CURLOPT_VERBOSE - Man Page

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_VERBOSE, long onoff);

Set the onoff parameter to 1 to make the library display a lot of verbose information about its operations on this handle. Useful for libcurl and/or protocol debugging and understanding. The verbose information is sent to stderr, or the stream set with CURLOPT_STDERR(3).

You hardly ever want this enabled in production use, you almost always want this used when you debug/report problems.

To also get all the protocol data sent and received, consider using the CURLOPT_DEBUGFUNCTION(3).

0, meaning disabled.

This functionality affects all supported protocols

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

    /* ask libcurl to show us the verbose output */
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

    /* Perform the request */
    curl_easy_perform(curl);
  }
}

Added in curl 7.1

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

CURLOPT_DEBUGFUNCTION(3), CURLOPT_ERRORBUFFER(3), CURLOPT_STDERR(3), curl_global_trace(3)

curl_easy_setopt(3), curl_global_trace(3), CURLOPT_CONNECT_ONLY(3), CURLOPT_COOKIEJAR(3), CURLOPT_DEBUGFUNCTION(3), CURLOPT_DOH_URL(3), CURLOPT_ERRORBUFFER(3), CURLOPT_NOPROGRESS(3), CURLOPT_PRIVATE(3), CURLOPT_PROGRESSFUNCTION(3), CURLOPT_STDERR(3), CURLOPT_XFERINFODATA(3), libcurl-easy(3), libcurl-errors(3), libcurl-symbols(3), libcurl-tutorial(3), nbdkit-curl-plugin(1).