LinuxQuestions.org - [C++] Linux API - get Console Font Color

Reading virtual terminal contents is AFAIK impossible. Size and current cursor position, however, is rather easy. Using the ncurses library:

Code:

#include <ncurses.h>

#include <stdio.h>



int main(void)

{

        int        rows, cols, row, col;



        WINDOW *w = initscr();

        getmaxyx(w, rows, cols);

        getyx(w, row, col);

        endwin();



        printf("Row %d of %d, column %d of %d.\n",

              1+row, rows, 1+col, cols);

        return 0;

}

If you do not want to add another library dependence, you can use the Linux-specific lower-level interfaces. See man tty_ioctl and man console_ioctl.

TIOCGWINSZ ioctl to the controlling terminal (stdout or stderr, whichever is a tty) will fill in a struct winsize, which contains the number of rows and columns in the terminal at that point. Install a SIGWINCH signal handler which does that ioctl again, if you want to be notified of changes.

ANSI escape sequence \033[6n (4 bytes) to the controlling terminal should inject the cursor position as \033[row;colR into standard input. In order to hide that sequence from the terminal, you'll need to manipulate the terminal attributes.

Here is a program which seems to work. I just threw it together, so there may be bugs lurking in it.

Code:

#include <termios.h>

#include <unistd.h>

#include <fcntl.h>

#include <sys/ioctl.h>

#include <errno.h>



#include <stdio.h>



int terminal_specs(int *const cols, int *const rows,

                  int *const col,  int *const row)

{

        int                in, out, result;

        char                buffer[16];

        struct winsize        ws;

        struct termios        t1, t2;



        /* Initialize zeros (unknown) */

        if (cols) *cols = 0;

        if (rows) *rows = 0;

        if (col)  *col  = 0;

        if (row)  *row  = 0;



        /* Open controlling tty for input. */

        do {

                in = open("/dev/tty", O_RDONLY | O_NONBLOCK);

        } while (in == -1 && errno == EINTR);

        if (in == -1)

                return errno;



        /* Reopen TTY for output. */

        do {

                out = open("/dev/tty", O_WRONLY);

        } while (out == -1 && errno == EINTR);

        if (out == -1) {

                int const saved_errno = errno;

                do {

                        result = close(in);

                } while (result == -1 && errno == EINTR);

                return saved_errno;

        }



        /* Determine terminal size. */

        if (!ioctl(out, TIOCGWINSZ, &ws)) {

                if (cols) *cols = ws.ws_col;

                if (rows) *rows = ws.ws_row;

        }



        /* Save current terminal settings. */

        tcgetattr(out, &t1);

        tcgetattr(out, &t2);



        /* Disable echo and signals for now. */

        t2.c_iflag &= ~( IGNBRK | IGNPAR );

        t2.c_oflag &= ~( OFILL );

        t2.c_oflag |=    ONOCR;

        t2.c_lflag &= ~( ISIG | ICANON | ECHO );

        tcsetattr(out, TCSANOW, &t2);



        /* Query cursor location. */

        if (row || col) {



                if (write(out, "\033[6n", 4) == 4) {

                        do {

                                result = read(in, buffer, sizeof(buffer) - 1);

                        } while (result == -1 && (errno == EINTR || errno == EWOULDBLOCK));

                        if (result > 0 && buffer[result - 1] == 'R') {

                                char *p = buffer;

                                int  nr = 0;

                                int  nc = 0;



                                buffer[result - 1] = 0;



                                /* parse [^0-9]*([0-9]*)[^0-9]*([0-9]*) */

                                while (*p && !(*p >= '0' && *p <= '9')) p++;

                                while (*p >= '0' && *p <= '9')

                                        nr = nr * 10 + (*(p++) - '0');

                                while (*p && !(*p >= '0' && *p <= '9')) p++;

                                while (*p >= '0' && *p <= '9')

                                        nc = nc * 10 + (*(p++) - '0');



                                if (row) *row = nr;

                                if (col) *col = nc;

                        }

                }

        }

                

        /* Restore terminal settings. */

        tcsetattr(out, TCSANOW, &t1);



        /* Close descriptors. */

        do {

                result = close(in);

        } while (result == -1 && errno == EINTR);

        do {

                result = close(out);

        } while (result == -1 && errno == EINTR);



        return 0;

}



int main(void)

{

        int        cols, rows, col, row;



        terminal_specs(&cols, &rows, &col, &row);



        if (cols > 0 && rows > 0 && col > 0 && row > 0)

                printf("Row %d of %d, column %d of %d\n", row, rows, col, cols);

        else

        if (cols > 0 && rows > 0)

                printf("%d rows, %d columns\n", rows, cols);

        else

        if (col > 0 && row > 0)

                printf("Row %d, column %d\n", row, col);



        return 0;

}

Note that I wrote the terminal_specs() function so that it does not need stdio at all. (I could have used sscanf(), but this way it's independent.)

If you call terminal_specs() first, before reading from standard input, standard input should be kept untouched.

Hope this helps.