typedef struct { char *name; } Widget;

int print_widget (FILE *stream, const struct printf_info *info, va_list *app) { Widget *w; char *buffer; int len;

/* Format the output into a string. */ w = va_arg (*app, Widget *); len = asprintf (&buffer, "<Widget %p: %s>", w, w->name); if (len == -1) return -1;

/* Pad to the minimum field width and print to the stream. */ len = fprintf (stream, "%*s", (info->left ? - info->width : info->width), buffer);

/* Clean up and return. */ free (buffer); return len; }

int main (void) { /* Make a widget to print. */ Widget mywidget; mywidget.name = "mywidget";

/* Register the print function for widgets. */ register_printf_function (’W’, print_widget, NULL); /* No arginfo. */

/* Now print the widget. */ printf ("|%W|\n", &mywidget); printf ("|%35W|\n", &mywidget); printf ("|%-35W|\n", &mywidget);

return 0; }

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