From Linux Man Pages
pattern - get and set a menu's pattern buffer
SYNOPSIS
#include <menu.h>
int set_menu_pattern(MENU *menu, const char *pattern);
char *menu_pattern(const MENU *menu);
DESCRIPTION
Every menu has an associated pattern match buffer. As input events that are printable ASCII characters come in,
they are appended to this match buffer and tested for a match, as described in driver(3MENU).
The function set_menu_pattern sets the pattern buffer for the given menu and tries to find the first matching
item. If it succeeds, that item becomes current; if not, the current item does not change.
The function menu_pattern returns the pattern buffer of the given menu.
RETURN VALUE
The function menu_pattern returns NULL on error. The function set_menu_pattern may return the following error
codes:
E_OK The routine succeeded.
E_SYSTEM_ERROR
System error occurred (see errno).
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
E_NO_MATCH
Character failed to match.
RELATED
ncurses(3), menu(3MENU).
NOTES
The header file <menu.h> automatically includes the header file <curses.h>.
PORTABILITY
These routines emulate the System V menu library. They were not supported on Version 7 or BSD versions.
pattern(3MENU)
CATEGORY