121 lines
4.6 KiB
Groff
121 lines
4.6 KiB
Groff
.\" You can view this file with:
|
|
.\" nroff -man [file]
|
|
.\" $Id$
|
|
.\"
|
|
.TH libcurl 3 "19 March 2002" "libcurl 7.9.6" "libcurl overview"
|
|
.SH NAME
|
|
libcurl \- client-side URL transfers
|
|
.SH DESCRIPTION
|
|
This is an overview on how to use libcurl in your C programs. There are
|
|
specific man pages for each function mentioned in here. There's also the
|
|
libcurl-the-guide document for a complete tutorial to programming with
|
|
libcurl.
|
|
|
|
There are a dozen custom bindings that bring libcurl access to your favourite
|
|
language. Look elsewhere for documentation on those.
|
|
|
|
All applications that use libcurl should call \fIcurl_global_init()\fP exactly
|
|
once before any libcurl function can be used. After all usage of libcurl is
|
|
complete, it \fBmust\fP call \fIcurl_global_cleanup()\fP. In between those two
|
|
calls, you can use libcurl as described below.
|
|
|
|
When using libcurl's "easy" interface you init your session and get a handle,
|
|
which you use as input to the easy interface functions you use. Use
|
|
\fIcurl_easy_init()\fP to get the handle. There is also the so called "multi"
|
|
interface, try the \fIlibcurl-multi(3)\fP man page for an overview of that.
|
|
|
|
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. \fIcurl_easy_setopt()\fP is there for this.
|
|
|
|
When all is setup, you tell libcurl to perform the transfer using
|
|
\fIcurl_easy_perform()\fP. It will then do the entire operation 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
|
|
\fIcurl_easy_cleanup()\fP. If you want persistant 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:
|
|
|
|
.RS
|
|
.TP 10
|
|
.B curl_version()
|
|
displays the libcurl version
|
|
.TP
|
|
.B curl_getdate()
|
|
converts a date string to time_t
|
|
.TP
|
|
.B curl_getenv()
|
|
portable environment variable reader
|
|
.TP
|
|
.B curl_easy_getinfo()
|
|
get information about a performed transfer
|
|
.TP
|
|
.B curl_formadd()
|
|
helps building a HTTP form POST
|
|
.TP
|
|
.B curl_formfree()
|
|
free a list built with curl_formparse()/curl_formadd()
|
|
.TP
|
|
.B curl_slist_append()
|
|
builds a linked list
|
|
.TP
|
|
.B curl_slist_free_all()
|
|
frees a whole curl_slist
|
|
.TP
|
|
.B curl_mprintf()
|
|
portable printf() functions
|
|
.TP
|
|
.B curl_strequal()
|
|
portable case insensitive string comparisons
|
|
.RE
|
|
|
|
.SH "LINKING WITH LIBCURL"
|
|
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.
|
|
.SH "LIBCURL SYMBOL NAMES"
|
|
All public functions in the libcurl interface are prefixed with 'curl_' (with
|
|
a lowercase c). You can find other functions in the library source code, but
|
|
other prefixes indicate the functions are private and may change without
|
|
further notice in the next release.
|
|
|
|
Only use documented functions and functionality!
|
|
.SH "PORTABILITY"
|
|
libcurl works
|
|
.B exactly
|
|
the same, on any of the platforms it compiles and builds on.
|
|
.SH "THREADS"
|
|
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.
|
|
.SH "PERSISTANT CONNECTIONS"
|
|
Persistent connections means that libcurl can re-use the same connection for
|
|
several transfers, if the conditions are right.
|
|
|
|
libcurl will *always* attempt to use persistent 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 persistent connections, 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
|