time.tex

用于嵌入式Linux系统的标准C的库函数

@node Timefns
@chapter Time Functions (@file{time.h})

This chapter groups functions used either for reporting on time
(elapsed, current, or compute time) or to perform calculations based
on time.

The header file @file{time.h} defines three types.  @code{clock_t} and
@code{time_t} are both used for representations of time particularly
suitable for arithmetic.  (In this implementation, quantities of type
@code{clock_t} have the highest resolution possible on your machine,
and quantities of type @code{time_t} resolve to seconds.)  @code{size_t}
is also defined if necessary for quantities representing sizes. 

@file{time.h} also defines the structure @code{tm} for the traditional
representation of Gregorian calendar time as a series of numbers, with
the following fields: 

@table @code
@item tm_sec
Seconds.

@item tm_min
Minutes.

@item tm_hour
Hours.

@item tm_mday
Day.

@item tm_mon
Month.

@item tm_year
Year (since 1900).

@item tm_wday
Day of week: the number of days since Sunday.

@item tm_yday
Number of days elapsed since last January 1.

@item tm_isdst
Daylight Savings Time flag: positive means DST in effect, zero means DST
not in effect, negative means no information about DST is available.
@end table

@menu
* asctime::     Format time as string
* clock::       Cumulative processor time
* ctime::       Convert time to local and format as string
* difftime::    Subtract two times
* gmtime::      Convert time to UTC (GMT) traditional representation
* localtime::   Convert time to local representation
* mktime::      Convert time to arithmetic representation
* strftime::    Flexible calendar time formatter
* time::        Get current calendar time (as single number)
* tzset::       Set timezone info
@end menu

@page
@include time/asctime.def

@page
@include time/clock.def

@page
@include time/ctime.def

@page
@include time/difftime.def

@page
@include time/gmtime.def

@page
@include time/lcltime.def

@page
@include time/mktime.def

@page
@include time/strftime.def

@page
@include time/time.def

@page
@include time/tzset.def