NetBSD/lib/libc/time/strftime.3

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.\"     from: @(#)strftime.3	5.12 (Berkeley) 6/29/91
.\"	$NetBSD: strftime.3,v 1.6 1999/02/07 17:33:30 augustss Exp $
.\"
.Dd June 29, 1991
.Dt STRFTIME 3
.Os
.Sh NAME
.Nm strftime
.Nd format date and time
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #include <time.h>
.Ft size_t
.Fn strftime "char *buf" "size_t maxsize" "const char *format" "const struct tm *timeptr"
.Sh DESCRIPTION
The
.Fn strftime
function formats the information from
.Fa timeptr
into the buffer
.Fa buf
according to the string pointed to by
.Fa format .
.Pp
The
.Fa format
string consists of zero or more conversion specifications and
ordinary characters.
All ordinary characters are copied directly into the buffer.
A conversion specification consists of a percent sign
.Ql %
and one other character.
.Pp
No more than
.Fa maxsize
characters will be placed into the array.
If the total number of resulting characters, including the terminating
null character, is not more than
.Fa maxsize ,
.Fn strftime
returns the number of characters in the array, not counting the
terminating null.
Otherwise, zero is returned.
.Pp
Each conversion specification is replaced by the characters as
follows which are then copied into the buffer.
.Bl -tag -width "xxxx"
.It Cm \&%A
is replaced by the locale's full weekday name.
.It Cm %a
is replaced by the locale's abbreviated weekday name.
.It Cm \&%B
is replaced by the locale's full month name.
.It Cm \&%b No or Cm \&%h
is replaced by the locale's abbreviated month name.
.It Cm \&%C
is replaced by the century (a year divided by 100 and truncated to an integer)
as a decimal number [00,99].
.It Cm \&%c
is replaced by the locale's appropriate date and time representation.
.It Cm \&%D
is replaced by the date in the format 
.Dq Li %m/%d/%y .
.It Cm \&%d
is replaced by the day of the month as a decimal number [01,31].
.It Cm \&%e
is replaced by the day of month as a decimal number [1,31];
single digits are preceded by a blank.
.It Cm \&%G
is replaced by the ISO 8601 year with century as a decimal number.
.TP
.It Cm \&%g
is replaced by the ISO 8601 year without century as a decimal number (00-99).
This is the year that includes the greater part of the week. (Monday as the
first day of a week). See also the
.Ql \&%V
conversion specification.
.TP
.It Cm \&%H
is replaced by the hour (24-hour clock) as a decimal number [00,23].
.It Cm \&%I
is replaced by the hour (12-hour clock) as a decimal number [01,12].
.It Cm \&%j
is replaced by the day of the year as a decimal number [001,366].
.It Cm \&%k
is replaced by the hour (24-hour clock) as a decimal number [0,23];
single digits are preceded by a blank.
.It Cm \&%l
is replaced by the hour (12-hour clock) as a decimal number [1,12];
single digits are preceded by a blank.
.It Cm \&%M
is replaced by the minute as a decimal number [00,59].
.It Cm %m
is replaced by the month as a decimal number [01,12].
.It Cm %n
is replaced by a newline.
.It Cm %p
is replaced by the locale's equivalent of either 
.Dq Tn AM
or
.Dq Tn PM .
.It Cm \&%R
is replaced by the time in the format
.Dq Li %H:%M .
.It Cm \&%r
is replaced by the locale's representation of 12-hour clock time 
using AM/PM notation.
.It Cm \&%T
is replaced by the time in the format
.Dq Li %H:%M:%S .
.It Cm \&%t
is replaced by a tab.
.It Cm \&%S
is replaced by the second as a decimal number [00,61].
.It Cm %s
is replaced by the number of seconds since the Epoch, UCT (see
.Xr mktime 3 ) .
.It Cm \&%U
is replaced by the week number of the year (Sunday as the first day of
the week) as a decimal number [00,53].
.It Cm \&%u
is replaced by the weekday (Monday as the first day of the week)
as a decimal number [1,7].
.It Cm \&%V
is replaced by the week number of the year (Monday as the first day of
the week) as a decimal number [01,53]. According to ISO 8601 the week
containing January 1 is week 1 if it has four or more days in the new year,
otherwise it is week 53 of the previous year, and the next week is week 1.
The year is given by the
.Ql \&%G
conversion specification.
.It Cm \&%W
is replaced by the week number of the year (Monday as the first day of
the week) as a decimal number [00,53].
.It Cm \&%w
is replaced by the weekday (Sunday as the first day of the week)
as a decimal number [0,6].
.It Cm \&%X
is replaced by the locale's appropriate time representation.
.It Cm \&%x
is replaced by the locale's appropriate date representation.
.It Cm \&%Y
is replaced by the year with century as a decimal number.
.It Cm \&%y
is replaced by the year without century as a decimal number [00,99].
.It Cm \&%Z
is replaced by the time zone name.
.It Cm %%
is replaced by
.Ql % .
.El
.Sh SEE ALSO
.Xr date 1 ,
.Xr ctime 3 ,
.Xr strptime 3 ,
.Xr printf 1 ,
.Xr printf 3
.Sh STANDARDS
The
.Fn strftime
function
conforms to
.St -ansiC .
The
.Ql \&%C ,
.Ql \&%D ,
.Ql \&%e ,
.Ql \&%g ,
.Ql \&%G ,
.Ql \&%h ,
.Ql \&%k ,
.Ql \&%l , 
.Ql \&%n ,
.Ql \&%r ,
.Ql \&%R ,
.Ql \&%s .
.Ql \&%t , 
.Ql \&%T , 
.Ql \&%u ,
and
.Ql \&%V
conversion specifications are extensions.
.Sh BUGS
There is no conversion specification for the phase of the moon.