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121 lines
4.6 KiB
Groff
121 lines
4.6 KiB
Groff
.\" You can view this file with:
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.\" nroff -man [file]
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.\" $Id$
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.\"
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.TH libcurl 3 "19 March 2002" "libcurl 7.9.6" "libcurl overview"
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.SH NAME
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libcurl \- client-side URL transfers
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.SH DESCRIPTION
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This is an overview on how to use libcurl in your C programs. There are
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specific man pages for each function mentioned in here. There's also the
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libcurl-the-guide document for a complete tutorial to programming with
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libcurl.
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There are a dozen custom bindings that bring libcurl access to your favourite
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language. Look elsewhere for documentation on those.
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All applications that use libcurl should call \fIcurl_global_init()\fP exactly
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once before any libcurl function can be used. After all usage of libcurl is
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complete, it \fBmust\fP call \fIcurl_global_cleanup()\fP. In between those two
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calls, you can use libcurl as described below.
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When using libcurl's "easy" interface you init your session and get a handle,
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which you use as input to the easy interface functions you use. Use
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\fIcurl_easy_init()\fP to get the handle. There is also the so called "multi"
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interface, try the \fIlibcurl-multi(3)\fP man page for an overview of that.
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You continue by setting all the options you want in the upcoming transfer,
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most important among them is the URL itself (you can't transfer anything
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without a specified URL as you may have figured out yourself). You might want
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to set some callbacks as well that will be called from the library when data
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is available etc. \fIcurl_easy_setopt()\fP is there for this.
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When all is setup, you tell libcurl to perform the transfer using
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\fIcurl_easy_perform()\fP. It will then do the entire operation and won't
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return until it is done (successfully or not).
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After the transfer has been made, you can set new options and make another
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transfer, or if you're done, cleanup the session by calling
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\fIcurl_easy_cleanup()\fP. If you want persistant connections, you don't
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cleanup immediately, but instead run ahead and perform other transfers using
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the same handle. See the chapter below for Persistant Connections.
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There is also a series of other helpful functions to use. They are:
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.RS
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.TP 10
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.B curl_version()
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displays the libcurl version
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.TP
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.B curl_getdate()
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converts a date string to time_t
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.TP
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.B curl_getenv()
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portable environment variable reader
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.TP
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.B curl_easy_getinfo()
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get information about a performed transfer
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.TP
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.B curl_formadd()
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helps building a HTTP form POST
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.TP
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.B curl_formfree()
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free a list built with curl_formparse()/curl_formadd()
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.TP
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.B curl_slist_append()
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builds a linked list
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.TP
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.B curl_slist_free_all()
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frees a whole curl_slist
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.TP
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.B curl_mprintf()
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portable printf() functions
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.TP
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.B curl_strequal()
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portable case insensitive string comparisons
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.RE
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.SH "LINKING WITH LIBCURL"
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On unix-like machines, there's a tool named curl-config that gets installed
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with the rest of the curl stuff when 'make install' is performed.
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curl-config is added to make it easier for applications to link with libcurl
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and developers to learn about libcurl and how to use it.
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Run 'curl-config --libs' to get the (additional) linker options you need to
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link with the particular version of libcurl you've installed.
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For details, see the curl-config.1 man page.
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.SH "LIBCURL SYMBOL NAMES"
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All public functions in the libcurl interface are prefixed with 'curl_' (with
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a lowercase c). You can find other functions in the library source code, but
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other prefixes indicate the functions are private and may change without
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further notice in the next release.
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Only use documented functions and functionality!
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.SH "PORTABILITY"
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libcurl works
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.B exactly
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the same, on any of the platforms it compiles and builds on.
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.SH "THREADS"
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Never ever call curl-functions simultaneously using the same handle from
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several threads. libcurl is thread-safe and can be used in any number of
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threads, but you must use separate curl handles if you want to use libcurl in
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more than one thread simultaneously.
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.SH "PERSISTANT CONNECTIONS"
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Persistent connections means that libcurl can re-use the same connection for
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several transfers, if the conditions are right.
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libcurl will *always* attempt to use persistent connections. Whenever you use
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curl_easy_perform(), libcurl will attempt to use an existing connection to do
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the transfer, and if none exists it'll open a new one that will be subject for
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re-use on a possible following call to curl_easy_perform().
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To allow libcurl to take full advantage of persistent connections, you should
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do as many of your file transfers as possible using the same curl handle. When
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you call curl_easy_cleanup(), all the possibly open connections held by
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libcurl will be closed and forgotten.
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Note that the options set with curl_easy_setopt() will be used in on every
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repeat curl_easy_perform() call
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