C语言实现自定义printf函数，添加时间戳并输出到指定文件

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

void myprintf(FILE *fp, const char *fmt, ...) { va_list args; va_start(args, fmt);

time_t rawtime;
struct tm *timeinfo;
char buffer[80];

time(&rawtime);
timeinfo = localtime(&rawtime);

strftime(buffer, 80, '%Y-%m-%d %H:%M:%S ', timeinfo);
fprintf(fp, '%s', buffer);

vfprintf(fp, fmt, args);

va_end(args);

}

int main() { FILE *fp = fopen('output.txt', 'w'); if (fp == NULL) { printf('Failed to open file\n'); return 1; }

myprintf(fp, 'Hello, world!\n');
myprintf(fp, 'The answer is %d\n', 42);

fclose(fp);
return 0;

}