Question

I am writing a simple Objective – C console app.
I only want to accept digits.
Even if i type a character which is not a digit, it should not be echoed back.
and I should have a character array that has all digits on which i can use atoi().

scanf has formatters but they dont work the way i want.
I know it should be possible. The way it works when u enter passwords in terminal,
they are just accepted but not echoed back.

I just want a variation of it.

Is there some C function that only accepts a character and returns it but doesn’t echoes it back on screen ?

Answer 1

Check out these link for more info What is Equivalent to getch() & getche() in Linux?

you can use getch() but if there is no getch() then you can try the below code.

#include <termios.h>
#include <stdio.h>

static struct termios old, new;

/* Initialize new terminal i/o settings */
void initTermios(int echo) 
{
  tcgetattr(0, &old); /* grab old terminal i/o settings */
  new = old; /* make new settings same as old settings */
  new.c_lflag &= ~ICANON; /* disable buffered i/o */
  new.c_lflag &= echo ? ECHO : ~ECHO; /* set echo mode */
  tcsetattr(0, TCSANOW, &new); /* use these new terminal i/o settings now */
}

/* Restore old terminal i/o settings */
void resetTermios(void) 
{
  tcsetattr(0, TCSANOW, &old);
}

/* Read 1 character - echo defines echo mode */
char getch_(int echo) 
{
  char ch;
  initTermios(echo);
  ch = getchar();
  resetTermios();
  return ch;
}

/* Read 1 character without echo */
char getch(void) 
{
  return getch_(0);
}

/* Read 1 character with echo */
char getche(void) 
{
  return getch_(1);
}

/* Let's test it out */
int main(void) {
  char c;
  printf("(getche example) please type a letter: ");
  c = getche();
  printf("\nYou typed: %c\n", c);
  printf("(getch example) please type a letter...");
  c = getch();
  printf("\nYou typed: %c\n", c);
  return 0;
} 

Getch function gets the characters but does not echo to screen.

Thanks