curses (ncurses) library question Post: 2853

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Top Forums Programming curses (ncurses) library question Post 2853 by TelePlayer on Thursday 7th of June 2001 03:28:38 PM

06-07-2001

Registered User

curses (ncurses) library question

Hi again. I'm using the curses functions simply to output data to
the screen in certain areas. Very simple, just using the full
screen, no windows.

The problem is that I'm calling mvprintw from within several child
processes in the same session, and the output is going
bananas. ie, no matter what x and y values I put in the
mvprintw, the output appears at the last cursor position of
another child process.

I found some info about a buffering problem, but I followed all
their suggestions and came up with the same result.

The code should output this:
0 2 4 6 8
1 3 5 7 9

but instead outputs this:
0 3 2 5 4 7 6 9 8
1

Here's the code: OH, and thanks to the kind person who replied
to my post about IPC...that helped me immensely. The ipc_
functions below are wrappers for the mutexes and shared
memory functions:

<pre>
int Print(int, int, char *);

struct shared_memory
{
int sem;
// void *pPrint;
WINDOW *win;
// SCREEN *scr;
};

struct shared_memory *sm = NULL;

int main(int argc, char** argv)
{
pid_t p;
int ch;
char temp[5];

sm = ipc_sram_alloc(1, sizeof(struct shared_memory));
if (sm == (void *)NULL)
exit(0);

// sm->pPrint = (void *)Print;

ipc_mutex_alloc(&sm->sem, 0);

if (sm->sem < 0)
printf("BAD mutex\r\n");

sm->win = initscr();
wclear(sm->win);
wrefresh(sm->win);

p = fork();
if (p == 0) // If we are a child process
{
for (ch = 0; ch < 10; ch += 2)
{
usleep(500000);
sprintf(temp, "%d", ch);
Print(9, ch + 1, temp);
usleep(500000);
}
exit(0);
}
else // otherwise we're in the parent
{
for (ch = 1; ch < 10; ch += 2)
{
usleep(500000);
sprintf(temp, "%d", ch);
Print(10, ch + 1, temp);
usleep(500000);
}
}

wait(NULL); // wait for child to die
endwin();
ipc_mutex_free(sm->sem);
ipc_sram_free(sm);
}

int Print(int row, int col, char *psz)
{
ipc_mutex_acquire(sm->sem);
mvwprintw(sm->win, row, col, psz);
wrefresh(sm->win);
// mvprintw(row, col, psz);
// refresh();
ipc_mutex_release(sm->sem);
return 0;
}
</pre>

Last edited by TelePlayer; 06-07-2001 at 05:27 PM..

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printw

curs_printw(3)						     Library Functions Manual						    curs_printw(3)

NAME

       curs_printw, printw, wprintw, mvprintw, mvwprintw, vw_printw, vwprintw - Print formatted output in Curses windows

SYNOPSIS

       #include <curses.h>

       int printw(
	       char *fmt[, arg]...  ); int wprintw(
	       WINDOW *win,
	       char *fmt[, arg]...  ); int mvprintw(
	       int y,
	       int x,
	       char *fmt[, arg]...  ); int mvwprintw(
	       WINDOW *win,
	       int y,
	       int x,
	       char *fmt[, arg]...  ); #include <stdarg.h> include <curses.h>

       int vw_printw(
	       WINDOW *win,
	       char *fmt,
	       va_list varglist ); #include <varargs.h> include <curses.h>

       int vwprintw(
	       WINDOW *win,
	       char *fmt,
	       va_list varglist );

LIBRARY

       Curses Library (libcurses)

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       printw, wprintw, mvprintw, mvwprintw, vw_printw, vwprintw:  XCURSES4.2

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

DESCRIPTION

       The  printw,  wprintw,  mvprintw,  and mvwprintw routines are analogous to printf family of routines (see printf(3)). In effect, the printw
       routines output the string that would be output by printf as though waddstr were used on the given window.

       The vw_printw routine is analogous to vprintf (see vprintf(3)) and performs the same operation as wprintw  but  uses  a	variable  argument
       list. The va_list type is a pointer to a list of arguments and is defined in <stdarg.h>.

       The vwprintw routine is equivalent to vw_printw except that va_list is defined in <varargs.h>. The vw_printw routine is recommended for use
       in new applications.

NOTES

       The header file <curses.h> automatically includes the header file <stdio.h>.

RETURN VALUES

       All routines return the integer ERR upon failure and OK upon successful completion.

SEE ALSO

       Functions: curses(3), printf(3)

       Others: standards(5)

																    curs_printw(3)