make http HEAD request in C using curl

check-url.c

// gcc *.c -lcurl && ./a.out http://example.com/path
#include <stdio.h>
#include <stdlib.h>
#include <curl/curl.h>

#define CHECK(setopt) do {			\
    CURLcode ret = (setopt);			\
    if (ret != CURLE_OK) {			\
      fputs("Failed " #setopt "\n", stderr);	\
      exit(ret);				\
    }						\
  } while(0)

static const long verbose = 1;
static const char *useragent = "check-url/0.0.1";

int main(int argc, char *argv[]) {
  CHECK(curl_global_init(CURL_GLOBAL_ALL));

 // get url to check from commmand-line
 if (argc != 2) {
   fprintf(stderr, "Usage: %s url\n", argv[0]);
   exit(1);
 }
 const char *url = argv[1];

 // make HEAD request
 CURL *hnd = curl_easy_init();
 if (hnd == NULL) {
   fputs("Failed to initialize\n", stderr);
   exit(2);
 }

 CHECK(curl_easy_setopt(hnd, CURLOPT_NOBODY, 1)); // HEAD
 CHECK(curl_easy_setopt(hnd, CURLOPT_VERBOSE, verbose));
 CHECK(curl_easy_setopt(hnd, CURLOPT_USERAGENT, useragent));
 CHECK(curl_easy_setopt(hnd, CURLOPT_NOPROGRESS, 1));
 CHECK(curl_easy_setopt(hnd, CURLOPT_FAILONERROR, 1)); //note: might fail for 401, 407
 CHECK(curl_easy_setopt(hnd, CURLOPT_URL, url));
 CURLcode ret = curl_easy_perform(hnd);
 curl_easy_cleanup(hnd);

 curl_global_cleanup();
 return (int)ret; // see http://curl.haxx.se/libcurl/c/libcurl-errors.html
}