strange behaviour of procmail when piping content to c++ executable -

i have working procmail config.
rc.filters :

:0 w :a.lock * ^from:(.*\<)?(try@gmail\.com)\> | $home/executable/a.out 

this file compiles , works, procmail delivers mail, , executable writes content output file.

#include <stdlib.h> #include <iostream> #include <fstream>  using namespace std;  int main(void) { ofstream myfile; myfile.open ("output.txt");      string line;     while (getline(cin, line))      {     myfile << line << endl;          }     myfile.close();     return exit_success; }  

the problem need cin object content pass constructor of mimetic library. need executable work:

#include <stdlib.h> #include <iostream> #include <fstream> #include <mimetic/mimetic.h>  using namespace std; using namespace mimetic;  int main(void) { ofstream myfile; myfile.open ("output.txt");  mimeentity me(cin);                          const header& h = me.header();   string subjectstring = h.subject(); myfile << subjectstring; myfile << "check";       myfile.close(); return exit_success; } 

if take mime message called message.txt , following second code :

cat message.txt | ./a.out  ./a.out < message.txt 

in both cases executable works , subject in output.txt
when invoked , content piped procmail doesn't work,
, in output.txt "check" means file @ least invoked.

the procmail.log states fine.

i don't know what's going on capture input std::cin string , pass std::istringstream constructed value mimeentity. way can inspect input std::cin while still having processed library:

std::istreambuf_iterator<char> begin(std::cin), end; std::string message(begin, end); out << "received >>>" << message << "<<<\n"; std::istringstream in(message); mimeentity me(in); // ...