Pipes: A first working version

1) pipes have their own dup2 control
 2) a filtering in input to change all joined | is also provided

src/Snel.cpp

@@ -9,7 +9,7 @@ int main(int argc, char* argv[]) try {
       std::ifstream file(argv[1]);
 
       while (std::getline (file, line, '\n')) {
-         s.parse(line).execute();
+         s.parse(snel::filter(line)).execute();
       }
    }
    else {   // interactive mode
@@ -19,7 +19,7 @@ int main(int argc, char* argv[]) try {
          std::getline (std::cin, line, '\n');
          if (line == "quit")
             break;
-         s.parse(line).execute();
+         s.parse(snel::filter(line)).execute();
       } while (1);
    }
    return 0;

src/sequencer.cpp

@@ -35,6 +35,28 @@ namespace snel {
       }
    }
 
+   std::string filter (const std::string in) {
+      std::string out;
+      char prev {0}, cur, next {0};
+
+      for (auto i = in.begin(); i != in.end() ; ++i) {
+         cur = *i;
+         if (cur == '|') {
+            if (prev != ' ')  out += ' ';
+            next = *++i;
+            if (next == '|' || next == ' ') {
+               out += cur; cur = next;  // syntax ok
+            }
+            else {
+               // syntax problem, insert a space
+               out += cur; out += ' '; cur = next;
+            }
+         }
+         prev = cur;
+         out += cur;
+      }
+      return out;
+   }
    /*
     * ========== ArgList ==========
     */
@@ -44,7 +66,7 @@ namespace snel {
             delete[] p;
       }
    }
-   ArgList& ArgList::push_back(const std::basic_string<type>& item) {
+   ArgList& ArgList::push_back(const std::string& item) {
       vtype it = new type[item.length()+1];
 
       // get data
@@ -92,7 +114,7 @@ namespace snel {
    }
    Child& Child::make_arguments () {
       bool in{false}, out{false}, err{false};
-      bool CanRedirectIn  = (pipe_.from) ? true : false;
+      bool CanRedirectIn  = (!pipe_.from) ? true : false;
       bool CanRedirectOut = (!pipe_.to) ? true : false;
 
       for (auto& t: command) {
@@ -132,8 +154,10 @@ namespace snel {
       return *this;
    }
 
-   bool Child::execute(const Child* previous) {
+   bool Child::execute(std::vector<Child>::iterator it, bool first) {
       bool stop = {false};
+      if (!first) --it;
+      Child& previous = *it;
 
       // Check parent redirection
       redirect_std_if (filenames[STDIN_],  STDIN_);
@@ -156,10 +180,9 @@ namespace snel {
             if ((dup2(pipe_.fd[1], STDOUT_)) == -1) // redirect output
                throw Error("Child pipe[to]: Can not redirect through pipe");
          }
-         else if ((previous!= nullptr) && pipe_.from) {  // receiveing child
+         else if (!first && pipe_.from) {  // receiveing child
-            std::cout << "from[0]=" << previous->pipe().fd[0] << " from[1]=" << previous->pipe().fd[1]<< std::endl;
+            close (previous.pipe().fd[1]); // close the write end
-            close (previous->pipe().fd[1]); // close the write end
+            if ((dup2(previous.pipe().fd[0], STDIN_)) == -1)  // redirect input
-            if ((dup2(previous->pipe().fd[0], STDIN_)) == -1)  // redirect input
                throw Error("Child pipe[from]: Can not redirect through pipe");
          }
          execvp(arguments.front(), arguments.data());
@@ -169,7 +192,8 @@ namespace snel {
       }
       else {   // parent
          if (pipe_.to)        close (pipe_.fd[1]);
-         else if (pipe_.from) close (previous->pipe().fd[0]);
+         else if (!first && pipe_.from)
+                              close (previous.pipe().fd[0]);
 
          int exit_status;
          waitpid(pid, &exit_status, 0);  // wait child process to finish
@@ -233,14 +257,16 @@ namespace snel {
    }
 
    Sequencer& Sequencer::execute() {
-      for (auto& batch : seq_)
+      for (auto& batch : seq_) {
+         bool first;
+         first = true;
          for (auto it = batch.begin() ; it != batch.end(); ++it) {
             Child& command = *it;
-            Child p = (it != batch.begin()) ? std::prev(it) : Child{};
+            if (command.make_arguments().execute(it, first))
-            if (command.make_arguments().execute(p))
                break;
-
+            first = false;
          }
+      }
       seq_.clear();
       return *this;
    }

src/sequencer.h

@@ -31,11 +31,13 @@ namespace snel {
    constexpr fd_t STDOUT_ = STDOUT_FILENO;
    constexpr fd_t STDERR_ = STDERR_FILENO;
 
+   std::string filter (const std::string in);
+
    /*!
     *
     */
    struct ArgList {
-      using type        = char;     // Basic data type
+      using type        = typename std::string::value_type;     // Basic data type
       using vtype       = type*;    // Vector type
       using vtype_ptr   = vtype*;   // Pointer to vector type
 
@@ -44,7 +46,7 @@ namespace snel {
       ArgList(const ArgList&) = default;
       ArgList(ArgList&&) = default;
 
-      ArgList& push_back(const std::basic_string<type>& item);
+      ArgList& push_back(const std::string& item);
       vtype front () { return args_.front(); }
       size_t size () { return args_.size(); }
 
@@ -73,12 +75,12 @@ namespace snel {
 
    public:
       ~Child ();
-      Child () noexcept = default;
+      Child () = default;
       Child (const command_t& c) : command{c} { }
       Child (command_t&& c) : command{std::move(c)} { }
 
       Child& make_arguments ();
-      bool execute (const Child* previous);
+      bool execute(std::vector<Child>::iterator it, bool first);
       Pipe& pipe() { return pipe_; }
    private:
       void redirect_std_if(std::string fn, fd_t std_fd);