C语言实现log日志的写入

转载自 https://blog.csdn.net/subaofa/article/details/53609857

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：cat 123.txt
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