📄 curl_easy_setopt.html
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<html><head><title>curl_easy_setopt man page</title><meta name="generator" content="roffit 0.7"><STYLE type="text/css">P.level0 { padding-left: 2em;}P.level1 { padding-left: 4em;}P.level2 { padding-left: 6em;}span.emphasis { font-style: italic;}span.bold { font-weight: bold;}span.manpage { font-weight: bold;}h2.nroffsh { background-color: #e0e0e0;}span.nroffip { font-weight: bold; font-size: 120%; font-family: monospace;}p.roffit { text-align: center; font-size: 80%;}</STYLE></head><body><p class="level0"><a name="NAME"></a><h2 class="nroffsh">NAME</h2><p class="level0">curl_easy_setopt - set options for a curl easy handle <a name="SYNOPSIS"></a><h2 class="nroffsh">SYNOPSIS</h2><p class="level0">#include <curl/curl.h> <p class="level0">CURLcode curl_easy_setopt(CURL *handle, CURLoption option, parameter); <a name="DESCRIPTION"></a><h2 class="nroffsh">DESCRIPTION</h2><p class="level0">curl_easy_setopt() is used to tell libcurl how to behave. By using the appropriate options to <span Class="emphasis">curl_easy_setopt</span>, you can change libcurl's behavior. All options are set with the <span Class="emphasis">option</span> followed by a <span Class="emphasis">parameter</span>. That parameter can be a <span Class="bold">long</span>, a <span Class="bold">function pointer</span>, an <span Class="bold">object pointer</span> or a <span Class="bold">curl_off_t</span>, depending on what the specific option expects. Read this manual carefully as bad input values may cause libcurl to behave badly! You can only set one option in each function call. A typical application uses many curl_easy_setopt() calls in the setup phase. <p class="level0">Options set with this function call are valid for all forthcoming transfers performed using this <span Class="emphasis">handle</span>. The options are not in any way reset between transfers, so if you want subsequent transfers with different options, you must change them between the transfers. You can optionally reset all options back to internal default with <a class="emphasis" href="./curl_easy_reset.html">curl_easy_reset(3)</a>. <p class="level0">Strings passed to libcurl as 'char *' arguments, will not be copied by the library. Instead you should keep them available until libcurl no longer needs them. Failing to do so will cause very odd behavior or even crashes. libcurl will need them until you call <a class="emphasis" href="./curl_easy_cleanup.html">curl_easy_cleanup(3)</a> or you set the same option again to use a different pointer. <p class="level0">The <span Class="emphasis">handle</span> is the return code from a <a class="emphasis" href="./curl_easy_init.html">curl_easy_init(3)</a> or <a class="emphasis" href="./curl_easy_duphandle.html">curl_easy_duphandle(3)</a> call. <a name="BEHAVIOR"></a><h2 class="nroffsh">BEHAVIOR OPTIONS</h2><p class="level0"><p class="level0"><a name="CURLOPTVERBOSE"></a><span class="nroffip">CURLOPT_VERBOSE</span> <p class="level1">Set the parameter to non-zero to get the library to display a lot of verbose information about its operations. Very useful for libcurl and/or protocol debugging and understanding. The verbose information will be sent to stderr, or the stream set with <a class="emphasis" href="#CURLOPTSTDERR">CURLOPT_STDERR</a>. <p class="level1">You hardly ever want this set in production use, you will almost always want this when you debug/report problems. Another neat option for debugging is the <a class="emphasis" href="#CURLOPTDEBUGFUNCTION">CURLOPT_DEBUGFUNCTION</a>. <p class="level0"><a name="CURLOPTHEADER"></a><span class="nroffip">CURLOPT_HEADER</span> <p class="level1">A non-zero parameter tells the library to include the header in the body output. This is only relevant for protocols that actually have headers preceding the data (like HTTP). <p class="level0"><a name="CURLOPTNOPROGRESS"></a><span class="nroffip">CURLOPT_NOPROGRESS</span> <p class="level1">A non-zero parameter tells the library to shut off the built-in progress meter completely. <p class="level1">Future versions of libcurl is likely to not have any built-in progress meter at all. <p class="level0"><a name="CURLOPTNOSIGNAL"></a><span class="nroffip">CURLOPT_NOSIGNAL</span> <p class="level1">Pass a long. If it is non-zero, libcurl will not use any functions that install signal handlers or any functions that cause signals to be sent to the process. This option is mainly here to allow multi-threaded unix applications to still set/use all timeout options etc, without risking getting signals. (Added in 7.10) <p class="level1">Consider building libcurl with ares support to enable asynchronous DNS lookups. It enables nice timeouts for name resolves without signals. <a name="CALLBACK"></a><h2 class="nroffsh">CALLBACK OPTIONS</h2><p class="level0"><p class="level0"><a name="CURLOPTWRITEFUNCTION"></a><span class="nroffip">CURLOPT_WRITEFUNCTION</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 there is data received that needs to be saved. 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>, it will not be zero terminated. Return the number of bytes actually taken care of. If that amount differs from the amount passed to your function, it'll signal an error to the library and it will abort the transfer and return <span Class="emphasis">CURLE_WRITE_ERROR</span>. <p class="level1">This function may be called with zero bytes data if the transfered file is empty. <p class="level1">Set this option to NULL to get the internal default function. The internal default function will write the data to the FILE * given with <a class="emphasis" href="#CURLOPTWRITEDATA">CURLOPT_WRITEDATA</a>. <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. ⌨️ 快捷键说明
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