Thread: A C Function clone of PHP's file get contents()

I've developing PHP for a very long time now and have only messed with C on occasion. I have therefore got far too used to simple functions such as file_get_contents() to retrieve the HTML / Data stored on an external http server.

I am looking for a simple method ie. preferable a function in C which does the same thing as the PHP function without using a library such as libcurl which needs compiling etc. I'm using gcc to compile and have only half managed to write one which involves -lsocket and -lnsl

Thank you all

Thanks for your response matsp, it's not a case that I don't want to use libraries, rather that my uni provides a shell which is restricted and I'm failing miserably to get libcurl compiled / installed on there.

I obviously can put such a file such as curl.h into the directory but it doesn't function without compilation

Not exactly supposed to I just wanted to add a feature to download a data file within my software rather than me manually going getting a data file and SCPing it across

As I think I said, I half got something working which I found on coding.debuntu.org/system/files/htmlget.c, problem is that this will retrieve only the root ie. www.google.com not www.google.com/this_directory/this_file.dat

If you (or anyone) could help me get this working in the later case then a function with these libraries could be used

Code:

#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <netdb.h>
#include <string.h>
int create_tcp_socket();
char *get_ip(char *host);
char *build_get_query(char *host, char *page);
void usage();

#define HOST "coding.debuntu.org"
#define PAGE "/"
#define PORT 80
#define USERAGENT "HTMLGET 1.0"

int main(int argc, char **argv)
{
  struct sockaddr_in *remote;
  int sock;
  int tmpres;
  char *ip;
  char *get;
  char buf[BUFSIZ+1];
  char *host;
  char *page;

  if(argc == 1){
    usage();
    exit(2);
  }  
  host = argv[1];
  if(argc > 2){
    page = argv[2];
  }else{
    page = PAGE;
  }
  sock = create_tcp_socket();
  ip = get_ip(host);
  fprintf(stderr, "IP is %s\n", ip); 
  remote = (struct sockaddr_in *)malloc(sizeof(struct sockaddr_in *));
  remote->sin_family = AF_INET;
  tmpres = inet_pton(AF_INET, ip, (void *)(&(remote->sin_addr.s_addr)));
  if( tmpres < 0)  
  {
    perror("Can't set remote->sin_addr.s_addr");
    exit(1);
  }else if(tmpres == 0)
  {
    fprintf(stderr, "%s is not a valid IP address\n", ip);
    exit(1);
  }
  remote->sin_port = htons(PORT);

  if(connect(sock, (struct sockaddr *)remote, sizeof(struct sockaddr)) < 0){
    perror("Could not connect");
    exit(1);
  }
  get = build_get_query(host, page);
  fprintf(stderr, "Query is:\n<<START>>\n%s<<END>>\n", get);
  
  //Send the query to the server
  int sent = 0;
  while(sent < strlen(get))
  { 
    tmpres = send(sock, get+sent, strlen(get)-sent, 0);
    if(tmpres == -1){
      perror("Can't send query");
      exit(1);
    }
    sent += tmpres;
  }
  //now it is time to receive the page
  memset(buf, 0, sizeof(buf));
  int htmlstart = 0;
  char * htmlcontent;
  while((tmpres = recv(sock, buf, BUFSIZ, 0)) > 0){
    if(htmlstart == 0)
    {
      /* Under certain conditions this will not work.
      * If the \r\n\r\n part is splitted into two messages
      * it will fail to detect the beginning of HTML content
      */
      htmlcontent = strstr(buf, "\r\n\r\n");
      if(htmlcontent != NULL){
        htmlstart = 1;
        htmlcontent += 4;
      }
    }else{
      htmlcontent = buf;
    }
    if(htmlstart){
      fprintf(stdout, htmlcontent);
    }
 
    memset(buf, 0, tmpres);
  }
  if(tmpres < 0)
  {
    perror("Error receiving data");
  }
  free(get);
  free(remote);
  free(ip);
  close(sock);
  return 0;
}

void usage()
{
  fprintf(stderr, "USAGE: htmlget host [page]\n\
\thost: the website hostname. ex: coding.debuntu.org\n\
\tpage: the page to retrieve. ex: index.html, default: /\n");
}


int create_tcp_socket()
{
  int sock;
  if((sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0){
    perror("Can't create TCP socket");
    exit(1);
  }
  return sock;
}


char *get_ip(char *host)
{
  struct hostent *hent;
  int iplen = 15; //XXX.XXX.XXX.XXX
  char *ip = (char *)malloc(iplen+1);
  memset(ip, 0, iplen+1);
  if((hent = gethostbyname(host)) == NULL)
  {
    herror("Can't get IP");
    exit(1);
  }
  if(inet_ntop(AF_INET, (void *)hent->h_addr_list[0], ip, iplen) == NULL)
  {
    perror("Can't resolve host");
    exit(1);
  }
  return ip;
}

char *build_get_query(char *host, char *page)
{
  char *query;
  char *getpage = page;
  char *tpl = "GET /%s HTTP/1.0\r\nHost: %s\r\nUser-Agent: %s\r\n\r\n";
  if(getpage[0] == '/'){
    getpage = getpage + 1;
    fprintf(stderr,"Removing leading \"/\", converting %s to %s\n", page, getpage);
  }
  // -5 is to consider the %s %s %s in tpl and the ending \0
  query = (char *)malloc(strlen(host)+strlen(getpage)+strlen(USERAGENT)+strlen(tpl)-5);
  sprintf(query, tpl, getpage, host, USERAGENT);
  return query;
}

I get a crash with your code when printing the downloaded html if it contains "%" characters. The fix is to change:

Code:

    if(htmlstart){
      fprintf(stdout, htmlcontent);
    }

to:

Code:

    if(htmlstart){
      fprintf(stdout, "%s", htmlcontent);
    }

-- Geoff