 @@ -1,321 +1,332 @@
-.\"	$NetBSD: ctime.3,v 1.32 2010/05/15 13:54:52 pgoyette Exp $
+.\"	$NetBSD: ctime.3,v 1.33 2010/10/27 19:16:04 christos Exp $
-.Dd February 2, 2010
+.Dd October 27, 2010
 .Dt CTIME 3
 .Os
 .Sh NAME
 .Nm asctime ,
 .Nm asctime_r ,
 .Nm ctime ,
 .Nm ctime_r ,
 .Nm difftime ,
 .Nm gmtime ,
 .Nm gmtime_r ,
 .Nm localtime ,
 .Nm localtime_r ,
 .Nm mktime
 .Nd convert date and time to ASCII
 .Sh LIBRARY
 .Lb libc
 .Sh SYNOPSIS
 .In time.h
 .Dv extern char *tzname[2];
 .Ft char *
 .Fn ctime "const time_t *clock"
 .Ft char *
 .Fn ctime_r "const time_t *clock"  "char *buf"
 .Ft double
 .Fn difftime "time_t time1" "time_t time0"
 .Ft char *
 .Fn asctime "const struct tm *tm"
 .Ft char *
 .Fn asctime_r "const struct tm restrict tm" "char * restrict buf"
 .Ft struct tm *
 .Fn localtime "const time_t *clock"
 .Ft struct tm *
 .Fn localtime_r "const time_t * restrict clock" "struct tm * restrict result"
 .Ft struct tm *
 .Fn gmtime "const time_t *clock"
 .Ft struct tm *
 .Fn gmtime_r "const time_t * restrict clock" "struct tm * restrict result"
 .Ft time_t
 .Fn mktime "struct tm *tm"
 .Sh DESCRIPTION
 .Fn ctime
-converts a long integer, pointed to by
+converts a
 .Tp time_t ,
 pointed to by
 .Fa clock ,
 representing the time in seconds since
 :00:00 UTC, 1970-01-01,
 and returns a pointer to a
 string of the form
 .D1 Thu Nov 24 18:22:48 1986\en\e0
 Years requiring fewer than four characters are padded with leading zeroes.
 For years longer than four characters, the string is of the form
 .D1 Thu Nov 24 18:22:48     81986\en\e0
 with five spaces before the year.
 These unusual formats are designed to make it less likely that older
 software that expects exactly 26 bytes of output will mistakenly output
 misleading values for out-of-range years.
 .Pp
-.Fn Localtime
+.Fn ctime_r
 is similar to
 .Fn ctime ,
 except it places the result of the convertion on the
 .Fa buf
 argument which should be 26 or more bytes long, instead of using a global
 static buffer.
 .Pp
 .Fn localtime
 and
 .Fn gmtime
 return pointers to
 .Va tm
 structures, described below.
 .Fn localtime
 corrects for the time zone and any time zone adjustments
 (such as Daylight Saving Time in the U.S.A.).
 After filling in the
 .Va tm
 structure,
 .Fn localtime
 sets the
 .Fa tm_isdst Ns 'th
 element of
 .Fa tzname
 to a pointer to an
 ASCII string that's the time zone abbreviation to be used with
 .Fn localtime Ns 's
 return value.
 .Pp
 .Fn gmtime
 converts to Coordinated Universal Time.
 .Pp
 The
 .Fn gmtime_r
 and
 .Fn localtime_r
 functions provide the same functionality as
 .Fn gmtime
 and
 .Fn localtime
 differing in that the caller must supply a buffer area
 .Fa result
 in which the result is stored; also,
 .Fn localtime_r
 does not imply initialization of the local time conversion information;
 the application may need to do so by calling
 .Xr tzset 3 .
 .Pp
 .Fn asctime
 converts a time value contained in a
-``tm'' structure to a string,
+.Dq tm
 structure to a string,
 as shown in the above example,
 and returns a pointer to the string.
 .Pp
 .Fn mktime
 converts the broken-down time,
 expressed as local time,
 in the structure pointed to by
 .Fa tm
 into a calendar time value with the same encoding as that of the values
 returned by the
 .Xr time 3
 function.
 The original values of the
 .Fa tm_wday
 and
 .Fa 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
 .Fa tm_isdst
 causes
 .Fn mktime
 to presume initially that summer time (for example, Daylight Saving Time
 in the U.S.A.) respectively,
 is or is not in effect for the specified time.
 A negative value for
 .Fa tm_isdst
 causes the
 .Fn mktime
 function to attempt to divine whether summer 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
 presented with the same argument.)
 On successful completion, the values of the
 .Fa tm_wday
 and
 .Fa tm_yday
 components of the structure are set appropriately,
 and the other components are set to represent the specified calendar time,
 but with their values forced to their normal ranges; the final value of
 .Fa tm_mday
 is not set until
 .Fa tm_mon
 and
 .Fa tm_year
 are determined.
 .Fn mktime
 returns the specified calendar time; if the calendar time cannot be
 represented, it returns
 .Va "(time_t)-1" .
 .Pp
 .Fn difftime
 returns the difference between two calendar times,
 .Fa ( time1 No - Fa time0 ) ,
 expressed in seconds.
 .Pp
 The structure (of type)
 .Va "struct tm"
 includes the following fields:
 .Bd -literal -offset indent
 int tm_sec;	/* seconds after the minute [0,61] */
 int tm_min;	/* minutes after the hour [0,59] */
 int tm_hour;	/* hours since midnight [0,23] */
 int tm_mday;	/* day of the month [1,31] */
 int tm_mon;	/* months since January [0,11] */
 int tm_year;	/* years since 1900 */
 int tm_wday;	/* day of week [0,6] (Sunday = 0) */
 int tm_yday;	/* day of year [0,365] (Jan 1 = 0) */
 int tm_isdst;	/* daylight savings flag */
 long tm_gmtoff;	/* offset from UTC in seconds */
 char *tm_zone;	/* abbreviation of timezone name */
 .Ed
 .Pp
 The
 .Fa tm_zone
 and
 .Fa tm_gmtoff
 fields exist, and are filled in, only if arrangements to do
 so were made when the library containing these functions was
 created.
 There is no guarantee that these fields will continue to exist
 in this form in future releases of this code.
 .Pp
 .Fa tm_isdst
 is non-zero if summer time is in effect.
 .Pp
 .Fa tm_gmtoff
 is the offset (in seconds) of the time represented
 from UTC, with positive values indicating east
 of the Prime Meridian.
 .Sh RETURN VALUES
 On success the
 .Fn asctime
 and
 .Fn ctime
 functions return a pointer to a static character buffer, and the
 .Fn asctime_r
 and
 .Fn ctime_r
 function return a pointer to the user-supplied buffer.
 On failure they all return
 .Dv NULL
 and no errors are defined for them.
 On success the
 .Fn gmtime ,
 and
 .Fn localtime
 functions return a pointer to a statically allocated
 .Va "struct tm"
 whereas the
 .Fn gmtime_r
 and
 .Fn localtime_r
 functions return a pointer to the user-supplied
 .Va "struct tm" .
 On failure they all return
 .Dv NULL
 and the global variable
 .Va errno
 is set to indicate the error.
 The
 .Fn mktime
 function returns the specified time since the Epoch as a
 .Va time_t
 type value.
 If the time cannot be represented, then
 .Fn mktime
 returns
 .Va "(time_t)-1"
 setting the global variable
 .Va errno
 to indicate the error.
 .Sh FILES
 .Bl -tag -width /usr/share/zoneinfo/posixrules -compact
 .It Pa /etc/localtime
 local time zone file
 .It Pa /usr/share/zoneinfo
 time zone information directory
 .It Pa /usr/share/zoneinfo/posixrules
 used with POSIX-style TZ's
 .It Pa /usr/share/zoneinfo/GMT
 for UTC leap seconds
 .El
 .Pp
 If
 .Pa /usr/share/zoneinfo/GMT
 is absent, UTC leap seconds are loaded from
 .Pa /usr/share/zoneinfo/posixrules .
 .Sh ERRORS
 The
 .Fn gmtime_r ,
 .Fn localtime_r ,
 .Fn gmtime ,
 .Fn localtime ,
 and
 .Fn mktime
 will fail when:
 .Bl -tag -width Er
 .It Bq Er EOVERFLOW
 The result cannot be represented.
 .El
 .Sh SEE ALSO
 .Xr getenv 3 ,
 .Xr strftime 3 ,
 .Xr time 3 ,
 .Xr tzset 3 ,
 .Xr tzfile 5
 .Sh STANDARDS
 The
 .Fn ctime ,
 .Fn difftime ,
 .Fn asctime ,
 .Fn localtime ,
 .Fn gmtime
 and
 .Fn mktime
 functions conform to
 .St -ansiC
 The
 .Fn ctime_r ,
 .Fn asctime_r ,
 .Fn localtime_r
 and
 .Fn gmtime_r
 functions conform to
 .St -p1003.1c-95 .
 .Sh NOTES
 The return values point to static data; the data is overwritten by
 each call.
 The
 .Fa tm_zone
 field of a returned
 .Va "struct tm"
 points to a static array of characters, which
 will also be overwritten at the next call
 (and by calls to
 .Xr tzset 3 ) .
 .Pp
 .Fn asctime
 and
 .Fn ctime
 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
 extra spaces, but this conflicts with longstanding
 tradition and with this implementation.
 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
 .Fn strftime
 instead.
 .Pp
 Avoid using out-of-range values with
 .Fn mktime
 when setting up lunch with promptness sticklers in Riyadh.
 .\" @(#)newctime.3	8.3
 .\" This file is in the public domain, so clarified as of
 .\" 2009-05-17 by Arthur David Olson.