1MKTIME(3P)                 POSIX Programmer's Manual                MKTIME(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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11

NAME

13       mktime — convert broken-down time into time since the Epoch
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SYNOPSIS

16       #include <time.h>
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18       time_t mktime(struct tm *timeptr);
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DESCRIPTION

21       The functionality described on this reference page is aligned with  the
22       ISO C  standard.  Any  conflict between the requirements described here
23       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2008
24       defers to the ISO C standard.
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26       The  mktime() function shall convert the broken-down time, expressed as
27       local time, in the structure pointed to by timeptr, into a  time  since
28       the  Epoch  value with the same encoding as that of the values returned
29       by time().  The original values of the tm_wday and  tm_yday  components
30       of the structure are ignored, and the original values of the other com‐
31       ponents are not restricted to the ranges described in <time.h>.
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33       A positive or 0 value for tm_isdst shall cause mktime() to presume ini‐
34       tially that Daylight Savings Time, respectively, is or is not in effect
35       for the specified time. A  negative  value  for  tm_isdst  shall  cause
36       mktime()  to  attempt  to determine whether Daylight Savings Time is in
37       effect for the specified time.
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39       Local timezone information shall  be  set  as  though  mktime()  called
40       tzset().
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42       The  relationship  between  the  tm  structure (defined in the <time.h>
43       header) and the time in seconds since the  Epoch  is  that  the  result
44       shall be as specified in the expression given in the definition of sec‐
45       onds since the Epoch (see the Base Definitions volume of  POSIX.1‐2008,
46       Section  4.15,  Seconds Since the Epoch) corrected for timezone and any
47       seasonal time adjustments, where the names in the structure and in  the
48       expression correspond.
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50       Upon  successful completion, the values of the tm_wday and tm_yday com‐
51       ponents of the structure shall be set appropriately, and the other com‐
52       ponents  are  set  to represent the specified time since the Epoch, but
53       with their values forced to the ranges indicated in the <time.h> entry;
54       the  final  value  of tm_mday shall not be set until tm_mon and tm_year
55       are determined.
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RETURN VALUE

58       The mktime() function shall return the specified time since  the  Epoch
59       encoded  as a value of type time_t.  If the time since the Epoch cannot
60       be represented, the function shall return the value (time_t)−1 and  set
61       errno to indicate the error.
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ERRORS

64       The mktime() function shall fail if:
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66       EOVERFLOW
67              The result cannot be represented.
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69       The following sections are informative.
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EXAMPLES

72       What day of the week is July 4, 2001?
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74           #include <stdio.h>
75           #include <time.h>
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77           struct tm time_str;
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79           char daybuf[20];
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81           int main(void)
82           {
83               time_str.tm_year = 2001 — 1900;
84               time_str.tm_mon = 7 — 1;
85               time_str.tm_mday = 4;
86               time_str.tm_hour = 0;
87               time_str.tm_min = 0;
88               time_str.tm_sec = 1;
89               time_str.tm_isdst = −1;
90               if (mktime(&time_str) == -1)
91                   (void)puts("-unknown-");
92               else {
93                   (void)strftime(daybuf, sizeof(daybuf), "%A", &time_str);
94                   (void)puts(daybuf);
95               }
96               return 0;
97           }
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APPLICATION USAGE

100       None.
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RATIONALE

103       None.
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FUTURE DIRECTIONS

106       None.
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SEE ALSO

109       asctime(),  clock(),  ctime(), difftime(), gmtime(), localtime(), strf‐
110       time(), strptime(), time(), tzset(), utime()
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112       The Base Definitions volume  of  POSIX.1‐2008,  Section  4.15,  Seconds
113       Since the Epoch, <time.h>
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116       Portions  of  this text are reprinted and reproduced in electronic form
117       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
118       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
119       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
120       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
121       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  In  the
122       event of any discrepancy between this version and the original IEEE and
123       The Open Group Standard, the original IEEE and The Open Group  Standard
124       is  the  referee document. The original Standard can be obtained online
125       at http://www.unix.org/online.html .
126
127       Any typographical or formatting errors that appear  in  this  page  are
128       most likely to have been introduced during the conversion of the source
129       files to man page format. To report such errors,  see  https://www.ker
130       nel.org/doc/man-pages/reporting_bugs.html .
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134IEEE/The Open Group                  2013                           MKTIME(3P)
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