rtc(7) —

NAME

rtc − real time clock interface

DESCRIPTION

The rtc driver supports the real time clock chip, allowing it to be set with the correct local time, and allowing the time to be read from the chip.

Ioctl Calls

RTCRTIME
This call is used to read the local time from the real time clock chip. The argument to the ioctl is the address of a buffer of RTCNREG unsigned characters (RTCNREG is defined is <sys/rtc.h>). The ioctl will fill in the buffer with the contents of the chip registers. Currently, RTCNREG is 14, and the meanings of the byte registers are as follows:

Register	Contents
0	Seconds
1	Second alarm
2	Minutes
3	Minute alarm
4	Hours
5	Hour alarm
6	Day of week
7	Date of month
8	Month
9	Year
A	Status register A
B	Status register B
C	Status register C
D	Status register D

For further information on the functions of these registers, see the IBM Personal Computer AT Technical Reference.

RTCSTIME
This call is used to set the time into the real time clock chip. The argument to the ioctl is the address of a buffer of RTCNREGP unsigned characters (RTCNREGP is defined is <sys/rtc.h>.) These bytes should be the desired chip register contents. Currently, RTCNREGP is 10, representing registers 0-9 as shown above. Note that only user root (the superuser) may open the real-time clock device for writing, and that the RTCSTIME ioctl will fail for any user other than root.

FILES

/dev/rtc

ADDED VALUE

This entry, supplied by SunSoft, Inc., contains enhancements to UNIX System V.