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