65 lines
1.7 KiB
Groff
65 lines
1.7 KiB
Groff
.TH READCLOCK 8
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.SH NAME
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readclock \- read or set a real time clock
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.SH SYNOPSIS
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\fBreadclock\fP [\fB\-nqwW2\fP]
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.SH DESCRIPTION
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.B Readclock
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reads the real time clock and sets the operating system time. It is usually
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the second thing done in
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.BR /etc/rc ,
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the first thing is setting the time zone by sourcing
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.BR /etc/profile .
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This means that the clock is assumed to tell the wall clock time. If you
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want to run the clock in GMT then you can put
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.B "TZ=GMT"
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(or any other TZ value) in front of the readclock command.
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.SH OPTIONS
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.TP
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.B \-n
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Play-act, don't set the time nor change the calibration data, just show what
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would be done.
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.TP
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.B \-q
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Quiet execution. Suppresses all output.
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.TP
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.B \-w
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Write the current time to the hardware clock. Dangerous, see
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.BR BUGS .
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Don't forget to use
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.B "TZ=GMT"
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in front of readclock if the clock should run in GMT.
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.TP
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.B \-W
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Like
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.BR \-w ,
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but also sets the status registers of the CMOS clock to their proper values.
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(For if the clock suddenly runs at an odd pace or has stopped and the BIOS
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doesn't repair it.)
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.TP
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.BR \-2 ,
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Add 20 to any year before 2000. If your CMOS clock year can't run past 2000,
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then you can set it to 1980 and use
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.B \-2
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to correct the year. Together with
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.B \-w
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the year minus 20 is written to the clock.
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.SH FILES
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.TP 20n
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/etc/profile
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Timezone and other shell initialization code.
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.SH "SEE ALSO"
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.BR date (1),
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.BR utime (1).
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.SH BUGS
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Reported to not work on some AT's.
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.PP
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May mess up the clock royally when setting it
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.RB ( \-w ).
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Only if you have a very standard AT and you are not afraid of having your
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CMOS setup reset to the default with a "checksum error" should you use
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.BR readclock
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to set the time of the CMOS clock. You have been warned.
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.SH AUTHOR
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Kees J. Bot (kjb@cs.vu.nl)
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