1strftime(3C) Standard C Library Functions strftime(3C)
2
6 strftime, cftime, ascftime - convert date and time to string
7
9 #include <time.h>
10 size_t strftime(char *restrict s, size_t maxsize,
12 const char *restrict format,
13 const struct tm *restrict timeptr);
14 int cftime(char *s, char *format, const time_t *clock);
17 int ascftime(char *s, const char *format,
20 const struct tm *timeptr);
21
24 The strftime(), ascftime(), and cftime() functions place bytes into the
25 array pointed to by s as controlled by the string pointed to by format.
26 The format string consists of zero or more conversion specifications
27 and ordinary characters. A conversion specification consists of a '%'
28 (percent) character and one or two terminating conversion characters
29 that determine the conversion specification's behavior. All ordinary
30 characters (including the terminating null byte) are copied unchanged
31 into the array pointed to by s. If copying takes place between objects
32 that overlap, the behavior is undefined. For strftime(), no more than
33 maxsize bytes are placed into the array.
34 If format is (char *)0, then the locale's default format is used. For
37 strftime() the default format is the same as %c; for cftime() and ascf‐
38 time() the default format is the same as %C. cftime() and ascftime()
39 first try to use the value of the environment variable CFTIME, and if
40 that is undefined or empty, the default format is used.
41 Each conversion specification is replaced by appropriate characters as
44 described in the following list. The appropriate characters are deter‐
45 mined by the LC_TIME category of the program's locale and by the values
46 contained in the structure pointed to by timeptr for strftime() and
47 ascftime(), and by the time represented by clock for cftime().
48 %% Same as %.
50 %a Locale's abbreviated weekday name.
53 %A Locale's full weekday name.
56 %b Locale's abbreviated month name.
59 %B Locale's full month name.
62 Default
65 %c Locale's appropriate date and time represented as:
66 %a %b %d %H:%M:%S %Y
68 This is the default behavior as well as standard-conforming
70 behavior for standards first supported by releases prior to
71 Solaris 2.4. See standards(5).
72 Standard conforming
75 %c Locale's appropriate date and time represented as:
76 %a %b %e %H:%M:%S %Y
78 This is standard-conforming behavior for standards first sup‐
80 ported by Solaris 2.4 through Solaris 10.
81 Default
84 %C Locale's date and time representation as produced by date(1).
85 This is the default behavior as well as standard-conforming
87 behavior for standards first supported by releases prior to
88 Solaris 2.4.
89 Standard conforming
92 %C Century number (the year divided by 100 and truncated to an inte‐
93 ger as a decimal number [01,99]).
94 This is standard-conforming behavior for standards first sup‐
96 ported by Solaris 2.4 through Solaris 10.
97 %d Day of month [01,31].
100 %D Date as %m/%d/%y.
103 %e Day of month [1,31]; single digits are preceded by a space.
106 %F Equivalent to %Y-%m-%d (the ISO 8601:2000 standard date format).
109 %g Week-based year within century [00,99].
112 %G Week-based year, including the century [0000,9999].
115 %h Locale's abbreviated month name.
118 %H Hour (24-hour clock) [00,23].
121 %I Hour (12-hour clock) [01,12].
124 %j Day number of year [001,366].
127 %k Hour (24-hour clock) [0,23]; single digits are preceded by a
130 space.
131 %l Hour (12-hour clock) [1,12]; single digits are preceded by a
134 space.
135 %m Month number [01,12].
138 %M Minute [00,59].
141 %n Insert a NEWLINE.
144 %p Locale's equivalent of either a.m. or p.m.
147 %r Appropriate time representation in 12-hour clock format with %p.
150 %R Time as %H:%M.
153 %S Seconds [00,60]; the range of values is [00,60] rather than
156 [00,59] to allow for the occasional leap second.
157 %t Insert a TAB.
160 %T Time as %H:%M:%S.
163 %u Weekday as a decimal number [1,7], with 1 representing Monday.
166 See NOTES below.
167 %U Week number of year as a decimal number [00,53], with Sunday as
170 the first day of week 1.
171 %V The ISO 8601 week number as a decimal number [01,53]. In the ISO
174 8601 week-based system, weeks begin on a Monday and week 1 of the
175 year is the week that includes both January 4th and the first
176 Thursday of the year. If the first Monday of January is the 2nd,
177 3rd, or 4th, the preceding days are part of the last week of the
178 preceding year. See NOTES below.
179 %w Weekday as a decimal number [0,6], with 0 representing Sunday.
182 %W Week number of year as a decimal number [00,53], with Monday as
185 the first day of week 1.
186 %x Locale's appropriate date representation.
189 %X Locale's appropriate time representation.
192 %y Year within century [00,99].
195 %Y Year, including the century (for example 1993).
198 %z Replaced by offset from UTC in ISO 8601:2000 standard format
201 (+hhmm or -hhmm), or by no characters if no time zone is deter‐
202 minable. For example, "-0430" means 4 hours 30 minutes behind UTC
203 (west of Greenwich). If tm_isdst is zero, the standard time off‐
204 set is used. If tm_isdst is greater than zero, the daylight sav‐
205 ings time offset if used. If tm_isdst is negative, no characters
206 are returned.
207 %Z Time zone name or abbreviation, or no bytes if no time zone
210 information exists.
211 If a conversion specification does not correspond to any of the above
215 or to any of the modified conversion specifications listed below, the
216 behavior is undefined and 0 is returned.
217 The difference between %U and %W (and also between modified conversion
220 specifications %OU and %OW) lies in which day is counted as the first
221 of the week. Week number 1 is the first week in January starting with a
222 Sunday for %U or a Monday for %W. Week number 0 contains those days
223 before the first Sunday or Monday in January for %U and %W, respec‐
224 tively.
225 Modified Conversion Specifications
227 Some conversion specifications can be modified by the E and O modifiers
228 to indicate that an alternate format or specification should be used
229 rather than the one normally used by the unmodified conversion specifi‐
230 cation. If the alternate format or specification does not exist in the
231 current locale, the behavior will be as if the unmodified specification
232 were used.
233 %Ec Locale's alternate appropriate date and time representation.
235 %EC Name of the base year (period) in the locale's alternate repre‐
238 sentation.
239 %Eg Offset from %EC of the week-based year in the locale's alterna‐
242 tive representation.
243 %EG Full alternative representation of the week-based year.
246 %Ex Locale's alternate date representation.
249 %EX Locale's alternate time representation.
252 %Ey Offset from %EC (year only) in the locale's alternate represen‐
255 tation.
256 %EY Full alternate year representation.
259 %Od Day of the month using the locale's alternate numeric symbols.
262 %Oe Same as %Od.
265 %Og Week-based year (offset from %C) in the locale's alternate rep‐
268 resentation and using the locale's alternate numeric symbols.
269 %OH Hour (24-hour clock) using the locale's alternate numeric sym‐
272 bols.
273 %OI Hour (12-hour clock) using the locale's alternate numeric sym‐
276 bols.
277 %Om Month using the locale's alternate numeric symbols.
280 %OM Minutes using the locale's alternate numeric symbols.
283 %OS Seconds using the locale's alternate numeric symbols.
286 %Ou Weekday as a number in the locale's alternate numeric symbols.
289 %OU Week number of the year (Sunday as the first day of the week)
292 using the locale's alternate numeric symbols.
293 %Ow Number of the weekday (Sunday=0) using the locale's alternate
296 numeric symbols.
297 %OW Week number of the year (Monday as the first day of the week)
300 using the locale's alternate numeric symbols.
301 %Oy Year (offset from %C) in the locale's alternate representation
304 and using the locale's alternate numeric symbols.
305 Selecting the Output Language
308 By default, the output of strftime(), cftime(), and ascftime() appear
309 in U.S. English. The user can request that the output of strftime(),
310 cftime(), or ascftime() be in a specific language by setting the
311 LC_TIME category using setlocale().
312 Time Zone
314 Local time zone information is used as though tzset(3C) were called.
315
317 The strftime(), cftime(), and ascftime() functions return the number of
318 characters placed into the array pointed to by s, not including the
319 terminating null character. If the total number of resulting characters
320 including the terminating null character is more than maxsize, strf‐
321 time() returns 0 and the contents of the array are indeterminate.
322
324 Example 1 An example of the strftime() function.
325 The following example illustrates the use of strftime() for the POSIX
328 locale. It shows what the string in str would look like if the struc‐
329 ture pointed to by tmptr contains the values corresponding to Thursday,
330 August 28, 1986 at 12:44:36.
331 strftime (str, strsize, "%A %b %d %j", tmptr)
334 This results in str containing "Thursday Aug 28 240".
338
341 See attributes(5) for descriptions of the following attributes:
342 ┌─────────────────────────────┬─────────────────────────────┐
347 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
348 ├─────────────────────────────┼─────────────────────────────┤
349 │CSI │Enabled │
350 ├─────────────────────────────┼─────────────────────────────┤
351 │Interface Stability │Committed │
352 ├─────────────────────────────┼─────────────────────────────┤
353 │MT-Level │MT-Safe │
354 ├─────────────────────────────┼─────────────────────────────┤
355 │Standard │See below. │
356 └─────────────────────────────┴─────────────────────────────┘
357 For strftime(), see standards(5).
360
362 date(1), ctime(3C), mktime(3C), setlocale(3C), strptime(3C), tzset(3C),
363 TIMEZONE(4), zoneinfo(4), attributes(5), environ(5), standards(5)
364
366 The conversion specification for %V was changed in the Solaris 7
367 release. This change was based on the public review draft of the ISO
368 C9x standard at that time. Previously, the specification stated that if
369 the week containing 1 January had fewer than four days in the new year,
370 it became week 53 of the previous year. The ISO C9x standard committee
371 subsequently recognized that that specification had been incorrect.
372 The conversion specifications for %g, %G, %Eg, %EG, and %Og were added
375 in the Solaris 7 release. This change was based on the public review
376 draft of the ISO C9x standard at that time. These specifications are
377 evolving. If the ISO C9x standard is finalized with a different con‐
378 clusion, these specifications will change to conform to the ISO C9x
379 standard decision.
380 The conversion specification for %u was changed in the Solaris 8
383 release. This change was based on the XPG4 specification.
384 If using the %Z specifier and zoneinfo timezones and if the input date
387 is outside the range 20:45:52 UTC, December 13, 1901 to 03:14:07 UTC,
388 January 19, 2038, the timezone name may not be correct.
389SunOS 5.11 5 Sep 2006 strftime(3C)