Need replace enter key c++

[leo2008]

I am trying to find a way to replace pressing enter key in c++.
below is c code.
can someone help me?
after press enter key detected, user needs to provide some inputs to proceed further, which means that I need to allow the program in C++ to key in another inputs if an <enter key> is pressed

void PressEnter ()
{
    printf("Press Enter to quit");
    fflush(stdin);
    getchar();
}

[JLBorges]

fflush(stdin); engenders undefined behaviour.

For input streams (and for update streams on which the last operation was input), the behavior is undefined.
https://en.cppreference.com/w/c/io/fflush

See if this works for you: https://www.cplusplus.com/forum/general/170262/#msg849987

[leo2008]

Actually once enter key is pressed, user needs to add some additional inputs like the below.
how can this be done?

Usage: "<TCP Server Port> <TCP Server IP> <hostname> "

[JLBorges]

See if this works for you:

#include <iostream>
#include <limits>

void pause( const char* prompt = "press enter to continue..." )
{
    std::cin.clear() ;
    auto stmbuf = std::cin.rdbuf() ;
    const int nothing = std::char_traits<char>::eof() ;
    const std::streamsize everything_upto = std::numeric_limits<std::streamsize>::max() ;
    const char new_line = '\n' ;

    if( stmbuf->in_avail() || ( stmbuf->sungetc() != nothing && std::cin.get() != '\n' ) )
        std::cin.ignore( everything_upto, new_line ) ;

    std::cout << prompt ;
    std::cin.ignore( everything_upto, new_line ) ;
}

int main()
{
    // some or no user inputs
    pause() ;
    // accept additional user inputs
}

[seeplus]

Unfortunately not with VS/Windows. Any existing chars in the input stream aren't removed before the prompt is displayed (which is what the if statement is attempting). So if existing input stream chars contain a '\n' char, then the .ignore() will return immediately.

What is needed is a cin.flush() function - but I don't know just using standard c++.

The issue is that even if there is cin data available, ->in_avail() returns 0 and ->sungetc() returns eof so the first .ignore() is not executed to remove existing input data before the prompt is displayed.

[seeplus]

If your compiler supports conio.h (and VS does), then the 'old' way of flushing the input buffer could be used:

void cinflush()
{
	std::cin.clear();

	for (; _kbhit(); _getch());
}

void pause(const char* prompt = "press enter to continue...")
{
	cinflush();

	std::cout << prompt;
	std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
}

Note that _kbhit() and _getch() might just be kbhit() and getch() without the leading -