ncurses displaying word at the center and make it into uppecase and lowercase

Question

#include <ncurses.h>
#include <unistd.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
int main(int argc, char *argv[]){
    int x,y,ch;
    if(argc != 2){
        fprintf(stderr,"there is no value to be show\n");
        exit(1);
    }
    getmaxyx(stdscr,y,x);
    
    initscr();
    start_color();
    init_pair(COLOR_RED, COLOR_RED, COLOR_BLACK);  
    init_pair(COLOR_GREEN, COLOR_GREEN, COLOR_BLACK);
    init_pair(COLOR_WHITE,COLOR_WHITE, COLOR_BLACK);
    keypad(stdscr,TRUE);
    
    crmode();
    
    noecho();
    while(ch != 'q'){
        mvprintw(y/2, x/2, "%s", argv[1]); 
        refresh();
        ch = getch();
        if(ch == 'u'){
            attron(COLOR_PAIR(COLOR_GREEN));
            mvprintw(y/2, x/2, "%s", strupr(argv[1]));
        }
        else if(ch == 'l'){
            attron(COLOR_PAIR(COLOR_RED));
            mvprintw(y/2, x/2, "%s", argv[1]);
        }
        else if(ch == 'o'){
            attron(COLOR_PAIR(COLOR_WHITE));
            mvprintw(y/2, x/2, "%s", argv[1]); 
        }
        else{
            continue;
        }
    }
    endwin();
    return 0;
}

So from this code I want to display string argv[1] at the center of the terminal. When the user press u I want to make it uppercase when the user press l I want to make it into the lowercase. At my code when I want to make the word into the uppercase I want to use strupr to make it into uppercase but cannot compile this code properly. It said implicit declaration for the strupr function.

And I think for putting into the center of the terminal I already make the proper program by using mvprintw(y/2,x/2) but despite of the word displayed at the center it displayed at the top left of the terminal. Is there somebody know where my mistake at?

rici · Answer 1 · 2022-05-25T04:56:56.243

You can't query getmaxyx until after you have initialized the screen with initscr. Or, better said, you can do the query but you won't get meaningful information.

strupr is not a standard C function, and I guess your C library doesn't implement it. You can implement it by looping over the string calling toupper:

char* my_strupr(char* str) {
  for (unsigned char* p = (unsigned char*)str; *p; ++p) {
    *p = toupper(*p);
  }
  return str;
}

That's not the best way of converting to upper case. It won't work if you have any non-ascii characters in your input. There are libraries which provide Unicode-aware string transformations, and you should think about using one of them. (Also, you might want to use the wide-char-enable ncurses. See the manual for details.)

ncurses displaying word at the center and make it into uppecase and lowercase

1 Answers1