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cftime(3c)
strftime(3C) Standard C Library Functions strftime(3C)
NAME
strftime, strftime_l, cftime, ascftime - convert date and time to
string
SYNOPSIS
#include <time.h>
size_t strftime(char *restrict s, size_t maxsize,
const char *restrict format,
const struct tm *restrict timeptr);
size_t strftime_l(char *restrict s, size_t maxsize,
const char *restrict format,
const struct tm *restrict timeptr,
locale_t locale);
int cftime(char *s, char *format, const time_t *clock);
int ascftime(char *s, const char *format,
const struct tm *timeptr);
DESCRIPTION
The strftime(), ascftime(), and cftime() functions place bytes into the
array pointed to by s as controlled by the string pointed to by format.
The format string consists of zero or more conversion specifications
and ordinary characters. A conversion specification consists of a '%'
(percent) character, an optional flag character, an optional field
width, and one or two terminating conversion characters that determine
the conversion specification's behavior. All ordinary characters (in‐
cluding the terminating null byte) are copied unchanged into the array
pointed to by s. If copying takes place between objects that overlap,
the behavior is undefined. For strftime(), no more than maxsize bytes
are placed into the array.
If format is NULL, then the locale's default format is used. For strf‐
time() the default format is the same as %c; for cftime() and ascf‐
time() the default format is the same as %C. cftime() and ascftime()
first try to use the value of the environment variable CFTIME, and if
that is undefined or empty, the default format is used.
Each conversion specification is replaced by appropriate characters as
described in the following list. The appropriate characters are deter‐
mined by the LC_TIME category of current locale or of locale specified
by locale, and by the values contained in the structure pointed to by
timeptr for strftime(), strftime_l(), and ascftime(), and by the time
represented by clock for cftime(). Supported optional flag characters
and optional field width are described at the end of the section.
Each conversion specification is introduced by the '%' character after
which the following appear in sequence:
An optional flag
0 (zero character)
Specifies that the character used as the padding character is
'0', even in cases where the conversion specification character
used with is specified with in the "Conversion Specifiers" sub‐
section such that digits are preceded by a space or a blank
character.
+ (plus-sign character)
Default and other standards prior to SUSv4:
This character is not recognized as an optional flag. In‐
stead, this character is recognized as a conversion speci‐
fier. See "Conversion Specifiers" section.
SUSv4 conforming:
Specifies that the character used as the padding character
is '0', and that if and only if the field being produced
consumes more than four bytes to represent a year (for %F,
%G, or %Y) or more than two bytes to represent the year di‐
vided by 100 (for %C) then a leading plus-sign character is
included if the year being processed is greater than or
equal to zero or a leading minus-sign character ('-') is
included if the year is less than zero.
#
If applicable, convert the case of the alphabetic characters to
the other case, i.e., uppercase to lowercase or lowercase to
uppercase, while trying to preserve the first so-called title
case character in the conversion to uppercase.
- (dash)
Do not pad anything for numeric values.
^
If applicable, convert lowercase characters into uppercase
characters.
_ (underscore)
Pad left with space (0x20) characters for numeric values.
An optional minimum field width
If the converted value has fewer bytes than the minimum field
width, the output will be padded on the left with the padding char‐
acter.
In SUSv4 conforming application, a leading '+' or '-' sign is in‐
cluded when counting bytes for the converted values, and a padding
is done after any leading '+' or '-' sign.
An optional E or O modifier
Subsection "Modified Conversion Specifications" describes about how
those modifiers work.
A terminating conversion specifier
The specifier indicates the type of conversion to be applied. Sub‐
section "Conversion Specifiers" describes about the specifiers sup‐
ported.
The results are unspecified if more than one flag character is speci‐
fied, a flag character is specified without a minimum field width; a
minimum field width is specified without a flag character; a modifier
is specified with a flag or with a minimum field width; or if a minimum
field width is specified for any conversion specifier other than C, F,
G, or Y.
All ordinary characters (including the terminating NUL character) are
copied unchanged into the array. If copying takes place between objects
that overlap, the behavior is undefined. No more than maxsize bytes are
placed into the array. Each conversion specifier is replaced by appro‐
priate characters as described in the following list. The appropriate
characters are determined using the LC_TIME category of the current lo‐
cale or locale specified by locale and by the values of zero or more
members of the broken-down time structure pointed to by timeptr, as
specified in brackets in the description. If any of the specified val‐
ues are outside the normal range, the characters stored are unspeci‐
fied.
Conversion Specifiers
The following conversion specifiers are supported:
+
Default and other standards prior to SUSv4
Locale's date and time representation as produced by date(1).
Plus sign is recognized as a conversion specifier.
SUSv4 conforming
This character is not recognized as a conversion specifier.
Instead, this character is recognized as an optional flag. See
"Description" section.
a Locale's abbreviated weekday name.
A Locale's full weekday name.
b Locale's abbreviated month name.
B Locale's full month name.
Standard conforming
c Locale's appropriate date and time represented as:
%a %b %e %H:%M:%S %Y
This is standard-conforming behavior for standards first supported
by Solaris 2.4 through Oracle Solaris 11.4.
Default
c Locale's appropriate date and time represented as:
%a %b %d %H:%M:%S %Y
This is the default behavior as well as standard-conforming behav‐
ior for standards first supported by releases prior to Solaris
2.4. See standards(7).
SUSv4 conforming
C Century number (the year divided by 100 and truncated to an inte‐
ger as a decimal number [01,99]).
If a minimum field width is not specified, the number of charac‐
ters placed into the array pointed to by s will be the number of
digits in the year divided by 100 or two, whichever is greater. If
a minimum field width is specified, the number of characters
placed into the array pointed to by s will be the number of digits
in the year divided by 100 or the minimum field width, whichever
is greater.
Other standard conforming
C Century number (the year divided by 100 and truncated to an inte‐
ger as a decimal number [01,99]).
This is the default behavior as well as standard-conforming behav‐
ior for standards first supported by releases prior to Oracle So‐
laris 11.
Default
C Locale's date and time representation as produced by date(1).
This is the default behavior as well as standard-conforming behav‐
ior for standards first supported by releases prior to Oracle So‐
laris 11.4.
d Day of month as a decimal number [01,31].
D Equivalent to %m/%d/%y.
e Day of month as a decimal number [1,31]; a single digit is pre‐
ceded by a space.
SUSv4 conforming
F Equivalent to %+4Y-%m-%d if no flag and no minimum field width are
specified.
If a minimum field width of x is specified, the year is output as
if by the Y specifier (described below) with whatever flag was
given and a minimum field width of x-6. If x is less than 6, the
behavior is as if x equals 6.
If the minimum field width is specified to be 10, and the year is
four digits long, then the output string produced will match the
ISO 8601:2000 standard subclause 4.1.2.2 complete representation,
extended format date representation of a specific day.
If a + flag is specified, a minimum field width of x is specified,
and x-7 bytes are sufficient to hold the digits of the year (not
including any needed sign character), then the output will match
the ISO 8601:2000 standard subclause 4.1.2.4 complete representa‐
tion, expanded format date representation of a specific day.
Default and other standards
F Equivalent to %Y-%m-%d (the ISO 8601:2000 standard + date in ex‐
tended format).
This is the default behavior as well as standard-conforming behav‐
ior for standards first supported by releases prior to Oracle So‐
laris 11.4.
g Last 2 digits of the week-based year as a decimal number [00,99].
SUSv4 conforming
G Week-based year as a decimal number (for example, 1977).
If a minimum field width is specified, the number of characters
placed into the array pointed to by s will be the number of digits
and leading sign characters (if any) in the year, or the minimum
field width, whichever is greater.
Default and other standards
G Week-based year, including the century [0000,9999].
This is the default behavior as well as standard-conforming behav‐
ior for standards first supported by releases prior to Oracle So‐
laris 11.4.
h Equivalent to b.
H Hour (24-hour clock) as a decimal number [00,23].
I Hour (12-hour clock) as a decimal number [01,12].
j Day number of year as a decimal number [001,366].
k Hour (24-hour clock) as a decimal number [0,23]; single digit is
preceded by a space.
l Hour (12-hour clock) as a decimal number [1,12]; single digit is
preceded by a space.
m Month as a decimal number [01,12].
M Minute as a decimal number [00,59].
n A NEWLINE.
p Locale's equivalent of either a.m. or p.m.
r Appropriate time representation in 12-hour clock format with %p.
In the POSIX locale this is equivalent to %I:%M:%S %p.
P Locale's equivalent of either a.m. or p.m. in lowercase if applic‐
able for the current locale, or in locale represented by locale in
strftime_l().
R Time in 24-hour notation as %H:%M.
s The number of seconds since the Epoch (00:00:00 UTC, January 1,
1970).
S Second as a decimal number [00,60]; the range of values is [00,60]
rather than [00,59] to allow for the occasional leap second.
t A TAB.
T Time as %H:%M:%S.
u Weekday as a decimal number [1,7], with 1 representing Monday. See
HISTORY below.
U Week number of year as a decimal number [00,53]. The first Sunday
of January is the first day of week 1; days in the new year before
this are in week 0.
V 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 HISTORY below.
w Weekday as a decimal number [0,6], with 0 representing Sunday.
W Week number of year as a decimal number [00,53], with Monday as
the first day of week 1. The first Monday of January is the first
day of week 1; days in the new year before this are in week 0.
x Locale's appropriate date representation.
X Locale's appropriate time representation.
SUSv4 conforming
Y Year as a decimal number (for example 1997).
If a minimum field width is specified, the number of characters
placed into the array pointed to by s will be the number of digits
and leading sign characters (if any) in the year, or the minimum
field width, whichever is greater.
Default and other standards
Y Year as a decimal number (for example 1997). This is the default
behavior as well as standard-conforming behavior for standards
first supported by releases prior to Oracle Solaris 11.4.
z Replaced by offset from UTC in ISO 8601:2004 standard basic format
(+hhmm or -hhmm), or by no characters if no time zone is deter‐
minable. For example, "-0430" means 4 hours 30 minutes behind UTC
(west of Greenwich). If tm_isdst is negative no characters are re‐
turned.
Z Time zone name or abbreviation, or no bytes if no time zone infor‐
mation exists.
% Replaced by %.
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 0 is returned.
The difference between %U and %W (and also between modified conversion
specifications %OU and %OW) 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 %U or a Monday for %W. Week number 0 contains those days be‐
fore the first Sunday or Monday in January for %U and %W, respectively.
Modified Conversion Specifications
Some conversion specifications can be modified by the E and O modifiers
to indicate that an alternate format or specification should be used
rather than the one normally used by the unmodified conversion specifi‐
cation. If the alternate format or specification does not exist in the
current locale, the behavior will be as if the unmodified specification
were used.
%Ec Locale's alternate appropriate date and time representation.
%EC Name of the base year (period) in the locale's alternate repre‐
sentation.
%Eg Offset from %EC of the week-based year in the locale's alterna‐
tive representation.
%EG Full alternative representation of the week-based year.
%Ex Locale's alternate date representation.
%EX Locale's alternate time representation.
%Ey Offset from %EC (year only) in the locale's alternate represen‐
tation.
%EY Full alternate year representation.
%OB Locale's full month name using the locale's alternate numeric
symbols if applicable.
%Od Day of the month using the locale's alternate numeric symbols.
%Oe Same as %Od.
%Og Week-based year (offset from %C) in the locale's alternate rep‐
resentation and using the locale's alternate numeric symbols.
%OH Hour (24-hour clock) using the locale's alternate numeric sym‐
bols.
%OI Hour (12-hour clock) using the locale's alternate numeric sym‐
bols.
%Om Month using the locale's alternate numeric symbols.
%OM Minutes using the locale's alternate numeric symbols.
%OS Seconds using the locale's alternate numeric symbols.
%Ou Weekday as a number in the locale's alternate numeric symbols.
%OU Week number of the year (Sunday as the first day of the week)
using the locale's alternate numeric symbols.
%OV Week number of the year (Monday as the first day of the week as
specified in the description for %V) using the locale's alter‐
nate numeric symbols.
%Ow Number of the weekday (Sunday=0) using the locale's alternate
numeric symbols.
%OW Week number of the year (Monday as the first day of the week)
using the locale's alternate numeric symbols.
%Oy Year (offset from %C) in the locale's alternate representation
and using the locale's alternate numeric symbols.
Selecting the Output Language
By default, the output of strftime(), cftime(), and ascftime() appear
in U.S. English. The user can request that the output of strftime(),
cftime(), or ascftime() be in a specific language by setting the
LC_TIME category using setlocale().
The strftime_l() function is equivalent to the strftime() function, ex‐
cept that the locale data used is from the locale represented by lo‐
cale.
The behavior is undefined if the locale argument to strftime_l() is the
special locale object LC_GLOBAL_LOCALE or is not a valid locale object
handle.
Time Zone
Local time zone information is used as though tzset(3C) were called.
RETURN VALUES
These functions return the number of bytes placed into the array
pointed to by s, not including the terminating null character. If the
total number of resulting bytes including the terminating null charac‐
ter is more than maxsize, strftime() and strftime_l() return 0 and the
contents of the array are indeterminate.
EXAMPLES
Example 1 An example of the strftime() function.
The following example illustrates the use of strftime() to format a
date and time in the ISO 8601:2019 extended format. It shows what the
string in str would look like if the structure pointed to by tmptr con‐
tains the values corresponding to Thursday, August 28, 1986 at
12:44:36.
strftime(str, strsize, "%FT%T", tmptr)
This results in str containing "1986-08-28T12:44:36".
Example 2 Locale appropriate date and time
Generate the long form date and time represented by the variable now in
the current locale appropriate order. Note that even in two different
English locales this results in a string of different lengths and field
order:
strftime(str, strsize, "%c", now)
en_US: "January 13, 2022 at 1:38:49 PM GMT"
en_GB: "13 January 2022 at 13:38:49 GMT"
Example 3 Using flag and field width at conversion specification.
Assuming the data structure pointed to by tmptr has the values corre‐
sponding to Sunday, December 5, 2009 at 12:00:00 and the current locale
is POSIX, with the following:
strftime(str, strsize, "Day:%#10A", tmptr);
The result in str would be "Day: SUNDAY" where Sunday is converted to
uppercase while preserving the initial title case character and with
four space (0x20) characters padded at left.
USAGE
Use of the strftime() or strftime_l() functions is strongly recommended
over the older ascftime() or cftime() functions, as the older functions
cannot check if more data is being written than will fit in the output
buffer, and the use of the CFTIME environment variable may lead to un‐
expected or overlength output being generated.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ CSIEnabled _ Interface StabilityCommitted _ MT-LevelMT-
Safe _ StandardSee below.
For strftime() and strftime_l(), see standards(7).
SEE ALSO
date(1), ctime(3C), duplocale(3C), freelocale(3C), mktime(3C), newlo‐
cale(3C), setlocale(3C), strptime(3C), tzset(3C), uselocale(3C), zone‐
info(5), attributes(7), environ(7), standards(7)
Managing System Locales in Internationalizing and Localizing Applica‐
tions in Oracle Solaris
HISTORY
The strftime_l() function was added to Oracle Solaris in the Solaris
11.4.0 release.
The ascftime(), cftime(), and strftime() functions have been included
in all Sun and Oracle releases of Solaris.
The conversion specifications for %C, %F, %G, and %Y were modified, and
optional flag character '+' was added in Oracle Solaris 11.4, to con‐
form to Single UNIX Specifications version 4 (SUSv4) or The Open Group
Base Specifications Issue 7 (XPG7).
The conversion specifications for %+, %P, %s, %OB, and %OV and also op‐
tional flag characters and optional field width were added in the So‐
laris 11 and OpenSolaris releases for a better compatibility with other
operating systems. The current form of %OV is also specified in the
Single UNIX Specification, Version 2 (SUSv2).
The conversion specification for %u was changed in the Solaris 8 re‐
lease. This change was based on the XPG4 specification.
The conversion specification for %V was changed in the Solaris 7 re‐
lease. This change was based on the public review draft of the ISO C99
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 C99 standard committee
subsequently recognized that that specification had been incorrect.
The conversion specifications for %g, %G, %Eg, %EG, and %Og were added
in the Solaris 7 release. This change was based on the public review
draft of the ISO C99 standard at that time.
Oracle Solaris 11.4 25 Nov 2024 strftime(3C)