ANSI C No-echo keyboard input.

Question

Hello Folks,

I've been Googling around with no luck. I'm looking for a way to do getc() or gets() or whatever that does not echo to the terminal. I saw kbhit() but this doesn't appear to be part of ANSI. Ideally, I'd like code that looks like

char s[100];
no_echo_gets(s); /* Won't echo to screen while being typed */
printf("%s\n", s);

Does anybody know a good ANSI compliant way to do this?

Answer 1

There isn't one; neither ANSI C nor ISO C++ have such a thing.

Answer 2

For UNIX-like systems you want to play with the ECHO flag...

#include <termios.h>
...
struct termios t;
tcgetattr(fd, &t);
t.c_lflag |= ~ECHO;
tcsetattr(fd, TCSANOW, &t);
...

Answer 3

This will depend on your environment, it is not something that the language provides. If you intend to do extensive character mode I/O, you might look into a library like curses. Otherwise, you will have to manipulate the terminal or the windows console manually.

Answer 4

You can't do it in a cross-platform manner using ANSI C. You'll have to use some OS-specific code, or use a library such as ncurses.

Answer 5

ANSI and ISO C do not define this functionality, however most C compilers have getch() or a close variation.

You'll need to do a preprocessor define for each compiler you're using that has a different library and function for this. It's not difficult, though you might consider it annoying.

Answer 6

Since your task is fairly basic, if you're lucky your system will have the getpass() function:

char * getpass(const char *prompt);

If you don't want a prompt, just do:

char s[129]; /* getpass() only reads up to 128 characters
              * at least on my system. It might work better
              * if you use a char* instead of a char[], but
              * it might work fine either way.
              */
s = getpass("");
printf("Your password was %s!\n", s);

getpass(), like all C functions related to echo and buffering, is non-standard, but present on Mac OS X, probably Linux, and is listed in the GNU C library, so it's probably present on any system using glibc.

The ANSI and ISO standards, as stated previously, do not specify a standard way to read input without echoing, or to read unbuffered input (i.e. on character at a time).