Termcap Tgetstr获取箭头键

Question

I'm trying to get the string representing the arrow key up from the termcap database. Using the following:

char *buffer = malloc(2048);
tgetent(buffer, getenv("TERM")); //TERM = xterm-256color
char *key_up = tgetstr("ku", &buffer); // gives me \EOA

ku String of input sent by typing the up-arrow key.

The problem is the arrow key up is actually passed as \\E[A when typing into the program. It's also passed like this to cat . I tried with different terminal emulators and shells and they all passed it the same way.

So I decided to hardcode this value for the key instead of using the ku value, and it works, but doesn't feel right.

Am I missing something here? How can I programmatically get the right ku value?

Answer 1

Terminal descriptions are written for full-screen applications, which are initialized using one or more terminal capabilities assigned to this. About half of the terminal descriptions initialize the terminal's cursor- and keypad-keys to use application mode . In application mode, those keys send different characters.

The ncurses FAQ My cursor keys do not work goes into more detail.

If you are trying to use a terminal description for some non-screen command-line application, you could make your command-parser treat both \\E[ (CSI) and \\EO (SS3) as the same thing, and ignore the difference between the two modes. That was done in some configuration for zsh , as mentioned in the xterm manual page .

By the way, if your "termcap" is actually an interface to a terminfo system (such as ncurses), it is not necessary to allocate the buffer, since that is ignored. ncurses' manual says:

• The emulation ignores the buffer pointer bp . The termcap library would store a copy of the terminal description in the area referenced by this pointer. However, ncurses stores its terminal descriptions in compiled binary form, which is not the same thing.