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在头文件<time.h>中定义



char * ctime（const time_t * time）;

(1)


errno_t ctime_s（char * buffer，rsize_t bufsz，const time_t * time）;

(2)

（自C11以来）

1）将时间以来的给定时间转换为当地日历，然后转换为文本表示，就像通过调用一样asctime(localtime(time))。

2）与（1）相同，只是该函数等同于asctime_s(buffer, bufsz, localtime_s(time, &(struct tm){0}))，并且在运行时检测到以下错误并调用当前安装的约束处理程序函数：

  • buffer或者time是空指针

  • bufsz小于26或大于RSIZE_MAX

与所有边界检查的函数一样，ctime_s只有__STDC_LIB_EXT1__在实现定义并且用户在包含之前定义__STDC_WANT_LIB_EXT1__为整数常量时1才能保证可用time.h。

结果字符串具有以下格式：

Www Mmm dd hh:mm:ss yyyy\n

  • Www-一周的一天（之一Mon，Tue，Wed，Thu，Fri，Sat，Sun）。

  • Mmm-月（一Jan，Feb，Mar，Apr，May，Jun，Jul，Aug，Sep，Oct，Nov，Dec）。

  • dd  - 每月的一天

  • hh - 小时

  • mm - 分钟

  • ss  - 秒

  • yyyy  - 年

该功能不支持本地化。

参数

时间

-

指向指定打印时间的time_t对象的指针

缓冲

-

指向大小至少为bufsz的char数组元素的指针

bufsz

-

最大输出字节数，通常是缓冲区指向的缓冲区的大小

返回值

1）指向保存日期和时间文本表示的静态空终止字符串的指针。该字符串可以在asctime和之间共享ctime，并且可以在每次调用这些函数时被覆盖。

2）成功时为零（在这种情况下，时间的字符串表示已经写入到所指向的数组buffer），或者在失败时为非零（在这种情况下，终止空字符总是被写入，buffer[0]除非buffer是空指针或者bufsz是零或大于RSIZE_MAX。

笔记

ctime返回一个指向静态数据的指针并且不是线程安全的。此外，它修改静态tm其可以与共享对象gmtime和localtime。POSIX将此功能标记为废弃，并推荐strftime使用。C标准也建议strftime不要使用ctime，ctime_s因为strftime它更灵活且对语言环境敏感。

ctimetime_t的值的行为可能未定义，导致字符串长于25个字符（例如，年份10000）。

例

#define __STDC_WANT_LIB_EXT1__ 1#include <time.h>#include <stdio.h>
 int main(void){
    time_t result = time(NULL);    printf("%s", ctime(&result));
 #ifdef __STDC_LIB_EXT1__
    char str[26];    ctime_s(str,sizeof str,&result);    printf("%s", str);#endif}

输出：

Tue May 26 21:51:03 2015Tue May 26 21:51:03 2015

参考

  • C11标准（ISO / IEC 9899：2011）：

    • 7.27.3.2 ctime函数（p：393）

    • K.3.8.2.2 ctime_s函数（p：626）

  • C99标准（ISO / IEC 9899：1999）：

    • 7.23.3.2 ctime函数（p：342）

  • C89 / C90标准（ISO / IEC 9899：1990）：

    • 4.12.3.2 ctime函数

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