text: /*
   * adder.c - a minimal CGI program that adds two numbers together
   */
  #include "csapp.h"
  
  int main(void) {
      char *buf, *p;
      char arg1[MAXLINE], arg2[MAXLINE], content[MAXLINE];
      int n1 = 0, n2 = 0;
  
      /* Extract the two arguments */
      if ((buf = getenv("QUERY_STRING")) != NULL) {
          p = strchr(buf, '&');
          *p = '\0';
          strcpy(arg1, buf);
          strcpy(arg2, p + 1);
          n1 = atoi(arg1);
          n2 = atoi(arg2);
      }
  
      /* Make the response body */
      sprintf(content, "Welcome to add.com: ");
      sprintf(content, "%sTHE Internet addition portal.\r\n<p>", content);
      sprintf(content, "%sThe answer is: %d + %d = %d\r\n<p>",
              content, n1, n2, n1 + n2);
      sprintf(content, "%sThanks for visiting!\r\n", content);
  
      /* Generate the HTTP response */
      printf("Content-length: %d\r\n", (int) strlen(content));
      printf("Content-type: text/html\r\n\r\n");
      printf("%s", content);
      fflush(stdout);
      exit(0);
  }
  