determing if a user pressed tab [duplicate] - c

Question

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How to detect that arrow key is pressed using C under Linux or Solaris?
(3 answers)
Closed 8 years ago.
So I am writing a program, and of the the tasks is to determine if a user has pressed tab. So when he presses tab, I should print something to the console(or do tab completition etc). My problem is how do I do it without the user pressing enter. I tried looking into ncurses but I couldn't find a simple example that would teach me how to do it with tab.
Edit:
Using Linux

Answer 1

You can act on input using ncurses and the getch() function. It's going to return you an int value for the key pressed, you can check for a tab via looking to see if the return was 9. This code will loop displaying what was pressed until it was a tab then it exits.
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <ncurses.h>
int main() {
int c;
initscr(); /* Start curses mode */
cbreak();
noecho();
while(9 != (c = getch())) {
printw("%c\n", c);
if(halfdelay(5) != ERR) { /* getch function waits 5 tenths of a second */
while(getch() == c)
if(halfdelay(1) == ERR) /* getch function waits 1 tenth of a second */
break;
}
printw("Got a %d\n", c);
cbreak();
}
endwin();
return 0;
}

Answer 2

Technically this is not a C language question but a matter of operating system or runtime environment. On POSIX systems you must set, at least, your terminal in non-canonical mode.
The canonical mode buffers keyboard inputs to process them further if needed (for example, this lets you erase chars before your application see them).
There is many ways to switch to non-canonical mode. Of course you can use many different libraries ncurses, etc. But the trick behind is a set of system calls called termios. What you have to do is to read current attributes of the POSIX terminal and modify them accordingly to your needs. For example :
struct termios old, new;
/* read terminal attributes */
tcgetattr(STDIN_FILENO,&old);
/* get old settings */
new=old;
/* modify the current settings (common: switch CANON and ECHO) */
new.c_lflag &=(~ICANON & ~ECHO);
/* push the settings on the terminal */
tcsetattr(STDIN_FILENO,TCSANOW,&new);
do_what_you_want_and_read_every_pressed_char();
/* ok, restore initial behavior */
tcsetattr(STDIN_FILENO,TCSANOW,&old);