Replacement to getch based code block in cpp

Stack Overflow Asked by sonu ishaq on July 24, 2020

I stumbled upon a code from 2016 written in the Turbo C++ IDE in windows
It was to accept passwords

char pass;
    for (length = 0;;)
        if (pass == 13)
        if ((pass >= 'A' && pass <= 'Z') || (pass >= 'a' && pass <= 'z') || (pass >= '0' && pass <= '9') || (pass == '!' || '@' || '#' || '$' || '%' || '^' || '&' || '*' || '(' || ')'))
            str[length] = pass;
            cout << "#";

is there any replacement for this without the getch method for linux to show output like this ******** ? I tried scanf but that didnt work cause it took the whole input first and gave the output later

One Answer

There is no standard replacement in C++.

Linux (and similar systems such as BSD), there is a legacy function getpass whose use is not recommended. I mention it because the documentation of that function in glibc suggests following:

This precise set of operations may not suit all possible situations. In this case, it is recommended that users write their own getpass substitute. For instance, a very simple substitute is as follows:

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

my_getpass (char **lineptr, size_t *n, FILE *stream)
  struct termios old, new;
  int nread;

  /* Turn echoing off and fail if we can’t. */
  if (tcgetattr (fileno (stream), &old) != 0)
    return -1;
  new = old;
  new.c_lflag &= ~ECHO;
  if (tcsetattr (fileno (stream), TCSAFLUSH, &new) != 0)
    return -1;

  /* Read the passphrase */
  nread = getline (lineptr, n, stream);

  /* Restore terminal. */
  (void) tcsetattr (fileno (stream), TCSAFLUSH, &old);

  return nread;

Note that the example is written in C, and is not valid C++. Small changes are required, in particular there is a C++ keyword new being used as a variable name. Simply rename it to something else.

Also note that the behaviour is to not echo at all, rather than echo *. This is conventional in POSIX systems, and safer because the it does not reveal the length of the passphrase.

Answered by eerorika on July 24, 2020

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