getting a char from keyboard using curses.h

问题

I'm trying to get a character from the keyboard using curses.h. This is my source (get_char_example.c):

#include <curses.h>
#include <stdio.h>

int main(void)
{
    char ch;

    printf("Enter a character: ");
    ch = getch();
    printf("\nIts ASCII code is %d\n", ch);

    return 0;
}

I use the following command to compile:

gcc get_char_example.c -o get_char_example

And I get the following error:

/tmp/ccjaXwRU.o: In function `main':

get_char_example.c:(.text+0x1c): undefined reference to `stdscr'
get_char_example.c:(.text+0x24): undefined reference to `wgetch'
collect2: error: ld returned 1 exit status

using: gcc (GCC) 7.2.0 Arch Linux 4.13.9-1-ARCH

Thanks in advance!

回答1:

It is a linker error (see this, nearly a duplicate). ncurses is generally known to pkg-config (which gives more dependencies, when required), so try to compile with:

 gcc -Wall -Wextra -g \
    $(pkg-config --cflags ncurses) \
    get_char_example.c \
    $(pkg-config --libs ncurses)

^{You want to Invoke GCC with all warnings and debug info; you would use GDB, perhaps under emacs or with ddd, for debugging.}

Even better, use some build automation tool (like make or ninja). With GNU make take inspiration from this to write your Makefile (where tab-s are significant).

On my Debian Sid, pkg-config --cflags ncurses gives -D_GNU_SOURCE -D_DEFAULT_SOURCE and pkg-config --libs ncurses gives -lncurses -ltinfo, so simply linking with -lncurses is not enough (and that is why this is not exactly a duplicate today in November 2017; a few years ago linking with simply -lncurses was enough, today it is not).

Use pkg-config --list-all to find all the packages and libraries known to pkg-config; when developing your libraries consider also providing some .pc file for it.

BTW, your program should start by initializing with initscr and use printw; Read Ncurses-programming-HowTo even if it is a bit old.

Notice also that using ASCII in the 21^st century is obsolete. Programs and computers use UTF-8 everywhere, and this has profound consequences you should be aware of (since an UTF-8 character can span several bytes). My French keyboard has keys for ², §, € and é (even with American keyboards your could paste them) and none of these are in ASCII. Consider also using some UTF-8 library like libunistring.

来源：https://stackoverflow.com/questions/47060311/getting-a-char-from-keyboard-using-curses-h

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gcc

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curses