hwclock: in man page move --date and --epoch from Functions to Options
Also improve the synopsis and some wording and a bit of formatting, add the --help option, and say that --show is the default function. Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
This commit is contained in:
Benno Schulenberg
Karel Zak
parent
e935db7891
commit
5474e57f3b
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@ -1,23 +1,23 @@
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.TH HWCLOCK 8 "06 August 2008"
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.TH HWCLOCK 8 "August 2011"
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.SH NAME
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hwclock \- query and set the hardware clock (RTC)
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hwclock \- query or set the hardware clock (RTC)
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.SH SYNOPSIS
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.B hwclock
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.RI [ functions ]
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.RI [ options ]
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.RI [ function ]
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.RI [ option ...]
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.SH DESCRIPTION
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.B hwclock
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is a tool for accessing the Hardware Clock. You can display the
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current time, set the Hardware Clock to a specified time, set the
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Hardware Clock to the System Time, and set the System Time from the
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Hardware Clock from the System Time, or set the System Time from the
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Hardware Clock.
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.PP
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You can also run
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.B hwclock
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periodically to insert or remove time from the Hardware Clock to
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compensate for systematic drift (where the clock consistently gains or
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loses time at a certain rate if left to run).
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periodically to add or subtract time from the Hardware Clock to
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compensate for systematic drift (where the clock consistently loses or
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gains time at a certain rate when left to run).
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.SH FUNCTIONS
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You need exactly one of the following options to tell
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@ -26,11 +26,12 @@ what function to perform:
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.PP
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.TP
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.BR \-r , \ \-\-show
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Read the Hardware Clock and print the time on Standard Output.
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Read the Hardware Clock and print the time on standard output.
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The time shown is always in local time, even if you keep your Hardware Clock
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in Coordinated Universal Time. See the
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.B \-\-utc
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option.
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Showing the Hardware Clock time is the default when no function is specified.
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.TP
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.B \-\-set
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@ -48,7 +49,7 @@ as
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.BR tzset (3)
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would interpret them.
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The obsolete tz_dsttime field of the kernel's timezone value is set
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to DST_NONE. (For details on what this field used to mean, see
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to DST_NONE. (For details on what this field used to mean, see
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.BR settimeofday (2).)
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This is a good option to use in one of the system startup scripts.
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@ -66,7 +67,7 @@ as
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.BR tzset (3)
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would interpret them.
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The obsolete tz_dsttime field of the kernel's timezone value is set
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to DST_NONE. (For details on what this field used to mean, see
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to DST_NONE. (For details on what this field used to mean, see
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.BR settimeofday (2).)
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This is an alternate option to
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@ -85,10 +86,12 @@ Print the kernel's Hardware Clock epoch value to standard output.
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This is the number of years into AD to which a zero year value in the
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Hardware Clock refers. For example, if you are using the convention
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that the year counter in your Hardware Clock contains the number of
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full years since 1952, then the kernel's Hardware Counter epoch value
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full years since 1952, then the kernel's Hardware Clock epoch value
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must be 1952.
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This epoch value is used whenever hwclock reads or sets the Hardware Clock.
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This epoch value is used whenever
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.B hwclock
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reads or sets the Hardware Clock.
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.TP
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.B \-\-setepoch
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Set the kernel's Hardware Clock epoch value to the value specified by the
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@ -96,41 +99,6 @@ Set the kernel's Hardware Clock epoch value to the value specified by the
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option. See the
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.B \-\-getepoch
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option for details.
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.TP
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.BR \-v , \ \-\-version
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Print the version of
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.B hwclock
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on Standard Output.
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.TP
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.BI \-\-date= date_string
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You need this option if you specify the
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.B \-\-set
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option. Otherwise, it is ignored.
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This specifies the time to which to set the Hardware Clock.
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The value of this option is an argument to the
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.BR date (1)
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program.
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For example,
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.sp
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.I hwclock --set --date="9/22/96 16:45:05"
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.sp
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The argument is in local time, even if you keep your Hardware Clock in
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Coordinated Universal time. See the
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.B \-\-utc
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option.
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.TP
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.BI \-\-epoch= year
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Specifies the year which is the beginning of the Hardware Clock's
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epoch. I.e. the number of years into AD to which a zero value in the
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Hardware Clock's year counter refers. It is used together with
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the \-\-setepoch option to set the kernel's idea of the epoch of the
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Hardware Clock, or otherwise to specify the epoch for use with
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direct ISA access.
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For example, on a Digital Unix machine:
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.sp
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.I hwclock --setepoch --epoch=1952
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.TP
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.BI \-\-predict
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@ -139,10 +107,53 @@ Predict what the RTC will read at time given by the
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option based on the adjtime file. This is useful for example if you
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need to set an RTC wakeup time to distant future and want to account
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for the RTC drift.
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.TP
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.BR \-h , \ \-\-help
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Display a help text and exit.
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.TP
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.BR \-V , \ \-\-version
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Display the version of
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.B hwclock
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and exit.
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.SH OPTIONS
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.PP
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The following options apply to most functions.
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The first two options apply to just a few specific functions,
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the others apply to most functions.
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.TP
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.BI \-\-date= date_string
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You need this option if you specify the
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.B \-\-set
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or
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.B \-\-predict
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functions, otherwise it is ignored.
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It specifies the time to which to set the Hardware Clock, or the
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time for which to predict the Hardware Clock reading.
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The value of this option is an argument to the
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.BR date (1)
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program.
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For example:
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.sp
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.B " hwclock" --set --date="2011-08-14 16:45:05"
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.sp
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The argument must be in local time, even if you keep your Hardware Clock in
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Coordinated Universal time. See the
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.B \-\-utc
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option.
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.TP
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.BI \-\-epoch= year
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Specifies the year which is the beginning of the Hardware Clock's
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epoch, that is the number of years into AD to which a zero value in the
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Hardware Clock's year counter refers. It is used together with
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the \fB\-\-setepoch\fR option to set the kernel's idea of the epoch of the
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Hardware Clock, or otherwise to specify the epoch for use with
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direct ISA access.
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For example, on a Digital Unix machine:
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.sp
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.B " hwclock" --setepoch --epoch=1952
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.TP
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.BR \-u , \ \-\-utc
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.TP
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@ -160,10 +171,12 @@ will be messed up.
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If you specify neither
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.B \-\-utc
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nor
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.B \-\-localtime
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, the default is whichever was specified the last time
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.BR \-\-localtime ,
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the default is whichever was specified the last time
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.B hwclock
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was used to set the clock (i.e. hwclock was successfully run with the
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was used to set the clock (i.e.
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.B hwclock
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was successfully run with the
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.BR \-\-set ,
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.BR \-\-systohc ,
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or
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@ -173,10 +186,10 @@ exist, the default is UTC time.
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.TP
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.B \-\-noadjfile
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disables the facilities provided by
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Disables the facilities provided by
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.IR /etc/adjtime .
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.B hwclock
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will not read nor write to that file with this option. Either
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will not read nor write to that file with this option. Either
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.B \-\-utc
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or
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.B \-\-localtime
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@ -184,11 +197,11 @@ must be specified when using this option.
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.TP
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.BI \-\-adjfile= filename
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overrides the default /etc/adjtime.
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Overrides the default /etc/adjtime.
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.TP
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.BR \-f , \ \-\-rtc=\fIfilename\fB
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overrides the default /dev file name, which is
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Overrides the default /dev file name, which is
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.IR /dev/rtc
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on many platforms but may be
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.IR /dev/rtc0 ,
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@ -197,8 +210,8 @@ and so on.
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.TP
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.B \-\-directisa
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is meaningful only on an ISA machine or an Alpha (which implements enough
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of ISA to be, roughly speaking, an ISA machine for
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This option is meaningful only on an ISA machine or an Alpha (which implements
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enough of ISA to be, roughly speaking, an ISA machine for
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.BR hwclock 's
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purposes). For other machines, it has no effect. This option tells
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.B hwclock
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@ -206,10 +219,9 @@ to use explicit I/O instructions to access the Hardware Clock.
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Without this option,
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.B hwclock
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will try to use the /dev/rtc device (which it assumes to be driven by the
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rtc device driver). If it is unable to open the device (for read), it will
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RTC device driver). If it is unable to open the device (for reading), it will
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use the explicit I/O instructions anyway.
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The rtc device driver was new in Linux Release 2.
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.TP
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.B \-\-badyear
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Indicates that the Hardware Clock is incapable of storing years outside
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@ -231,9 +243,9 @@ knows it's working with a brain-damaged clock, it ignores the year part of
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the Hardware Clock value and instead tries to guess the year based on the
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last calibrated date in the adjtime file, by assuming that that date is
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within the past year. For this to work, you had better do a
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.I hwclock \-\-set
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.B hwclock \-\-set
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or
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.I hwclock \-\-systohc
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.B hwclock \-\-systohc
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at least once a year!
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Though
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@ -278,14 +290,14 @@ is mounted.
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(If you find you need one of these options to make
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.B hwclock
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work, contact the maintainer to see if the program can be improved
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to detect your system automatically. Output of `hwclock --debug'
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to detect your system automatically. Output of `hwclock --debug'
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and `cat /proc/cpuinfo' may be of interest.)
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Option
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.B \-\-jensen
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means you are running on a Jensen model.
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means you are running on a Jensen model. And
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.B \-\-funky\-toy
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means that on your machine, one has to use the UF bit instead
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means that on your machine one has to use the UF bit instead
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of the UIP bit in the Hardware Clock to detect a time transition. "Toy"
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in the option name refers to the Time Of Year facility of the machine.
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