libcurl-share

Section: libcurl share interface (3)
Updated: November 05, 2020
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NAME

libcurl-share - how to use the share interface

DESCRIPTION

This is an overview on how to use the libcurl share interface in your C programs. There are specific man pages for each function mentioned in here.

All functions in the share interface are prefixed with curl_share.

OBJECTIVES

The share interface was added to enable sharing of data between curl "handles".

ONE SET OF DATA - MANY TRANSFERS

You can have multiple easy handles share data between them. Have them update and use the same cookie database, DNS cache, TLS session cache and/or connection cache! This way, each single transfer will take advantage from data updates made by the other transfer(s).

SHARE OBJECT

You create a shared object with curl_share_init(3). It returns a handle for a newly created one.

You tell the shared object what data you want it to share by using curl_share_setopt(3).

Since you can use this share from multiple threads, and libcurl has no internal thread synchronization, you must provide mutex callbacks if you're using this multi-threaded. You set lock and unlock functions with curl_share_setopt(3) too.

Then, you make an easy handle to use this share, you set the CURLOPT_SHARE(3) option with curl_easy_setopt(3), and pass in share handle. You can make any number of easy handles share the same share handle.

To make an easy handle stop using that particular share, you set CURLOPT_SHARE(3) to NULL for that easy handle. To make a handle stop sharing a particular data, you can CURLSHOPT_UNSHARE it.

When you're done using the share, make sure that no easy handle is still using it, and call curl_share_cleanup(3) on the handle.