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?
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);
...
The getpass command is present in Linux. But you can make a prettier version, the system echo alone doesn't kill the need for an enter command, while knocking down buffering doesn't kill the production of a carraige return after data entry. Combining the two gives a good approximation of a quiet entry. You can add an asterisk to give a secret entry appearance so here is a combination of two suggestions:
#include <stdio.h>
#include <termios.h>
#include <unistd.h>
int getche(void);
int main(int argc, char **argv){
int i=0;
char d,c='h',s[6];
printf("Enter five secret letters\n");
s[5]='\0'; //Set string terminator for string five letters long
do{
d=getche();//Fake getche command silently digests each character
printf("*");
s[i++]=d;} while (i<5);
printf("\nThank you!!\n Now enter one more letter.\n");
c=getchar();
printf("You just typed %c,\nbut the last letter of your secret string was %c\n",c,d);
printf("Your secret string was: %s\n",s);
return 0;
}
/* reads from keypress, echoes */
int getche(void)
{
struct termios oldattr, newattr;
int ch;
tcgetattr( STDIN_FILENO, &oldattr );
newattr = oldattr;
newattr.c_lflag &= ~( ICANON | ECHO);\\knock down keybuffer
tcsetattr( STDIN_FILENO, TCSANOW, &newattr );
system("stty -echo");\\shell out to kill echo
ch = getchar();
system("stty echo");
tcsetattr( STDIN_FILENO, TCSANOW, &oldattr );
return ch;
}
Maybe you can try like this:
#include<stdio.h>
char s[100];
system("stty -echo");
scanf("%s",s); /* Won't echo to screen while being typed */
system("stty echo");
printf("You have entered:");
printf("%s\n", s);
return 0;
}
In Linux, the system function "stty -echo" is to type in sth without echo. Hope this will help.
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.
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 = getpass("");
if (s != NULL)
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).
There isn't one; neither ANSI C nor ISO C++ have such a thing.
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.
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.
-Adam
