I have a c++ application which reads in commands from the user. The problem is that I want to read control characters. Some of the control characters are the same as other keys.
For instance, ctrl-j is the same as ENTER, and ctrl-h is the same as backspace. How can I make it so these keys read differently? I know it has to be possible since programs like vi handle ctrl-j differently than the enter key.
Thanks!
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I have read all those man pages, and unless I missed something obvious, they don't tell me how to solve my problem.
I'm using ncurses in my application to get keyboard input, but there are no library functions which help me. I've tried reading keyboard input in raw() mode, but they still come in the same.
I've also tried using 4 different terminal types with no luck (linux, xterm, xterm2, debian).
Enter is always the same as Ctrl-M. Sometimes crtl-M gets converted to Ctrl-J. That is achieved by the terminal setting ICRNL (Translate carriage return to newline on input (unless IGNCR is set)). You can do this in your program using tcsetattr(). You should save your terminal settings on entry (use tcgetattr()) and restore them on exit using tcsetattr() (if you use atexit() to set it up, no need to restrict where you call exit()).
see "man termios" or "man tcsetattr" (actually same manual page on my system).
> Enter is always the same as Ctrl-M.
disagreed, except "Enter" sends the keycode for CR aka Carriage Return aka Return ;-)
> Sometimes crtl-M gets converted to Ctrl-J.
this is done as i described/alluded, but it is most likely done by either stty or the corresponding termio (termcap/terminfo)
> Does vi know the difference between Enter and Ctrl-M?
vi uses termcap, but only if it contains a special vi entry otherwise it uses a hardcoded dumb setting, it does not use terminfo
Things are totally different if your vim lies to you and anounces itself as vi.
That's why a *real* vi never has problems reading any key defined in US-ASCII :)
Just my 2 pence ...
> Enter is always the same as Ctrl-M.
As far as the resultant Ascii - that's all I meant. You agreed with that bit
> Sometimes crtl-M gets converted to Ctrl-J.
Done by the OS (linux) depending on the settings of the serial port. tcsetattr / termio / termios / ioctl are interfaces to the OS to change this behavior
> Does vi know the difference between Enter and Ctrl-M?
I just meant for the asker to try it out and prove to himself that vi couldn't tell the difference (I was fairly confident it couldn't, anyway)
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by: ahoffmannPosted on 2008-02-03 at 11:20:00ID: 20809642
man getc
man tgetstr
man curses
man termcap
man terminfo
which API to use may depend on your application ...