/usr/man2/cat.3/tm.3.Z
NAME
tm - seconds resolution time conversion support
SYNOPSIS
#include <tm.h>
DESCRIPTION
The tm library supports conversion between string date specifications,
seconds reolution time_t clock values and Tm_t. Tm_t contains the ele-
ments of struct tm along with these additions:
unsigned _ast_int4_t tm_nsec
The subsecond portion of the time in nanoseconds.
Tm_zone_t* tm_zone
The time zone name.
localtime() and gmtime() (see ctime(3)) are used to determine local
time zone and savings time information.
time_t values are the number of seconds since the epoch, Jan 1 00:00:00
GMT 1970, with leap seconds omitted.
The global variable int tm_info.flags contains flags that allow all
programs using the library to be controlled in a consistent manner.
tm_info.flags is initialized by the tminit() routine described below,
and may be explicitly reset after tminit() is called. The flags are:
TM_ADJUST
Set by tminit() if localtime() and gmtime() do not compensate
for leap seconds.
TM_LEAP
time_t values are interpreted as if they include leap seconds.
Set by tminit() if the leap option is set in the TM_OPTIONS
environment variable.
TM_UTC Times are relative to UTC (universal coordinated time, i.e.,
GMT.) Otherwise times are relative to the local time zone. Set
by tminit() if the time zone name matches one of tm_info.for-
mat[43] through tm_info.format[46] described below. If the time
zone name is not determined by localtime() then the environment
variables TZNAME (as described in BSD 4.3) and TZ (as described
in System V) are checked, in order. If this fails then the time
zone name is constructed using the local time zone offset.
The routines are:
time_t tmdate(const char* date, char** end, time_t* clock)
Parses the date specification date using the tm_info.format
string table (described below) and returns the equivalent time_t
value. If non-NULL, end is set to the position of the first
unrecognized character in date. clock is used to provide
default values for omitted components in date. If clock is NULL
then the current time is used.
Tm_t* tmfix(Tm_t* tp)
Corrects any out of bounds fields in tp and returns tp as its
value. The corrections start with tp->tm_sec and propagate down
to tp->tm_year. For example, if tp->tm_sec were 61 then it
would change to 1 and tp->tm_min would be incremented by 1, and
so on. tp->tm_isdst is not changed -- call tmtime() to deter-
mine its proper value after the tmfix() adjustments.
char* tmfmt(char* buf, size_t len, const char* format, time_t* clock)
Formats the date pointed to by clock into the buffer buf with
size len bytes according to the format specification format. If
format is NULL or empty then the string tm_info.format[40] is
used. If clock is NULL then the current time is used. A
pointer to the end of buf (i.e., the terminating '\0') is
returned.
format is in printf(3) style, where %field names a fixed size
field, zero padded if necessary, and \c and \nnn sequences are
as in C. Invalid %field specifications and all other characters
are copied without change. field may be preceded by %- to turn
off padding or %_ to pad with space, otherwise numeric fields
are padded with 0 and string fields are padded with space.
field may also be preceded by E for alternate era representation
or O for alternate digit representation (if supported by the
current locale.) Finally, an integral width preceding field
truncates the field to width characters. sequences are inter-
preted as in the C language. String field values are taken from
the tm_info.format string table. The fields are:
% % character.
a Abbreviated weekday name.
A Full weekday name.
b Abbreviated month name.
c ctime(3) style date without the trailing newline.
C date(1) style date.
d Day of month number.
D Date as mm/dd/yy.
e Blank padded day of month number.
E Unpadded day of month number.
f Locale default override date format.
F Locale default date format (tm_info.format[40].)
h Abbreviated month name.
H 24-hour clock hour.
i International date(1) date that includes the time zone
type name (tm_info.format[107].)
I 12-hour clock hour.
j 1-offset Julian date.
J 0-offset Julian date.
k date(1) style date (tm_info.format[106].)
K Language neutral, all numeric, no embedded space date
with larger to smaller time units from left to right,
suitable for sorting: '"%Y-%m-%d+%H:%M:%S"'.
l ls(1) -l date that lists recent dates with %g and distant
dates with %G.
m Month number.
M Minutes.
n newline character.
N The time zone type or nation code.
p Meridian (e.g., AM or PM.)
q The nanosecond part of the time.
%Q<delim>recent<delim>distant<delim>
Recent dates are formatted with recent and distand dates
are formatted with distant, where <delim> is any charac-
ter not appearing in recent or distant.
r 12-hour time as hh:mm:ss meridian.
R 24-hour time as hh:mm.
s Seconds since the epoch. .prec preceding s appends prec
nanosecond digits, 9 if prec is omitted.
S seconds.subseconds since the epoch.
t tab character.
T 24-hour time as hh:mm:ss.
u Weeday number with 1 for Monday, 7 for Sunday.
U Week number with Sunday as the first day.
V ISO week number (i18n is fun.)
w Weekday number with 0 for Sunday, 6 for Saturday.
W Week number with Monday as the first day.
x Local date style, using tm_info.format[39], that includes
the month, day and year.
X Local time style, using tm_info.format[38], that includes
the hours and minutes.
y 2-digit year (you'll be sorry.)
Y 4-digit year.
z Time zone SHHMM west of GMT offset where S is + or -.
Z Time zone name.
=[=]][-+]]flag
Set (default or +) or clear (-) flag in tm_info.flags for
the remainder of format, or for the remainder of the
process if == is specified. flag may be:
l (TM_LEAP) Enable leap second adjustments.
s (TM_SUBSECOND) Append nanosecond .%N to %S.
u (TM_UTC) UTC time zone.
# Equivalent to %s.
?alternate
Use alternate format is a default format override has not
been specified. e.g., ls(1) uses %?%l. Export
TM_OPTIONS="format='override'" to override the default.
void tminit(Tm_zone_t* zone)
Implicitly called by the other tm library routines to initialize
global data, including the tm_info.format table and the
tm_info.flags global flags. Global data should only be modified
after an explicit call to tminit. If zone != 0 then it speci-
fies a time zone other that the local time zone.
void tmset(Tm_zone_t* zone);
tmset sets the reference timezoe to zone. tm_info.local points
to the local timezone and tm_info.zone points to the current
reference timezone.
time_t tmleap(time_t* clock)
Returns a time_t value for the time pointed to by clock with
leap seconds adjusted for external routines that do not handle
leap seconds. If clock is NULL then the current time is used.
Adjustments are only done if the TM_ADJUST flag is set in
tm_info.flags.
Tm_t* tmmake(time_t* clock)
Returns a pointer to the Tm_t struct corresponding to the time
pointed to by clock. If clock is NULL then the current time is
used.
time_t tmtime(Tm_t* tp, int west)
Returns the time_t value corresponding to tp. If west is
TM_LOCALZONE then tm is relative to the local time zone, other-
wise west is the number of minutes west of UTC with daylight
savings time taken into account. tp->tm_wday, tp->tm_yday and
tp->tm_isdst are ignored in the conversion.
The library routines use a table of date strings pointed to by char**
tm_info.format. The indices in tm_info.format are fixed by category.
tm_info.format may be changed to point to other tables according to
local language and date conventions. The contents by index (showing
the USA English values) are:
0-11 3-character abbreviated month names.
12-23 Full month names.
24-30 3-character abbreviated weekday names.
31-37 Full weekday names.
38 tmfmt() local time format used by the %X field.
39 tmfmt() local date format used by the %x field.
40 tmfmt() format used if the format argument is NULL or
empty.
41-42 Meridian names: AM, PM.
43-46 UTC time zone names: GMT, UTC, UCT, CUT.
47-50 Daylight savings time suffix names: DST.
51-54 Suffixes to be ignored when matching strings in tmfmt().
55-61 Time part names: second, hour, minute, day, week, month,
year.
62-65 Hours of the day names: midnight, morning, noon, evening.
66-68 Relative day names: yesterday, today, tomorrow.
69-71 Past relative time references: last, ago, past.
72-75 Current relative time references: this, now, current.
75-77 Future relative time references: next, hence, coming.
78-80 Exact relative time references: exactly.
81-84 Noise words to be ignored: at, in, on.
85-94 Ordinal suffixes: st, nd, rd, th, th, th, th, th, th, th.
95-104 Digit names.
105 The tmfmt() format equivalent for ctime(3):
'"%a%b%e%T%Y"'.
106 The tmfmt() date(1) default format: '"%a%b%e%T%Z%Y"'.
107 The tmfmt() date(1) international format:
'"%a%b%e%T%z%Z%Y"'
108 The tmfmt() ls(1) recent date format: '"%b%e%H:%M"'.
109 The tmfmt() ls(1) distant date format: '"%b%e%Y"'.
110 The tmfmt() date(1) meridian date format: '"%I:%M:%S%p"'.
111 The ERA name.
112 ERA alternative for 39.
113 ERA alternative for 38.
114 ERA alternative for 40.
115 The ERA year.
116-125
Ordinal names: first, no second!, third, fourth, fifth,
sixth, seventh, eighth, ninth, tenth.
126-128
Final time references, as in the last in the list: final,
ending, nth.
Low level support functions and data are described in <tm.h>.
EXAMPLES
#include <tm.h>
main() {
int i;
time_t t;
char buf[128];
struct {
char* date;
char* format;
} x[] = {
"now", "%i",
"2 months ago", "%C",
"this Wednesday noon", "%x %I:%M %p",
"last December 25", "%A",
0, 0
};
for (i = 0; x[i].date; i++) {
t = tmdate(x[i].date, (char*)0, (time_t*)0);
(void)tmfmt(buf, sizeof(buf), x[i].format, &t);
puts(buf);
}
}
produces
Fri Sep 30 12:10:14 USA EDT 1988
Fri Jul 1 00:00:00 EDT 1988
10/05/88 12:00 PM
Friday
SEE ALSO
date(1), time(2), ctime(3)
BUGS
The C library static struct tm values may get clobbered by tm library
routines as the ctime(3) and localtime(3) routines typically return
pointers to a single static struct tm area. tmdate() uses an internal
international time zone name table that will probably always be incom-
plete.
TM(3)
See also Time::tm(3)
See also tmx(3)
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