curl_easy_setopt.html

专门介绍网络爬虫设计的论文,写得非常好啊.希望大家好好学习

<p class="level1">Set the <span Class="emphasis">stream</span> argument with the <a class="emphasis" href="#CURLOPTWRITEDATA">CURLOPT_WRITEDATA</a> option. 
<p class="level1">The callback function will be passed as much data as possible in all invokes, but you cannot possibly make any assumptions. It may be one byte, it may be thousands. The maximum amount of data that can be passed to the write callback is defined in the curl.h header file: CURL_MAX_WRITE_SIZE. 
<p class="level0"><a name="CURLOPTWRITEDATA"></a><span class="nroffip">CURLOPT_WRITEDATA</span> 
<p class="level1">Data pointer to pass to the file write function. If you use the <a class="emphasis" href="#CURLOPTWRITEFUNCTION">CURLOPT_WRITEFUNCTION</a> option, this is the pointer you'll get as input. If you don't use a callback, you must pass a 'FILE *' as libcurl will pass this to fwrite() when writing data. 
<p class="level1">The internal <a class="emphasis" href="#CURLOPTWRITEFUNCTION">CURLOPT_WRITEFUNCTION</a> will write the data to the FILE * given with this option, or to stdout if this option hasn't been set. 
<p class="level1">If you're using libcurl as a win32 DLL, you <span Class="bold">MUST</span> use the <a class="emphasis" href="#CURLOPTWRITEFUNCTION">CURLOPT_WRITEFUNCTION</a> if you set this option or you will experience crashes. 
<p class="level1">This option is also known with the older name <span Class="emphasis">CURLOPT_FILE</span>, the name <a class="emphasis" href="#CURLOPTWRITEDATA">CURLOPT_WRITEDATA</a> was introduced in 7.9.7. 
<p class="level0"><a name="CURLOPTREADFUNCTION"></a><span class="nroffip">CURLOPT_READFUNCTION</span> 
<p class="level1">Function pointer that should match the following prototype: <span class="bold">size_t function( void *ptr, size_t size, size_t nmemb, void *stream);</span> This function gets called by libcurl as soon as it needs to read data in order to send it to the peer. The data area pointed at by the pointer <span Class="emphasis">ptr</span> may be filled with at most <span Class="emphasis">size</span> multiplied with <span Class="emphasis">nmemb</span> number of bytes. Your function must return the actual number of bytes that you stored in that memory area. Returning 0 will signal end-of-file to the library and cause it to stop the current transfer. 
<p class="level1">If you stop the current transfer by returning 0 "pre-maturely" (i.e before the server expected it, like when you've told you will upload N bytes and you upload less than N bytes), you may experience that the server "hangs" waiting for the rest of the data that won't come. 
<p class="level1">The read callback may return <span Class="emphasis">CURL_READFUNC_ABORT</span> to stop the current operation immediately, resulting in a <span Class="emphasis">CURLE_ABORTED_BY_CALLBACK</span> error code from the transfer (Added in 7.12.1) 
<p class="level1">If you set the callback pointer to NULL, or doesn't set it at all, the default internal read function will be used. It is simply doing an fread() on the FILE * stream set with <a class="emphasis" href="#CURLOPTREADDATA">CURLOPT_READDATA</a>. 
<p class="level0"><a name="CURLOPTREADDATA"></a><span class="nroffip">CURLOPT_READDATA</span> 
<p class="level1">Data pointer to pass to the file read function. If you use the <a class="emphasis" href="#CURLOPTREADFUNCTION">CURLOPT_READFUNCTION</a> option, this is the pointer you'll get as input. If you don't specify a read callback but instead rely on the default internal read function, this data must be a valid readable FILE *. 
<p class="level1">If you're using libcurl as a win32 DLL, you MUST use a <a class="emphasis" href="#CURLOPTREADFUNCTION">CURLOPT_READFUNCTION</a> if you set this option. 
<p class="level1">This option is also known with the older name <span Class="emphasis">CURLOPT_INFILE</span>, the name <a class="emphasis" href="#CURLOPTREADDATA">CURLOPT_READDATA</a> was introduced in 7.9.7. 
<p class="level0"><a name="CURLOPTIOCTLFUNCTION"></a><span class="nroffip">CURLOPT_IOCTLFUNCTION</span> 
<p class="level1">Function pointer that should match the <span Class="emphasis">curl_ioctl_callback</span> prototype found in <span Class="emphasis">&lt;curl/curl.h&gt;</span>. This function gets called by libcurl when something special I/O-related needs to be done that the library can't do by itself. For now, rewinding the read data stream is the only action it can request. The rewinding of the read data stream may be necessary when doing a HTTP PUT or POST with a multi-pass authentication method.  (Option added in 7.12.3) 
<p class="level0"><a name="CURLOPTIOCTLDATA"></a><span class="nroffip">CURLOPT_IOCTLDATA</span> 
<p class="level1">Pass a pointer that will be untouched by libcurl and passed as the 3rd argument in the ioctl callback set with <a class="emphasis" href="#CURLOPTIOCTLFUNCTION">CURLOPT_IOCTLFUNCTION</a>.  (Option added in 7.12.3) 
<p class="level0"><a name="CURLOPTSOCKOPTFUNCTION"></a><span class="nroffip">CURLOPT_SOCKOPTFUNCTION</span> 
<p class="level1">Function pointer that should match the <span Class="emphasis">curl_sockopt_callback</span> prototype found in <span Class="emphasis">&lt;curl/curl.h&gt;</span>. This function gets called by libcurl after the socket() call but before the connect() call. The callback's <span Class="emphasis">purpose</span> argument identifies the exact purpose for this particular socket, and currently only one value is supported: <span Class="emphasis">CURLSOCKTYPE_IPCXN</span> for the primary connection (meaning the control connection in the FTP case). Future versions of libcurl may support more purposes. It passes the newly created socket descriptor so additional setsockopt() calls can be done at the user's discretion.  A non-zero return code from the callback function will signal an unrecoverable error to the library and it will close the socket and return <span Class="emphasis">CURLE_COULDNT_CONNECT</span>.  (Option added in 7.15.6.) 
<p class="level0"><a name="CURLOPTSOCKOPTDATA"></a><span class="nroffip">CURLOPT_SOCKOPTDATA</span> 
<p class="level1">Pass a pointer that will be untouched by libcurl and passed as the first argument in the sockopt callback set with <a class="emphasis" href="#CURLOPTSOCKOPTFUNCTION">CURLOPT_SOCKOPTFUNCTION</a>. (Option added in 7.15.6.) 
<p class="level0"><a name="CURLOPTPROGRESSFUNCTION"></a><span class="nroffip">CURLOPT_PROGRESSFUNCTION</span> 
<p class="level1">Function pointer that should match the <span Class="emphasis">curl_progress_callback</span> prototype found in <span Class="emphasis">&lt;curl/curl.h&gt;</span>. This function gets called by libcurl instead of its internal equivalent with a frequent interval during operation (roughly once per second) no matter if data is being transfered or not.  Unknown/unused argument values passed to the callback will be set to zero (like if you only download data, the upload size will remain 0). Returning a non-zero value from this callback will cause libcurl to abort the transfer and return <span Class="emphasis">CURLE_ABORTED_BY_CALLBACK</span>. 
<p class="level1">If you transfer data with the multi interface, this function will not be called during periods of idleness unless you call the appropriate libcurl function that performs transfers. Usage of the <a class="bold" href="#CURLOPTPROGRESSFUNCTION">CURLOPT_PROGRESSFUNCTION</a> callback is not recommended when using the multi interface. 
<p class="level1"><a class="emphasis" href="#CURLOPTNOPROGRESS">CURLOPT_NOPROGRESS</a> must be set to FALSE to make this function actually get called. 
<p class="level0"><a name="CURLOPTPROGRESSDATA"></a><span class="nroffip">CURLOPT_PROGRESSDATA</span> 
<p class="level1">Pass a pointer that will be untouched by libcurl and passed as the first argument in the progress callback set with <a class="emphasis" href="#CURLOPTPROGRESSFUNCTION">CURLOPT_PROGRESSFUNCTION</a>. 
<p class="level0"><a name="CURLOPTHEADERFUNCTION"></a><span class="nroffip">CURLOPT_HEADERFUNCTION</span> 
<p class="level1">Function pointer that should match the following prototype: <span class="emphasis">size_t function( void *ptr, size_t size, size_t nmemb, void *stream);</span>. This function gets called by libcurl as soon as it has received header data. The header callback will be called once for each header and only complete header lines are passed on to the callback. Parsing headers should be easy enough using this. The size of the data pointed to by <span Class="emphasis">ptr</span> is <span Class="emphasis">size</span> multiplied with <span Class="emphasis">nmemb</span>. Do not assume that the header line is zero terminated! The pointer named <span Class="emphasis">stream</span> is the one you set with the <a class="emphasis" href="#CURLOPTWRITEHEADER">CURLOPT_WRITEHEADER</a> option. The callback function must return the number of bytes actually taken care of, or return -1 to signal error to the library (it will cause it to abort the transfer with a <span Class="emphasis">CURLE_WRITE_ERROR</span> return code). 
<p class="level1">Since 7.14.1: When a server sends a chunked encoded transfer, it may contain a trailer. That trailer is identical to a HTTP header and if such a trailer is received it is passed to the application using this callback as well. There are several ways to detect it being a trailer and not an ordinary header: 1) it comes after the response-body. 2) it comes after the final header line (CR LF) 3) a Trailer: header among the response-headers mention what header to expect in the trailer. 
<p class="level0"><a name="CURLOPTWRITEHEADER"></a><span class="nroffip">CURLOPT_WRITEHEADER</span> 
<p class="level1">(This option is also known as <span Class="bold">CURLOPT_HEADERDATA</span>) Pass a pointer to be used to write the header part of the received data to. If you don't use your own callback to take care of the writing, this must be a valid FILE *. See also the <a class="emphasis" href="#CURLOPTHEADERFUNCTION">CURLOPT_HEADERFUNCTION</a> option above on how to set a custom get-all-headers callback. 
<p class="level0"><a name="CURLOPTDEBUGFUNCTION"></a><span class="nroffip">CURLOPT_DEBUGFUNCTION</span> 
<p class="level1">Function pointer that should match the following prototype: <span class="emphasis">int curl_debug_callback (CURL *, curl_infotype, char *, size_t, void *);</span> <a class="emphasis" href="#CURLOPTDEBUGFUNCTION">CURLOPT_DEBUGFUNCTION</a> replaces the standard debug function used when <a class="emphasis" href="#CURLOPTVERBOSE">CURLOPT_VERBOSE </a> is in effect. This callback receives debug information, as specified with the <span Class="bold">curl_infotype</span> argument. This function must return 0.  The data pointed to by the char * passed to this function WILL NOT be zero terminated, but will be exactly of the size as told by the size_t argument. 
<p class="level1">Available curl_infotype values: 
<p class="level2">
<p class="level1"><a name="CURLINFOTEXT"></a><span class="nroffip">CURLINFO_TEXT</span> 
<p class="level2">The data is informational text. 
<p class="level1"><a name="CURLINFOHEADERIN"></a><span class="nroffip">CURLINFO_HEADER_IN</span> 
<p class="level2">The data is header (or header-like) data received from the peer. 
<p class="level1"><a name="CURLINFOHEADEROUT"></a><span class="nroffip">CURLINFO_HEADER_OUT</span> 
<p class="level2">The data is header (or header-like) data sent to the peer. 
<p class="level1"><a name="CURLINFODATAIN"></a><span class="nroffip">CURLINFO_DATA_IN</span> 
<p class="level2">The data is protocol data received from the peer. 
<p class="level1"><a name="CURLINFODATAOUT"></a><span class="nroffip">CURLINFO_DATA_OUT</span> 
<p class="level2">The data is protocol data sent to the peer. 
<p class="level1">
<p class="level0"><a name="CURLOPTDEBUGDATA"></a><span class="nroffip">CURLOPT_DEBUGDATA</span> 
<p class="level1">Pass a pointer to whatever you want passed in to your <a class="emphasis" href="#CURLOPTDEBUGFUNCTION">CURLOPT_DEBUGFUNCTION</a> in the last void * argument. This pointer is not used by libcurl, it is only passed to the callback. 
<p class="level0"><a name="CURLOPTSSLCTXFUNCTION"></a><span class="nroffip">CURLOPT_SSL_CTX_FUNCTION</span> 
<p class="level1">Function pointer that should match the following prototype: <span class="bold">CURLcode sslctxfun(CURL *curl, void *sslctx, void *parm);</span> This function gets called by libcurl just before the initialization of an SSL connection after having processed all other SSL related options to give a last chance to an application to modify the behaviour of openssl's ssl initialization. The <span Class="emphasis">sslctx</span> parameter is actually a pointer to an openssl <span Class="emphasis">SSL_CTX</span>. If an error is returned no attempt to establish a connection is made and the perform operation will return the error code from this callback function.  Set the <span Class="emphasis">parm</span> argument with the <a class="emphasis" href="#CURLOPTSSLCTXDATA">CURLOPT_SSL_CTX_DATA</a> option. This option was introduced in 7.11.0. 
<p class="level1">This function will get called on all new connections made to a server, during the SSL negotiation. The SSL_CTX pointer will be a new one every time. 
<p class="level1">To use this properly, a non-trivial amount of knowledge of the openssl libraries is necessary. Using this function allows for example to use openssl callbacks to add additional validation code for certificates, and even to change the actual URI of an HTTPS request (example used in the lib509 test case).  See also the example section for a replacement of the key, certificate and trust file settings. 
<p class="level0"><a name="CURLOPTSSLCTXDATA"></a><span class="nroffip">CURLOPT_SSL_CTX_DATA</span> 
<p class="level1">Data pointer to pass to the ssl context callback set by the option <a class="emphasis" href="#CURLOPTSSLCTXFUNCTION">CURLOPT_SSL_CTX_FUNCTION</a>, this is the pointer you'll get as third parameter, otherwise <span Class="bold">NULL</span>. (Added in 7.11.0) 
<p class="level0"><a name="CURLOPTCONVTONETWORKFUNCTION"></a><span class="nroffip">CURLOPT_CONV_TO_NETWORK_FUNCTION</span> 
<p class="level1">
<p class="level0"><a name="CURLOPTCONVFROMNETWORKFUNCTION"></a><span class="nroffip">CURLOPT_CONV_FROM_NETWORK_FUNCTION</span> 
<p class="level1">
<p class="level0"><a name="CURLOPTCONVFROMUTF8FUNCTION"></a><span class="nroffip">CURLOPT_CONV_FROM_UTF8_FUNCTION</span> 
<p class="level1">Function pointers that should match the following prototype: CURLcode function(char *ptr, size_t length); 
<p class="level1">These three options apply to non-ASCII platforms only.  They are available only if <span Class="bold">CURL_DOES_CONVERSIONS</span> was defined when libcurl was built. When this is the case, <a class="emphasis" href="./curl_version_info.html">curl_version_info(3)</a> will return the CURL_VERSION_CONV feature bit set. 
<p class="level1">The data to be converted is in a buffer pointed to by the ptr parameter.  The amount of data to convert is indicated by the length parameter.  The converted data overlays the input data in the buffer pointed to by the ptr parameter. CURLE_OK should be returned upon successful conversion.  A CURLcode return value defined by curl.h, such as CURLE_CONV_FAILED, should be returned if an error was encountered. 
<p class="level1"><a class="bold" href="#CURLOPTCONVTONETWORKFUNCTION">CURLOPT_CONV_TO_NETWORK_FUNCTION</a> and <a class="bold" href="#CURLOPTCONVFROMNETWORKFUNCTION">CURLOPT_CONV_FROM_NETWORK_FUNCTION</a> convert between the host encoding and the network encoding.  They are used when commands or ASCII data are sent/received over the network. 
<p class="level1"><a class="bold" href="#CURLOPTCONVFROMUTF8FUNCTION">CURLOPT_CONV_FROM_UTF8_FUNCTION</a> is called to convert from UTF8 into the host encoding.  It is required only for SSL processing. 
<p class="level1">If you set a callback pointer to NULL, or don't set it at all, the built-in libcurl iconv functions will be used.  If HAVE_ICONV was not defined when libcurl was built, and no callback has been established, conversion will return the CURLE_CONV_REQD error code. 
<p class="level1">If HAVE_ICONV is defined, CURL_ICONV_CODESET_OF_HOST must also be defined. For example: