time.h(3head)

1time.h(3HEAD)                       Headers                      time.h(3HEAD)
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NAME

6       time.h, time - time types
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SYNOPSIS

9       #include <time.h>
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DESCRIPTION

13       The  <time.h> header declares the structure tm, which includes the fol‐
14       lowing members:
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16         int tm_sec     /* seconds [0,60] */
17         int tm_min     /* minutes [0,59] */
18         int tm_hour    /* hour [0,23] */
19         int tm_mday    /* day of month [1,31] */
20         int tm_mon     /* month of year [0,11] */
21         int tm_year    /* years since 1900 */
22         int tm_wday    /* day of week [0,6] (Sunday =0) */
23         int tm_yday    /* day of year [0,365] */
24         int tm_isdst   /* daylight savings flag */
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28       The value of tm_isdst is positive if Daylight Saving Time is in effect,
29       0  if Daylight Saving Time is not in effect, and negative if the infor‐
30       mation is not available.
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33       The <time.h> header defines the following symbolic names:
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35       NULL                        Null pointer constant.
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38       CLOCKS_PER_SEC              A number used to convert the value returned
39                                   by  the  clock() function into seconds. See
40                                   clock(3C).
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43       CLOCK_PROCESS_CPUTIME_ID    The identifier of the CPU-time clock  asso‐
44                                   ciated with the process making a clock() or
45                                   timer*() function call.
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48       CLOCK_THREAD_CPUTIME_ID     The identifier of the CPU-time clock  asso‐
49                                   ciated  with the thread making a clock() or
50                                   timer*() function call.
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54       The <time.h> header declares the timespec structure, which has the fol‐
55       lowing members:
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57         time_t tv_sec     /* seconds */
58         long   tv_nsec     /* nanoseconds */
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62       The  <time.h>  header  declares the itimerspec structure, which has the
63       following members:
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65         struct timespec it_interval     /* timer period */
66         struct timespec it_value     /* timer expiration */
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70       The following manifest constants are defined:
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72       CLOCK_REALTIME     The identifier of the system-wide realtime clock.
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75       TIMER_ABSTIME      Flag indicating time is absolute. For functions tak‐
76                          ing  timer objects, this refers to the clock associ‐
77                          ated with the timer.
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80       CLOCK_MONOTONIC    The identifier for the system-wide monotonic  clock,
81                          which  is  defined  as a clock whose value cannot be
82                          set with clock_settime() and that cannot have  back‐
83                          ward clock jumps. The maximum possible clock jump is
84                          implementation-defined. See clock_settime(3C).
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88       The clock_t, size_t, time_t, clockid_t, and timer_t types  are  defined
89       as described in <sys/types.h>. See types.h(3HEAD).
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92       Although the value of CLOCKS_PER_SEC is required to be 1 million on all
93       standard-conforming systems, it can be variable on other  systems,  and
94       it  should  not  be  assumed that CLOCKS_PER_SEC is a compile-time con‐
95       stant.
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98       The <time.h> header provides a declaration for getdate_err.
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101       The following are declared as variables:
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103         extern int daylight;
104         extern long timezone;
105         extern char *tzname[];
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109       Inclusion of the <time.h> header can make visible all symbols from  the
110       <signal.h> header.
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USAGE

113       The range [0,60] for tm_sec allows for the occasional leap second.
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116       tm_year  is  a signed value; therefore, years before 1900 can be repre‐
117       sented.
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120       To obtain the number of clock ticks per second returned by the  times()
121       function,  applications  should call sysconf(_SC_CLK_TCK). See times(2)
122       and sysconf(3C).
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ATTRIBUTES

125       See attributes(5) for descriptions of the following attributes:
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130       ┌─────────────────────────────┬─────────────────────────────┐
131       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
132       ├─────────────────────────────┼─────────────────────────────┤
133       │Interface Stability          │Committed                    │
134       ├─────────────────────────────┼─────────────────────────────┤
135       │Standard                     │See standards(5).            │
136       └─────────────────────────────┴─────────────────────────────┘
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NAME

SYNOPSIS

DESCRIPTION

USAGE

ATTRIBUTES

SEE ALSO