C libcurl get output into a string

Question

I want to store the result of this curl function in a variable, how can I do so?

#include <stdio.h> #include <curl/curl.h>  int main(void) {   CURL *curl;   CURLcode res;    curl = curl_easy_init();   if(curl) {     curl_easy_setopt(curl, CURLOPT_URL, "curl.haxx.se");     res = curl_easy_perform(curl);      /* always cleanup */     curl_easy_cleanup(curl);   }   return 0; } 

thanks, I solved it like this:

#include <stdio.h> #include <stdlib.h> #include <curl/curl.h>  function_pt(void *ptr, size_t size, size_t nmemb, void *stream){     printf("%d", atoi(ptr)); }  int main(void) {   CURL *curl;   curl = curl_easy_init();   if(curl) {     curl_easy_setopt(curl, CURLOPT_URL, "curl.haxx.se");     curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, function_pt);     curl_easy_perform(curl);     curl_easy_cleanup(curl);   }   system("pause");   return 0; } 

Answer 1

You can set a callback function to receive incoming data chunks using curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, myfunc);

The callback will take a user defined argument that you can set using curl_easy_setopt(curl, CURLOPT_WRITEDATA, p)

Here's a snippet of code that passes a buffer struct string {*ptr; len} to the callback function and grows that buffer on each call using realloc().

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <curl/curl.h>  struct string {   char *ptr;   size_t len; };  void init_string(struct string *s) {   s->len = 0;   s->ptr = malloc(s->len+1);   if (s->ptr == NULL) {     fprintf(stderr, "malloc() failed\n");     exit(EXIT_FAILURE);   }   s->ptr[0] = '\0'; }  size_t writefunc(void *ptr, size_t size, size_t nmemb, struct string *s) {   size_t new_len = s->len + size*nmemb;   s->ptr = realloc(s->ptr, new_len+1);   if (s->ptr == NULL) {     fprintf(stderr, "realloc() failed\n");     exit(EXIT_FAILURE);   }   memcpy(s->ptr+s->len, ptr, size*nmemb);   s->ptr[new_len] = '\0';   s->len = new_len;    return size*nmemb; }  int main(void) {   CURL *curl;   CURLcode res;    curl = curl_easy_init();   if(curl) {     struct string s;     init_string(&s);      curl_easy_setopt(curl, CURLOPT_URL, "curl.haxx.se");     curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writefunc);     curl_easy_setopt(curl, CURLOPT_WRITEDATA, &s);     res = curl_easy_perform(curl);      printf("%s\n", s.ptr);     free(s.ptr);      /* always cleanup */     curl_easy_cleanup(curl);   }   return 0; }