---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLSHOPT_SHARE
Section: 3
Source: libcurl
See-also:
  - CURLSHOPT_UNSHARE (3)
  - curl_share_cleanup (3)
  - curl_share_init (3)
  - curl_share_setopt (3)
Protocol:
  - All
Added-in: 7.10.3
---

# NAME

CURLSHOPT_SHARE - add data to share

# SYNOPSIS

~~~c
#include <curl/curl.h>

CURLSHcode curl_share_setopt(CURLSH *share, CURLSHOPT_SHARE, int type);
~~~

# DESCRIPTION

The *type* parameter specifies what specific data that should be shared
and kept in the share object that was created with curl_share_init(3).
The given *type* must be one of the values described below. You can set
CURLSHOPT_SHARE(3) multiple times with different data arguments to have
the share object share multiple types of data. Unset a type again by setting
CURLSHOPT_UNSHARE(3).

Do not add types to a shared object that is being in use. Add them only
between transfers.

If any of the data is to be shared in multiple threads then mutex callbacks
must be set as well. See CURLSHOPT_LOCKFUNC(3) and CURLSHOPT_UNLOCKFUNC(3).

## CURL_LOCK_DATA_COOKIE

Cookie data is shared across the easy handles using this shared object. Note
that this does not activate an easy handle's cookie handling. You can do that
separately by using CURLOPT_COOKIEFILE(3) for example.

It is not supported to share cookies between multiple concurrent threads.

## CURL_LOCK_DATA_DNS

Cached DNS hosts are shared across the easy handles using this shared
object. Note that when you use the multi interface, all easy handles added to
the same multi handle share the DNS cache by default without using this option.

## CURL_LOCK_DATA_SSL_SESSION

SSL sessions are shared across the easy handles using this shared object. This
reduces the time spent in the SSL handshake when reconnecting to the same
server.

Note that when you use the multi interface, all easy handles added to the same
multi handle share the SSL session cache by default without using this option.

## CURL_LOCK_DATA_CONNECT

Put the connection cache in the share object and make all easy handles using
this share object share the connection cache.

It is not supported to share connections between multiple concurrent threads.

Connections that are used for HTTP/2 or HTTP/3 multiplexing only get
additional transfers added to them if the existing connection is held by the
same multi or easy handle. libcurl does not support doing multiplexed streams
in different threads using a shared connection.

Note that when you use the multi interface, all easy handles added to the same
multi handle share the connection cache by default without using this option.

Connection limits set with CURLMOPT_MAX_HOST_CONNECTIONS(3) and
CURLMOPT_MAX_TOTAL_CONNECTIONS(3) also apply to transfers using a shared
connection cache. Each transfer applies the limits of the multi handle it
runs on to the shared cache.

## CURL_LOCK_DATA_PSL

The Public Suffix List stored in the share object is made available to all
easy handle bound to the later. Since the Public Suffix List is periodically
refreshed, this avoids updates in too many different contexts.

Added in 7.61.0.

Note that when you use the multi interface, all easy handles added to the same
multi handle share the PSL cache by default without using this option.

## CURL_LOCK_DATA_HSTS

The in-memory HSTS cache.

It is not supported to share the HSTS between multiple concurrent threads.

Added in 7.88.0

# %PROTOCOLS%

# EXAMPLE

~~~c
int main(void)
{
  CURLSHcode sh;
  CURLSH *share = curl_share_init();
  sh = curl_share_setopt(share, CURLSHOPT_SHARE, CURL_LOCK_DATA_COOKIE);
  if(sh)
    printf("Error: %s\n", curl_share_strerror(sh));
}
~~~

# %AVAILABILITY%

# RETURN VALUE

CURLSHE_OK (zero) means that the option was set properly, non-zero means an
error occurred. See libcurl-errors(3) for the full list with
descriptions.
