CURLOPT\_SSH\_HOSTKEYDATA(3) Library Functions Manual CURLOPT\_SSH\_HOSTKEYDATA(3)

# [NAME](#NAME)

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

# [SYNOPSIS](#SYNOPSIS)

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

# [DESCRIPTION](#DESCRIPTION)

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

# [DEFAULT](#DEFAULT)

NULL

# [PROTOCOLS](#PROTOCOLS)

This functionality affects scp and sftp

# [EXAMPLE](#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](#NOTES)

Works only with the libssh2 backend.

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.84.0

# [RETURN VALUE](#RETURN_VALUE)

[*curl\_easy\_setopt(3)*](/man/os/curl/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)*](/man/os/curl/libcurl-errors.3).

# [SEE ALSO](#SEE_ALSO)

[**CURLOPT\_SSH\_HOSTKEYFUNCTION**(3)](/man/os/curl/CURLOPT_SSH_HOSTKEYFUNCTION.3)

2026-10-14 libcurl

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Document: CURLOPT_SSH_HOSTKEYDATA(3) from curl 8.23.0-r0 (Chainguard OS)
Source: https://github.com/curl/curl.git