Tribblix: manual page: CURLOPT

CURLOPT_DEBUGFUNCTION(3) Introduction to Library Functions

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

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).