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ares_library_init(3) [centos man page]

ARES_LIBRARY_INIT(3)					     Library Functions Manual					      ARES_LIBRARY_INIT(3)

ares_library_init - c-ares library initialization SYNOPSIS
#include <ares.h> int ares_library_init(int flags) cc file.c -lcares DESCRIPTION
The ares_library_init function performs initializations internally required by the c-ares library that must take place before any other function provided by c-ares can be used in a program. This function must be called at least once within the life of a program, before the program actually executes any other c-ares library function. Initializations done by this function remain effective until a number of calls to ares_library_cleanup(3) equal to the number of calls to this function are performed. Successive calls to this function do nothing further, only the first call done when c-ares is in an uninitialized state is actually effec- tive. The flags parameter is a bit pattern that tells c-ares exactly which features should be initialized, as described below. Set the desired bits by ORing the values together. In normal operation you should specify ARES_LIB_INIT_ALL. Don't use any other value unless you are familiar with it and trying to control some internal c-ares feature. This function is not thread safe. You have to call it once the program has started, but this call must be done before the program starts any other thread. This is required to avoid potential race conditions in library initialization, and also due to the fact that ares_library_init(3) might call functions from other libraries that are thread unsafe, and could conflict with any other thread that is already using these other libraries. Win32/64 application DLLs shall not call ares_library_init(3) from the DllMain function. Doing so will produce deadlocks and other prob- lems. FLAGS
ARES_LIB_INIT_ALL Initialize everything possible. This sets all known bits. ARES_LIB_INIT_WIN32 Initialize Win32/64 specific libraries. ARES_LIB_INIT_NONE Initialize nothing extra. This sets no bit. RETURN VALUE
Upon successful completion, ares_library_init() will return 0. Otherwise, a non-zero error number will be returned to indicate the error. Except for ares_strerror(3), you shall not call any other c-ares function upon ares_library_init(3) failure. AVAILABILITY
This function was first introduced in c-ares version 1.7.0 along with the definition of preprocessor symbol CARES_HAVE_ARES_LIBRARY_INIT as an indication of the availability of this function. Its recursive behavior, which requires a matching number of calls to ares_library_cleanup() in order to deinitialize the library, is present since c-ares version 1.10.0. Earlier versions would deinitialize the library on the first call to ares_library_cleanup(). Since the introduction of this function it is absolutely mandatory to call it for any Win32/64 program using c-ares. Non-Win32/64 systems can still use c-ares version 1.7.0 without calling ares_library_init(3) due to the fact that currently it is nearly a do-nothing function on non-Win32/64 platforms at this point. SEE ALSO
ares_library_cleanup(3), ares_strerror(3) AUTHOR
Yang Tse Copyright 1998 by the Massachusetts Institute of Technology. Copyright (C) 2004-2009 by Daniel Stenberg. 19 May 2009 ARES_LIBRARY_INIT(3)

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ARES_GET_SERVERS(3)					     Library Functions Manual					       ARES_GET_SERVERS(3)

ares_get_servers - Retrieve name servers from an initialized ares_channel SYNOPSIS
#include <ares.h> int ares_get_servers(ares_channel channel, struct ares_addr_node **servers) DESCRIPTION
The ares_get_servers(3) function retrieves name servers configuration from the channel data identified by channel, as a linked list of ares_addr_node structs storing a pointer to the first node at the address specified by servers. Function caller may traverse the returned name server linked list, or may use it directly as suitable input for the ares_set_servers(3) function, but shall not shrink or extend the list on its own. Each node of the name server linked list is stored in memory dynamically allocated and managed by c-ares. It is the caller's responsibility to free the resulting linked list, using ares_free_data(3) , once the caller does not need it any longer. This function is capable of handling IPv4 and IPv6 name server addresses simultaneously, rendering ares_save_options(3) with optmask ARES_OPT_SERVERS functionally obsolete except for IPv4-only name server usage. RETURN VALUES
ares_get_servers(3) may return any of the following values: ARES_SUCCESS The name servers configuration was successfuly retrieved ARES_ENOMEM The memory was exhausted ARES_ENODATA The channel data identified by channel was invalid. SEE ALSO
ares_set_servers(3), ares_init_options(3), ares_save_options(3) AVAILABILITY
ares_get_servers(3) was added in c-ares 1.7.1 AUTHOR
Implementation of this function and associated library internals are based on code, comments and feedback provided in November and December of 2008 by Daniel Stenberg, Gregor Jasny, Phil Blundell and Yang Tse, December 2009 by Cedric Bail, February 2010 by Jakub Hrozek. On March 2010 Yang Tse shuffled all the bits and this function popped out. Copyright 1998 by the Massachusetts Institute of Technology. Copyright (C) 2008-2010 by Daniel Stenberg 5 March 2010 ARES_GET_SERVERS(3)
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