| <html lang="en"> |
| <head> |
| <title>strftime - Untitled</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="Untitled"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Timefns.html#Timefns" title="Timefns"> |
| <link rel="prev" href="mktime.html#mktime" title="mktime"> |
| <link rel="next" href="time.html#time" title="time"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="strftime"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="time.html#time">time</a>, |
| Previous: <a rel="previous" accesskey="p" href="mktime.html#mktime">mktime</a>, |
| Up: <a rel="up" accesskey="u" href="Timefns.html#Timefns">Timefns</a> |
| <hr> |
| </div> |
| |
| <h3 class="section">8.8 <code>strftime</code>—convert date and time to a formatted string</h3> |
| |
| <p><a name="index-strftime-439"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <time.h> |
| size_t strftime(char *<var>s</var>, size_t <var>maxsize</var>, |
| const char *<var>format</var>, const struct tm *<var>timp</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| <code>strftime</code> converts a <code>struct tm</code> representation of the time (at |
| <var>timp</var>) into a null-terminated string, starting at <var>s</var> and occupying |
| no more than <var>maxsize</var> characters. |
| |
| <p>You control the format of the output using the string at <var>format</var>. |
| <code>*</code><var>format</var> can contain two kinds of specifications: text to be |
| copied literally into the formatted string, and time conversion |
| specifications. Time conversion specifications are two- and |
| three-character sequences beginning with `<code>%</code>' (use `<code>%%</code>' to |
| include a percent sign in the output). Each defined conversion |
| specification selects only the specified field(s) of calendar time |
| data from <code>*</code><var>timp</var>, and converts it to a string in one of the |
| following ways: |
| |
| <dl> |
| <dt><code>%a</code><dd>The abbreviated weekday name according to the current locale. [tm_wday] |
| |
| <br><dt><code>%A</code><dd>The full weekday name according to the current locale. |
| In the default "C" locale, one of `<code>Sunday</code>', `<code>Monday</code>', `<code>Tuesday</code>', |
| `<code>Wednesday</code>', `<code>Thursday</code>', `<code>Friday</code>', `<code>Saturday</code>'. [tm_wday] |
| |
| <br><dt><code>%b</code><dd>The abbreviated month name according to the current locale. [tm_mon] |
| |
| <br><dt><code>%B</code><dd>The full month name according to the current locale. |
| In the default "C" locale, one of `<code>January</code>', `<code>February</code>', |
| `<code>March</code>', `<code>April</code>', `<code>May</code>', `<code>June</code>', `<code>July</code>', |
| `<code>August</code>', `<code>September</code>', `<code>October</code>', `<code>November</code>', |
| `<code>December</code>'. [tm_mon] |
| |
| <br><dt><code>%c</code><dd>The preferred date and time representation for the current locale. |
| [tm_sec, tm_min, tm_hour, tm_mday, tm_mon, tm_year, tm_wday] |
| |
| <br><dt><code>%C</code><dd>The century, that is, the year divided by 100 then truncated. For |
| 4-digit years, the result is zero-padded and exactly two characters; |
| but for other years, there may a negative sign or more digits. In |
| this way, `<code>%C%y</code>' is equivalent to `<code>%Y</code>'. [tm_year] |
| <br><dt><code>%d</code><dd>The day of the month, formatted with two digits (from `<code>01</code>' to |
| `<code>31</code>'). [tm_mday] |
| |
| <br><dt><code>%D</code><dd>A string representing the date, in the form `<code>"%m/%d/%y"</code>'. |
| [tm_mday, tm_mon, tm_year] |
| |
| <br><dt><code>%e</code><dd>The day of the month, formatted with leading space if single digit |
| (from `<code>1</code>' to `<code>31</code>'). [tm_mday] |
| |
| <br><dt><code>%Ex</code><dd>In some locales, the E modifier selects alternative representations of |
| certain modifiers <code>x</code>. In newlib, it is ignored, and treated as %<code>x</code>. |
| |
| <br><dt><code>%F</code><dd>A string representing the ISO 8601:2000 date format, in the form |
| `<code>"%Y-%m-%d"</code>'. [tm_mday, tm_mon, tm_year] |
| |
| <br><dt><code>%g</code><dd>The last two digits of the week-based year, see specifier %G (from |
| `<code>00</code>' to `<code>99</code>'). [tm_year, tm_wday, tm_yday] |
| |
| <br><dt><code>%G</code><dd>The week-based year. In the ISO 8601:2000 calendar, week 1 of the year |
| includes January 4th, and begin on Mondays. Therefore, if January 1st, |
| 2nd, or 3rd falls on a Sunday, that day and earlier belong to the last |
| week of the previous year; and if December 29th, 30th, or 31st falls |
| on Monday, that day and later belong to week 1 of the next year. For |
| consistency with %Y, it always has at least four characters. |
| Example: "%G" for Saturday 2nd January 1999 gives "1998", and for |
| Tuesday 30th December 1997 gives "1998". [tm_year, tm_wday, tm_yday] |
| |
| <br><dt><code>%h</code><dd>Synonym for "%b". [tm_mon] |
| |
| <br><dt><code>%H</code><dd>The hour (on a 24-hour clock), formatted with two digits (from |
| `<code>00</code>' to `<code>23</code>'). [tm_hour] |
| |
| <br><dt><code>%I</code><dd>The hour (on a 12-hour clock), formatted with two digits (from |
| `<code>01</code>' to `<code>12</code>'). [tm_hour] |
| |
| <br><dt><code>%j</code><dd>The count of days in the year, formatted with three digits |
| (from `<code>001</code>' to `<code>366</code>'). [tm_yday] |
| |
| <br><dt><code>%k</code><dd>The hour (on a 24-hour clock), formatted with leading space if single |
| digit (from `<code>0</code>' to `<code>23</code>'). Non-POSIX extension (c.p. %I). [tm_hour] |
| |
| <br><dt><code>%l</code><dd>The hour (on a 12-hour clock), formatted with leading space if single |
| digit (from `<code>1</code>' to `<code>12</code>'). Non-POSIX extension (c.p. %H). [tm_hour] |
| |
| <br><dt><code>%m</code><dd>The month number, formatted with two digits (from `<code>01</code>' to `<code>12</code>'). |
| [tm_mon] |
| |
| <br><dt><code>%M</code><dd>The minute, formatted with two digits (from `<code>00</code>' to `<code>59</code>'). [tm_min] |
| |
| <br><dt><code>%n</code><dd>A newline character (`<code>\n</code>'). |
| |
| <br><dt><code>%Ox</code><dd>In some locales, the O modifier selects alternative digit characters |
| for certain modifiers <code>x</code>. In newlib, it is ignored, and treated as %<code>x</code>. |
| |
| <br><dt><code>%p</code><dd>Either `<code>AM</code>' or `<code>PM</code>' as appropriate, or the corresponding strings for |
| the current locale. [tm_hour] |
| |
| <br><dt><code>%P</code><dd>Same as '<code>%p</code>', but in lowercase. This is a GNU extension. [tm_hour] |
| |
| <br><dt><code>%r</code><dd>Replaced by the time in a.m. and p.m. notation. In the "C" locale this |
| is equivalent to "%I:%M:%S %p". In locales which don't define a.m./p.m. |
| notations, the result is an empty string. [tm_sec, tm_min, tm_hour] |
| |
| <br><dt><code>%R</code><dd>The 24-hour time, to the minute. Equivalent to "%H:%M". [tm_min, tm_hour] |
| |
| <br><dt><code>%S</code><dd>The second, formatted with two digits (from `<code>00</code>' to `<code>60</code>'). The |
| value 60 accounts for the occasional leap second. [tm_sec] |
| |
| <br><dt><code>%t</code><dd>A tab character (`<code>\t</code>'). |
| |
| <br><dt><code>%T</code><dd>The 24-hour time, to the second. Equivalent to "%H:%M:%S". [tm_sec, |
| tm_min, tm_hour] |
| |
| <br><dt><code>%u</code><dd>The weekday as a number, 1-based from Monday (from `<code>1</code>' to |
| `<code>7</code>'). [tm_wday] |
| |
| <br><dt><code>%U</code><dd>The week number, where weeks start on Sunday, week 1 contains the first |
| Sunday in a year, and earlier days are in week 0. Formatted with two |
| digits (from `<code>00</code>' to `<code>53</code>'). See also <code>%W</code>. [tm_wday, tm_yday] |
| |
| <br><dt><code>%V</code><dd>The week number, where weeks start on Monday, week 1 contains January 4th, |
| and earlier days are in the previous year. Formatted with two digits |
| (from `<code>01</code>' to `<code>53</code>'). See also <code>%G</code>. [tm_year, tm_wday, tm_yday] |
| |
| <br><dt><code>%w</code><dd>The weekday as a number, 0-based from Sunday (from `<code>0</code>' to `<code>6</code>'). |
| [tm_wday] |
| |
| <br><dt><code>%W</code><dd>The week number, where weeks start on Monday, week 1 contains the first |
| Monday in a year, and earlier days are in week 0. Formatted with two |
| digits (from `<code>00</code>' to `<code>53</code>'). [tm_wday, tm_yday] |
| |
| <br><dt><code>%x</code><dd>Replaced by the preferred date representation in the current locale. |
| In the "C" locale this is equivalent to "%m/%d/%y". |
| [tm_mon, tm_mday, tm_year] |
| |
| <br><dt><code>%X</code><dd>Replaced by the preferred time representation in the current locale. |
| In the "C" locale this is equivalent to "%H:%M:%S". [tm_sec, tm_min, tm_hour] |
| |
| <br><dt><code>%y</code><dd>The last two digits of the year (from `<code>00</code>' to `<code>99</code>'). [tm_year] |
| (Implementation interpretation: always positive, even for negative years.) |
| |
| <br><dt><code>%Y</code><dd>The full year, equivalent to <code>%C%y</code>. It will always have at least four |
| characters, but may have more. The year is accurate even when tm_year |
| added to the offset of 1900 overflows an int. [tm_year] |
| |
| <br><dt><code>%z</code><dd>The offset from UTC. The format consists of a sign (negative is west of |
| Greewich), two characters for hour, then two characters for minutes |
| (-hhmm or +hhmm). If tm_isdst is negative, the offset is unknown and no |
| output is generated; if it is zero, the offset is the standard offset for |
| the current time zone; and if it is positive, the offset is the daylight |
| savings offset for the current timezone. The offset is determined from |
| the TZ environment variable, as if by calling tzset(). [tm_isdst] |
| |
| <br><dt><code>%Z</code><dd>The time zone name. If tm_isdst is negative, no output is generated. |
| Otherwise, the time zone name is based on the TZ environment variable, |
| as if by calling tzset(). [tm_isdst] |
| |
| <br><dt><code>%%</code><dd>A single character, `<code>%</code>'. |
| </dl> |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| When the formatted time takes up no more than <var>maxsize</var> characters, |
| the result is the length of the formatted string. Otherwise, if the |
| formatting operation was abandoned due to lack of room, the result is |
| <code>0</code>, and the string starting at <var>s</var> corresponds to just those |
| parts of <code>*</code><var>format</var> that could be completely filled in within the |
| <var>maxsize</var> limit. |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| ANSI C requires <code>strftime</code>, but does not specify the contents of |
| <code>*</code><var>s</var> when the formatted string would require more than |
| <var>maxsize</var> characters. Unrecognized specifiers and fields of |
| <code>timp</code> that are out of range cause undefined results. Since some |
| formats expand to 0 bytes, it is wise to set <code>*</code><var>s</var> to a nonzero |
| value beforehand to distinguish between failure and an empty string. |
| This implementation does not support <code>s</code> being NULL, nor overlapping |
| <code>s</code> and <code>format</code>. |
| |
| <p><code>strftime</code> requires no supporting OS subroutines. |
| |
| <p><br> |
| <strong>Bugs</strong><br> |
| <code>strftime</code> ignores the LC_TIME category of the current locale, hard-coding |
| the "C" locale settings. |
| |
| <p><br> |
| |
| </body></html> |
| |