1 | @node Timefns |
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2 | @chapter Time Functions (@file{time.h}) |
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3 | |
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4 | This chapter groups functions used either for reporting on time |
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5 | (elapsed, current, or compute time) or to perform calculations based |
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6 | on time. |
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7 | |
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8 | The header file @file{time.h} defines three types. @code{clock_t} and |
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9 | @code{time_t} are both used for representations of time particularly |
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10 | suitable for arithmetic. (In this implementation, quantities of type |
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11 | @code{clock_t} have the highest resolution possible on your machine, |
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12 | and quantities of type @code{time_t} resolve to seconds.) @code{size_t} |
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13 | is also defined if necessary for quantities representing sizes. |
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14 | |
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15 | @file{time.h} also defines the structure @code{tm} for the traditional |
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16 | representation of Gregorian calendar time as a series of numbers, with |
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17 | the following fields: |
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18 | |
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19 | @table @code |
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20 | @item tm_sec |
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21 | Seconds, between 0 and 60 inclusive (60 allows for leap seconds). |
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22 | |
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23 | @item tm_min |
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24 | Minutes, between 0 and 59 inclusive. |
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25 | |
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26 | @item tm_hour |
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27 | Hours, between 0 and 23 inclusive. |
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28 | |
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29 | @item tm_mday |
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30 | Day of the month, between 1 and 31 inclusive. |
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31 | |
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32 | @item tm_mon |
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33 | Month, between 0 (January) and 11 (December). |
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34 | |
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35 | @item tm_year |
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36 | Year (since 1900), can be negative for earlier years. |
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37 | |
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38 | @item tm_wday |
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39 | Day of week, between 0 (Sunday) and 6 (Saturday). |
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40 | |
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41 | @item tm_yday |
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42 | Number of days elapsed since last January 1, between 0 and 365 inclusive. |
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43 | |
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44 | @item tm_isdst |
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45 | Daylight Savings Time flag: positive means DST in effect, zero means DST |
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46 | not in effect, negative means no information about DST is available. |
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47 | Although for mktime(), negative means that it should decide if DST is in |
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48 | effect or not. |
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49 | @end table |
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50 | |
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51 | @menu |
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52 | * asctime:: Format time as string |
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53 | * clock:: Cumulative processor time |
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54 | * ctime:: Convert time to local and format as string |
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55 | * difftime:: Subtract two times |
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56 | * gmtime:: Convert time to UTC (GMT) traditional representation |
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57 | * localtime:: Convert time to local representation |
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58 | * mktime:: Convert time to arithmetic representation |
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59 | * strftime:: Convert date and time to a user-formatted string |
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60 | * time:: Get current calendar time (as single number) |
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61 | * __tz_lock:: Lock time zone global variables |
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62 | * tzset:: Set timezone info |
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63 | @end menu |
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64 | |
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65 | @page |
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66 | @include time/asctime.def |
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67 | |
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68 | @page |
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69 | @include time/clock.def |
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70 | |
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71 | @page |
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72 | @include time/ctime.def |
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73 | |
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74 | @page |
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75 | @include time/difftime.def |
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76 | |
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77 | @page |
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78 | @include time/gmtime.def |
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79 | |
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80 | @page |
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81 | @include time/lcltime.def |
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82 | |
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83 | @page |
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84 | @include time/mktime.def |
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85 | |
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86 | @page |
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87 | @include time/strftime.def |
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88 | |
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89 | @page |
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90 | @include time/time.def |
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91 | |
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92 | @page |
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93 | @include time/tzlock.def |
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94 | |
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95 | @page |
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96 | @include time/tzset.def |
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