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TM 3
NAME
tm - seconds resolution time conversion support
SYNOPSIS
.L "#include <tm.h>"
DESCRIPTION
The tm library supports conversion between string date specifications, seconds reolution .L time_t clock values and .LR Tm_t . .L Tm_t contains the elements of .L "struct tm" along with these additions:

.L "unsigned _ast_int4_t tm_nsec" The subsecond portion of the time in nanoseconds.

.L "Tm_zone_t* tm_zone" The time zone name.

.L localtime() and .L gmtime() (see ctime (3)) are used to determine local time zone and savings time information.

.L 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 .L "int tm_info.flags" contains flags that allow all programs using the library to be controlled in a consistent manner. .L tm_info.flags is initialized by the .L tminit() routine described below, and may be explicitly reset after .L tminit() is called. The flags are:

.L TM_ADJUST Set by .L tminit() if .L localtime() and .L gmtime() do not compensate for leap seconds.

.L TM_LEAP .L time_t values are interpreted as if they include leap seconds. Set by .L tminit() if the .L leap option is set in the .L TM_OPTIONS environment variable.

.L TM_UTC Times are relative to UTC (universal coordinated time, i.e., GMT .) Otherwise times are relative to the local time zone. Set by .L tminit() if the time zone name matches one of .L tm_info.format[43] through .L tm_info.format[46] described below. If the time zone name is not determined by .L localtime() then the environment variables .L TZNAME (as described in BSD 4.3) and .L 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:

.L "time_t tmdate(const char* date, char** end, time_t* clock)" Parses the date specification .L date using the .L tm_info.format string table (described below) and returns the equivalent .L time_t value. If .RL non- NULL , .L end is set to the position of the first unrecognized character in .LR date . .L clock is used to provide default values for omitted components in .LR date . If .L clock is .L NULL then the current time is used.

.L "Tm_t* tmfix(Tm_t* tp)" Corrects any out of bounds fields in .L tp and returns .L tp as its value. The corrections start with .L tp->tm_sec and propagate down to .LR tp->tm_year . For example, if .L tp->tm_sec were 61 then it would change to 1 and .L tp->tm_min would be incremented by 1, and so on. .L tp->tm_isdst is not changed -- call .L tmtime() to determine its proper value after the .L tmfix() adjustments.

.L "char* tmfmt(char* buf, size_t len, const char* format, time_t* clock)" Formats the date pointed to by .L clock into the buffer .L buf with size .L len bytes according to the format specification .LR format . If .L format is .L NULL or empty then the string .L tm_info.format[40] is used. If .L clock is .L NULL then the current time is used. A pointer to the end of .L buf (i.e., the terminating .LR "'\e0'" ) is returned.

.L format is in printf (3) style, where % field names a fixed size field, zero padded if necessary, and \ec and \ennn 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 interpreted as in the C language. String field values are taken from the .L tm_info.format string table. The fields are:

0 % % 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 .RL ( 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 .RL ( tm_info.format[107] .)

I 12-hour clock hour.

j 1-offset Julian date.

J 0-offset Julian date.

k date (1) style date .RL ( 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: .LR '"%Y-%m-%d+%H:%M:%S"' .

l ls (1) -l date that lists recent dates with .L %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 character 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 .LR tm_info.format[39] , that includes the month, day and year.

X Local time style, using .LR 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 .L tm_info.flags for the remainder of format , or for the remainder of the process if == is specified. flag may be:

l .L (TM_LEAP) Enable leap second adjustments.

s .L (TM_SUBSECOND) Append nanosecond .%N to %S .

u .L (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 \f5TM_OPTIONS="format='override\f5'" to override the default.

.L "void tminit(Tm_zone_t* zone)" Implicitly called by the other tm library routines to initialize global data, including the .L tm_info.format table and the .L tm_info.flags global flags. Global data should only be modified after an explicit call to .LR tminit . If .L "zone != 0" then it specifies a time zone other that the local time zone.

.L "void tmset(Tm_zone_t* zone);" .L tmset sets the reference timezoe to .LR zone . .L tm_info.local points to the local timezone and .L tm_info.zone points to the current reference timezone.

.L "time_t tmleap(time_t* clock)" Returns a .L time_t value for the time pointed to by .L clock with leap seconds adjusted for external routines that do not handle leap seconds. If .L clock is .L NULL then the current time is used. Adjustments are only done if the .L TM_ADJUST flag is set in .LR tm_info.flags .

.L "Tm_t* tmmake(time_t* clock)" Returns a pointer to the .L Tm_t struct corresponding to the time pointed to by .LR clock . If .L clock is .L NULL then the current time is used.

.L "time_t tmtime(Tm_t* tp, int west)" Returns the .L time_t value corresponding to .LR tp . If .L west is .L TM_LOCALZONE then .L tm is relative to the local time zone, otherwise .L west is the number of minutes west of UTC with daylight savings time taken into account. .LR tp->tm_wday , .LR tp->tm_yday and .L tp->tm_isdst are ignored in the conversion.

The library routines use a table of date strings pointed to by .LR "char** tm_info.format" . The indices in .L tm_info.format are fixed by category. .L 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 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 .L tmfmt() local time format used by the %X field.

39 .L tmfmt() local date format used by the %x field.

40 .L tmfmt() format used if the .L format argument is .L 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 .LR 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 .L tmfmt() format equivalent for ctime (3): .LR '"%a %b %e %T %Y"' .

106 The .L tmfmt() date (1) default format: .LR '"%a %b %e %T %Z %Y"' .

107 The .L tmfmt() date (1) international format: .LR '"%a %b %e %T %z %Z %Y"' .

108 The .L tmfmt() ls (1) recent date format: .LR '"%b %e %H:%M"' .

109 The .L tmfmt() ls (1) distant date format: .LR '"%b %e %Y"' .

110 The .L tmfmt() date (1) meridian date format: .LR '"%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 .LR <tm.h> .

EXAMPLES
.EX #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 .EX 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 .L "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 .L "struct tm" area. .L tmdate() uses an internal international time zone name table that will probably always be incomplete.