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Diffstat (limited to 'newtzset.3')
| -rw-r--r-- | newtzset.3 | 227 |
1 files changed, 169 insertions, 58 deletions
diff --git a/newtzset.3 b/newtzset.3 index 07c5e0c605a7..8aaa0ff41732 100644 --- a/newtzset.3 +++ b/newtzset.3 @@ -3,33 +3,89 @@ tzset \- initialize time conversion information .SH SYNOPSIS .nf -.B void tzset() +.ie \n(.g .ds - \f(CW-\fP +.el .ds - \- +.B #include <time.h> .PP -.B cc ... -ltz +.B timezone_t tzalloc(char const *TZ); +.PP +.B void tzfree(timezone_t tz); +.PP +.B void tzset(void); +.PP +.B cc ... \*-ltz .fi .SH DESCRIPTION -.I Tzset -uses the value of the environment variable +.ie '\(en'' .ds en \- +.el .ds en \(en +.ie '\(lq'' .ds lq \&"\" +.el .ds lq \(lq\" +.ie '\(rq'' .ds rq \&"\" +.el .ds rq \(rq\" +.de q +\\$3\*(lq\\$1\*(rq\\$2 +.. +The +.B tzalloc +function +allocates and returns a timezone object described by +.BR TZ . +If .B TZ -to set time conversion information used by -.IR localtime . +is not a valid timezone description, or if the object cannot be allocated, +.B tzalloc +returns a null pointer and sets +.BR errno . +.PP +The +.B tzfree +function +frees a timezone object +.BR tz , +which should have been successfully allocated by +.BR tzalloc . +This invalidates any +.B tm_zone +pointers that +.B tz +was used to set. +.PP +The +.B tzset +function +acts like +.BR tzalloc(getenv("TZ")) , +except it saves any resulting timezone object into internal +storage that is accessed by +.BR localtime , +.BR localtime_r , +and +.BR mktime . +The anonymous shared timezone object is freed by the next call to +.BR tzset . +If the implied call to +.B tzalloc +fails, +.B tzset +falls back on Universal Time (UT). +.PP If .B TZ -does not appear in the environment, -the best available approximation to local wall clock time, as specified -by the -.IR tzfile (5)-format +is null, the best available approximation to local (wall +clock) time, as specified by the +.BR tzfile (5)-format file .B localtime -in the system time conversion information directory, is used by -.IR localtime . +in the system time conversion information directory, is used. If .B TZ -appears in the environment but its value is a null string, -Coordinated Universal Time (UTC) is used (without leap second -correction). If +is the empty string, +UT is used, with the abbreviation "UTC" +and without leap second correction; please see +.BR newctime (3) +for more about UT, UTC, and leap seconds. If .B TZ -appears in the environment and its value is not a null string: +is nonnull and nonempty: .IP if the value begins with a colon, it is used as a pathname of a file from which to read the time conversion information; @@ -46,7 +102,7 @@ it is used as an absolute pathname; otherwise, it is used as a pathname relative to a system time conversion information directory. The file must be in the format specified in -.IR tzfile (5). +.BR tzfile (5). .PP When .B TZ @@ -61,23 +117,31 @@ Where: .IR std " and " dst Three or more bytes that are the designation for the standard .RI ( std ) -or summer -.RI ( dst ) +or the alternative +.RI ( dst , +such as daylight saving time) time zone. Only .I std is required; if .I dst -is missing, then summer time does not apply in this locale. +is missing, then daylight saving time does not apply in this locale. Upper- and lowercase letters are explicitly allowed. Any characters except a leading colon .RB ( : ), digits, comma .RB ( , ), -minus -.RB ( \(mi ), -plus -.RB ( \(pl ), -and ASCII NUL are allowed. +ASCII minus +.RB ( \*- ), +ASCII plus +.RB ( + ), +and NUL bytes are allowed. +Alternatively, a designation can be surrounded by angle brackets +.B < +and +.BR > ; +in this case, the designation can contain any characters other than +.B > +and NUL. .TP .I offset Indicates the value one must add to the local time to arrive at @@ -103,17 +167,17 @@ is required. If no .I offset follows .IR dst , -summer time is assumed to be one hour ahead of standard time. One or +daylight saving time is assumed to be one hour ahead of standard time. One or more digits may be used; the value is always interpreted as a decimal number. The hour must be between zero and 24, and the minutes (and -seconds) \(em if present \(em between zero and 59. If preceded by a -.RB `` \(mi '', +seconds) \*(en if present \*(en between zero and 59. If preceded by a +.q "\*-" , the time zone shall be east of the Prime Meridian; otherwise it shall be west (which may be indicated by an optional preceding -.RB `` \(pl ''). +.q "+" . .TP .I rule -Indicates when to change to and back from summer time. The +Indicates when to change to and back from daylight saving time. The .I rule has the form: .RS @@ -123,13 +187,17 @@ has the form: .IP where the first .I date -describes when the change from standard to summer time occurs and the +describes when the change from standard to daylight saving time occurs and the second .I date describes when the change back happens. Each .I time field describes when, in current local time, the change to the other time is made. +As an extension to POSIX, daylight saving is assumed to be in effect +all year if it begins January 1 at 00:00 and ends December 31 at +24:00 plus the difference between daylight saving and standard time, +leaving no room for standard time in the calendar. .IP The format of .I date @@ -140,8 +208,8 @@ is one of the following: The Julian day .I n .RI "(1\ \(<=" "\ n\ " "\(<=\ 365). -Leap days are not counted; that is, in all years \(em including leap -years \(em February 28 is day 59 and March 1 is day 60. It is +Leap days are not counted; that is, in all years \*(en including leap +years \*(en February 28 is day 59 and March 1 is day 60. It is impossible to explicitly refer to the occasional February 29. .TP .I n @@ -161,10 +229,8 @@ of month of the year .RI "(1\ \(<=" "\ n\ " "\(<=\ 5, .RI "1\ \(<=" "\ m\ " "\(<=\ 12, -where week 5 means ``the last -.I d -day in month -.IR m '' +where week 5 means +.q "the last \fId\fP day in month \fIm\fP" which may occur in either the fourth or the fifth week). Week 1 is the first week in which the .IR d' th @@ -175,27 +241,80 @@ The .I time has the same format as .I offset -except that no leading sign -.RB (`` \(mi '' +except that POSIX does not allow a leading sign (\c +.q "\*-" or -.RB `` \(pl '') -is allowed. The default, if +.q "+" ). +As an extension to POSIX, the hours part of +.I time +can range from \-167 through 167; this allows for unusual rules such +as +.q "the Saturday before the first Sunday of March" . +The default, if .I time is not given, is .BR 02:00:00 . .RE .LP +Here are some examples of +.B TZ +values that directly specify the timezone; they use some of the +extensions to POSIX. +.TP +.B EST5 +stands for US Eastern Standard +Time (EST), 5 hours behind UT, without daylight saving. +.TP +.B <+12>\*-12<+13>,M11.1.0,M1.2.1/147 +stands for Fiji time, 12 hours ahead +of UT, springing forward on November's first Sunday at 02:00, and +falling back on January's second Monday at 147:00 (i.e., 03:00 on the +first Sunday on or after January 14). The abbreviations for standard +and daylight saving time are +.q "+12" +and +.q "+13". +.TP +.B IST\*-2IDT,M3.4.4/26,M10.5.0 +stands for Israel Standard Time (IST) and Israel Daylight Time (IDT), +2 hours ahead of UT, springing forward on March's fourth +Thursday at 26:00 (i.e., 02:00 on the first Friday on or after March +23), and falling back on October's last Sunday at 02:00. +.TP +.B <\*-04>4<\*-03>,J1/0,J365/25 +stands for permanent daylight saving time, 3 hours behind UT with +abbreviation +.q "\*-03". +There is a dummy fall-back transition on December 31 at 25:00 daylight +saving time (i.e., 24:00 standard time, equivalent to January 1 at +00:00 standard time), and a simultaneous spring-forward transition on +January 1 at 00:00 standard time, so daylight saving time is in effect +all year and the initial +.B <\*-04> +is a placeholder. +.TP +.B <\*-03>3<\*-02>,M3.5.0/\*-2,M10.5.0/\*-1 +stands for time in western Greenland, 3 hours behind UT, where clocks +follow the EU rules of +springing forward on March's last Sunday at 01:00 UT (\-02:00 local +time, i.e., 22:00 the previous day) and falling back on October's last +Sunday at 01:00 UT (\-01:00 local time, i.e., 23:00 the previous day). +The abbreviations for standard and daylight saving time are +.q "\*-03" +and +.q "\*-02". +.PP If no .I rule is present in .BR TZ , the rules specified by the -.IR tzfile (5)-format +.BR tzfile (5)-format file .B posixrules in the system time conversion information directory are used, with the -standard and summer time offsets from UTC replaced by those specified by +standard and daylight saving time offsets from UT replaced by those specified by the .I offset values in @@ -206,34 +325,26 @@ For compatibility with System V Release 3.1, a semicolon may be used to separate the .I rule from the rest of the specification. -.PP -If the -.B TZ -environment variable does not specify a -.IR tzfile (5)-format -and cannot be interpreted as a direct specification, -UTC is used. .SH FILES -.ta \w'/usr/local/etc/zoneinfo/posixrules\0\0'u -/usr/local/etc/zoneinfo time zone information directory +.ta \w'/usr/share/zoneinfo/posixrules\0\0'u +/usr/share/zoneinfo timezone information directory .br -/usr/local/etc/zoneinfo/localtime local time zone file +/usr/share/zoneinfo/localtime local timezone file .br -/usr/local/etc/zoneinfo/posixrules used with POSIX-style TZ's +/usr/share/zoneinfo/posixrules used with POSIX-style TZ's .br -/usr/local/etc/zoneinfo/GMT for UTC leap seconds +/usr/share/zoneinfo/GMT for UTC leap seconds .sp If -.B /usr/local/etc/zoneinfo/GMT +.B /usr/share/zoneinfo/GMT is absent, UTC leap seconds are loaded from -.BR /usr/local/etc/zoneinfo/posixrules . +.BR /usr/share/zoneinfo/posixrules . .SH SEE ALSO getenv(3), newctime(3), newstrftime(3), time(2), tzfile(5) -.\" @(#)newtzset.3 8.2 .\" This file is in the public domain, so clarified as of .\" 2009-05-17 by Arthur David Olson. |