www.LinuxHowtos.org howtos, tips&tricks and tutorials for linux

from small one page howto to huge articles all in one place

Other .linuxhowtos.org sites:gentoo.linuxhowtos.org

Last additions:

using iotop to find disk usage hogs

words:

887

views:

209584

userrating:

May 25th. 2007:

Words

486

Views

258592

why adblockers are bad

Workaround and fixes for the current Core Dump Handling vulnerability affected kernels

words:

161

views:

149881

userrating:

April, 26th. 2006:

Words

Views

107373

New subdomain: toolsntoys.linuxhowtos.org

You are here: manpages

CURLOPT_DEBUGFUNCTION

Section: C Library Functions (3)
Updated: 202-0-19
Index Return to Main Contents

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.

WARNING: this callback may receive sensitive contents from headers and data, including information sent as CURLINFO_TEXT.

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;
  (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 result;

  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/");
    result = curl_easy_perform(curl);
    /* Check for errors */
    if(result != CURLE_OK)
      fprintf(stderr, "curl_easy_perform() failed: %sn",
              curl_easy_strerror(result));

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