console_read()

read data directly from the video buffer of a console

Synopsis:

#include <sys/console.h>
int console_read( struct _console_ctrl *cc,
                  int console,
                  unsigned byte_offset,
                  unsigned char *buf,
                  int n,
                  int *row, *column, *type );

Description:

The console_read() function reads data directly from the video buffer of the indicated console.

The argument cc is a pointer to a control structure that was returned by a previous call to console_open(). The argument console has a value of 1 to represent the device named /dev/con1, a value of 2 for /dev/con2, and so on. A value of 0 for console indicates the default console (that is, the one used by console_open()). A value of -1 for console indicates the currently visible console.

n device-dependent bytes are read from the console's video buffer (starting at byte_offset), and are stored in buf.

The values pointed to by row, column, and type indicate the current cursor position and type. Any of these arguments may be NULL, in which case, the corresponding variable is not set.

Cursor coordinates start at (0,0) in the upper left corner of the screen. Cursor types are defined in <sys/console.h>.

Returns:

0: Success
-1: An error occurred. errno is set to indicate the error.

Errors:

EACCES: You don't have read permission for the console.
EINVAL: The control structure is invalid.
ENXIO: The console value is invalid.

Examples:

#include <sys/console.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>

int main( void )
  {
    struct _console_ctrl *cc;
    int fd;
    int row, col, type;
    char c, attr, *buf;

    /* Open up a channel to the console driver */
    fd = open( "/dev/con1", O_RDWR );
    cc = console_open( fd, O_RDWR );
    close( fd );

    /* Read the entire 80x25 (IBM compatible) screen
       that is currently being displayed */
    buf = calloc( 80*25, 2 );
    console_read( cc, 0, 0, buf, 80*25*2,
                  &row, &col, &type);

    /* Read the single character at the (row, col)
       position of the screen */
    console_read( cc, 0, 2*( col + 80*row ), &c, 1,
                  NULL, NULL, NULL );

    /* Read the attribute of the single character at the
       ( row, col ) position of the screen */
    console_read( cc, 0, 2*( col + 80*row )+1, &attr, 1,
                  NULL, NULL, NULL );

    /* Close the channel */
    console_close( cc );
    return (EXIT_SUCCESS);
  }

Classification:

QNX

Safety:
Interrupt handler	No
Signal handler	Yes, but modifies errno
Thread	Yes