blocks|key|70084|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|70085|我可以使用strptime()解析到几分之一秒，但是手册页提到了setlocale()，所以我担心我需要做些什么。我有吗？|blockquote|offset|length|style|CODE|70086|70087|70088|是的，遗憾的是；根据区域设置，%25S可能会占用小数秒，并且可能会查找小数逗号而不是小数点。|70089|就我个人而言，我会完全手工完成这项工作，使用strtok和strtol，填充struct+tm的适当字段。您不必填写tm_yday和tm_wday即可使mktime正常工作。|70090|我假设我可以用TZ偏移量的分钟数来修改我从strptime获得的tm_min。对，是这样?|70091|70092|这比看起来要难。根据时区偏移量的实际值，您将需要调整tm_hr和tm_min+(实际上，常见的情况是整型小时数，因此您将调整tm_hr而不是tm_min)，如果调整将时间推到了一天的界限上，您将需要标准化小时并确定日、月和年。|70093|您还必须确保tm_isdst和tm_gmtoff为零，并且tm_zone为空。|70094|70095|我可以只在开始时清除TZ和tzset()一次吗？|70096|70097|70098|在一个“预期方式”有效的系统上，是的。然而，“预期的方式”并不能保证工作，事实上，如果你没有timegm，我希望它不能工作。|70099|使用timegm。如果你没有timegm，那就用get+it+from+gnulib。|70100|entityMap|0|LINK|mutability|MUTABLE|url|https://www.gnu.org/software/gnulib/manual/html_node/timegm.html#timegm^0|0|5|A|W|B|0|0|0|0|M|6|T|6|12|9|1M|7|1U|7|24|6|0|W|6|0|0|Q|5|W|6|1Q|5|1Y|6|0|6|8|F|9|T|7|0|0|0|0|0|1A|6|0|2|6|E|6|10|6|O|I|0|0^^$0|@$1|2|3|-4|4|5|6|1B|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|1C|7|@$D|1D|E|1E|F|G]|$D|1F|E|1G|F|G]]|8|@]|9|$]]|$1|H|3|-4|4|5|6|1H|7|@]|8|@]|9|$]]|$1|I|3|-4|4|5|6|1I|7|@]|8|@]|9|$]]|$1|J|3|K|4|5|6|1J|7|@]|8|@]|9|$]]|$1|L|3|M|4|5|6|1K|7|@$D|1L|E|1M|F|G]|$D|1N|E|1O|F|G]|$D|1P|E|1Q|F|G]|$D|1R|E|1S|F|G]|$D|1T|E|1U|F|G]|$D|1V|E|1W|F|G]]|8|@]|9|$]]|$1|N|3|O|4|5|6|1X|7|@$D|1Y|E|1Z|F|G]]|8|@]|9|$]]|$1|P|3|-4|4|5|6|20|7|@]|8|@]|9|$]]|$1|Q|3|R|4|5|6|21|7|@$D|22|E|23|F|G]|$D|24|E|25|F|G]|$D|26|E|27|F|G]|$D|28|E|29|F|G]]|8|@]|9|$]]|$1|S|3|T|4|5|6|2A|7|@$D|2B|E|2C|F|G]|$D|2D|E|2E|F|G]|$D|2F|E|2G|F|G]]|8|@]|9|$]]|$1|U|3|-4|4|5|6|2H|7|@]|8|@]|9|$]]|$1|V|3|W|4|C|6|2I|7|@]|8|@]|9|$]]|$1|X|3|-4|4|5|6|2J|7|@]|8|@]|9|$]]|$1|Y|3|-4|4|5|6|2K|7|@]|8|@]|9|$]]|$1|Z|3|10|4|5|6|2L|7|@$D|2M|E|2N|F|G]]|8|@]|9|$]]|$1|11|3|12|4|5|6|2O|7|@$D|2P|E|2Q|F|G]|$D|2R|E|2S|F|G]|$D|2T|E|2U|F|G]]|8|@$D|2V|E|2W|1|2X]]|9|$]]|$1|13|3|-4|4|5|6|2Y|7|@]|8|@]|9|$]]]|14|$15|$4|16|17|18|9|$19|1A]]]]

<blockquote>
 I can use <code>strptime()</code> to parse up to the fractional seconds, but the man page mentions <code>setlocale()</code> so I worry that I need to do something with that. Do I?
</blockquote>

Yes, unfortunately; depending on the locale, %S might consume fractional seconds, and might look for a decimal comma rather than a decimal point.

Personally, I would do this completely by hand, with <code>strtok</code> and <code>strtol</code>, filling in the appropriate fields of the <code>struct tm</code>. You do not have to fill in <code>tm_yday</code> and <code>tm_wday</code> for <code>mktime</code> to work.

<blockquote>
 I assume I can just modify <code>tm_min</code> I got from strptime with the number of minutes of TZ offset. Correct?
</blockquote>

This is harder than it looks. Depending on the actual value of the timezone offset, you will need to adjust <code>tm_hr</code> as well as <code>tm_min</code> (in fact, the common case is a whole number of hours, so you'll adjust <code>tm_hr</code> and not <code>tm_min</code>), and if the adjustment pushed the time over a day boundary you will need to normalize the hour and fix up the day, month, and year.

You must also make sure that <code>tm_isdst</code> and <code>tm_gmtoff</code> are zero and <code>tm_zone</code> is NULL.

<blockquote>
 Can I just clear TZ and tzset() once at the beginning?
</blockquote>

On a system where the "expected way" works, yes. However, the "expected way" is not guaranteed to work, and in fact if you don't have <code>timegm</code> I would expect it not to work.

Use <code>timegm</code>. If you don't have <code>timegm</code>, <a href="https://www.gnu.org/software/gnulib/manual/html_node/timegm.html#timegm" rel="nofollow noreferrer">get it from <code>gnulib</code></a>.

blocks|key|69533|text|事实证明，写你自己的极简主义'mktime+w/o时区胡言乱语‘并不是那么难。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|69534|#define+divis(y,n)+(((y)+%25+(n))+==+0)
#define+isLY(y)+(divis((y),4)+&&+(!divis((y),100)+%7C%7C+divis((y),400)))
#define+nLY(y)++(((y)+-+1969)+/+4+-+((y)+-+1901)+/+100+%2B+((y)+-+1601)+/+400)

static+int++++++mdays[]+++++++++=+{31,28,31,30,31,30,31,31,30,31,30,31};

/*
+*+mktime+implicitly+applies+the+local+timezone,+this+doesn't.
+*+This+also+only+works+with+valid+values,+no+checking+or+normalizing+happens.
+*/
static+time_t+epoch+(
++++++++struct+tm+*+++++tm
)+{
++++++++int+++++years+++++++++++=+tm->tm_year+%2B+1900;
++++++++int+++++months++++++++++=+tm->tm_mon;
++++++++int+++++days++++++++++++=+tm->tm_mday+-+1;
++++++++int+++++hours+++++++++++=+tm->tm_hour;
++++++++int+++++minutes+++++++++=+tm->tm_min;
++++++++int+++++seconds+++++++++=+tm->tm_sec;

++++++++if+((months+>+1)+&&+isLY(years))+%2B%2Bdays;
++++++++while+(months--+>+0)+days+%2B=+mdays[months];
++++++++days+%2B=+(365+*+(years+-+1970))+%2B+nLY(years);
++++++++return+(time_t)((86400+*+days)+%2B+(3600+*+hours)+%2B+(60+*+minutes)+%2B+seconds);
}|code-block|syntax|javascript|69535|因此，我将把这一点与@zwol的答案中的建议结合起来，即“手动”解析字符串，而不必处理strptime()、mktime()和struct+tm可能的特性。|offset|length|style|CODE|69536|entityMap^0|0|0|17|A|1I|8|1R|9|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]|$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|N|$]]

Turns out that writing your own minimalist 'mktime w/o timezone nonsense' isn't that hard.

<pre><code>#define divis(y,n) (((y) % (n)) == 0)
#define isLY(y) (divis((y),4) &amp;&amp; (!divis((y),100) || divis((y),400)))
#define nLY(y) (((y) - 1969) / 4 - ((y) - 1901) / 100 + ((y) - 1601) / 400)

static int mdays[] = {31,28,31,30,31,30,31,31,30,31,30,31};

/*
 * mktime implicitly applies the local timezone, this doesn't.
 * This also only works with valid values, no checking or normalizing happens.
 */
static time_t epoch (
 struct tm * tm
) {
 int years = tm-&gt;tm_year + 1900;
 int months = tm-&gt;tm_mon;
 int days = tm-&gt;tm_mday - 1;
 int hours = tm-&gt;tm_hour;
 int minutes = tm-&gt;tm_min;
 int seconds = tm-&gt;tm_sec;

 if ((months &gt; 1) &amp;&amp; isLY(years)) ++days;
 while (months-- &gt; 0) days += mdays[months];
 days += (365 * (years - 1970)) + nLY(years);
 return (time_t)((86400 * days) + (3600 * hours) + (60 * minutes) + seconds);
}
</code></pre>

So, I'll combine this with the suggestion in @zwol 's answer to just parse the string 'by hand' rather than have to deal with <code>strptime()</code>, <code>mktime()</code> and <code>struct tm</code>'s possible idiosyncrasies.

What is the correct way to parse ISO8601 datetimes into a time_t?

The input strings are a particular variant of ISO8601 datetimes:

<blockquote>
 1991-02-03T04:05:06.000-07:00 
 (I do not need to worry about the 'Z' or implied localtime variants)
</blockquote>

I can use <code>strptime()</code> to parse up to the fractional seconds, but the man page mentions <code>setlocale()</code> so I worry that I need to do something with that. Do I? Or is that just for things like month and day names?

There doesn't seem to be any way to skip over (or handle) the fractional seconds in strptime, and my version of it doesn't seem to support '%z' anyway (and <code>tm_gmtoff</code> is non-standard), so I'm stuck parsing the fractional seconds and time zone offset of the input 'by hand'. Easy enough.

So I assume I can just modify <code>tm_min</code> I got from strptime with the number of minutes of TZ offset. Correct?

Then we come to <code>mktime()</code>. It appears that the expected way to force it to function in UTC is:

<blockquote>
 get TZ, clear TZ, <code>tzset()</code>, <code>mktime()</code>, reset TZ, <code>tzset()</code> 
 (there is a <code>timegm()</code> but is non-standard)
</blockquote>

I'm going to be processing lots of these strings and I don't care about any other time processing in this program, so this seems like a lot of worthless overhead, Can I just clear TZ and <code>tzset()</code> once at the beginning?

How to parse ISO8601 into a time_t?

将ISO8601 datetimes解析为time_t的正确方法是什么？输入字符串是ISO8601日期时间的特定变体： 1991-02-03T04:05:06.000-07:00(我不需要担心'Z‘或隐含的本地时间变体)我可以使用strptime()解析到几分之一秒，但是手册页提到了setlocale()，所以我担心我...

问如何将ISO8601解析为time_t？
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何将ISO8601解析为time_t？EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何将ISO8601解析为time_t？
EN