NAME | SYNOPSIS | API RESTRICTIONS | DESCRIPTION | NOTES | ATTRIBUTES | SEE ALSO
$(OS_DIR)/lib/libc.a #include <time.h>struct tm * localtime(const time_t * clock);
The function or functions documented here may not be used safely in all application contexts with all APIs provided in the ChorusOS 5.0 product.
See API(5FEA) for details.
The ctime() , gmtime() and localtime() functions take as an argument a time value representing the time in seconds since the Epoch (00:00:00 UTC, January 1, 1970).
The localtime() function converts the time value pointed to by clock , and returns a pointer to a struct tm (described below) which contains the broken-out time information for the value, after adjusting for the current time zone (and any other factors such as Daylight Saving Time). Time zone adjustments are performed as specified by the TZ environment variable (see tzset (3STDC). The function localtime() uses tzset (3STDC) to initialize time conversion information if tzset (3STDC) has not already been called by the process.
The gmtime() function also converts the time value, but without any time zone adjustment, and returns a pointer to a tm structure (described below).
The ctime() function adjusts the time value for the current time zone in the same manner as localtime() , and returns a pointer to a 26-character string of the form: Thu Nov 24 18:22:48 1986.
The asctime() function converts the broken--down time in the structure tm pointed to by *tm to the form shown in the example above.
The mktime() function converts the broken-down time, expressed as local time, in the structure pointed to by tm into a time value with the same encoding as that of the values returned by the time (3STDC) function; that is, seconds from the Epoch, UTC .
The original values of the tm_wday and tm_yday components of the structure are ignored, and the original values of the other components are not restricted to their normal ranges. (A positive or zero value for tm_isdst causes mktime() to presume initially that summer time (for example, Daylight Saving Time) is or is not in effect for the time specified. A negative value for tm_isdst causes the mktime() function to attempt to define whether summer time is in effect for the time specified.)
On successful completion, the values of the tm_wday and tm_yday components of the structure are set appropriately, and the other components are set to represent the calendar time specified, but with their values forced to their normal ranges; the final value of tm_mday is not set until tm_mon and tm_year are determined. The mktime() function returns the calendar time specified; if the calendar time cannot be represented, it returns -1;
The difftime() function returns the difference between two calendar times, (time1 - time0), expressed in seconds.
External declarations as well as the tm structure definition are in the time.h include file. The tm structure includes at least the following fields:
int tm_sec; /* seconds (0 - 60) */ int tm_min; /* minutes (0 - 59) */ int tm_hour; /* hours (0 - 23) */ int tm_mday; /* day of month (1 - 31) */ int tm_mon; /* month of year (0 - 11) */ int tm_year; /* year - 1900 */ int tm_wday; /* day of week (Sunday = 0) */ int tm_yday; /* day of year (0 - 365) */ int tm_isdst; /* is summer time in effect? */ char *tm_zone; /* abbreviation of timezone name */ long tm_gmtoff; /* offset from UTC in seconds */ |
The field tm_isdst is non-zero if summer time is in effect.
The field tm_gmtoff is the offset (in seconds) of the time represented from UTC , with positive values indicating east of the Prime Meridian.
asctime (3STDC), ctime (3STDC), localtime (3STDC) and gmtime (3STDC) return their result in a global variable which make them difficult to use in a multithreaded program. gmtime (3STDC) , ctime_r (3STDC), localtime (3STDC) and gmtime_r (3STDC) should be used instead.
See attributes(5) for descriptions of the following attributes:
ATTRIBUTE TYPE | ATTRIBUTE VALUE |
---|---|
Interface Stability | Evolving |
asctime_r(3STDC) , ctime_r(3STDC) , getenv(3STDC) , gmtime_r(3STDC) , localtime_r(3STDC) , time(3STDC) , tzset(3STDC)
NAME | SYNOPSIS | API RESTRICTIONS | DESCRIPTION | NOTES | ATTRIBUTES | SEE ALSO