如何获得以C表示的unix时间戳?

I would like to get the current timestamp and print it out using fprintf.

我想要得到当前的时间戳并使用fprintf打印出来。

4 个解决方案

#1

For 32-bit systems:

32位系统:

fprintf(stdout, "%u\n", (unsigned)time(NULL));

For 64-bit systems:

64位系统:

fprintf(stdout, "%lu\n", (unsigned long)time(NULL));

#2

Is just casting the value returned by time()

只是转换time()返回的值

#include <stdio.h>
#include <time.h>

int main(void) {
    printf("Timestamp: %d\n",(int)time(NULL));
    return 0;
}

what you want?

是你想要的吗?

$ gcc -Wall -Wextra -pedantic -std=c99 tstamp.c && ./a.out
Timestamp: 1343846167

To get microseconds since the epoch, from C11 on, the portable way is to use

从C11开始，为了得到微秒，便携式的方法就是使用。

int timespec_get(struct timespec *ts, int base)

Unfortunately, C11 is not yet available everywhere, so as of now, the closest to portable is using one of the POSIX functions clock_gettime or gettimeofday (marked obsolete in POSIX.1-2008, which recommends clock_gettime).

不幸的是，C11在任何地方都没有可用，所以到目前为止，最接近便携的是使用一个POSIX函数clock_gettime或gettimeofday(在POSIX.1-2008中被标记为过时，它推荐clock_gettime)。

The code for both functions is nearly identical:

两种功能的代码几乎相同:

#include <stdio.h>
#include <time.h>
#include <stdint.h>
#include <inttypes.h>

int main(void) {

    struct timespec tms;

    /* The C11 way */
    /* if (! timespec_get(&tms, TIME_UTC)) { */

    /* POSIX.1-2008 way */
    if (clock_gettime(CLOCK_REALTIME,&tms)) {
        return -1;
    }
    /* seconds, multiplied with 1 million */
    int64_t micros = tms.tv_sec * 1000000;
    /* Add full microseconds */
    micros += tms.tv_nsec/1000;
    /* round up if necessary */
    if (tms.tv_nsec % 1000 >= 500) {
        ++micros;
    }
    printf("Microseconds: %"PRId64"\n",micros);
    return 0;
}

#3

With second precision, you can print tv_sec field of timeval structure that you get from gettimeofday() function. For example:

通过第二个精度，您可以打印从gettimeofday()函数获得的tv_sec时间结构字段。例如:

#include <sys/time.h>
#include <stdio.h>

int main()
{
    struct timeval tv;
    gettimeofday(&tv, NULL);
    printf("Seconds since Jan. 1, 1970: %ld\n", tv.tv_sec);
    return 0;
}

Example of compiling and running:

编译和运行示例:

$ gcc -Wall -o test ./test.c 
$ ./test 
Seconds since Jan. 1, 1970: 1343845834

Note, however, that its been a while since epoch and so long int is used to fit a number of seconds these days.

然而，请注意，这是一段时间以来的新纪元，如此长的int一直被用来适应数秒的时间。

There are also functions to print human-readable times. See this manual page for details. Here goes an example using ctime():

还有打印人类可读时间的功能。详情请参阅本手册页。这里有一个使用ctime()的例子:

#include <time.h>
#include <stdio.h>

int main()
{
    time_t clk = time(NULL);
    printf("%s", ctime(&clk));
    return 0;
}

Example run & output:

示例运行&输出:

$ gcc -Wall -o test ./test.c 
$ ./test 
Wed Aug  1 14:43:23 2012
$

#4

#include <stdio.h>
#include <time.h>

int main ()
{
   time_t seconds;

   seconds = time(NULL);
   printf("Seconds since January 1, 1970 = %ld\n", seconds);

   return(0);
}

And will get similar result:
Seconds since January 1, 1970 = 1476107865

并将得到类似的结果:自1970年1月1日以来的秒= 1476107865

#1