password via istream (new thread)

[cyb3r]

sorry folks...i had quoted the question in the book (by Stroustrup) wrongly..
the actual question was

write manipulators that turn character echoing on and off

this is the correct one. unlike a command, itz just a quote..hope you understand.
pease refer this for more details.

its on the exercise section of the chapter 21.Streams which is at the end of it, and page is 656.

The C++ Programming Language 3rd ed
from the Creator Of C++,
Bjarne Stroustrup.
Addison Wesley Publications.

[brewbuck]

Stroutroup is just trying to hammer in the idea of an iostream manipulator. I don't think he ever intended that the answer to the question would be PORTABLE. Look up how to do this on your platform, then write a manipulator that does it.

[cyb3r]

and the problem no. is 19.

i am trying out this one...hope i get it.

[Daved]

I think you've gotten your answer as well as you are going to get it. We don't know a standard way to do it. Stroustrup was probably expecting you to use a non-standard method platform dependent method to do that.

[CornedBee]

Here's a Linux C program equivalent to the Windows pause command. It may give you an idea.

#include <unistd.h>
#include <termios.h>
#include <string.h>

int main()
{
  printf("Press any key to continue.\n");
  struct termios trm;
  memset(&trm, 0, sizeof(struct termios));
  cfmakeraw(&trm);
  struct termios old;
  tcgetattr(STDIN_FILENO, &old);
  tcsetattr(STDIN_FILENO, TCSAFLUSH, &trm);
  char buf;
  read(STDIN_FILENO, &buf, 1);
  tcsetattr(STDIN_FILENO, TCSAFLUSH, &old);
  return 0;
}

Note that cfmakeraw fills the termios structure with settings that put the terminal in "raw" mode: no echo and no waiting for a full line.
For your purposes, you'll want to get the old mode with tcsetattr, disable the ECHO bit in the c_lflag field, and set the modified attributes. To enable echo again, do the reverse. To be entirely correct, you should store the initial mode in the stream using the stream storage interface (now that's an interesting little beast - a good thing to learn about, even if its use is limited in general) and listen to the stream shutting down event (erase_event) to restore the original state. Otherwise, the program shutting down in no-echo mode might screw up your terminal, and you don't want that.

Of course all this applies only to POSIX. Windows is an entirely different matter. As we said, there's no portable way.