#include <stdio.h>
void write_data2file()
{
    FILE *fp;
    char buffer[100];
    memset(buffer,0,sizeof(buffer));
    fp=fopen("data.log","a+");
    if( NULL != fp )
    {
        sprintf(buffer,"I want to write some data \n");
        fputs(buffer,fp);
        fclose(fp);
     }
     else
     {
         printf("Cant't Open log file\n");
     }
}