CURLOPT_IOCTLDATA(3) Library Functions Manual CURLOPT_IOCTLDATA(3)
NAME
CURLOPT_IOCTLDATA - pointer passed to I/O callback
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_IOCTLDATA, void *pointer);
DESCRIPTION
Pass the pointer that is untouched by libcurl and passed as the 3rd ar-
gument in the ioctl callback set with CURLOPT_IOCTLFUNCTION(3).
DEFAULT
NULL
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
#include <unistd.h> /* for lseek */
struct data {
int fd; /* our file descriptor */
};
static curlioerr ioctl_callback(CURL *handle, int cmd, void *clientp)
{
struct data *io = (struct data *)clientp;
if(cmd == CURLIOCMD_RESTARTREAD) {
lseek(io->fd, 0, SEEK_SET);
return CURLIOE_OK;
}
return CURLIOE_UNKNOWNCMD;
}
int main(void)
{
struct data ioctl_data;
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_IOCTLFUNCTION, ioctl_callback);
curl_easy_setopt(curl, CURLOPT_IOCTLDATA, &ioctl_data);
}
}
DEPRECATED
Deprecated since 7.18.0.
AVAILABILITY
Added in curl 7.12.3
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).
SEE ALSO
CURLOPT_IOCTLFUNCTION(3), CURLOPT_SEEKFUNCTION(3)
libcurl 2026-07-12 CURLOPT_IOCTLDATA(3)
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