windows - How do I find out the browser's proxy settings? -

i writing command-line tool windows uses libcurl download files internet.

obviously, downloading doesn't work when user behind proxy server, because proxy needs configured. want keep tool simple possible however, , not have burden user having configure proxy. tool doesn't have config file, user otherwise have pass in proxy settings on every command, or set environment variable or somesuch -- way hassle.

so thought, everyone's browser set properly, proxy configured , everything. true basic user because otherwise "their internet wouldn't work".

so figure can find out whether use proxy looking @ ie's proxy settings.

how go this? more specifically:

• is there 1 set of "proxy settings" in windows, used browsers (probably ie's), or have write different routines ie, firefox, opera, etc?
• i know can read values directly out of appropriate registry locations if configured manually, work "automatically detect proxy server?" have bother option, or (almost) never used?

before people start suggesting alternatives: i'm using c, i'm limited win32 api, , really want keep using c , libcurl.

the function you're looking winhttpgetieproxyconfigforcurrentuser(), documented @ http://msdn.microsoft.com/en-us/library/aa384096(vs.85).aspx. function used firefox , opera proxy settings default, although can override them per-browser. don't that, though. right thing (which else does) ie settings , assume they're correct, since are.

here's sample of relevant logic, should adapt needs:

if( winhttpgetieproxyconfigforcurrentuser( &ieproxyconfig ) ) {     if( ieproxyconfig.fautodetect )     {         fautoproxy = true;     }      if( ieproxyconfig.lpszautoconfigurl != null )     {         fautoproxy = true;         autoproxyoptions.lpszautoconfigurl = ieproxyconfig.lpszautoconfigurl;     } } else {     // use autoproxy     fautoproxy = true; }  if( fautoproxy ) {     if ( autoproxyoptions.lpszautoconfigurl != null )     {         autoproxyoptions.dwflags = winhttp_autoproxy_config_url;     }     else     {         autoproxyoptions.dwflags = winhttp_autoproxy_auto_detect;         autoproxyoptions.dwautodetectflags = winhttp_auto_detect_type_dhcp | winhttp_auto_detect_type_dns_a;     }      // basic flags want     autoproxyoptions.fautologonifchallenged = true;      // here reset fautoproxy in case auto-proxy isn't     // configured url     fautoproxy = winhttpgetproxyforurl( hiopen, pwszurl, &autoproxyoptions, &autoproxyinfo ); }  if ( fautoproxy ) {     // set proxy options libcurl based on autoproxyinfo } else {     if( ieproxyconfig.lpszproxy != null )     {         // ie has explicit proxy. set proxy options libcurl here         // based on ieproxyconfig         //         // note ie gives single or double colon         // proxy or bypass list, means "no proxy"     }     else     {         // there no auto proxy , no manually configured proxy     } }