begVar < s.size()-1
+        (varBeg = s.find(sigil, varBeg)) != std::string::npos
+     && varBeg < s.size()-1
     )
     {
-        if (begVar == 0 || s[begVar-1] != '\\')
+        if (varBeg == 0 || s[varBeg-1] != '\\')
         {
             // Find end of first occurrence
-            string::size_type endVar = begVar;
-            string::size_type delim = 0;
+            std::string::size_type varEnd = varBeg;
+            std::string::size_type delim = 0;
 
             // The type/position of the ":-" or ":+" alternative values
             int altType = 0;
-            string::size_type altPos = string::npos;
+            auto altPos = std::string::npos;
 
-            if (s[begVar+1] == '{')
+            if (s[varBeg+1] == '{')
             {
-                endVar = s.find('}', begVar);
+                varEnd = s.find('}', varBeg);
                 delim = 1;
 
                 // check for ${parameter:-word} or ${parameter:+word}
-                if (endVar != string::npos)
+                if (varEnd != std::string::npos)
                 {
-                    altPos = begVar;
-                    altType = findParameterAlternative(s, altPos, endVar);
+                    altPos = varBeg;
+                    altType = findParameterAlternative(s, altPos, varEnd);
                 }
             }
             else
             {
-                string::const_iterator iter = s.cbegin() + begVar + 1;
+                string::const_iterator iter = s.cbegin() + varBeg + 1;
 
                 // more generous in accepting keywords than for env variables
                 while
@@ -242,19 +244,19 @@ Foam::string& Foam::stringOps::inplaceExpand
                 )
                 {
                     ++iter;
-                    ++endVar;
+                    ++varEnd;
                 }
             }
 
-            if (endVar == string::npos)
+            if (varEnd == std::string::npos)
             {
                 // likely parsed '${...' without closing '}' - abort
                 break;
             }
-            else if (endVar == begVar)
+            else if (varEnd == varBeg)
             {
                 // parsed '${}' or $badChar  - skip over
-                begVar = endVar + 1;
+                varBeg = varEnd + 1;
             }
             else
             {
@@ -262,23 +264,23 @@ Foam::string& Foam::stringOps::inplaceExpand
                 (
                     s.substr
                     (
-                        begVar + 1 + delim,
+                        varBeg + 1 + delim,
                         (
-                            (altPos == string::npos ? endVar : altPos)
-                          - begVar - 2*delim
+                            (altPos == std::string::npos ? varEnd : altPos)
+                          - varBeg - 2*delim
                         )
                     ),
                     false
                 );
 
                 std::string altValue;
-                if (altPos != string::npos)
+                if (altPos != std::string::npos)
                 {
                     // had ":-" or ":+" alternative value
                     altValue = s.substr
                     (
                         altPos + 2,
-                        endVar - altPos - 2*delim
+                        varEnd - altPos - 2*delim
                     );
                 }
 
@@ -287,54 +289,52 @@ Foam::string& Foam::stringOps::inplaceExpand
 
                 if (fnd.found())
                 {
-                    if (altPos != string::npos && altType == '+')
+                    if (altPos != std::string::npos && altType == '+')
                     {
                         // was found, use ":+" alternative
                         s.std::string::replace
                         (
-                            begVar,
-                            endVar - begVar + 1,
+                            varBeg,
+                            varEnd - varBeg + 1,
                             altValue
                         );
-                        begVar += altValue.size();
+                        varBeg += altValue.size();
                     }
                     else
                     {
                         // was found, use value
                         s.std::string::replace
                         (
-                            begVar,
-                            endVar - begVar + 1,
+                            varBeg,
+                            varEnd - varBeg + 1,
                             *fnd
                         );
-                        begVar += (*fnd).size();
+                        varBeg += (*fnd).size();
                     }
                 }
-                else if (altPos != string::npos && altType == '-')
+                else if (altPos != std::string::npos && altType == '-')
                 {
                     // was not found, use ":-" alternative
                     s.std::string::replace
                     (
-                        begVar,
-                        endVar - begVar + 1,
+                        varBeg,
+                        varEnd - varBeg + 1,
                         altValue
                     );
-                    begVar += altValue.size();
+                    varBeg += altValue.size();
                 }
                 else
                 {
                     // substitute with nothing, also for ":+" alternative
-                    s.std::string::erase(begVar, endVar - begVar + 1);
+                    s.std::string::erase(varBeg, varEnd - varBeg + 1);
                 }
             }
         }
         else
         {
-            ++begVar;
+            ++varBeg;
         }
     }
-
-    return s;
 }
 
 
@@ -346,7 +346,8 @@ Foam::string Foam::stringOps::expand
 )
 {
     string s(original);
-    return inplaceExpand(s, dict, sigil);
+    inplaceExpand(s, dict, sigil);
+    return s;
 }
 
 
@@ -360,12 +361,7 @@ Foam::string Foam::stringOps::getVariable
 {
     string value;
 
-    const entry* eptr = dict.lookupScopedEntryPtr
-    (
-        name,
-        true,
-        false
-    );
+    const entry* eptr = dict.lookupScopedEntryPtr(name, true, false);
 
     if (eptr)
     {
@@ -387,7 +383,7 @@ Foam::string Foam::stringOps::getVariable
         if (value.empty() && !name.empty())
         {
             // The type/position of the ":-" or ":+" alternative values
-            string::size_type altPos = 0;
+            std::string::size_type altPos = 0;
 
             // check for parameter:-word or parameter:+word
             const int altType =
@@ -438,13 +434,13 @@ Foam::string Foam::stringOps::getVariable
 Foam::string Foam::stringOps::expand
 (
     const string& s,
-    string::size_type& index,
+    std::string::size_type& index,
     const dictionary& dict,
     const bool allowEnvVars,
     const bool allowEmpty
 )
 {
-    string newString;
+    string out;
 
     while (index < s.size())
     {
@@ -453,55 +449,55 @@ Foam::string Foam::stringOps::expand
             // Recurse to parse variable name
             index += 2;
             string val = expand(s, index, dict, allowEnvVars, allowEmpty);
-            newString.append(val);
+            out.append(val);
         }
         else if (s[index] == '}')
         {
-            return getVariable(newString, dict, allowEnvVars, allowEmpty);
+            return getVariable(out, dict, allowEnvVars, allowEmpty);
         }
         else
         {
-            newString.append(string(s[index]));
+            out.append(string(s[index]));
         }
         ++index;
     }
 
-    return newString;
+    return out;
 }
 
 
-Foam::string& Foam::stringOps::inplaceExpand
+void Foam::stringOps::inplaceExpand
 (
-    string& s,
+    std::string& s,
     const dictionary& dict,
     const bool allowEnvVars,
     const bool allowEmpty,
     const char sigil
 )
 {
-    string::size_type begVar = 0;
+    std::string::size_type varBeg = 0;
 
     // Expand $VAR or ${VAR}
     // Repeat until nothing more is found
     while
     (
-        (begVar = s.find(sigil, begVar)) != string::npos
-     && begVar < s.size()-1
+        (varBeg = s.find(sigil, varBeg)) != std::string::npos
+     && varBeg < s.size()-1
     )
     {
-        if (begVar == 0 || s[begVar-1] != '\\')
+        if (varBeg == 0 || s[varBeg-1] != '\\')
         {
-            if (s[begVar+1] == '{')
+            if (s[varBeg+1] == '{')
             {
                 // Recursive variable expansion mode
-                auto stringStart = begVar;
-                begVar += 2;
+                auto stringStart = varBeg;
+                varBeg += 2;
                 string varValue
                 (
                     expand
                     (
                         s,
-                        begVar,
+                        varBeg,
                         dict,
                         allowEnvVars,
                         allowEmpty
@@ -511,16 +507,16 @@ Foam::string& Foam::stringOps::inplaceExpand
                 s.std::string::replace
                 (
                     stringStart,
-                    begVar - stringStart + 1,
+                    varBeg - stringStart + 1,
                     varValue
                 );
 
-                begVar = stringStart+varValue.size();
+                varBeg = stringStart+varValue.size();
             }
             else
             {
-                string::const_iterator iter = s.cbegin() + begVar + 1;
-                string::size_type endVar = begVar;
+                std::string::const_iterator iter = s.cbegin() + varBeg + 1;
+                std::string::size_type varEnd = varBeg;
 
                 // more generous in accepting keywords than for env variables
                 while
@@ -536,15 +532,15 @@ Foam::string& Foam::stringOps::inplaceExpand
                 )
                 {
                     ++iter;
-                    ++endVar;
+                    ++varEnd;
                 }
 
                 const word varName
                 (
                     s.substr
                     (
-                        begVar + 1,
-                        endVar - begVar
+                        varBeg + 1,
+                        varEnd - varBeg
                     ),
                     false
                 );
@@ -562,57 +558,55 @@ Foam::string& Foam::stringOps::inplaceExpand
 
                 s.std::string::replace
                 (
-                    begVar,
+                    varBeg,
                     varName.size()+1,
                     varValue
                 );
-                begVar += varValue.size();
+                varBeg += varValue.size();
             }
         }
         else
         {
-            ++begVar;
+            ++varBeg;
         }
     }
 
     // Standard handling of "~/", "./" etc.
     standardExpansions(s);
-
-    return s;
 }
 
 
-Foam::string& Foam::stringOps::inplaceExpand
+void Foam::stringOps::inplaceExpand
 (
-    string& s,
+    std::string& s,
     const dictionary& dict,
     const char sigil
 )
 {
-    string::size_type begVar = 0;
+    std::string::size_type varBeg = 0;
 
     // Expand $VAR or ${VAR}
     // Repeat until nothing more is found
     while
     (
-        (begVar = s.find(sigil, begVar)) != string::npos
-     && begVar < s.size()-1
+        (varBeg = s.find(sigil, varBeg)) != std::string::npos
+     && varBeg < s.size()-1
     )
     {
-        if (begVar == 0 || s[begVar-1] != '\\')
+        if (varBeg == 0 || s[varBeg-1] != '\\')
         {
             // Find end of first occurrence
-            string::size_type endVar = begVar;
-            string::size_type delim = 0;
+            std::string::size_type varEnd = varBeg;
+            std::string::size_type delim = 0;
 
-            if (s[begVar+1] == '{')
+            if (s[varBeg+1] == '{')
             {
-                endVar = s.find('}', begVar);
+                varEnd = s.find('}', varBeg);
                 delim = 1;
             }
             else
             {
-                string::const_iterator iter = s.cbegin() + begVar + 1;
+                string::const_iterator iter = s.cbegin() + varBeg + 1;
 
                 // more generous in accepting keywords than for env variables
                 while
@@ -628,19 +622,19 @@ Foam::string& Foam::stringOps::inplaceExpand
                 )
                 {
                     ++iter;
-                    ++endVar;
+                    ++varEnd;
                 }
             }
 
-            if (endVar == string::npos)
+            if (varEnd == std::string::npos)
             {
                 // likely parsed '${...' without closing '}' - abort
                 break;
             }
-            else if (endVar == begVar)
+            else if (varEnd == varBeg)
             {
                 // parsed '${}' or $badChar  - skip over
-                begVar = endVar + 1;
+                varBeg = varEnd + 1;
             }
             else
             {
@@ -648,8 +642,8 @@ Foam::string& Foam::stringOps::inplaceExpand
                 (
                     s.substr
                     (
-                        begVar + 1 + delim,
-                        endVar - begVar - 2*delim
+                        varBeg + 1 + delim,
+                        varEnd - varBeg - 2*delim
                     ),
                     false
                 );
@@ -687,26 +681,24 @@ Foam::string& Foam::stringOps::inplaceExpand
 
                     s.std::string::replace
                     (
-                        begVar,
-                        endVar - begVar + 1,
+                        varBeg,
+                        varEnd - varBeg + 1,
                         buf.str()
                     );
-                    begVar += buf.str().size();
+                    varBeg += buf.str().size();
                 }
                 else
                 {
                     // not defined - leave original string untouched
-                    begVar = endVar + 1;
+                    varBeg = varEnd + 1;
                 }
             }
         }
         else
         {
-            ++begVar;
+            ++varBeg;
         }
     }
-
-    return s;
 }
 
 
@@ -717,51 +709,52 @@ Foam::string Foam::stringOps::expand
 )
 {
     string s(original);
-    return inplaceExpand(s, allowEmpty);
+    inplaceExpand(s, allowEmpty);
+    return s;
 }
 
 
-Foam::string& Foam::stringOps::inplaceExpand
+void Foam::stringOps::inplaceExpand
 (
-    string& s,
+    std::string& s,
     const bool allowEmpty
 )
 {
-    string::size_type begVar = 0;
+    std::string::size_type varBeg = 0;
 
     // Expand $VARS
     // Repeat until nothing more is found
     while
     (
-        (begVar = s.find('$', begVar)) != string::npos
-     && begVar < s.size()-1
+        (varBeg = s.find('$', varBeg)) != std::string::npos
+     && varBeg < s.size()-1
     )
     {
-        if (begVar == 0 || s[begVar-1] != '\\')
+        if (varBeg == 0 || s[varBeg-1] != '\\')
         {
             // Find end of first occurrence
-            string::size_type endVar = begVar;
-            string::size_type delim = 0;
+            std::string::size_type varEnd = varBeg;
+            std::string::size_type delim = 0;
 
             // The type/position of the ":-" or ":+" alternative values
             int altType = 0;
-            string::size_type altPos = string::npos;
+            std::string::size_type altPos = std::string::npos;
 
-            if (s[begVar+1] == '{')
+            if (s[varBeg+1] == '{')
             {
-                endVar = s.find('}', begVar);
+                varEnd = s.find('}', varBeg);
                 delim = 1;
 
                 // check for ${parameter:-word} or ${parameter:+word}
-                if (endVar != string::npos)
+                if (varEnd != std::string::npos)
                 {
-                    altPos = begVar;
-                    altType = findParameterAlternative(s, altPos, endVar);
+                    altPos = varBeg;
+                    altType = findParameterAlternative(s, altPos, varEnd);
                 }
             }
             else
             {
-                string::const_iterator iter = s.cbegin() + begVar + 1;
+                string::const_iterator iter = s.cbegin() + varBeg + 1;
 
                 while
                 (
@@ -770,20 +763,20 @@ Foam::string& Foam::stringOps::inplaceExpand
                 )
                 {
                     ++iter;
-                    ++endVar;
+                    ++varEnd;
                 }
             }
 
 
-            if (endVar == string::npos)
+            if (varEnd == std::string::npos)
             {
                 // likely parsed '${...' without closing '}' - abort
                 break;
             }
-            else if (endVar == begVar)
+            else if (varEnd == varBeg)
             {
                 // parsed '${}' or $badChar  - skip over
-                begVar = endVar + 1;
+                varBeg = varEnd + 1;
             }
             else
             {
@@ -791,53 +784,53 @@ Foam::string& Foam::stringOps::inplaceExpand
                 (
                     s.substr
                     (
-                        begVar + 1 + delim,
+                        varBeg + 1 + delim,
                         (
-                            (altPos == string::npos ? endVar : altPos)
-                          - begVar - 2*delim
+                            (altPos == std::string::npos ? varEnd : altPos)
+                          - varBeg - 2*delim
                         )
                     ),
                     false
                 );
 
                 std::string altValue;
-                if (altPos != string::npos)
+                if (altPos != std::string::npos)
                 {
                     // had ":-" or ":+" alternative value
                     altValue = s.substr
                     (
                         altPos + 2,
-                        endVar - altPos - 2*delim
+                        varEnd - altPos - 2*delim
                     );
                 }
 
                 const string varValue = getEnv(varName);
                 if (varValue.size())
                 {
-                    if (altPos != string::npos && altType == '+')
+                    if (altPos != std::string::npos && altType == '+')
                     {
                         // was found, use ":+" alternative
                         s.std::string::replace
                         (
-                            begVar,
-                            endVar - begVar + 1,
+                            varBeg,
+                            varEnd - varBeg + 1,
                             altValue
                         );
-                        begVar += altValue.size();
+                        varBeg += altValue.size();
                     }
                     else
                     {
                         // was found, use value
                         s.std::string::replace
                         (
-                            begVar,
-                            endVar - begVar + 1,
+                            varBeg,
+                            varEnd - varBeg + 1,
                             varValue
                         );
-                        begVar += varValue.size();
+                        varBeg += varValue.size();
                     }
                 }
-                else if (altPos != string::npos)
+                else if (altPos != std::string::npos)
                 {
                     // use ":-" or ":+" alternative values
                     if (altType == '-')
@@ -845,22 +838,22 @@ Foam::string& Foam::stringOps::inplaceExpand
                         // was not found, use ":-" alternative
                         s.std::string::replace
                         (
-                            begVar,
-                            endVar - begVar + 1,
+                            varBeg,
+                            varEnd - varBeg + 1,
                             altValue
                         );
-                        begVar += altValue.size();
+                        varBeg += altValue.size();
                     }
                     else
                     {
                         // was not found, ":+" alternative implies
                         // substitute with nothing
-                        s.std::string::erase(begVar, endVar - begVar + 1);
+                        s.std::string::erase(varBeg, varEnd - varBeg + 1);
                     }
                 }
                 else if (allowEmpty)
                 {
-                    s.std::string::erase(begVar, endVar - begVar + 1);
+                    s.std::string::erase(varBeg, varEnd - varBeg + 1);
                 }
                 else
                 {
@@ -872,18 +865,16 @@ Foam::string& Foam::stringOps::inplaceExpand
         }
         else
         {
-            ++begVar;
+            ++varBeg;
         }
     }
 
     // Standard handling of "~/", "./" etc.
     standardExpansions(s);
-
-    return s;
 }
 
 
-bool Foam::stringOps::inplaceReplaceVar(string& s, const word& varName)
+bool Foam::stringOps::inplaceReplaceVar(std::string& s, const word& varName)
 {
     if (s.empty() || varName.empty())
     {
@@ -911,7 +902,7 @@ Foam::string Foam::stringOps::trimLeft(const string& s)
 {
     if (!s.empty())
     {
-        string::size_type beg = 0;
+        std::string::size_type beg = 0;
         while (beg < s.size() && std::isspace(s[beg]))
         {
             ++beg;
@@ -927,11 +918,11 @@ Foam::string Foam::stringOps::trimLeft(const string& s)
 }
 
 
-Foam::string& Foam::stringOps::inplaceTrimLeft(string& s)
+void Foam::stringOps::inplaceTrimLeft(std::string& s)
 {
     if (!s.empty())
     {
-        string::size_type beg = 0;
+        std::string::size_type beg = 0;
         while (beg < s.size() && std::isspace(s[beg]))
         {
             ++beg;
@@ -942,8 +933,6 @@ Foam::string& Foam::stringOps::inplaceTrimLeft(string& s)
             s.erase(0, beg);
         }
     }
-
-    return s;
 }
 
 
@@ -951,15 +940,15 @@ Foam::string Foam::stringOps::trimRight(const string& s)
 {
     if (!s.empty())
     {
-        string::size_type sz = s.size();
-        while (sz && std::isspace(s[sz-1]))
+        auto n = s.size();
+        while (n && std::isspace(s[n-1]))
         {
-            --sz;
+            --n;
         }
 
-        if (sz < s.size())
+        if (n < s.size())
         {
-            return s.substr(0, sz);
+            return s.substr(0, n);
         }
     }
 
@@ -967,20 +956,18 @@ Foam::string Foam::stringOps::trimRight(const string& s)
 }
 
 
-Foam::string& Foam::stringOps::inplaceTrimRight(string& s)
+void Foam::stringOps::inplaceTrimRight(std::string& s)
 {
     if (!s.empty())
     {
-        string::size_type sz = s.size();
-        while (sz && std::isspace(s[sz-1]))
+        auto n = s.size();
+        while (n && std::isspace(s[n-1]))
         {
-            --sz;
+            --n;
         }
 
-        s.resize(sz);
+        s.resize(n);
     }
-
-    return s;
 }
 
 
@@ -990,13 +977,51 @@ Foam::string Foam::stringOps::trim(const string& original)
 }
 
 
-Foam::string& Foam::stringOps::inplaceTrim(string& s)
+void Foam::stringOps::inplaceTrim(std::string& s)
 {
     inplaceTrimRight(s);
     inplaceTrimLeft(s);
+}
 
+
+Foam::string Foam::stringOps::lower(const string& original)
+{
+    string s(original);
+    inplaceLower(s);
     return s;
 }
 
 
+void Foam::stringOps::inplaceLower(std::string& s)
+{
+    for (auto iter = s.begin(); iter != s.end(); ++iter)
+    {
+        *iter = static_cast<std::string::value_type>
+        (
+            std::tolower(static_cast<unsigned char>(*iter))
+        );
+    }
+}
+
+
+Foam::string Foam::stringOps::upper(const string& original)
+{
+    string s(original);
+    inplaceUpper(s);
+    return s;
+}
+
+
+void Foam::stringOps::inplaceUpper(std::string& s)
+{
+    for (auto iter = s.begin(); iter != s.end(); ++iter)
+    {
+        *iter = static_cast<std::string::value_type>
+        (
+            std::toupper(static_cast<unsigned char>(*iter))
+        );
+    }
+}
+
+
 // ************************************************************************* //
diff --git a/src/OpenFOAM/primitives/strings/stringOps/stringOps.H b/src/OpenFOAM/primitives/strings/stringOps/stringOps.H
index 7146891d37..de89b954a7 100644
--- a/src/OpenFOAM/primitives/strings/stringOps/stringOps.H
+++ b/src/OpenFOAM/primitives/strings/stringOps/stringOps.H
@@ -122,9 +122,9 @@ namespace stringOps
     //
     //  \note the leading sigil can be changed to avoid conflicts with other
     //  string expansions
-    string& inplaceExpand
+    void inplaceExpand
     (
-        string& s,
+        std::string& s,
         const HashTable<string, word, string::hash>& mapping,
         const char sigil = '$'
     );
@@ -168,7 +168,7 @@ namespace stringOps
     string expand
     (
         const string& s,
-        string::size_type& index,
+        std::string::size_type& index,
         const dictionary& dict,
         const bool allowEnvVars,
         const bool allowEmpty
@@ -186,9 +186,9 @@ namespace stringOps
     //
     //  \note the leading sigil can be changed to avoid conflicts with other
     //  string expansions
-    string& inplaceExpand
+    void inplaceExpand
     (
-        string& s,
+        std::string& s,
         const dictionary& dict,
         const bool allowEnvVars,
         const bool allowEmpty,
@@ -205,9 +205,9 @@ namespace stringOps
     //
     //  \note the leading sigil can be changed to avoid conflicts with other
     //  string expansions
-    string& inplaceExpand
+    void inplaceExpand
     (
-        string& s,
+        std::string& s,
         const dictionary& dict,
         const char sigil = '$'
     );
@@ -276,9 +276,9 @@ namespace stringOps
     //
     //  \sa
     //  Foam::findEtcFile
-    string& inplaceExpand
+    void inplaceExpand
     (
-        string& s,
+        std::string& s,
         const bool allowEmpty = false
     );
 
@@ -286,26 +286,39 @@ namespace stringOps
     //- Replace environment variable contents with its name.
     //  This is essentially the inverse operation for inplaceExpand.
     //  Return true if a replacement was successful.
-    bool inplaceReplaceVar(string& s, const word& varName);
+    bool inplaceReplaceVar(std::string& s, const word& varName);
 
 
     //- Return string trimmed of leading whitespace
     string trimLeft(const string& s);
 
     //- Trim leading whitespace inplace
-    string& inplaceTrimLeft(string& s);
+    void inplaceTrimLeft(std::string& s);
 
     //- Return string trimmed of trailing whitespace
     string trimRight(const string& s);
 
     //- Trim trailing whitespace inplace
-    string& inplaceTrimRight(string& s);
+    void inplaceTrimRight(std::string& s);
 
     //- Return string trimmed of leading and trailing whitespace
     string trim(const string& original);
 
     //- Trim leading and trailing whitespace inplace
-    string& inplaceTrim(string& s);
+    void inplaceTrim(std::string& s);
+
+
+    //- Return string transformed with std::tolower on each character
+    string lower(const string& original);
+
+    //- Inplace transform string with std::tolower on each character
+    void inplaceLower(std::string& s);
+
+    //- Return string transformed with std::toupper on each character
+    string upper(const string& original);
+
+    //- Inplace transform string with std::toupper on each character
+    void inplaceUpper(std::string& s);
 
 
     //- Using printf-formatter for a word representation of the primitive.