---
name: "evs_initialize"
section: "3"
platform: "linux"
package: "corosync-dev"
version: "1.4.6-1.1"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/evs_initialize"
---

# evs\_initialize(3)

Create a new connection to the EVS service

## NAME

evs\_initialize - Create a new connection to the EVS service

## SYNOPSIS

**#include \<corosync/evs.h\>**

**int evs\_initialize(evs\_handle\_t \****handle***, evs\_callbacks\_t \****callbacks***);**

## DESCRIPTION

The **evs\_initialize** function is used to initialize a connection to the extended virtual synchrony API.

Each application may have several connections to the EVS API.  Each  application uses the *handle* argument to uniquely identify the connection.  The *handle* argument is then used in other function calls to identify the connection to be used for communication with the EVS service.

Every time an EVS event occurs, one of the callbacks specified by the argument *callbacks* is called.  The callback functions are described by the following type definitions:

-

  ```
  typedef void (*evs_deliver_fn_t) (
  	unsigned int nodeid,
          const void *msg,
          size_t msg_len);
  typedef void (*evs_confchg_fn_t) (
  	unsigned int *member_list, size_t member_list_entries,
  	unsigned int *left_list, size_t left_list_entries,
  	unsigned int *joined_list, size_t joined_list_entries);
  ```

-

  The *callbacks* argument is of the type:

-

  ```

  ```

  typedef struct {\
           evs\_deliver\_fn\_t evs\_deliver\_fn;\
           evs\_confchg\_fn\_t evs\_confchg\_fn; } evs\_callbacks\_t;

-

  When a configuration change occurs or a message is to be delivered one of the callbacks is called from the **evs\_dispatch()** function.  If a configuration change occurs, *evs\_confchg\_fn* is called.  If a delivery of a message occurs, *evs\_deliver\_fn* is called.

## RETURN VALUE

This call returns the EVS\_OK value if successful, otherwise an error is returned.

## ERRORS

The errors are undocumented.

## SEE ALSO

[**evs\_overview**(8)](/evs_overview/8.md), [**evs\_finalize**(3)](/evs_finalize/3.md), [**evs\_fd\_get**(3)](/evs_fd_get/3.md), [**evs\_dispatch**(3)](/evs_dispatch/3.md), [**evs\_join**(3)](/evs_join/3.md), [**evs\_leave**(3)](/evs_leave/3.md), [**evs\_mcast\_joined**(3)](/evs_mcast_joined/3.md), [**evs\_mcast\_groups**(3)](/evs_mcast_groups/3.md), [**evs\_membership\_get**(3)](/evs_membership_get/3.md) [**evs\_context\_get**(3)](/evs_context_get/3.md) [**evs\_context\_set**(3)](/evs_context_set/3.md)