.\" generated by cd2nroff 0.1 from CURLOPT_IOCTLDATA.md
.TH CURLOPT_IOCTLDATA 3 "March 22 2024" libcurl
.SH NAME
CURLOPT_IOCTLDATA \- pointer passed to I/O callback
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_IOCTLDATA, void *pointer);
.fi
.SH DESCRIPTION
Pass the \fIpointer\fP that is untouched by libcurl and passed as the 3rd
argument in the ioctl callback set with \fICURLOPT_IOCTLFUNCTION(3)\fP.
.SH DEFAULT
By default, the value of this parameter is NULL.
.SH PROTOCOLS
Used with HTTP
.SH EXAMPLE
.nf
#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);
  }
}
.fi
.SH AVAILABILITY
Added in 7.12.3. Deprecated since 7.18.0.
.SH RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
.SH SEE ALSO
.BR CURLOPT_IOCTLFUNCTION (3),
.BR CURLOPT_SEEKFUNCTION (3)