Can't get sprintf, strcat and char arrays working together

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  • MimiMi
    New Member
    • Aug 2007
    • 42
    #1

    Can't get sprintf, strcat and char arrays working together

    I'm trying to put together a http response header. It seems to work, except for that I don't get the data string added correctly!

    I wouldn't be surprised if my problems have something to do with my still existing confusion over arrays and pointers in C since I'm still a newbie, but anyhow, here's the code:

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

#define WEBBUF_SIZE 32768

int webbuflen;
char webbuf[WEBBUF_SIZE];

static char OKheader[] = "HTTP/1.1 200 OK\r\n";
static char texthtmlheader[] = "Connection: close\r\nContent-Type: text/html\r\n";
static char contentLenheader[] = "Content-Length: ";

static char data[] = "<html><head><title>Testing</title></head><body>Test,test,test, testing, test.</body></html>\n";

int main()
{ 
  http_response();
  return 0;
}

int getTimeStamp(unsigned char* timestring)
{ 
  struct tm *ptr;
  time_t tm;
  tm = time(NULL);
  ptr = localtime(&tm);
  strftime(timestring ,100 , "Date: %a, %d %b %Y %H:%M:%S GMT\r\n",ptr);
  return 0;
}

int http_response()
{
  char tmp[10];
  char datestring[60];
  char header[1048];

  //Get content-length (length of data) as a string
  sprintf(tmp,"%d%s",(strlen(data)+1),"\r\n\r\n");
  strcat(contentLenheader,tmp);

  getTimeStamp(datestring);

  //write everything to header
  sprintf(header, "%s%s%s%s", OKheader,datestring, texthtmlheader,contentLenheader);

  //Appending data to header
  strcat(header,data);

  //Adding header to webbuf
  webbuflen = sprintf(webbuf, "%s",header);
  
  printf("\nWebbuflen is now: %d",webbuflen);
  printf("\nAnd webbuf is: \n\n%s",webbuf);
  
  return 0;
}
    I get this printout when I run this program:

    Webbuflen is now: 123
    And webbuf is:

    HTTP/1.1 200 OK
    Date: Fri, 22 Feb 2008 09:14:59 GMT
    Connection: close
    Content-Type: text/html
    Content-Length: 93


    But I would like to get:

    HTTP/1.1 200 OK
    Date: Fri, 22 Feb 2008 09:14:59 GMT
    Connection: close
    Content-Type: text/html
    Content-Length: 93

    <html><head><ti tle>Testing</title></head><body>Test ,test,test, testing, test.</body></html>

    Any help or pointers in the right direction is greatly appreciated!
    Cheers!
    Tags: None
    • arthurshen
      New Member
      • Feb 2008
      • 8
      #2
      Originally posted by MimiMi
      I'm trying to put together a http response header. It seems to work, except for that I don't get the data string added correctly!

      I wouldn't be surprised if my problems have something to do with my still existing confusion over arrays and pointers in C since I'm still a newbie, but anyhow, here's the code:

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

#define WEBBUF_SIZE 32768

int webbuflen;
char webbuf[WEBBUF_SIZE];

static char OKheader[] = "HTTP/1.1 200 OK\r\n";
static char texthtmlheader[] = "Connection: close\r\nContent-Type: text/html\r\n";
static char contentLenheader[] = "Content-Length: ";

static char data[] = "<html><head><title>Testing</title></head><body>Test,test,test, testing, test.</body></html>\n";

int main()
{ 
  http_response();
  return 0;
}

int getTimeStamp(unsigned char* timestring)
{ 
  struct tm *ptr;
  time_t tm;
  tm = time(NULL);
  ptr = localtime(&tm);
  strftime(timestring ,100 , "Date: %a, %d %b %Y %H:%M:%S GMT\r\n",ptr);
  return 0;
}

int http_response()
{
  char tmp[10];
  char datestring[60];
  char header[1048];

  //Get content-length (length of data) as a string
  sprintf(tmp,"%d%s",(strlen(data)+1),"\r\n\r\n");
  strcat(contentLenheader,tmp);

  getTimeStamp(datestring);

  //write everything to header
  sprintf(header, "%s%s%s%s", OKheader,datestring, texthtmlheader,contentLenheader);

  //Appending data to header
  strcat(header,data);

  //Adding header to webbuf
  webbuflen = sprintf(webbuf, "%s",header);
  
  printf("\nWebbuflen is now: %d",webbuflen);
  printf("\nAnd webbuf is: \n\n%s",webbuf);
  
  return 0;
}
      I get this printout when I run this program:

      Webbuflen is now: 123
      And webbuf is:

      HTTP/1.1 200 OK
      Date: Fri, 22 Feb 2008 09:14:59 GMT
      Connection: close
      Content-Type: text/html
      Content-Length: 93


      But I would like to get:

      HTTP/1.1 200 OK
      Date: Fri, 22 Feb 2008 09:14:59 GMT
      Connection: close
      Content-Type: text/html
      Content-Length: 93

      <html><head><ti tle>Testing</title></head><body>Test ,test,test, testing, test.</body></html>

      Any help or pointers in the right direction is greatly appreciated!
      Cheers!
      Dear:MimiMi

      Increasing your contentLenheade r[] size.Then you will find out your answer.Good luck :)

        Comment

        • MimiMi
          New Member
          • Aug 2007
          • 42
          #3
          Originally posted by arthurshen
          Dear:MimiMi

          Increasing your contentLenheade r[] size.Then you will find out your answer.Good luck :)
          Thank you so much! That solved the problem!
          I still don't understand why though.. Do you (or anybody else) mind trying to explain why my solution didn't work, please :) ?

            Comment

            • arthurshen
              New Member
              • Feb 2008
              • 8
              #4
              Originally posted by MimiMi
              Thank you so much! That solved the problem!
              I still don't understand why though.. Do you (or anybody else) mind trying to explain why my solution didn't work, please :) ?
              Dear:MimiMi

              First,you need to know how array initiated in C.

              Initiated automatically by compiler.It's look like your

              solution.Or declare array by yourself.

              What's difference between them ???

              Then research strcat() function,and you will getting

              something wrong on line 39 in your codes.

              Finally,I am glad to answer your question.It's also help

              me to practice me English.ha ha~~ :)

              (Wish you understand what I say) 冏rz

                Comment

                • MimiMi
                  New Member
                  • Aug 2007
                  • 42
                  #5
                  Hi and thanks again for taking the time! I think I understand it a little bit better now, so again, thank you!

                  Cheers!

                    Comment

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