libcurl使用心得

约定不等于承诺〃 2022-01-10 12:09 361阅读 0赞

## [libcurl使用心得][libcurl] ##

Libcurl为一个免费开源的，客户端url传输库，支持FTP，FTPS，TFTP，HTTP，HTTPS，GOPHER，TELNET，DICT，FILE和LDAP，跨平台，支持Windows，Unix，Linux等，线程安全，支持Ipv6。并且易于使用。

[http://curl.haxx.se/libcurl/][http_curl.haxx.se_libcurl]

从http://curl.haxx.se/libcurl/ 下载一个稳定的版本，注意选择OS。  
在使用之前请大家多阅读libcurl的文档：因为如果要实际运用到项目中，最好对libcurl有具体的了解，具体在  
[http://curl.haxx.se/libcurl/c/][http_curl.haxx.se_libcurl_c]  
[curl\_easy\_setopt()][curl_easy_setopt]  
[curl\_easy\_perform()][curl_easy_perform]  
[curl\_easy\_getinfo()][curl_easy_getinfo]  
这三个函数的使用上，需要多去钻研，多看Samples，你才能灵活使用libcurl。  
感谢这篇文章:  
[http://blog.163.com/xu\_chao2000/blog/static/27770610200801303252802/][http_blog.163.com_xu_chao2000_blog_static_27770610200801303252802]  
给了我许多启发，再次感谢！  
  
给出我的一个简单的代码例子：  
说明:  
1.关键在curl\_easy\_setopt函数设置option,可以设置ftp,http,get,post等许多选项，请根据具体使用情况设置。  
  
2.对取回来的数据需要进行判断，比如http下载文件，如果文件不存在，需要进行处理。因为writer是可以将buf填充404 not found等网页内容的，不能将这个内容当成文件内容，所以需要判断http web返回来的code，进行判断。  
  
3.我有个问题，就是想得到服务器上filename的具体名称，verbose调试已经返回了，但是我在getinfo的时候，试过好多选项，但未找到这个存放真实服务器文件名的选项，如果有知道的麻烦告诉我，谢谢了！

![None.gif][] \#include  " curl/curl.h "   
![None.gif][]\#pragma comment(lib,  " libcurl.lib " )  
![None.gif][]  
![None.gif][]long writer(void  \* data, int size, int nmemb, string  & content);  
![None.gif][]bool CurlInit(CURL  \*& curl, const char\* url,string  & content);  
![None.gif][]bool GetURLDataBycurl(const char\* URL, string  & content);  
![None.gif][]  
![None.gif][] void  main()  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] ![dot.gif][] \{  
![InBlock.gif][] char \*url ="http://www.baidu.com/img/baidu.gif";  
![InBlock.gif][] string content;  
![InBlock.gif][]if ( GetURLDataBycurl(url,content))  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] printf("%s\\n",content);  
![InBlock.gif][]  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][] getchar();  
![ExpandedBlockEnd.gif][]\}   
![None.gif][]  
![None.gif][]bool CurlInit(CURL  \*& curl, const char\* url,string  & content)  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] ![dot.gif][] \{  
![InBlock.gif][] CURLcode code;  
![InBlock.gif][] string error;  
![InBlock.gif][] curl = curl\_easy\_init();  
![InBlock.gif][]if (curl == NULL)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] printf( "Failed to create CURL connection\\n");  
![InBlock.gif][]return false;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][] code = curl\_easy\_setopt(curl, CURLOPT\_ERRORBUFFER, error);  
![InBlock.gif][]if (code != CURLE\_OK)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] printf( "Failed to set error buffer \[%d\]\\n", code );  
![InBlock.gif][]return false;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][] curl\_easy\_setopt(curl, CURLOPT\_VERBOSE, 1L);  
![InBlock.gif][] code = curl\_easy\_setopt(curl, CURLOPT\_URL, url);  
![InBlock.gif][]if (code != CURLE\_OK)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] printf("Failed to set URL \[%s\]\\n", error);  
![InBlock.gif][]return false;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][] code = curl\_easy\_setopt(curl, CURLOPT\_FOLLOWLOCATION, 1);  
![InBlock.gif][]if (code != CURLE\_OK)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] printf( "Failed to set redirect option \[%s\]\\n", error );  
![InBlock.gif][]return false;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][] code = curl\_easy\_setopt(curl, CURLOPT\_WRITEFUNCTION, writer);  
![InBlock.gif][]if (code != CURLE\_OK)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] printf( "Failed to set writer \[%s\]\\n", error);  
![InBlock.gif][]return false;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][] code = curl\_easy\_setopt(curl, CURLOPT\_WRITEDATA, &content);  
![InBlock.gif][]if (code != CURLE\_OK)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] printf( "Failed to set write data \[%s\]\\n", error );  
![InBlock.gif][]return false;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]return true;  
![ExpandedBlockEnd.gif][]\}   
![None.gif][]  
![None.gif][]long writer(void  \* data, int size, int nmemb, string  & content)  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] ![dot.gif][] \{  
![InBlock.gif][] long sizes = size \* nmemb;  
![InBlock.gif][] string temp(data,sizes);  
![InBlock.gif][] content \+= temp;  
![InBlock.gif][]return sizes;  
![ExpandedBlockEnd.gif][]\}   
![None.gif][]  
![None.gif][]bool GetURLDataBycurl(const char\* URL, string  & content)  
![ExpandedBlockStart.gif][]![ContractedBlock.gif][] ![dot.gif][] \{  
![InBlock.gif][] CURL \*curl = NULL;  
![InBlock.gif][] CURLcode code;  
![InBlock.gif][] string error;  
![InBlock.gif][]  
![InBlock.gif][] code = curl\_global\_init(CURL\_GLOBAL\_DEFAULT);  
![InBlock.gif][]if (code != CURLE\_OK)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] printf( "Failed to global init default \[%d\]\\n", code );  
![InBlock.gif][]return false;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![InBlock.gif][]if ( !CurlInit(curl,URL,content) )  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] printf( "Failed to global init default \[%d\]\\n" );  
![InBlock.gif][]return PM\_FALSE;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][] code = curl\_easy\_perform(curl);  
![InBlock.gif][]if (code != CURLE\_OK)  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] printf( "Failed to get '%s' \[%s\]\\n", URL, error);  
![InBlock.gif][]return false;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][] long retcode =0;  
![InBlock.gif][] code = curl\_easy\_getinfo(curl, CURLINFO\_RESPONSE\_CODE , &retcode);  
![InBlock.gif][]if ( (code == CURLE\_OK) && retcode ==200 )  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][] double length =0;  
![InBlock.gif][] code = curl\_easy\_getinfo(curl, CURLINFO\_CONTENT\_LENGTH\_DOWNLOAD , &length);  
![InBlock.gif][] printf("%d",retcode);  
![InBlock.gif][] FILE \* file = fopen("1.gif","wb");  
![InBlock.gif][] fseek(file,0,SEEK\_SET);  
![InBlock.gif][] fwrite(content.c\_str(),1,length,file);  
![InBlock.gif][] fclose(file);  
![InBlock.gif][]  
![InBlock.gif][]//struct curl\_slist \*list;  
![InBlock.gif][]//code = curl\_easy\_getinfo(curl,CURLINFO\_COOKIELIST,&list);  
![InBlock.gif][]//curl\_slist\_free\_all (list);  
![InBlock.gif][]  
![InBlock.gif][]return true;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]else  
![ExpandedSubBlockStart.gif][]![ContractedSubBlock.gif][]![dot.gif][]\{  
![InBlock.gif][]// debug1( "%s \\n ",getStatusCode(retcode));  
![InBlock.gif][]return false;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][] curl\_easy\_cleanup(curl);  
![InBlock.gif][]return false;  
![ExpandedBlockEnd.gif][]\}

[libcurl]: http://www.cppblog.com/qiujian5628/archive/2008/06/28/54873.html
[http_curl.haxx.se_libcurl]: http://curl.haxx.se/libcurl/
[http_curl.haxx.se_libcurl_c]: http://curl.haxx.se/libcurl/c/
[curl_easy_setopt]: http://curl.haxx.se/libcurl/c/curl_easy_setopt.html
[curl_easy_perform]: http://curl.haxx.se/libcurl/c/curl_easy_perform.html
[curl_easy_getinfo]: http://curl.haxx.se/libcurl/c/curl_easy_getinfo.html
[http_blog.163.com_xu_chao2000_blog_static_27770610200801303252802]: http://blog.163.com/xu_chao2000/blog/static/27770610200801303252802/
[None.gif]: /images/20220110/38af191f0b76440ea21b866a54336083.png
[ExpandedBlockStart.gif]: http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif
[ContractedBlock.gif]: http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif
[dot.gif]: /images/20220110/d51b4e957e3e46208123d536fd7b9028.png
[InBlock.gif]: /images/20220110/d80f9a767e554c3d961c316fad7f8304.png
[ExpandedSubBlockStart.gif]: http://www.cppblog.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif
[ContractedSubBlock.gif]: http://www.cppblog.com/Images/OutliningIndicators/ContractedSubBlock.gif
[ExpandedSubBlockEnd.gif]: /images/20220110/a87bc0ad8a8d4e80ad3bbf45c4c10f14.png
[ExpandedBlockEnd.gif]: /images/20220110/a9796143a1cd414fb7cba0943e2cf6c8.png