mirror of
https://github.com/curl/curl.git
synced 2024-11-27 05:50:21 +08:00
121 lines
4.7 KiB
Groff
121 lines
4.7 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 are also the
|
|
\fIlibcurl-easy\fP man page, the \fIlibcurl-multi\fP man page, the
|
|
\fIlibcurl-share\fP man page and the \fIlibcurl-the-guide\fP document for
|
|
further reading on how to do programming with libcurl.
|
|
|
|
There exist more than 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.
|
|
|
|
To transfer files, you always set up an "easy handle" using
|
|
\fIcurl_easy_init()\fP, but when you want the file(s) transfered you have the
|
|
option of using the "easy" interface, or the "multi" interface.
|
|
|
|
The easy interface is a synchronous interface with which you call
|
|
\fIcurl_easy_perform\fP and let it perform the transfer. When it is completed,
|
|
the function return and you can continue. More details are found in the
|
|
\fIlibcurl-easy\fP man page.
|
|
|
|
The multi interface on the other hand is an asynchronous interface, that you
|
|
call and that performs only a little piece of the tranfer on each invoke. It
|
|
is perfect if you want to do things while the transfer is in progress, or
|
|
similar. The multi interface allows you to select() on libcurl action, and
|
|
even to easily download multiple files simultaneously using a single thread.
|
|
|
|
You can have multiple easy handles share certain data, even if they are used
|
|
in different threads. This magic is setup using the share interface, as
|
|
described in the \fIlibcurl-share\fP man page.
|
|
|
|
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
|
|
\fIcurl_easy_perform()\fP or \fIcurl_multi_perform()\fP, 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
|
|
\fIcurl_easy_perform()\fP or \fIcurl_multi_perform()\fP.
|
|
|
|
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 \fIcurl_easy_cleanup()\fP, all the possibly open connections held by
|
|
libcurl will be closed and forgotten.
|
|
|
|
Note that the options set with \fIcurl_easy_setopt()\fP will be used in on
|
|
every repeated \fIcurl_easy_perform()\fP call.
|