---
name: "CURLOPT_SSH_HOSTKEYDATA"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_SSH_HOSTKEYDATA"
---

# CURLOPT\_SSH\_HOSTKEYDATA(3)

pointer to pass to the SSH host key callback

## NAME

CURLOPT\_SSH\_HOSTKEYDATA - pointer to pass to the SSH host key callback

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSH_HOSTKEYDATA, void *pointer);
```

## DESCRIPTION

Pass a void \* as parameter. This *pointer* is passed along untouched to the callback set with *[CURLOPT\_SSH\_HOSTKEYFUNCTION(3)](/CURLOPT_SSH_HOSTKEYFUNCTION/3.md)*.

## DEFAULT

NULL

## PROTOCOLS

This functionality affects scp and sftp

## EXAMPLE

```
struct mine {
  void *custom;
};
static int hostkeycb(void *clientp,   /* CURLOPT_SSH_HOSTKEYDATA */
                     int keytype,     /* CURLKHTYPE */
                     const char *key, /* host key to check */
                     size_t keylen)   /* length of the key */
{
  /* 'clientp' points to the callback_data struct */
  /* investigate the situation and return the correct value */
  return CURLKHMATCH_OK;
}
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    struct mine callback_data;
    curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/thisfile.txt");
    curl_easy_setopt(curl, CURLOPT_SSH_HOSTKEYFUNCTION, hostkeycb);
    curl_easy_setopt(curl, CURLOPT_SSH_HOSTKEYDATA, &callback_data);
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## NOTES

Works only with the libssh2 backend.

## AVAILABILITY

Added in curl 7.84.0

## RETURN VALUE

*[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see *[libcurl-errors(3)](/libcurl-errors/3.md)*.

## SEE ALSO

[**CURLOPT\_SSH\_HOSTKEYFUNCTION**(3)](/CURLOPT_SSH_HOSTKEYFUNCTION/3.md)