Ubuntu Manpage: curl_global_init - Global libcurl initialization

Provided by: libcurl4-doc_8.5.0-2ubuntu10.6_all

NAME

       curl_global_init - Global libcurl initialization

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_global_init(long flags);

DESCRIPTION

       This  function  sets  up  the  program environment that libcurl needs. Think of it as an extension of the
       library loader.

       This function must be called at least once within a program (a program is all  the  code  that  shares  a
       memory  space)  before  the  program  calls  any other function in libcurl. The environment it sets up is
       constant for the life of the program and is the same for every program, so multiple calls have  the  same
       effect as one call.

       The  flags  option is a bit pattern that tells libcurl exactly what features to init, as described below.
       Set  the  desired  bits  by  ORing  the  values  together.   In  normal  operation,  you   must   specify
       CURL_GLOBAL_ALL.  Do not use any other value unless you are familiar with it and mean to control internal
       operations of libcurl.

       This function is thread-safe since libcurl 7.84.0 if curl_version_info(3) has the CURL_VERSION_THREADSAFE
       feature bit set (most platforms).

       If  this is not thread-safe, you must not call this function when any other thread in the program (i.e. a
       thread sharing the same memory) is running.  This does not just  mean  no  other  thread  that  is  using
       libcurl. Because curl_global_init(3) calls functions of other libraries that are similarly thread unsafe,
       it could conflict with any other thread that uses these other libraries.

       If you are initializing libcurl from a Windows DLL you should not initialize it from DllMain or a  static
       initializer because Windows holds the loader lock during that time and it could cause a deadlock.

       See  the  description  in  libcurl(3)  of  global environment requirements for details of how to use this
       function.

FLAGS

CURL_GLOBAL_ALL
Initialize everything possible. This sets all known bits except CURL_GLOBAL_ACK_EINTR.

CURL_GLOBAL_SSL
(This flag's presence or absence serves no meaning since 7.57.0. The description below is for
older libcurl versions.)

Initialize SSL.

The implication here is that if this bit is not set, the initialization of the SSL layer needs to
be done by the application or at least outside of libcurl. The exact procedure how to do SSL
initialization depends on the TLS backend libcurl uses.

Doing TLS based transfers without having the TLS layer initialized may lead to unexpected
behaviors.

CURL_GLOBAL_WIN32
Initialize the Win32 socket libraries.

The implication here is that if this bit is not set, the initialization of winsock has to be done
by the application or you risk getting undefined behaviors. This option exists for when the
initialization is handled outside of libcurl so there is no need for libcurl to do it again.

CURL_GLOBAL_NOTHING
Initialize nothing extra. This sets no bit.

CURL_GLOBAL_DEFAULT
A sensible default. It initializes both SSL and Win32. Right now, this equals the functionality of
the CURL_GLOBAL_ALL mask.

CURL_GLOBAL_ACK_EINTR
This bit has no point since 7.69.0 but its behavior is instead the default.

Before 7.69.0: when this flag is set, curl acknowledges EINTR condition when connecting or when
waiting for data. Otherwise, curl waits until full timeout elapses. (Added in 7.30.0)

EXAMPLE

       int main(void)
       {
         curl_global_init(CURL_GLOBAL_DEFAULT);

         /* use libcurl, then before exiting... */

         curl_global_cleanup();
       }

AVAILABILITY

       Added in 7.8

RETURN VALUE

       If this function returns non-zero, something went wrong and you cannot use the other curl functions.