diff options
Diffstat (limited to 'newctime.3')
| -rw-r--r-- | newctime.3 | 104 |
1 files changed, 65 insertions, 39 deletions
@@ -51,7 +51,9 @@ asctime, ctime, difftime, gmtime, localtime, mktime \- convert date and time .de q \\$3\*(lq\\$1\*(rq\\$2 .. -.I Ctime +The +.B ctime +function converts a long integer, pointed to by .IR clock , and returns a pointer to a @@ -86,45 +88,55 @@ and can therefore represent timestamps that predate the introduction of UTC and are some other flavor of Universal Time (UT). Some implementations support leap seconds, in contradiction to POSIX. .PP -.I Localtime +The +.B localtime and -.I gmtime +.B gmtime +functions return pointers to .q "tm" structures, described below. -.I Localtime +The +.B localtime +function corrects for the time zone and any time zone adjustments (such as Daylight Saving Time in the United States). After filling in the .q "tm" structure, -.I localtime +.B localtime sets the .BR tm_isdst 'th element of .B tzname to a pointer to a string that's the time zone abbreviation to be used with -.IR localtime 's +.BR localtime 's return value. .PP -.I Gmtime +The +.B gmtime +function converts to Coordinated Universal Time. .PP -.I Asctime +The +.B asctime +function converts a time value contained in a .q "tm" structure to a string, as shown in the above example, and returns a pointer to the string. .PP -.I Mktime +The +.B mktime +function converts the broken-down time, expressed as local time, in the structure pointed to by .I tm into a calendar time value with the same encoding as that of the values returned by the -.I time +.B time function. The original values of the .B tm_wday @@ -136,14 +148,14 @@ to their normal ranges. (A positive or zero value for .B tm_isdst causes -.I mktime +.B mktime to presume initially that daylight saving time respectively, is or is not in effect for the specified time. A negative value for .B tm_isdst causes the -.I mktime +.B mktime function to attempt to divine whether daylight saving time is in effect for the specified time; in this case it does not use a consistent rule and may give a different answer when later @@ -161,29 +173,37 @@ is not set until and .B tm_year are determined. -.I Mktime +The +.B mktime +function returns the specified calendar time; If the calendar time cannot be represented, it returns \-1. .PP -.I Difftime +The +.B difftime +function returns the difference between two calendar times, .RI ( time1 \- .IR time0 ), expressed in seconds. .PP -.IR Ctime_r , -.IR localtime_r , -.IR gmtime_r , +The +.BR ctime_r , +.BR localtime_r , +.BR gmtime_r , and -.I asctime_r +.B asctime_r +functions are like their unsuffixed counterparts, except that they accept an additional argument specifying where to store the result if successful. .PP -.IR Localtime_rz +The +.B localtime_rz and -.I mktime_z +.B mktime_z +functions are like their unsuffixed counterparts, except that they accept an extra initial .B zone @@ -193,9 +213,9 @@ If is null, UT is used; otherwise, .B zone should be have been allocated by -.I tzalloc +.B tzalloc and should not be freed until after all uses (e.g., by calls to -.IR strftime ) +.BR strftime ) of the filled-in .B tm_zone fields. @@ -227,21 +247,25 @@ includes the following fields: .fi .RE .PP -.I Tm_isdst +The +.B tm_isdst +field is non-zero if daylight saving time is in effect. .PP -.I Tm_gmtoff +The +.B tm_gmtoff +field is the offset (in seconds) of the time represented from UT, with positive values indicating east of the Prime Meridian. The field's name is derived from Greenwich Mean Time, a precursor of UT. .PP In -.B struct tm +.B "struct tm" the -.I tm_zone +.B tm_zone and -.I tm_gmtoff +.B tm_gmtoff fields exist, and are filled in, only if arrangements to do so were made when the library containing these functions was created. @@ -273,11 +297,11 @@ time(2), tzfile(5) .SH NOTES The return values of -.IR asctime , -.IR ctime , -.IR gmtime , +.BR asctime , +.BR ctime , +.BR gmtime , and -.I localtime +.B localtime point to static data overwritten by each call. The @@ -288,19 +312,21 @@ field of a returned .B "struct tm" both point to an array of characters that can be freed or overwritten by later calls to the functions -.IR localtime , -.IR tzfree , +.BR localtime , +.BR tzfree , and -.IR tzset , +.BR tzset , if these functions affect the timezone information that specifies the abbreviation in question. The remaining functions and data are thread-safe. .PP -.IR Asctime , -.IR asctime_r , -.IR ctime , +The +.BR asctime , +.BR asctime_r , +.BR ctime , and -.I ctime_r +.B ctime_r +functions behave strangely for years before 1000 or after 9999. The 1989 and 1999 editions of the C Standard say that years from \-99 through 999 are converted without @@ -311,7 +337,7 @@ is undefined if the year is before 1000 or after 9999. Traditional implementations of these two functions are restricted to years in the range 1900 through 2099. To avoid this portability mess, new programs should use -.I strftime +.B strftime instead. .\" This file is in the public domain, so clarified as of .\" 2009-05-17 by Arthur David Olson. |