strftime(3C)strftime(3C)NAMEstrftime() - convert date and time to string
SYNOPSISDESCRIPTION
The function converts the contents of a structure (see ctime(3C)) to a
formatted date and time string.
places characters into the array pointed to by s as controlled by the
string pointed to by format. The format string consists of zero or
more directives and ordinary characters. A directive consists of a
character, an optional field width and precision specification, and a
terminating character that determines the directive's behavior. All
ordinary characters (including the terminating null character are
copied unchanged into the array. No more than maxsize characters are
placed into the array. Each directive is replaced by the appropriate
characters as described in the following list. The appropriate charac‐
ters are determined by the program's locale, by the values contained in
the structure pointed to by timeptr, and by the environment variable
(see below).
Directives
The following directives, shown without the optional field width and
precision specification, are replaced by the indicated characters:
Locale's abbreviated weekday name.
Locale's full weekday name.
Locale's abbreviated month name.
Locale's full month name.
Locale's appropriate date and time representation.
The century number (the year divided by 100 and truncated to an
integer)
as a decimal number [00-99].
Day of the month as a decimal number [01,31].
Equivalent to the directive string
Day of the month as a decimal number [1,31]; a single digit is
preceded by a space.
Equivalent to the directive string
(the ISO 8601:2000 standard date format)
Last 2 digits of the week-based year as a decimal number
[00,99].
Week-based year as a decimal number (for example, 1977).
Equivalent to
Hour (24-hour clock) as a decimal number [00,23].
Hour (12-hour clock) as a decimal number [01,12].
Day of the year as a decimal number [001,366].
Month as a decimal number [01,12].
Minute as a decimal number [00,59].
The New-line character.
Locale's equivalent of either
AM or PM.
The time in AM and PM notation; in the POSIX locale this is
equivalent to
The time in 24 hour notation
Second as a decimal number [00,61].
The Tab character.
The time in hours, minutes, and seconds
The weekday as a decimal number [1(Monday),7].
Week number of the year
(Sunday as the first day of the week) as a decimal
number [00,53]. All days in a new year preceding the
first Sunday are considered to be in week 0.
The week number of the year (Monday as the first day of the
week) as a
decimal number [01,53]. If the week containing Janu‐
ary 1st has four or more days in the new year, then it
is considered week 1; otherwise, it is the last week
of the previous year, and the next week is week 1.
Weekday as a decimal number [0(Sunday),6].
Week number of the year
(Monday as the first day of the week) as a decimal
number [00,53]. All days in a new year preceding the
first Monday are considered to be in week 0.
Locale's appropriate date representation.
Locale's appropriate time representation.
Year without century as a decimal number [00,99].
Year with century as a decimal number.
Offset from UTC in the ISO 8601:2000 standards format (
or or by no characters if no timezone is determinable.
Time zone name (or by no characters if no time zone exists).
The percent (%) character.
The following directives are provided for backward compatibility with
the directives supported by and the functions. These directives may be
removed in a future release. It is recommended that the directives
above be used in preference to those below.
Locale's combined Emperor/Era name and year (use
instead).
instead).
Locale's Emperor/Era name (use
instead).
Locale's Emperor/Era year (use
instead).
If a directive is not one of the above, the behavior is undefined.
and give values according to the ISO 8601:2000 standard week-based
year. In this system, weeks begin on a Monday and week 1 of the year
is the week that includes January 4th, which is also the week that
includes the first Thursday of the year, and is also the first week
that contains at least four days in 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; thus, for Saturday 2nd January 1999,
is replaced by 1998 and is replaced by 53. If December 29th, 30th, or
31st is a Monday, it and any following days are part of week 1 of the
following year. Thus, for Tuesday 30th December 1997, is replaced by
1998 and is replaced by 01.
Modified Conversion Specifiers
Some conversion specifiers can be modified by the E or O modifier char‐
acters to indicate that an alternative format or specification should
be used rather than the one normally used by the unmodified conversion
specifier. If the alternative format or specification does not exist
for the current locale, the behavior will be as if the unmodified con‐
version specification were used. Alternative numeric symbols refers to
those symbols defined by the (see langinfo(5)) in the locale.
The locales alternative appropriate date and time representa‐
tion.
The name of the base year (period/Emperor/Era) in the locale's
alternative
representation.
The locale's alternative date representation
The locale's alternative time representation.
The offset from
(year only) in the locale's alternative representa‐
tion.
The full alternative year representation.
The day of the month, using the locale's alternative numeric
symbols,
filled as needed with leading zeros if there is any
alternative symbol for zero, otherwise with leading
spaces.
the day of the month, using the locale's alternative numeric
symbols, filled as needed with leading spaces.
The hour (24-hour clock) using the locale's alternative numeric
symbols.
The hour (12-hour clock) using the locale's alternative numeric
symbols.
The month using the locale's alternative numeric symbols.
The minutes using the locale's alternative numeric symbols.
The seconds using the locale's alternative numeric symbols.
The weekday as a number in the locale's alternative representa‐
tion (Monday=1).
The week number of the year
(Sunday as the first day of the week, rules corre‐
sponding to using the locale's alternative numeric
symbols.
The week number of the year
(Monday as the first day of the week, rules corre‐
sponding to using that locale's alternative numeric
symbols.
The number of the weekday (Sunday=0) using the locale's alterna‐
tive numeric symbols.
The week number of the year (Monday as the first day of the
week) using the locale's alternative numeric symbols.
The year (offset from
in the locale's alternative representation and using
the locale's alternative symbols.
Field Width and Precision
An optional field width and precision specification can immediately
follow the initial of a directive in the following order:
The decimal digit string
w specifies a minimum field width in which the result of the
conversion is right- or left-justified. It is right-justi‐
fied (with space padding) by default. If the optional flag
is specified, it is left-justified with space padding on the
right. If the optional flag is specified, it is right-justi‐
fied and padded with zeros on the left.
The decimal digit string
p specifies the minimum number of digits to appear for the
and directives, and the maximum number of bytes to be used
from the and directives. In the first case, if a directive
supplies fewer digits than specified by the precision, it
will be expanded with leading zeros. In the second case, if
a directive supplies more bytes than specified by the preci‐
sion, excess bytes will truncated on the right.
If no field width or precision is specified for a or directive, a
default of is used for all but for which is used.
EXTERNAL INFLUENCES
Locale
The category determines the characters to be substituted for those
directives described above as being from the locale.
The category determines the interpretation of the bytes within format
as single and/or multi-byte characters.
The category determines the characters used to form numbers for those
directives that produce numbers in the output. If (see langinfo(5)) is
defined for the locale, the characters so specified are used in place
of the default ASCII characters. If both and is defined for the
locale, will take precedence over
Environment Variables
determines the time zone name substituted for the directive. The time
zone name is determined by calling the function which sets the external
variable (see ctime(3C)).
International Code Set Support
Single- and multi-byte character code sets are supported.
RETURN VALUE
If the total number of resulting bytes including the terminating null
byte is not more than maxsize, returns the number of bytes placed into
the array pointed to by s, not including the terminating null byte.
Otherwise, zero is returned and the contents of the array are indeter‐
minate.
EXAMPLES
If the timeptr argument contains the following values:
the following combinations of the category and format strings produce
the indicated output:
LC_TIME Format String Output
─────────────────────────────────────────────────────
en_US.roman8 %x Mon, Jul 4, 1988
de_De.roman8 %x Mo., 4. Juli 1988
en_US.roman8 %X 03:09:04 PM
fr_FR.roman8 %X 15h09 04
any* %H:%M:%S 15:09:04
any* %.1H:%.1M:%.1S 15:9:4
any* %2.1H:%-3M:%03.1S 15:9 :004
* The directives used in these examples are not affected by the cate‐
gory of the locale.
WARNINGS
If the arguments s and format are defined such that they overlap, the
behavior is undefined.
The function is called upon every invocation of (whether or not the
time zone name is copied to the output array).
The range of values for ([0,61]) extends to 61 to allow for the occa‐
sional one or two leap seconds. However, the system does not accumu‐
late leap seconds and the structure generated by the functions and (see
ctime(3C)) never reflects any leap seconds.
Results are undefined if values contained in the structure pointed to
by timeptr exceed the ranges defined for the structure (see ctime(3C))
or are not consistent (such as if the element is set to 0, indicating
the first day of January, while the element is set to 11, indicating a
day in December).
AUTHOR
was developed by HP.
SEE ALSOdate(1), ctime(3C), getdate(3C), setlocale(3C), environ(5), lang‐
info(5), thread_safety(5).
STANDARDS CONFORMANCEstrftime(3C)