version 1 showing authors affecting page license.
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CTIME |
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!!!CTIME |
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NAME |
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SYNOPSIS |
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DESCRIPTION |
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CONFORMING TO |
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SEE ALSO |
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---- |
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!!NAME |
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asctime, ctime, gmtime, localtime, mktime - transform binary date and time to ASCII |
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!!SYNOPSIS |
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__#include |
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__''timeptr''__); |
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char *ctime(const time_t *__''timep''__); |
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struct tm *gmtime(const time_t *__''timep''__); |
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struct tm *localtime(const time_t *__''timep''__); |
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time_t mktime(struct tm *__''timeptr''__); |
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extern char *__''tzname''__[[2]; |
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long int__ ''timezone''__; |
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extern int__ ''daylight''__; |
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__ |
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!!DESCRIPTION |
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The __ctime()__, __gmtime()__ and __localtime()__ |
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functions all take an argument of data type ''time_t'' |
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which represents calendar time. When interpreted as an |
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absolute time value, it represents the number of seconds |
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elapsed since 00:00:00 on January 1, 1970, Coordinated |
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Universal Time (UTC). |
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The __asctime()__ and __mktime()__ functions both take |
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an argument representing broken-down time which is a binary |
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representation separated into year, month, day, etc. |
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Broken-down time is stored in the structure ''tm'' which |
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is defined in '''' as follows: |
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struct tm |
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{ |
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int tm_sec; /* seconds */ |
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int tm_min; /* minutes */ |
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int tm_hour; /* hours */ |
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int tm_mday; /* day of the month */ |
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int tm_mon; /* month */ |
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int tm_year; /* year */ |
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int tm_wday; /* day of the week */ |
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int tm_yday; /* day in the year */ |
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int tm_isdst; /* daylight saving time */ |
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}; |
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The members of the ''tm'' structure are: |
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''tm_sec'' |
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The number of seconds after the minute, normally in the |
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range 0 to 59, but can be up to 61 to allow for leap |
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seconds. |
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''tm_min'' |
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The number of minutes after the hour, in the range 0 to |
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59. |
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''tm_hour'' |
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The number of hours past midnight, in the range 0 to |
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23. |
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''tm_mday'' |
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The day of the month, in the range 1 to 31. |
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''tm_mon'' |
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The number of months since January, in the range 0 to |
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11. |
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''tm_year'' |
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The number of years since 1900. |
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''tm_wday'' |
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The number of days since Sunday, in the range 0 to |
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6. |
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''tm_yday'' |
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The number of days since January 1, in the range 0 to |
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365. |
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''tm_isdst'' |
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A flag that indicates whether daylight saving time is in |
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effect at the time described. The value is positive if |
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daylight saving time is in effect, zero if it is not, and |
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negative if the information is not available. |
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The __ctime()__ function converts the calendar time |
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''timep'' into a string of the form |
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The abbreviations for the days of the week are `Sun', `Mon', |
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`Tue', `Wed', `Thu', `Fri', and `Sat'. The abbreviations for |
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the months are `Jan', `Feb', `Mar', `Apr', `May', `Jun', |
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`Jul', `Aug', `Sep', `Oct', `Nov', and `Dec'. The return |
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value points to a statically allocated string which might be |
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overwritten by subsequent calls to any of the date and time |
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functions. The function also sets the external variable |
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''tzname'' with information about the current time |
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zone. |
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The __gmtime()__ function converts the calendar time |
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''timep'' to broken-down time representation, expressed |
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in Coordinated Universal Time (UTC). |
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The __localtime()__ function converts the calendar time |
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''timep'' to broken-time representation, expressed |
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relative to the user's specified time zone. The function |
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sets the external variables ''tzname'' with information |
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about the current time zone, ''timezone'' with the |
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difference between Coordinated Universal Time (UTC) and |
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local standard time in seconds, and ''daylight'' to a |
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non-zero value if standard US daylight savings time rules |
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apply. |
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The __asctime()__ function converts the broken-down time |
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value ''timeptr'' into a string with the same format as |
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__ctime()__. The return value points to a statically |
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allocated string which might be overwritten by subsequent |
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calls to any of the date and time functions. |
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The __mktime()__ function converts a broken-down time |
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structure, expressed as local time, to calendar time |
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representation. The function ignores the specified contents |
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of the structure members ''tm_wday'' and ''tm_yday'' |
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and recomputes them from the other information in the |
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broken-down time structure. If structure members are outside |
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their legal interval, they will be normalized (so that, |
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e.g., 40 October is changed into 9 November). Calling |
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__mktime()__ also sets the external variable |
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''tzname'' with information about the current time zone. |
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If the specified broken-down time cannot be represented as |
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calendar time (seconds since the epoch), __mktime()__ |
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returns a value of (time_t)(-1) and does not alter the |
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''tm_wday'' and ''tm_yday'' members of the broken-down |
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time structure. |
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!!CONFORMING TO |
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SVID 3, POSIX, BSD 4.3, ISO 9899 |
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!!SEE ALSO |
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date(1), gettimeofday(2), time(2), |
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tzset(3), difftime(3), |
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strftime(3). |
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---- |