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.TH CURLOPT_DEBUGFUNCTION 3 "March 23, 2020" "libcurl 7.70.0" "curl_easy_setopt options"

.SH NAME
CURLOPT_DEBUGFUNCTION \- debug callback
.SH SYNOPSIS
.nf
#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 *userptr);

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DEBUGFUNCTION,
                          debug_callback);
.SH DESCRIPTION
Pass a pointer to your callback function, which should match the prototype
shown above.

\fICURLOPT_DEBUGFUNCTION(3)\fP replaces the standard debug function used when
\fICURLOPT_VERBOSE(3)\fP is in effect. This callback receives debug
information, as specified in the \fItype\fP argument. This function must
return 0. The \fIdata\fP pointed to by the char * passed to this function WILL
NOT be zero terminated, but will be exactly of the \fIsize\fP as told by the
\fIsize\fP argument.

The \fIuserptr\fP argument is the pointer set with \fICURLOPT_DEBUGDATA(3)\fP.

Available curl_infotype values:
.IP CURLINFO_TEXT
The data is informational text.
.IP CURLINFO_HEADER_IN
The data is header (or header-like) data received from the peer.
.IP CURLINFO_HEADER_OUT
The data is header (or header-like) data sent to the peer.
.IP CURLINFO_DATA_IN
The data is protocol data received from the peer.
.IP CURLINFO_DATA_OUT
The data is protocol data sent to the peer.
.IP CURLINFO_SSL_DATA_OUT
The data is SSL/TLS (binary) data sent to the peer.
.IP CURLINFO_SSL_DATA_IN
The data is SSL/TLS (binary) data received from the peer.
.SH DEFAULT
NULL
.SH PROTOCOLS
All
.SH EXAMPLE
.nf
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 *userp)
{
  const char *text;
  (void)handle; /* prevent compiler warning */
  (void)userp;

  switch (type) {
  case CURLINFO_TEXT:
    fprintf(stderr, "== Info: %s", data);
  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, "http://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;
}
.fi
.SH AVAILABILITY
Always
.SH RETURN VALUE
Returns CURLE_OK
.SH "SEE ALSO"
.BR CURLOPT_VERBOSE "(3), " CURLOPT_DEBUGDATA "(3), "