path: root/usr/src/man/man3c/strftime.3c

'\" te
.\" Copyright (c) 2014 Gary Mills
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.TH STRFTIME 3C "Jan 3, 2014"
.SH NAME
strftime, cftime, ascftime \- convert date and time to string
.SH SYNOPSIS
.LP
.nf
#include <time.h>

\fBsize_t\fR \fBstrftime\fR(\fBchar *restrict\fR \fIs\fR, \fBsize_t\fR \fImaxsize\fR,
     \fBconst char *restrict\fR \fIformat\fR,
     \fBconst struct tm *restrict\fR \fItimeptr\fR);
.fi

.LP
.nf
\fBint\fR \fBcftime\fR(\fBchar *\fR\fIs\fR, \fBchar *\fR\fIformat\fR, \fBconst time_t *\fR\fIclock\fR);
.fi

.LP
.nf
\fBint\fR \fBascftime\fR(\fBchar *\fR\fIs\fR, \fBconst char *\fR\fIformat\fR,
     \fBconst struct tm *\fR\fItimeptr\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBstrftime()\fR, \fBascftime()\fR, and \fBcftime()\fR functions place
bytes into the array pointed to by \fIs\fR as controlled by the string pointed
to by \fIformat\fR. The \fIformat\fR string consists of zero or more conversion
specifications and ordinary characters.  A conversion specification consists of
a '\fB%\fR' (percent) character and one or two terminating conversion
characters that determine the conversion specification's behavior.  All
ordinary characters (including the terminating null byte) are copied unchanged
into the array pointed to by \fIs\fR. If copying takes place between objects
that overlap, the behavior is undefined. For \fBstrftime()\fR, no more than
\fImaxsize\fR bytes are placed into the array.
.sp
.LP
If \fIformat\fR is \fB(char *)0\fR, then the locale's default format is used.
For \fBstrftime()\fR the default format is the same as \fB%c\fR; for
\fBcftime()\fR and \fBascftime()\fR the default format is the same as \fB%+\fR.
\fBcftime()\fR and \fBascftime()\fR first try to use the value of the
environment variable \fBCFTIME\fR, and if that is undefined or empty, the
default format is used.
.sp
.LP
Each conversion specification is replaced by appropriate characters as
described in the following list. The appropriate characters are determined by
the \fBLC_TIME\fR category of the program's locale and by the values contained
in the structure pointed to by \fItimeptr\fR for \fBstrftime()\fR and
\fBascftime()\fR, and by the time represented by \fIclock\fR for
\fBcftime()\fR.
.sp
.ne 2
.na
\fB\fB%%\fR\fR
.ad
.RS 6n
Same as \fB%\fR.
.RE

.sp
.ne 2
.na
\fB\fB%a\fR\fR
.ad
.RS 6n
Locale's abbreviated weekday name.
.RE

.sp
.ne 2
.na
\fB\fB%A\fR\fR
.ad
.RS 6n
Locale's full weekday name.
.RE

.sp
.ne 2
.na
\fB\fB%b\fR\fR
.ad
.RS 6n
Locale's abbreviated month name.
.RE

.sp
.ne 2
.na
\fB\fB%B\fR\fR
.ad
.RS 6n
Locale's full month name.
.RE

.sp
.ne 2
.na
\fB\fB%c\fR\fR
.ad
.RS 6n
Locale's appropriate date and time representation.
In the C locale, this format is:
.sp
.in +2
.nf
%a %b %e %H:%M:%S %Y
.fi
.in -2
.sp
Other locales may have different locale-specific formats.
.RE

.sp
.ne 2
.na
\fB\fB%C\fR\fR
.ad
.RS 6n
Century number (the year divided by 100 and truncated to an integer as a
decimal number [01,99]).
.RE

.sp
.ne 2
.na
\fB\fB%d\fR\fR
.ad
.RS 6n
Day of month [01,31].
.RE

.sp
.ne 2
.na
\fB\fB%D\fR\fR
.ad
.RS 6n
Date as \fB%m\fR/\fB%d\fR/\fB%y\fR.
.RE

.sp
.ne 2
.na
\fB\fB%e\fR\fR
.ad
.RS 6n
Day of month [1,31]; single  digits are preceded by a space.
.RE

.sp
.ne 2
.na
\fB\fB%F\fR\fR
.ad
.RS 6n
Equivalent to \fB%Y\fR-\fB%m\fR-\fB%d\fR (the ISO 8601:2000 standard date
format).
.RE

.sp
.ne 2
.na
\fB\fB%g\fR\fR
.ad
.RS 6n
Week-based year within century [00,99].
.RE

.sp
.ne 2
.na
\fB\fB%G\fR\fR
.ad
.RS 6n
Week-based year, including the century [0000,9999].
.RE

.sp
.ne 2
.na
\fB\fB%h\fR\fR
.ad
.RS 6n
Locale's abbreviated month name.
.RE

.sp
.ne 2
.na
\fB\fB%H\fR\fR
.ad
.RS 6n
Hour (24-hour clock) [00,23].
.RE

.sp
.ne 2
.na
\fB\fB%I\fR\fR
.ad
.RS 6n
Hour (12-hour clock) [01,12].
.RE

.sp
.ne 2
.na
\fB\fB%j\fR\fR
.ad
.RS 6n
Day number of year [001,366].
.RE

.sp
.ne 2
.na
\fB\fB%k\fR\fR
.ad
.RS 6n
Hour (24-hour clock) [0,23]; single digits are preceded by a space.
.RE

.sp
.ne 2
.na
\fB\fB%l\fR\fR
.ad
.RS 6n
Hour (12-hour clock) [1,12]; single digits are preceded by a space.
.RE

.sp
.ne 2
.na
\fB\fB%m\fR\fR
.ad
.RS 6n
Month number [01,12].
.RE

.sp
.ne 2
.na
\fB\fB%M\fR\fR
.ad
.RS 6n
Minute [00,59].
.RE

.sp
.ne 2
.na
\fB\fB%n\fR\fR
.ad
.RS 6n
Insert a NEWLINE.
.RE

.sp
.ne 2
.na
\fB\fB%p\fR\fR
.ad
.RS 6n
Locale's equivalent of either a.m. or p.m.
.RE

.sp
.ne 2
.na
\fB\fB%r\fR\fR
.ad
.RS 6n
Appropriate time representation in 12-hour clock format with \fB%p\fR.
.RE

.sp
.ne 2
.na
\fB\fB%R\fR\fR
.ad
.RS 6n
Time as \fB%H\fR:\fB%M\fR.
.RE

.sp
.ne 2
.na
\fB\fB%s\fR\fR
.ad
.RS 6n
Seconds since 00:00:00 UTC, January 1, 1970.
.RE

.sp
.ne 2
.na
\fB\fB%S\fR\fR
.ad
.RS 6n
Seconds [00,60]; the range of values is [00,60] rather than [00,59] to allow
for the occasional leap second.
.RE

.sp
.ne 2
.na
\fB\fB%t\fR\fR
.ad
.RS 6n
Insert a TAB.
.RE

.sp
.ne 2
.na
\fB\fB%T\fR\fR
.ad
.RS 6n
Time as \fB%H\fR:\fB%M\fR:\fB%S\fR.
.RE

.sp
.ne 2
.na
\fB\fB%u\fR\fR
.ad
.RS 6n
Weekday as a decimal number [1,7], with 1 representing Monday. See \fBNOTES\fR
below.
.RE

.sp
.ne 2
.na
\fB\fB%U\fR\fR
.ad
.RS 6n
Week number of year as a decimal number [00,53], with Sunday as the first day
of week 1.
.RE

.sp
.ne 2
.na
\fB\fB%v\fR\fR
.ad
.RS 6n
Date as \fB%e\fR-\fB%b\fR-\fB%Y\fR.
.RE

.sp
.ne 2
.na
\fB\fB%V\fR\fR
.ad
.RS 6n
The ISO 8601 week number as a decimal number [01,53]. In the ISO 8601
week-based system, weeks begin on a Monday and week 1 of the year is the week
that includes both January 4th and the first Thursday of the year.  If the
first Monday of January is the 2nd, 3rd, or 4th, the preceding days are part of
the last week of the preceding year.  See \fBNOTES\fR below.
.RE

.sp
.ne 2
.na
\fB\fB%w\fR\fR
.ad
.RS 6n
Weekday as a decimal number [0,6], with 0 representing Sunday.
.RE

.sp
.ne 2
.na
\fB\fB%W\fR\fR
.ad
.RS 6n
Week number of year as a decimal number [00,53], with Monday as the first day
of week 1.
.RE

.sp
.ne 2
.na
\fB\fB%x\fR\fR
.ad
.RS 6n
Locale's appropriate date representation.
.RE

.sp
.ne 2
.na
\fB\fB%X\fR\fR
.ad
.RS 6n
Locale's appropriate time representation.
.RE

.sp
.ne 2
.na
\fB\fB%y\fR\fR
.ad
.RS 6n
Year within century [00,99].
.RE

.sp
.ne 2
.na
\fB\fB%Y\fR\fR
.ad
.RS 6n
Year, including the century (for example 1993).
.RE

.sp
.ne 2
.na
\fB\fB%z\fR\fR
.ad
.RS 6n
Replaced by offset from UTC in ISO 8601:2000 standard format (\fB+hhmm\fR or
\fB-hhmm\fR), or by no characters if no time zone is determinable. For example,
"-0430" means 4 hours 30 minutes behind UTC (west of Greenwich). If
\fBtm_isdst\fR is zero, the standard time offset is used.  If \fBtm_isdst\fR is
greater than zero, the daylight savings time offset if used. If \fBtm_isdst\fR
is negative, no characters are returned.
.RE

.sp
.ne 2
.na
\fB\fB%Z\fR\fR
.ad
.RS 6n
Time zone name or abbreviation, or no bytes if no time zone information exists.
.RE

.sp
.ne 2
.na
\fB\fB%+\fR\fR
.ad
.RS 6n
Locale's date and time representation as produced by \fBdate\fR(1).
.RE

.sp
.LP
If a conversion specification does not correspond to any of the above or to any
of the modified conversion specifications listed below, the behavior is
undefined and \fB0\fR is returned.
.sp
.LP
The difference between \fB%U\fR and \fB%W\fR (and also between modified
conversion specifications \fB%OU\fR and \fB%OW\fR) lies in which day is counted
as the first of the week. Week number 1 is the first week in January starting
with a Sunday for \fB%U\fR or a Monday for \fB%W\fR. Week number 0 contains
those days before the first Sunday or Monday in January for \fB%U\fR and
\fB%W\fR, respectively.
.SS "Modified Conversion Specifications"
.sp
.LP
Some conversion specifications can be modified by the \fBE\fR and \fBO\fR
modifiers to indicate that an alternate format or specification should be used
rather than the one normally used by the unmodified conversion specification.
If the alternate format or specification does not exist in the current locale,
the behavior will be as if the unmodified specification were used.
.sp
.ne 2
.na
\fB\fB%Ec\fR\fR
.ad
.RS 7n
Locale's alternate appropriate date and time representation.
.RE

.sp
.ne 2
.na
\fB\fB%EC\fR\fR
.ad
.RS 7n
Name of the base year (period) in the locale's alternate representation.
.RE

.sp
.ne 2
.na
\fB\fB%Eg\fR\fR
.ad
.RS 7n
Offset from \fB%EC\fR of the week-based year in the locale's alternative
representation.
.RE

.sp
.ne 2
.na
\fB\fB%EG\fR\fR
.ad
.RS 7n
Full alternative representation of the week-based year.
.RE

.sp
.ne 2
.na
\fB\fB%Ex\fR\fR
.ad
.RS 7n
Locale's alternate date representation.
.RE

.sp
.ne 2
.na
\fB\fB%EX\fR\fR
.ad
.RS 7n
Locale's alternate time representation.
.RE

.sp
.ne 2
.na
\fB\fB%Ey\fR\fR
.ad
.RS 7n
Offset from \fB%EC\fR (year only) in the locale's alternate representation.
.RE

.sp
.ne 2
.na
\fB\fB%EY\fR\fR
.ad
.RS 7n
Full alternate year representation.
.RE

.sp
.ne 2
.na
\fB\fB%Od\fR\fR
.ad
.RS 7n
Day of the month using the locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%Oe\fR\fR
.ad
.RS 7n
Same as \fB%Od\fR.
.RE

.sp
.ne 2
.na
\fB\fB%Og\fR\fR
.ad
.RS 7n
Week-based year (offset from \fB%C\fR) in the locale's alternate representation
and using the locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%OH\fR\fR
.ad
.RS 7n
Hour (24-hour clock) using the locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%OI\fR\fR
.ad
.RS 7n
Hour (12-hour clock) using the locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%Om\fR\fR
.ad
.RS 7n
Month using the locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%OM\fR\fR
.ad
.RS 7n
Minutes using the locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%OS\fR\fR
.ad
.RS 7n
Seconds using the locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%Ou\fR\fR
.ad
.RS 7n
Weekday as a number in the locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%OU\fR\fR
.ad
.RS 7n
Week number of the year (Sunday as the first day of the week) using the
locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%Ow\fR\fR
.ad
.RS 7n
Number of the weekday (Sunday=0) using the  locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%OW\fR\fR
.ad
.RS 7n
Week number of the year (Monday as the first day of the week) using the
locale's alternate numeric symbols.
.RE

.sp
.ne 2
.na
\fB\fB%Oy\fR\fR
.ad
.RS 7n
Year (offset from \fB%C\fR) in the locale's alternate representation and using
the locale's alternate numeric symbols.
.RE

.SS "Selecting the Output Language"
.sp
.LP
By default, the output of \fBstrftime()\fR, \fBcftime()\fR, and
\fBascftime()\fR appear in U.S. English. The user can request that the output
of \fBstrftime()\fR, \fBcftime()\fR, or \fBascftime()\fR be in a specific
language by setting the \fBLC_TIME\fR category using \fBsetlocale()\fR.
.SS "Time Zone"
.sp
.LP
Local time zone information is used as though \fBtzset\fR(3C) were called.
.SH RETURN VALUES
.sp
.LP
The \fBstrftime()\fR, \fBcftime()\fR, and \fBascftime()\fR functions return the
number of characters placed into the array pointed to by \fIs\fR, not including
the terminating null character. If the total number of resulting characters
including the terminating null character is more than \fImaxsize\fR,
\fBstrftime()\fR returns \fB0\fR and the contents of the array are
indeterminate.
.SH EXAMPLES
.LP
\fBExample 1 \fRAn example of the \fBstrftime()\fR function.
.sp
.LP
The following example illustrates the use of \fBstrftime()\fR for the
\fBPOSIX\fR locale. It shows what the string in \fIstr\fR would look like if
the structure pointed to by \fItmptr\fR contains the values corresponding to
Thursday, August 28, 1986 at 12:44:36.

.sp
.in +2
.nf
\fBstrftime (str, strsize, "%A %b %d %j", tmptr)\fR
.fi
.in -2

.sp
.LP
This results in \fIstr\fR containing "Thursday Aug 28 240".

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
CSI	Enabled
_
Interface Stability	Committed
_
MT-Level	MT-Safe
_
Standard	See below.
.TE

.sp
.LP
For \fBstrftime()\fR, see \fBstandards\fR(5).
.SH SEE ALSO
.sp
.LP
\fBdate\fR(1), \fBctime\fR(3C), \fBmktime\fR(3C), \fBsetlocale\fR(3C),
\fBstrptime\fR(3C), \fBtzset\fR(3C), \fBTIMEZONE\fR(4), \fBzoneinfo\fR(4),
\fBattributes\fR(5), \fBenviron\fR(5), \fBstandards\fR(5)
.SH NOTES
.sp
.LP
The conversion specification for \fB%V\fR was changed in the Solaris 7 release.
This change was based on the public review draft of the ISO C9x standard at
that time. Previously, the specification stated that if the week containing 1
January had fewer than four days in the new year, it became week 53 of the
previous year. The ISO C9x standard committee subsequently recognized that that
specification had been incorrect.
.sp
.LP
The conversion specifications for \fB%g\fR, \fB%G\fR, \fB%Eg\fR, \fB%EG\fR, and
\fB%Og\fR were added in the Solaris 7 release.  This change was based on the
public review draft of the ISO C9x standard at that time. These specifications
are evolving.  If the ISO C9x standard is finalized with a different
conclusion, these specifications will change to conform to the ISO C9x standard
decision.
.sp
.LP
The conversion specification for \fB%u\fR was changed in the Solaris 8 release.
This change was based on the XPG4 specification.
.sp
.LP
If using the \fB%Z\fR specifier and \fBzoneinfo\fR timezones and if the input
date is outside the range 20:45:52 UTC, December  13, 1901 to 03:14:07 UTC,
January 19, 2038, the timezone name may not be correct.
.sp
.LP
The conversion specification for \fB%+\fR was added in illumos.
It is not part of any standard, although it is available on a number
of other platforms.
Its use is discouraged for conforming applications.