diff --git a/README.md b/README.md
index 3fbb47e..1f443a3 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,4 @@
 # lxsh
 Extended shell linker
+
+Work in progress
diff --git a/include/struc.hpp b/include/struc.hpp
index 46ac262..902d845 100644
--- a/include/struc.hpp
+++ b/include/struc.hpp
@@ -168,7 +168,7 @@ class subarg
 {
 public:
   // type
-  enum argtype { string, subshell };
+  enum argtype { string, subshell, arithmetic };
   argtype type;
 
   // ctor
diff --git a/src/generate.cpp b/src/generate.cpp
index e07e83d..1329db4 100644
--- a/src/generate.cpp
+++ b/src/generate.cpp
@@ -124,7 +124,6 @@ std::string generate_resolve(std::vector<std::string> args, int ind)
       throw std::runtime_error("Cannot cd to '"+cddir+"'");
   }
 
-
   // exec call
   auto p=ztd::shp("exec "+cmd);
 
@@ -210,6 +209,8 @@ std::string generate_include(std::vector<std::string> args, int ind)
       file=import_file(it);
       if(opts['d'])
         file = stringReplace(file, "\"", "\\\"");
+      if(opts['s'])
+        file = stringReplace(file, "'", "'\\''");
       if(opts['r'])
         ret += file;
       else
@@ -378,6 +379,10 @@ std::string subarg::generate(int ind)
   {
     ret += val;
   }
+  else if(type == subarg::arithmetic)
+  {
+    ret += "$(("+val+"))";
+  }
   else if(type == subarg::subshell)
   {
     // includes and resolves inside command substitutions
diff --git a/src/parse.cpp b/src/parse.cpp
index 9151784..fc8c7e1 100644
--- a/src/parse.cpp
+++ b/src/parse.cpp
@@ -79,6 +79,25 @@ uint32_t skip_unread(const char* in, uint32_t size, uint32_t start)
 
 std::pair<block, uint32_t> parse_subshell(const char* in, uint32_t size, uint32_t start);
 
+// parse an arithmetic
+// ends at ))
+// for now, uses subshell parsing then takes raw string value
+// temporary, to improve
+std::pair<subarg, uint32_t> parse_arithmetic(const char* in, uint32_t size, uint32_t start)
+{
+  subarg ret(subarg::arithmetic);
+  uint32_t i=start;
+
+  auto pp=parse_subshell(in, size, i);
+  i=pp.second;
+  if(i >= size || in[i]!=')')
+    throw ztd::format_error( "Unexpected token ')', expecting '))'", g_origin, in, i );
+  ret.val = std::string(in+start, i-start-1);
+  i++;
+
+  return std::make_pair(ret, i);
+}
+
 // parse one argument
 // must start at a read char
 // ends at either " \t|&;\n()"
@@ -114,12 +133,22 @@ std::pair<arg, uint32_t> parse_arg(const char* in, uint32_t size, uint32_t start
         {
           i+=2;
         }
+        else if( word_eq("$((", in, size, i) ) // arithmetic operation
+        {
+          // add previous subarg
+          ret.sa.push_back(subarg(std::string(in+j, i-j)));
+          i+=3;
+          // get arithmetic
+          auto r=parse_arithmetic(in, size, i);
+          ret.sa.push_back(r.first);
+          j = i = r.second;
+        }
         else if( word_eq("$(", in, size, i) ) // substitution
         {
-          // add string subarg
+          // add previous subarg
           ret.sa.push_back(subarg(std::string(in+j, i-j)));
           i+=2;
-          // add subshell subarg
+          // get subshell
           auto r=parse_subshell(in, size, i);
           ret.sa.push_back(subarg(r.first));
           j = i = r.second;
@@ -142,10 +171,22 @@ std::pair<arg, uint32_t> parse_arg(const char* in, uint32_t size, uint32_t start
         throw ztd::format_error("Unterminated single quote", g_origin, in, q);
       i++;
     }
+    else if( word_eq("$((", in, size, i) ) // arithmetic operation
+    {
+      // add previous subarg
+      ret.sa.push_back(subarg(std::string(in+j, i-j)));
+      i+=3;
+      // get arithmetic
+      auto r=parse_arithmetic(in, size, i);
+      ret.sa.push_back(r.first);
+      j = i = r.second;
+    }
     else if( word_eq("$(", in, size, i) ) // substitution
     {
+      // add previous subarg
       ret.sa.push_back(subarg(std::string(in+j, i-j)));
       i+=2;
+      // get subshell
       auto r=parse_subshell(in, size, i);
       ret.sa.push_back(subarg(r.first));
       j = i = r.second;