76 lines
1.5 KiB
Text
76 lines
1.5 KiB
Text
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.TH SECONDS 9
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.SH NAME
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seconds, ticks, fastticks, HZ, MS2HZ, MS2TK, TK2MS, TK2SEC \- kernel times and time conversions
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.SH SYNOPSIS
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.ta \w'\fL#define 'u
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.B
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long seconds(void)
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.PP
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.B
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vlong fastticks(uvlong *hz)
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.PP
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.EX
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#define HZ ...
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#define MS2HZ (1000/HZ)
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#define TK2SEC(t) ((t)/HZ)
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#define TK2MS(t) ((t)*(1000/HZ))
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.EE
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.SH DESCRIPTION
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.I Seconds
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returns the system's idea of the current time as the number of seconds
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since the start of the epoch
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(00:00:00 GMT, January 1, 1970).
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.PP
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The
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.B ticks
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field of the
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.B Mach
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structure returns the number of system-dependent clock ticks on the
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given processor since system boot.
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On a multiprocessor,
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.B MACHP(0)
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is sometimes used to provide a reference time, since the tick value
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might vary slightly across processors.
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.PP
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.I Fastticks
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returns the number of ticks since boot as measured by the
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fastest clock provided by the platform.
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The frequency of the clock, in ticks per second,
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is returned through
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.IR hz ,
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unless it is nil.
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.PP
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The system clock frequencies are platform-dependent.
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Several symbolic constants and macro functions are defined by
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the file
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.B mem.h
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to convert between different time units:
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.TF TK2SEC(t)
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.PD
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.TP
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.B HZ
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The number of clock ticks per second.
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.TP
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.B MS2HZ
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Milliseconds per clock tick.
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.TP
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.BI TK2SEC( t )
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Convert
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.I t
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clock ticks to seconds (truncating not rounding).
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.TP
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.BI TK2MS( t )
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Convert
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.I t
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clock ticks to milliseconds.
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.SH SOURCE
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.B /sys/src/9/*/mem.h
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.br
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.B /sys/src/9/*/clock.c
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.br
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.B /sys/src/9/*/devarch.c
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.br
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.B /sys/src/9/*/timer.c
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.br
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.B /sys/src/9/port/tod.c
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