c++ - Why does getchar work like a buffer instead of working as expected in real-time -

this first question on stackoverflow. pardon me if haven't searched not seem find explanation this. attempting example bjourne stroustroup's papers. added bits see array re-sized type text.

but doesn't seem work way! getchar() waits till done entering characters , execute loop. per logic, doesn't go loop, character, perform actions , iterate. wondering if implementation specific, or intended this?

i on ubuntu 14.04 lts using codeblocks gcc 4.8.2. source in cpp files if matters.

while(true) {     int c = getchar();     if(c=='\n' || c==eof)     {         text[i] = 0;         break;     }     text[i] = c;      if(i == maxsize-1)     {         maxsize = maxsize+maxsize;         text = (char*)realloc(text,maxsize);         if(text == 0) exit(1);         cout << "\n increasing array size " << maxsize << endl;     }      i++; } 

the output follows:

array size now: 10 please enter text: sample text. have liked see memory being realloced right here, apparently that's not how works!

increasing array size 20

increasing array size 40

increasing array size 80

increasing array size 160

you have entered: sample text. have liked see memory being realloced right here, apparently that's not how works!

array size now: 160

this has nothing getchar directly. "problem" underlying terminal, buffer input. input sent program after press enter. in linux (dunno if there way in windows) can workaround calling

/bin/stty raw 

in terminal or calling

system ("/bin/stty raw"); 

in program. cause getchar return input character you.

dont forget reset tty behaviour calling

/bin/stty cooked 

when done!

here example (for linux):

#include <stdio.h> #include <stdlib.h>  using namespace std;  int main() {     system ("/bin/stty raw");     char c = getchar();     system ("/bin/stty cooked");     return 0; } 

also have @ post: how avoid press enter getchar()

also, suggested in comments, have here: http://linux.die.net/man/3/termios on command tcsetattr, should work cross-platform.