NAME¶

std::basic_filebuf::showmanyc - std::basic_filebuf::showmanyc

Synopsis¶

protected:
virtual std::streamsize showmanyc()

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

Parameters¶

(none)

Return value¶

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

Notes¶

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"

Example¶

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

Possible output:¶

showmanyc() returns 267

See also¶

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