Boost asio - async reading established number of chars from stdin -

i wanna write boost::asio app reading stdin boost::asio::streambuf. anyway function works on streambuf made stdin_fileno boost::asio::async_read_until. other ones throws errors. there possibility read 100 first character stdin boost asio function?

in principle works

#include <boost/asio.hpp> #include <boost/asio/posix/stream_descriptor.hpp>  using namespace boost::asio; using boost::system::error_code;  #include <iostream>  int main() {     io_service svc;     posix::stream_descriptor in(svc, stdin_fileno);      char buf[100];     async_read(in, buffer(buf,sizeof(buf)), [&](error_code ec, size_t br) {              std::cout << std::string(buf, br) << std::flush;              if (ec)                 std::cerr << ec.message();          });      svc.run(); } 

when used as

cat input.txt | ./test | wc -c 

will output 100 expected (and echo input). can use live terminal input:

./test | wc -c 

when input shorter 100 bytes, ec.message() "end of file" printed too.

what does not work on linux is:

 ./test < input.txt 

you receive:

terminate called after throwing instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::system::system_error> >'   what():  assign: operation not permitted 

this because regular files not supported async operations: strange exception throw - assign: operation not permitted