curl_global_init
Section: C Library Functions (3)
Updated: 202-0-19
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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 on most platforms. Then curl_version_info(3) has
the threadsafe feature set (added in 7.84.0).
If this is not thread-safe (the bit mentioned above is not set), 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 only mean other threads that use
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 flagaqs 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.
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
int main(void)
{
CURLcode result;
result = curl_global_init(CURL_GLOBAL_DEFAULT);
if(result == CURLE_OK) {
/* use libcurl, then before exiting... */
curl_global_cleanup();
}
}
AVAILABILITY
Added in curl 7.8
RETURN VALUE
If this function returns non-zero, something went wrong and you cannot use the
other curl functions.
SEE ALSO
curl_easy_init(3),
curl_global_cleanup(3),
curl_global_init_mem(3),
curl_global_sslset(3),
curl_global_trace(3),
libcurl(3)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- FLAGS
-
- PROTOCOLS
-
- EXAMPLE
-
- AVAILABILITY
-
- RETURN VALUE
-
- SEE ALSO
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