....ordinary webserver cannot and should not write files to /var/www/.....

/*
*Scale65  Write data to Serial Port and Read it
*
*/ 
#include <termios.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

#define MODEMDEVICE "/dev/ttyS0"


int main(void) 
{
    char buf[64];
    int pos=0, num, num2,num3;
    FILE *fp1, *fp2;   
    int i, n3;

    system("stty -F /dev/ttyS0 1:0:80000dad:0:3:1c:7f:15:4:5:1:0:11:13:1a:0:12:f:17:16:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0");

    fp1 = fopen(MODEMDEVICE, "w+");
    fp2 = fopen("/tmp/testfile.txt", "w+");
    if(fp1 == NULL)
    {
        printf("initiation error. \n");
            return 1;
    }

    setvbuf(fp1, NULL, _IONBF, 0);
    fprintf(fp1, "%s","W\r\n");
    memset(buf, 0, sizeof(buf));
    fread(buf, 1, 7,fp1 );
    fputs(buf, stdout);
    for(i= 0; i < strlen(buf) ; i++)
        printf("%c", buf[i]);

    printf("You entered the string %s\n",buf);

    fclose(fp1);
    fwrite(buf, 1, 7,fp2 );
    fclose(fp2);

}