模拟log日志的写入。

调用write_log(pFile, format, ...);方法，即可写入日志，默认在行首加入时间显示。

代码如下：log.c

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

int write_log (FILE* pFile, const char *format, ...) {
va_list arg;
int done;

va_start (arg, format);
//done = vfprintf (stdout, format, arg);

time_t time_log = time(NULL);
struct tm* tm_log = localtime(&time_log);
fprintf(pFile, "%04d-%02d-%02d %02d:%02d:%02d ", tm_log->tm_year + 1900, tm_log->tm_mon + 1, tm_log->tm_mday, tm_log->tm_hour, tm_log->tm_min, tm_log->tm_sec);

done = vfprintf (pFile, format, arg);
va_end (arg);

fflush(pFile);
return done;
}

int main() {
FILE* pFile = fopen("123.txt", "a");
write_log(pFile, "%s %d %f\n", "is running", 10, 55.55);
fclose(pFile);

return 0;
}

编译运行：

gcc log.c -o log

./log 

返回结果：

2016-12-13 13:10:02 is running 10 55.550000
2016-12-13 13:10:04 is running 10 55.550000
2016-12-13 13:10:04 is running 10 55.550000