ISO 8601：2004中的C预处理器__TIMESTAMP__ [英] C preprocessor __TIMESTAMP__ in ISO 8601:2004

问题描述

如何在ISO 8601：2004中进行 __ TIMESTAMP __ 更换？

How can I have a __TIMESTAMP__ replacement in ISO 8601:2004?

__TIMESTAMP __

Sat Jul  6 02:50:06 2013

vs

__ TIMESTAMP_ISO __

2013-07-06T00:50:06Z

推荐答案

哦，你们乐观！你真的不希望一个标准注意另一个，你会吗？ __ TIMESTAMP __ define不在标准C中，只是你知道。这将是非常好的有一个格式，如你的建议 __ TIMESTAMP_ISO __ （你会永远想要祖鲁时间，还是最好有本地时区偏移？），但坦率地说

Oh ye optimist! You wouldn't really expect one standard to pay attention to another, would you? The __TIMESTAMP__ define is not in standard C, just so as you are aware. It would be great to have a format like your proposed __TIMESTAMP_ISO__ (would you always want Zulu time, or would it be better to have the local time zone offset?), but frankly, the easiest way to get it added might be a patch to GCC and Clang and so on.

您可以尝试使用 asctime（） / code>，由 user1034749 的

You can try monkeying with asctime() as suggested by user1034749's answer, but I'd rather not try that.

在GCC 4.8.1中 answer ，但我不想尝试。 /gcc.gnu.org/onlinedocs/\">手动，有一个有趣的警告抑制：

In the GCC 4.8.1 manual, there's an interesting warning suppression:

-Wno-builtin-macro-redefined

如果重新定义某些内置宏，则不要发出警告。这抑制了重新定义 __ TIMESTAMP __ ， __ TIME __ ， __ DATE __ ， __ FILE __ 和
__ BASE_FILE __ 。

这表明你可以尝试：

gcc ... -Wno-builtin-macro-redefined -D__TIMESTAMP__=$(date +'"%Y-%m-%dT%H:%M:%S"') ...

（请注意，从 date 获取字符串所需的象形文字必须用双引号括起。）然而，一些早期版本的GCC支持选项;我不记得以前看到它。您仍然可以重新定义 __ TIMESTAMP __ ：

(Note the hieroglyphics necessary to get the string from date surrounded by double quotes.) However, some earlier versions of GCC do not support the option; I don't recall seeing it before. You can still redefine __TIMESTAMP__:

$ gcc -std=c99   -Wall -Wextra  -O xx.c -o xx
$ ./xx 
Fri Jul  5 19:56:25 2013
$ gcc -std=c99 -Wall -Wextra -D__TIMESTAMP__=$(date +'"%Y-%m-%dT%H:%M:%S"') -O xx.c -o xx  
<command-line>: warning: "__TIMESTAMP__" redefined
$ ./xx
2013-07-05T20:10:28
$

$ b b

不是很漂亮，但它工作...哦，只是为了记录，源代码是（琐碎）：

Not very pretty, but it works... Oh, and just for the record, the source code was (trivial):

#include <stdio.h>

int main(void)
{
    printf("%s\n", __TIMESTAMP__);
    return 0;
}

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