an example on how you can use the write callback to receive data in a memory

chunk

docs/examples/getinmemory.c

+/*****************************************************************************
+ *                                  _   _ ____  _     
+ *  Project                     ___| | | |  _ \| |    
+ *                             / __| | | | |_) | |    
+ *                            | (__| |_| |  _ <| |___ 
+ *                             \___|\___/|_| \_\_____|
+ *
+ * $Id$
+ *
+ * Example source code to show how the callback function can be used to
+ * download data into a chunk of memory instead of storing it in a file.
+ *
+ * This exact source code has not been verified to work.
+ */
+
+/* to make this work under windows, use the win32-functions from the
+   win32socket.c file as well */
+
+#include <stdio.h>
+
+#include <curl/curl.h>
+#include <curl/types.h>
+#include <curl/easy.h>
+
+struct MemoryStruct {
+  char *memory;
+  size_t size;
+};
+
+size_t
+WriteMemoryCallback(void *ptr, size_t size, size_t nmemb, void *data)
+{
+  register int realsize = size * nmemb;
+  struct MemoryStruct *mem = (struct MemoryStruct *)data;
+  
+  mem->memory = (char *)realloc(mem->memory, mem->size + realsize + 1);
+  if (mem->memory) {
+    memcpy(&(mem->memory[mem->size]), ptr, realsize);
+    mem->size += realsize;
+    mem->memory[mem->size] = 0;
+  }
+  return realsize;
+}
+
+int main(int argc, char **argv)
+{
+  CURL *curl;
+  CURLcode res;
+
+  struct MemoryStruct chunk;
+
+  chunk.memory=NULL; /* we expect realloc(NULL, size) to work */
+  chunk.size = 0;    /* no data at this point */
+
+  /* init the curl session */
+  curl_handle = curl_easy_init();
+
+  /* specify URL to get */
+  curl_easy_setopt(curl_handle, CURLOPT_URL, "http://cool.haxx.se/");
+
+  /* send all data to this function  */
+  curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
+
+  /* we pass our 'chunk' struct to the callback function */
+  curl_easy_setopt(curl_handle, CURLOPT_FILE, (void *)&chunk);
+
+  /* get it! */
+  curl_easy_perform(curl_handle);
+
+  /* cleanup curl stuff */
+  curl_easy_cleanup(curl_handle);
+
+  /*
+   * Now, our chunk.memory points to a memory block that is chunk.size
+   * bytes big and contains the remote file.
+   *
+   * Do something nice with it!
+   */
+
+  return 0;
+}