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NetBSD 6.1.5 - man page for cnbell (netbsd section 9)

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CONS(9) 			  BSD Kernel Developer's Manual 			  CONS(9)

NAME
     cnbell, cnflush, cngetc, cngetsn, cnhalt, cnpollc, cnputc -- console access interface

SYNOPSIS
     #include <dev/cons.h>

     void
     cnbell(u_int pitch, u_int period, u_int volume);

     void
     cnflush(void);

     int
     cngetc(void);

     int
     cngetsn(char *cp, int size);

     void
     cnhalt(void);

     void
     cnpollc(int on);

     void
     cnputc(int c);

DESCRIPTION
     These functions operate over the current console device.  The console must be initialized
     before these functions can be used.

     Console input polling functions cngetc(), cngetsn() and cnpollc() are only to be used during
     initial system boot, e.g., when asking for root and dump device or to get necessary user
     input within mountroothooks.  Once the system boots, user input is read via standard tty(4)
     facilities.

     The following is a brief description of each function:

     cnbell()	Ring a bell at appropriate pitch, for duration of period milliseconds at given
		volume.  Note that the volume value is ignored commonly.

     cnflush()	Waits for all pending output to finish.

     cngetc()	Poll (busy wait) for an input and return the input key.  Returns 0 if there is no
		console input device.  cnpollc() must be called before cngetc() could be used.
		cngetc() should be used during kernel startup only.

     cngetsn()	Read one line of user input, stop reading once the newline key is input.  Input
		is echoed back.  This uses cnpollc() and cngetc().  Number of read characters is
		size at maximum, user is notified by console bell when the end of input buffer is
		reached.  <Backspace> key works as expected.  <@> or <CTRL>-u make cngetsn() dis-
		card input read so far, print newline and wait for next input.	cngetsn() returns
		number of characters actually read, excluding the final newline.  cp is not zero-
		ended before return.  cngetsn() should be used during kernel startup only.

     cnhalt()	Terminates the console device (i.e. cleanly shuts down the console hardware.)

     cnpollc()	Switch the console driver to polling mode if on is nonzero, or back to interrupt
		driven mode if on is zero.  cnpollc() should be used during kernel startup only.

     cnputc()	Console kernel output character routine.  Commonly, kernel code uses printf(9)
		rather than using this low-level interface.

EXAMPLES
     This waits until a <Enter> key is pressed:

	   int c;

	   cnpollc(1);
	   for(;;) {
		   c = cngetc();
		   if ((c == '\r' || (c == '\n')) {
			   printf("\n");
			   break;
		   }
	   }
	   cnpollc(0);

SEE ALSO
     pckbd(4), pcppi(4), tty(4), wscons(4), wskbd(4), printf(9), spl(9), wscons(9)

BSD					   June 8, 2010 				      BSD
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