rtc(7) UNIX System V 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 in <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
your hardware technical reference manual.
RTCSTIME
This call is used to set the time into the real time clock chip.
The argument to ioctl is the address of a buffer of RTCNREGP
unsigned characters (RTCNREGP is defined in <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 the super-user may open the real time clock device for
writing and that the RTCSTIME ioctl will fail for any other than
the super-user.
FILES
/dev/rtc
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