std::basic_filebuf<CharT,Traits>::showmanyc (3) - Linux Manuals

std::basic_filebuf<CharT,Traits>::showmanyc: std::basic_filebuf<CharT,Traits>::showmanyc


std::basic_filebuf<CharT,Traits>::showmanyc - std::basic_filebuf<CharT,Traits>::showmanyc


virtual std::streamsize showmanyc()

If implemented, returns the number of characters left to read from the file.



Return value

The number of characters available for reading from the file, or -1 if the end of file was reached.


This function is optional. If not implemented, this function returns 0 (since the base class version std::basic_streambuf::showmanyc gets called)
Whether implemented or not, this function is normally called by std::basic_streambuf::in_avail if the get area is empty.
The name of this function stands for "stream: how many characters?", so it is pronounced "S how many C", rather than "show many C"


implementation test to see if showmanyc() is implemented for filebuf
// Run this code

  #include <fstream>
  #include <iostream>

  struct mybuf : std::filebuf
       using std::filebuf::showmanyc;

  int main()
      mybuf fin;"main.cpp", std::ios_base::in);
      std::cout << "showmanyc() returns " << fin.showmanyc() << '\n';

Possible output:

  showmanyc() returns 267

See also

         obtains the number of characters immediately available in the get area
in_avail (public member function of std::basic_streambuf<CharT,Traits>)
         extracts already available blocks of characters
readsome (public member function of std::basic_istream<CharT,Traits>)