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">&nbsp;#define CURL_ICONV_CODESET_OF_HOST "IBM-1047" 
<p class="level1">The iconv code in libcurl will default the network and UTF8 codeset names as follows: 
<p class="level1">&nbsp;#define CURL_ICONV_CODESET_OF_NETWORK "ISO8859-1" 
<p class="level1">&nbsp;#define CURL_ICONV_CODESET_FOR_UTF8   "UTF-8" 
<p class="level1">You will need to override these definitions if they are different on your system. <a name="ERROR"></a><h2 class="nroffsh">ERROR OPTIONS</h2>
<p class="level0">
<p class="level0"><a name="CURLOPTERRORBUFFER"></a><span class="nroffip">CURLOPT_ERRORBUFFER</span> 
<p class="level1">Pass a char * to a buffer that the libcurl may store human readable error messages in. This may be more helpful than just the return code from <span Class="emphasis">curl_easy_perform</span>. The buffer must be at least CURL_ERROR_SIZE big. 
<p class="level1">Use <a class="emphasis" href="#CURLOPTVERBOSE">CURLOPT_VERBOSE</a> and <a class="emphasis" href="#CURLOPTDEBUGFUNCTION">CURLOPT_DEBUGFUNCTION</a> to better debug/trace why errors happen. 
<p class="level1">If the library does not return an error, the buffer may not have been touched. Do not rely on the contents in those cases. 
<p class="level1">
<p class="level0"><a name="CURLOPTSTDERR"></a><span class="nroffip">CURLOPT_STDERR</span> 
<p class="level1">Pass a FILE * as parameter. Tell libcurl to use this stream instead of stderr when showing the progress meter and displaying <a class="emphasis" href="#CURLOPTVERBOSE">CURLOPT_VERBOSE</a> data. 
<p class="level0"><a name="CURLOPTFAILONERROR"></a><span class="nroffip">CURLOPT_FAILONERROR</span> 
<p class="level1">A non-zero parameter tells the library to fail silently if the HTTP code returned is equal to or larger than 400. The default action would be to return the page normally, ignoring that code. 
<p class="level1">This method is not fail-safe and there are occasions where non-successful response codes will slip through, especially when authentication is involved (response codes 401 and 407). 
<p class="level1">You might get some amounts of headers transferred before this situation is detected, like for when a "100-continue" is received as a response to a POST/PUT and a 401 or 407 is received immediately afterwards. <a name="NETWORK"></a><h2 class="nroffsh">NETWORK OPTIONS</h2>
<p class="level0">
<p class="level0"><a name="CURLOPTURL"></a><span class="nroffip">CURLOPT_URL</span> 
<p class="level1">The actual URL to deal with. The parameter should be a char * to a zero terminated string. The string must remain present until curl no longer needs it, as it doesn't copy the string. 
<p class="level1">If the given URL lacks the protocol part ("http://" or "ftp://" etc), it will attempt to guess which protocol to use based on the given host name. If the given protocol of the set URL is not supported, libcurl will return on error (<span Class="emphasis">CURLE_UNSUPPORTED_PROTOCOL</span>) when you call <a class="emphasis" href="./curl_easy_perform.html">curl_easy_perform(3)</a> or <a class="emphasis" href="./curl_multi_perform.html">curl_multi_perform(3)</a>. Use <a class="emphasis" href="./curl_version_info.html">curl_version_info(3)</a> for detailed info on which protocols that are supported. 
<p class="level1">The string given to CURLOPT_URL must be url-encoded and following the RFC 2396 (<a href="http://curl.haxx.se/rfc/rfc2396.txt">http://curl.haxx.se/rfc/rfc2396.txt</a>). 
<p class="level1"><a class="emphasis" href="#CURLOPTURL">CURLOPT_URL</a> is the only option that <span Class="bold">must</span> be set before <a class="emphasis" href="./curl_easy_perform.html">curl_easy_perform(3)</a> is called. 
<p class="level0"><a name="CURLOPTPROXY"></a><span class="nroffip">CURLOPT_PROXY</span> 
<p class="level1">Set HTTP proxy to use. The parameter should be a char * to a zero terminated string holding the host name or dotted IP address. To specify port number in this string, append :[port] to the end of the host name. The proxy string may be prefixed with [protocol]:// since any such prefix will be ignored. The proxy's port number may optionally be specified with the separate option <a class="emphasis" href="#CURLOPTPROXYPORT">CURLOPT_PROXYPORT</a>. 
<p class="level1">When you tell the library to use an HTTP proxy, libcurl will transparently convert operations to HTTP even if you specify an FTP URL etc. This may have an impact on what other features of the library you can use, such as <a class="emphasis" href="#CURLOPTQUOTE">CURLOPT_QUOTE</a> and similar FTP specifics that don't work unless you tunnel through the HTTP proxy. Such tunneling is activated with <a class="emphasis" href="#CURLOPTHTTPPROXYTUNNEL">CURLOPT_HTTPPROXYTUNNEL</a>. 
<p class="level1">libcurl respects the environment variables <span Class="bold">http_proxy</span>, <span Class="bold">ftp_proxy</span>, <span Class="bold">all_proxy</span> etc, if any of those is set. The <a class="emphasis" href="#CURLOPTPROXY">CURLOPT_PROXY</a> option does however override any possibly set environment variables. 
<p class="level1">Setting the proxy string to "" (an empty string) will explicitly disable the use of a proxy, even if there is an environment variable set for it. 
<p class="level1">Since 7.14.1, the proxy host string given in environment variables can be specified the exact same way as the proxy can be set with <a class="emphasis" href="#CURLOPTPROXY">CURLOPT_PROXY</a>, include protocol prefix (http://) and embedded user + password. 
<p class="level0"><a name="CURLOPTPROXYPORT"></a><span class="nroffip">CURLOPT_PROXYPORT</span> 
<p class="level1">Pass a long with this option to set the proxy port to connect to unless it is specified in the proxy string <a class="emphasis" href="#CURLOPTPROXY">CURLOPT_PROXY</a>. 
<p class="level0"><a name="CURLOPTPROXYTYPE"></a><span class="nroffip">CURLOPT_PROXYTYPE</span> 
<p class="level1">Pass a long with this option to set type of the proxy. Available options for this are <span Class="emphasis">CURLPROXY_HTTP</span>, <span Class="emphasis">CURLPROXY_SOCKS4</span> (added in 7.15.2) <span Class="emphasis">CURLPROXY_SOCKS5</span>. The HTTP type is default. (Added in 7.10) 
<p class="level0"><a name="CURLOPTHTTPPROXYTUNNEL"></a><span class="nroffip">CURLOPT_HTTPPROXYTUNNEL</span> 
<p class="level1">Set the parameter to non-zero to get the library to tunnel all operations through a given HTTP proxy. There is a big difference between using a proxy and to tunnel through it. If you don't know what this means, you probably don't want this tunneling option. 
<p class="level0"><a name="CURLOPTINTERFACE"></a><span class="nroffip">CURLOPT_INTERFACE</span> 
<p class="level1">Pass a char * as parameter. This set the interface name to use as outgoing network interface. The name can be an interface name, an IP address or a host name. 
<p class="level0"><a name="CURLOPTLOCALPORT"></a><span class="nroffip">CURLOPT_LOCALPORT</span> 
<p class="level1">Pass a long. This sets the local port number of the socket used for connection. This can be used in combination with <a class="emphasis" href="#CURLOPTINTERFACE">CURLOPT_INTERFACE</a> and you are recommended to use <a class="emphasis" href="#CURLOPTLOCALPORTRANGE">CURLOPT_LOCALPORTRANGE</a> as well when this is set. Note that port numbers are only valid 1 - 65535. (Added in 7.15.2) 
<p class="level0"><a name="CURLOPTLOCALPORTRANGE"></a><span class="nroffip">CURLOPT_LOCALPORTRANGE</span> 
<p class="level1">Pass a long. This is the number of attempts libcurl should do to find a working local port number. It starts with the given <a class="emphasis" href="#CURLOPTLOCALPORT">CURLOPT_LOCALPORT</a> and adds one to the number for each retry. Setting this value to 1 or below will make libcurl do only one try for exact port number. Note that port numbers by nature is a scarce resource that will be busy at times so setting this value to something too low might cause unnecessary connection setup failures. (Added in 7.15.2) 
<p class="level0"><a name="CURLOPTDNSCACHETIMEOUT"></a><span class="nroffip">CURLOPT_DNS_CACHE_TIMEOUT</span> 
<p class="level1">Pass a long, this sets the timeout in seconds. Name resolves will be kept in memory for this number of seconds. Set to zero (0) to completely disable caching, or set to -1 to make the cached entries remain forever. By default, libcurl caches this info for 60 seconds. 
<p class="level0"><a name="CURLOPTDNSUSEGLOBALCACHE"></a><span class="nroffip">CURLOPT_DNS_USE_GLOBAL_CACHE</span> 
<p class="level1">Pass a long. If the value is non-zero, it tells curl to use a global DNS cache that will survive between easy handle creations and deletions. This is not thread-safe and this will use a global variable. 
<p class="level1"><span Class="bold">WARNING:</span> this option is considered obsolete. Stop using it. Switch over to using the share interface instead! See <a class="emphasis" href="#CURLOPTSHARE">CURLOPT_SHARE</a> and <a class="emphasis" href="./curl_share_init.html">curl_share_init(3)</a>. 
<p class="level0"><a name="CURLOPTBUFFERSIZE"></a><span class="nroffip">CURLOPT_BUFFERSIZE</span> 
<p class="level1">Pass a long specifying your preferred size (in bytes) for the receive buffer in libcurl.  The main point of this would be that the write callback gets called more often and with smaller chunks. This is just treated as a request, not an order. You cannot be guaranteed to actually get the given size. (Added in 7.10) 
<p class="level1">This size is by default set as big as possible (CURL_MAX_WRITE_SIZE), so it only makes sense to use this option if you want it smaller. 
<p class="level0"><a name="CURLOPTPORT"></a><span class="nroffip">CURLOPT_PORT</span> 
<p class="level1">Pass a long specifying what remote port number to connect to, instead of the one specified in the URL or the default port for the used protocol. 
<p class="level0"><a name="CURLOPTTCPNODELAY"></a><span class="nroffip">CURLOPT_TCP_NODELAY</span> 
<p class="level1">Pass a long specifying whether the TCP_NODELAY option should be set or cleared (1 = set, 0 = clear). The option is cleared by default. This will have no effect after the connection has been established. 
<p class="level1">Setting this option will disable TCP's Nagle algorithm. The purpose of this algorithm is to try to minimize the number of small packets on the network (where "small packets" means TCP segments less than the Maximum Segment Size (MSS) for the network). 
<p class="level1">Maximizing the amount of data sent per TCP segment is good because it amortizes the overhead of the send. However, in some cases (most notably telnet or rlogin) small segments may need to be sent without delay. This is less efficient than sending larger amounts of data at a time, and can contribute to congestion on the network if overdone. <a name="NAMES"></a><h2 class="nroffsh">NAMES and PASSWORDS OPTIONS (Authentication)</h2>
<p class="level0">
<p class="level0"><a name="CURLOPTNETRC"></a><span class="nroffip">CURLOPT_NETRC</span> 
<p class="level1">This parameter controls the preference of libcurl between using user names and passwords from your <span Class="emphasis">~/.netrc</span> file, relative to user names and passwords in the URL supplied with <a class="emphasis" href="#CURLOPTURL">CURLOPT_URL</a>. 
<p class="level1">libcurl uses a user name (and supplied or prompted password) supplied with <a class="emphasis" href="#CURLOPTUSERPWD">CURLOPT_USERPWD</a> in preference to any of the options controlled by this parameter. 
<p class="level1">Pass a long, set to one of the values described below. 
<p class="level2">
<p class="level1"><a name="CURLNETRCOPTIONAL"></a><span class="nroffip">CURL_NETRC_OPTIONAL</span> 
<p class="level2">The use of your <span Class="emphasis">~/.netrc</span> file is optional, and information in the URL is to be preferred.  The file will be scanned with the host and user name (to find the password only) or with the host only, to find the first user name and password after that <span Class="emphasis">machine</span>, which ever information is not specified in the URL. 
<p class="level2">Undefined values of the option will have this effect. 
<p class="level1"><a name="CURLNETRCIGNORED"></a><span class="nroffip">CURL_NETRC_IGNORED</span> 
<p class="level2">The library will ignore the file and use only the information in the URL. 
<p class="level2">This is the default. 
<p class="level1"><a name="CURLNETRCREQUIRED"></a><span class="nroffip">CURL_NETRC_REQUIRED</span> 
<p class="level2">This value tells the library that use of the file is required, to ignore the information in the URL, and to search the file with the host only. 
<p class="level1">Only machine name, user name and password are taken into account (init macros and similar things aren't supported).