NAME

       CURLOPT_DEBUGFUNCTION - debug callback

SYNOPSIS

       #include <curl/curl.h>

       typedef enum {
         CURLINFO_TEXT = 0,
         CURLINFO_HEADER_IN,    /* 1 */
         CURLINFO_HEADER_OUT,   /* 2 */
         CURLINFO_DATA_IN,      /* 3 */
         CURLINFO_DATA_OUT,     /* 4 */
         CURLINFO_SSL_DATA_IN,  /* 5 */
         CURLINFO_SSL_DATA_OUT, /* 6 */
         CURLINFO_END
       } curl_infotype;

       int debug_callback(CURL *handle,
                          curl_infotype type,
                          char *data,
                          size_t size,
                          void *clientp);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DEBUGFUNCTION,
                                 debug_callback);

DESCRIPTION

       Pass a pointer to your callback function, which should match the prototype shown above.

       CURLOPT_DEBUGFUNCTION(3) replaces the standard debug function used when CURLOPT_VERBOSE(3)
       is in effect. This callback receives debug information, as specified in the type argument.
       This  function must return 0. The data pointed to by the char * passed to this function is
       not null-terminated, but is exactly of the size as told by the size argument.

       The clientp argument is the pointer set with CURLOPT_DEBUGDATA(3).

       Available curl_infotype values:

       CURLINFO_TEXT
              The data is informational text.

       CURLINFO_HEADER_IN
              The data is header (or header-like) data received from the peer.

       CURLINFO_HEADER_OUT
              The data is header (or header-like) data sent to the peer.

       CURLINFO_DATA_IN
              The data is the unprocessed protocol data received from the peer. Even if the  data
              is  encoded  or  compressed,  it  is  not provided decoded nor decompressed to this
              callback.  If  you  need  the  data  in  decoded   and   decompressed   form,   use
              CURLOPT_WRITEFUNCTION(3).

       CURLINFO_DATA_OUT
              The data is protocol data sent to the peer.

       CURLINFO_SSL_DATA_OUT
              The data is SSL/TLS (binary) data sent to the peer.

       CURLINFO_SSL_DATA_IN
              The data is SSL/TLS (binary) data received from the peer.

       WARNING:  This  callback  may  be  called  with the curl handle set to an internal handle.
       (Added in 8.4.0)

       If  you  need  to  distinguish  your  curl  handle  from   internal   handles   then   set
       CURLOPT_PRIVATE(3) on your handle.

DEFAULT

       NULL

PROTOCOLS

       This functionality affects all supported protocols

EXAMPLE

       static
       void dump(const char *text,
                 FILE *stream, unsigned char *ptr, size_t size)
       {
         size_t i;
         size_t c;
         unsigned int width = 0x10;

         fprintf(stream, "%s, %10.10ld bytes (0x%8.8lx)\n",
                 text, (long)size, (long)size);

         for(i = 0; i < size; i += width) {
           fprintf(stream, "%4.4lx: ", (long)i);

           /* show hex to the left */
           for(c = 0; c < width; c++) {
             if(i + c < size)
               fprintf(stream, "%02x ", ptr[i + c]);
             else
               fputs("   ", stream);
           }

           /* show data on the right */
           for(c = 0; (c < width) && (i + c < size); c++) {
             char x = (ptr[i + c] >= 0x20 && ptr[i + c] < 0x80) ? ptr[i + c] : '.';
             fputc(x, stream);
           }

           fputc('\n', stream); /* newline */
         }
       }

       static
       int my_trace(CURL *handle, curl_infotype type,
                    char *data, size_t size,
                    void *clientp)
       {
         const char *text;
         (void)handle; /* prevent compiler warning */
         (void)clientp;

         switch(type) {
         case CURLINFO_TEXT:
           fputs("== Info: ", stderr);
           fwrite(data, size, 1, stderr);
         default: /* in case a new one is introduced to shock us */
           return 0;

         case CURLINFO_HEADER_OUT:
           text = "=> Send header";
           break;
         case CURLINFO_DATA_OUT:
           text = "=> Send data";
           break;
         case CURLINFO_SSL_DATA_OUT:
           text = "=> Send SSL data";
           break;
         case CURLINFO_HEADER_IN:
           text = "<= Recv header";
           break;
         case CURLINFO_DATA_IN:
           text = "<= Recv data";
           break;
         case CURLINFO_SSL_DATA_IN:
           text = "<= Recv SSL data";
           break;
         }

         dump(text, stderr, (unsigned char *)data, size);
         return 0;
       }

       int main(void)
       {
         CURL *curl;
         CURLcode res;

         curl = curl_easy_init();
         if(curl) {
           curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, my_trace);

           /* the DEBUGFUNCTION has no effect until we enable VERBOSE */
           curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

           /* example.com is redirected, so we tell libcurl to follow redirection */
           curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);

           curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
           res = curl_easy_perform(curl);
           /* Check for errors */
           if(res != CURLE_OK)
             fprintf(stderr, "curl_easy_perform() failed: %s\n",
                     curl_easy_strerror(res));

           /* always cleanup */
           curl_easy_cleanup(curl);
         }
         return 0;
       }

AVAILABILITY

       Added in curl 7.9.6

RETURN VALUE

       Returns CURLE_OK

SEE ALSO

       CURLINFO_CONN_ID(3),    CURLINFO_XFER_ID(3),   CURLOPT_DEBUGDATA(3),   CURLOPT_VERBOSE(3),
       curl_global_trace(3)