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<PRE>
<!-- Manpage converted by man2html 3.0.1 -->
</PRE>
<H2>NAME</H2><PRE>
libcurl - client-side URL transfers
</PRE>
<H2>DESCRIPTION</H2><PRE>
This is an overview on how to use libcurl in your C pro
grams. There are specific man pages for each function men
tioned in here. There's also the libcurl-the-guide document
for a complete tutorial to programming with libcurl.
libcurl can also be used directly from within your Java,
PHP, Perl, Ruby or Tcl programs as well, look elsewhere for
documentation on this!
All applications that use libcurl should call
<I>curl</I><B>_</B><I>global</I><B>_</B><I>init()</I> exactly once before any libcurl function
can be used. After all usage of libcurl is complete, it <B>must</B>
call <I>curl</I><B>_</B><I>global</I><B>_</B><I>cleanup()</I>. In between those two calls, you
can use libcurl as described below.
When using libcurl you init your session and get a handle,
which you use as input to the following interface functions
you use. Use <I>curl</I><B>_</B><I>easy</I><B>_</B><I>init()</I> to get the handle.
You continue by setting all the options you want in the
upcoming transfer, most important among them is the URL
itself (you can't transfer anything without a specified URL
as you may have figured out yourself). You might want to set
some callbacks as well that will be called from the library
when data is available etc. <I>curl</I><B>_</B><I>easy</I><B>_</B><I>setopt()</I> is there for
this.
When all is setup, you tell libcurl to perform the transfer
using <I>curl</I><B>_</B><I>easy</I><B>_</B><I>perform()</I>. It will then do the entire oper
ation and won't return until it is done (successfully or
not).
After the transfer has been made, you can set new options
and make another transfer, or if you're done, cleanup the
session by calling <I>curl</I><B>_</B><I>easy</I><B>_</B><I>cleanup()</I>. If you want persis
tant connections, you don't cleanup immediately, but instead
run ahead and perform other transfers using the same handle.
See the chapter below for Persistant Connections.
There is also a series of other helpful functions to use.
They are:
<B>curl_version()</B>
displays the libcurl version
<B>curl_getdate()</B>
converts a date string to time_t
<B>curl_getenv()</B>
portable environment variable reader
<B>curl_easy_getinfo()</B>
get information about a performed transfer
<B>curl_formadd()</B>
helps building a HTTP form POST
<B>curl_formfree()</B>
free a list built with curl_form
parse()/curl_formadd()
<B>curl_slist_append()</B>
builds a linked list
<B>curl_slist_free_all()</B>
frees a whole curl_slist
<B>curl_mprintf()</B>
portable printf() functions
<B>curl_strequal()</B>
portable case insensitive string comparisons
</PRE>
<H2>LINKING WITH LIBCURL</H2><PRE>
Starting with 7.7.2 (on unix-like machines), there's a tool
named curl-config that gets installed with the rest of the
curl stuff when 'make install' is performed.
curl-config is added to make it easier for applications to
link with libcurl and developers to learn about libcurl and
how to use it.
Run 'curl-config --libs' to get the (additional) linker
options you need to link with the particular version of
libcurl you've installed.
For details, see the curl-config.1 man page.
</PRE>
<H2>LIBCURL SYMBOL NAMES</H2><PRE>
All public functions in the libcurl interface are prefixed
with 'curl_' (with a lowercase c). You can find other func
tions in the library source code, but other prefixes indi
cate the functions are private and may change without fur
ther notice in the next release.
Only use documented functions and functionality!
</PRE>
<H2>PORTABILITY</H2><PRE>
libcurl works <B>exactly</B> the same, on any of the platforms it
compiles and builds on.
There's only one caution, and that is the win32 platform
that may(*) require you to init the winsock stuff before you
use the libcurl functions. Details on this are noted on the
curl_easy_init() man page.
(*) = it appears as if users of the cygwin environment get
this done automatically, also libcurl 7.8.1 and later can
handle this for you.
</PRE>
<H2>THREADS</H2><PRE>
Never ever call curl-functions simultaneously using the same
handle from several threads. libcurl is thread-safe and can
be used in any number of threads, but you must use separate
curl handles if you want to use libcurl in more than one
thread simultaneously.
</PRE>
<H2>PERSISTANT CONNECTIONS</H2><PRE>
With libcurl 7.7, persistant connections were added. Persis
tant connections means that libcurl can re-use the same con
nection for several transfers, if the conditions are right.
libcurl will *always* attempt to use persistant connections.
Whenever you use curl_easy_perform(), libcurl will attempt
to use an existing connection to do the transfer, and if
none exists it'll open a new one that will be subject for
re-use on a possible following call to curl_easy_perform().
To allow libcurl to take full advantage of persistant con
nections, you should do as many of your file transfers as
possible using the same curl handle. When you call
curl_easy_cleanup(), all the possibly open connections held
by libcurl will be closed and forgotten.
Note that the options set with curl_easy_setopt() will be
used in on every repeat curl_easy_perform() call
</PRE>
<H2>COMPATIBILITY WITH OLDER LIBCURLS</H2><PRE>
Repeated curl_easy_perform() calls on the same handle were
not supported in pre-7.7 versions, and caused confusion and
undefined behaviour.
</PRE>
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