289 lines
7.9 KiB
Plaintext
289 lines
7.9 KiB
Plaintext
.TH TMDATE 2
|
|
.SH NAME
|
|
tmnow, tzload, tmtime, tmparse, tmfmt, tmnorm - convert date and time
|
|
.SH SYNOPSIS
|
|
.B #include <u.h>
|
|
.br
|
|
.B #include <libc.h>
|
|
.PP
|
|
.ft L
|
|
.nf
|
|
.EX
|
|
typedef struct Tm Tm;
|
|
typedef struct Tmfmt Tmfmt;
|
|
typedef struct Tzone Tzone;
|
|
|
|
struct Tm {
|
|
int nsec; /* nanoseconds (range 0..1e9) */
|
|
int sec; /* seconds (range 0..59) */
|
|
int min; /* minutes (0..59) */
|
|
int hour; /* hours (0..23) */
|
|
int mday; /* day of the month (1..31) */
|
|
int mon; /* month of the year (0..11) */
|
|
int year; /* C.E year - 1900 */
|
|
int wday; /* day of week (0..6, Sunday = 0) */
|
|
int yday; /* day of year (0..365) */
|
|
char zone[]; /* time zone name */
|
|
int tzoff; /* time zone delta from GMT, seconds */
|
|
Tzone *tz; /* the time zone (optional) */
|
|
};
|
|
|
|
Tzone *tzload(char *name);
|
|
Tm *tmnow(Tm *tm, Tzone *tz);
|
|
Tm *tmtime(Tm *tm, vlong abs, Tzone *tz);
|
|
Tm *tmtimens(Tm *tm, vlong abs, int ns, Tzone *tz);
|
|
Tm *tmparse(Tm *dst, char *fmt, char *tm, Tzone *zone, char **ep);
|
|
vlong tmnorm(Tm *tm);
|
|
Tmfmt tmfmt(Tm *tm, char *fmt);
|
|
void tmfmtinstall(void);
|
|
.EE
|
|
.SH DESCRIPTION
|
|
.PP
|
|
This family of functions handles simple date and time manipulation.
|
|
.PP
|
|
Time zones are loaded by name.
|
|
They can be specified as the abbreviated timezone name,
|
|
the full timezone name, the path to a timezone file,
|
|
or an absolute offset in the HHMM form.
|
|
.PP
|
|
When given as a timezone, any instant-dependent adjustments such as leap
|
|
seconds and daylight savings time will be applied to the derived fields of
|
|
struct Tm, but will not affect the absolute time.
|
|
The time zone name local always refers to the time in /env/timezone.
|
|
The nil timezone always refers to GMT.
|
|
.PP
|
|
Tzload loads a timezone by name. The returned timezone is
|
|
cached for the lifetime of the program, and should not be freed.
|
|
Loading a timezone repeatedly by name loads from the cache, and
|
|
does not leak.
|
|
.PP
|
|
Tmnow gets the current time of day in the requested time zone.
|
|
.PP
|
|
Tmtime converts the second resolution timestamp 'abs'
|
|
into a Tm struct in the requested timezone.
|
|
Tmtimens does the same, but with a nanosecond accuracy.
|
|
.PP
|
|
Tmtimens is identical to tmtime, but accepts a nanosecond argument.
|
|
.PP
|
|
Tmparse parses a time from a string according to the format argument.
|
|
Leading whitespace is ignored.
|
|
The point at which the parsing stopped is returned in
|
|
.IR ep .
|
|
If
|
|
.I ep
|
|
is nil, trailing garbage is ignored.
|
|
The result is returned in the timezone requested.
|
|
If there is a timezone in the date, and a timezone is provided
|
|
when parsing, then the zone is shifted to the provided timezone.
|
|
Parsing is case-insensitive
|
|
.PP
|
|
The format argument contains zero or more of the following components:
|
|
.TP
|
|
.B Y, YY, YYYY
|
|
Represents the year.
|
|
.I YY
|
|
prints the year in 2 digit form.
|
|
.TP
|
|
.B M, MM, MMM, MMMM
|
|
The month of the year, in unpadded numeric, padded numeric, short name, or long name,
|
|
respectively.
|
|
.TP
|
|
.B D, DD
|
|
The day of month in unpadded or padded numeric form, respectively.
|
|
.TP
|
|
.B W, WW, WWW
|
|
The day of week in numeric, short or long name form, respectively.
|
|
.TP
|
|
.B h, hh
|
|
The hour in unpadded or padded form, respectively
|
|
.TP
|
|
.B m, mm
|
|
The minute in unpadded or padded form, respectively
|
|
.TP
|
|
.B s, ss
|
|
The second in unpadded or padded form, respectively
|
|
.TP
|
|
.B t, tt, ttt
|
|
The milliseconds in unpadded and padded form, respectively.
|
|
.B u, uu, uuu, uuuu
|
|
The microseconds in unpadded. padded form modulo milliseconds,
|
|
or unpadded, padded forms of the complete value, respectively.
|
|
.B n, nn, nnn, nnnn, nnnnn, nnnnnn
|
|
The nanoseconds in unpadded and padded form modulo milliseconds,
|
|
the unpadded and padded form modulo microseconds,
|
|
and the unpadded and padded complete value, respectively.
|
|
.TP
|
|
.B Z, ZZ, ZZZ
|
|
The timezone in [+-]HHMM and [+-]HH:MM, and named form, respectively.
|
|
If the named timezone matches the name of the local zone, then the
|
|
local timezone will be used.
|
|
Otherwise, we will attempt to use the named zones listed in RFC5322.
|
|
.TP
|
|
.B a, A
|
|
Lower and uppercase 'am' and 'pm' specifiers, respectively.
|
|
.TP
|
|
.B [...]
|
|
Quoted text, copied directly to the output.
|
|
.TP
|
|
.B _
|
|
When formatting, this inserts padding into the date format.
|
|
The padded width of a field is the sum of format and specifier
|
|
characters combined. When
|
|
For example,
|
|
.I __h
|
|
will format to a width of 3. When parsing, this acts as whitespace.
|
|
.TP
|
|
.B ?
|
|
When parsing, all formats of the following argument are tried from most to least specific.
|
|
For example,
|
|
.I ?M
|
|
will match
|
|
.IR January ,
|
|
.IR Jan ,
|
|
.IR 01 ,
|
|
and
|
|
.IR 1 ,
|
|
in that order. When formatting,
|
|
.B ?
|
|
is ignored.
|
|
.TP
|
|
.B ~
|
|
When parsing a date, this slackens range enforcement, accepting
|
|
out of range values such as January
|
|
.IR 32 ,
|
|
which would get normalized to February 1st.
|
|
.PP
|
|
Any characters not specified above are copied directly to output,
|
|
without modification.
|
|
|
|
.PP
|
|
Tmfmt produces a format description structure suitable for passing
|
|
to
|
|
.IR fmtprint (2) .
|
|
If fmt is nil, we default to the format used in
|
|
.IR ctime (2).
|
|
The format of the format string is identical to
|
|
.IR tmparse.
|
|
|
|
.PP
|
|
When parsing, any amount of whitespace is treated as a single token.
|
|
All string matches are case insensitive, and zero padding is optional.
|
|
|
|
.PP
|
|
Tmnorm takes a manually adjusted Tm structure, and normalizes it,
|
|
returning the absolute timestamp that the date represents.
|
|
Normalizing recomputes the
|
|
.I year, mon, mday, hr, min, sec
|
|
and
|
|
.I tzoff
|
|
fields.
|
|
If
|
|
.I tz
|
|
is non-nil, then
|
|
.I tzoff
|
|
will be recomputed, taking into account daylight savings
|
|
for the absolute time.
|
|
The values not used in the computation are recomputed for
|
|
the resulting absolute time.
|
|
All out of range values are wrapped.
|
|
For example, December 32 will roll over to Jan 1 of the
|
|
following year.
|
|
.PP
|
|
Tmfmtinstall installs a time format specifier %τ. The time
|
|
format behaves as in tmfmt
|
|
|
|
.SH EXAMPLES
|
|
.PP
|
|
All examples assume tmfmtinstall has been called.
|
|
.PP
|
|
Get the current date in the local timezone, UTC, and
|
|
US_Pacific time. Print it using the default format.
|
|
|
|
.IP
|
|
.EX
|
|
Tm t;
|
|
Tzone *zl, *zp;
|
|
if((zl = tzload("local") == nil)
|
|
sysfatal("load zone: %r");
|
|
if((zp = tzload("US_Pacific") == nil)
|
|
sysfatal("load zone: %r");
|
|
print("local: %τ\\n", tmfmt(tmnow(&t, zl), nil));
|
|
print("gmt: %τ\\n", tmfmt(tmnow(&t, nil), nil));
|
|
print("eastern: %τ\\n", tmfmt(tmnow(&t, zp), nil));
|
|
.EE
|
|
.PP
|
|
Compare if two times are the same, regardless of timezone.
|
|
Done with full, strict error checking.
|
|
|
|
.IP
|
|
.EX
|
|
#define Fmt "?WWW, ?MM ?DD hh:mm:ss ?Z YYYY"
|
|
Tm a, b;
|
|
char *e, *est, *pst;
|
|
|
|
pst = "Tue Dec 10 12:36:00 PST 2019";
|
|
est = "Tue Dec 10 15:36:00 EST 2019";
|
|
f(tmparse(&a, Fmt, pst, nil, &e) == nil)
|
|
sysfatal("failed to parse: %r");
|
|
if(*e != '\\0')
|
|
sysfatal("trailing junk %s", e);
|
|
if(tmparse(&b, Fmt, est, nil, &e) == nil)
|
|
sysfatal("failed to parse: %r");
|
|
if(*e != '\\0')
|
|
sysfatal("trailing junk %s", e);
|
|
if(tmnorm(a) == tmnorm(b) && a.nsec == b.nsec)
|
|
print("same\\n");
|
|
else
|
|
print("different\\n");
|
|
.EE
|
|
|
|
.PP
|
|
Convert from one timezone to another.
|
|
|
|
.IP
|
|
.EX
|
|
Tm here, there;
|
|
Tzone *zl, *zp;
|
|
if((zl = tzload("local")) == nil)
|
|
sysfatal("load zone: %r");
|
|
if((zp = tzload("US_Pacific")) == nil)
|
|
sysfatal("load zone: %r");
|
|
if(tmnow(&here, zl) == nil)
|
|
sysfatal("get time: %r");
|
|
if(tmtime(&there, tmnorm(&here), zp) == nil)
|
|
sysfatal("shift time: %r");
|
|
.EE
|
|
|
|
.PP
|
|
Add a day. Because cross daylight savings, only 23 hours are added.
|
|
|
|
.IP
|
|
.EX
|
|
Tm t;
|
|
char *date = "Sun Nov 2 13:11:11 PST 2019";
|
|
if(tmparse(&t, "W MMM D hh:mm:ss z YYYY, date, nil) == nil)
|
|
print("failed to parse");
|
|
t.day++;
|
|
tmnorm(&t);
|
|
print("%τ", tmfmt(&t, nil)); /* Mon Nov 3 13:11:11 PST 2019 */
|
|
.EE
|
|
|
|
.SH BUGS
|
|
.PP
|
|
Checking the timezone name against the local timezone is a
|
|
dirty hack. The same date string may parse differently for
|
|
people in different timezones.
|
|
.PP
|
|
Tmparse and ctime don't mix.
|
|
Tmparse preserves timezone names, including names like '+0200'.
|
|
Ctime expects timezone names to be exactly three characters.
|
|
Use the
|
|
.I %τ
|
|
format character instead of ctime.
|
|
.PP
|
|
The timezone information that we ship is out of date.
|
|
.PP
|
|
The Plan 9 timezone format has no way to express leap seconds.
|
|
.PP
|
|
We provide no way to manipulate timezones.
|