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curl_easy_setopt(3)             libcurl Manual             curl_easy_setopt(3)



NAME
       curl_easy_setopt - set options for a curl easy handle

SYNOPSIS
       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLoption option, parameter);

DESCRIPTION
       curl_easy_setopt() is used to tell libcurl how to behave. By using the appropriate options to curl_easy_setopt,
       you can change libcurl's behavior.  All options are set with the option followed by a parameter. That parameter
       can  be  a  long,  a function pointer, an object pointer or a curl_off_t, 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.

       Options set with this function call are valid for all forthcoming transfers performed using this  handle.   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
       curl_easy_reset(3).

       Strings  passed to libcurl as 'char *' arguments, are copied by the library; thus the string storage associated
       to the pointer argument may be overwritten after  curl_easy_setopt()  returns.  Exceptions  to  this  rule  are
       described in the option details below.

       Before  version  7.17.0, strings were not copied. Instead the user was forced keep them available until libcurl
       no longer needed them.

       The handle is the return code from a curl_easy_init(3) or curl_easy_duphandle(3) call.

BEHAVIOR OPTIONS
       CURLOPT_VERBOSE
              Set the parameter to 1 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 CURLOPT_STDERR.

              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 CURLOPT_DEBUGFUNCTION.

       CURLOPT_HEADER
              A  parameter  set to 1 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).

       CURLOPT_NOPROGRESS
              Pass a long. If set to 1, it tells the library to shut off the progress meter completely. It  will  also
              present the CURLOPT_PROGRESSFUNCTION from getting called.

              Future versions of libcurl are likely to not have any built-in progress meter at all.

       CURLOPT_NOSIGNAL
              Pass  a  long.  If it is 1, libcurl will not use any functions that install signal handlers or any func-
              tions 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)

              If this option is set and libcurl has been built with the standard  name  resolver,  timeouts  will  not
              occur while the name resolve takes place.  Consider building libcurl with c-ares support to enable asyn-
              chronous DNS lookups, which enables nice timeouts for name resolves without signals.

              Setting CURLOPT_NOSIGNAL to 1 makes libcurl NOT ask the system to ignore SIGPIPE signals,  which  other-
              wise  are  sent  by  the  system  when trying to send data to a socket which is closed in the other end.
              libcurl makes an effort to never cause such SIGPIPEs to trigger, but some operating systems have no  way
              to  avoid  them  and  even  on  those  that have there are some corner cases when they may still happen,
              contrary to our desire. In addition, using CURLAUTH_NTLM_WB authentication could cause a SIGCHLD  signal
              to be raised.

       CURLOPT_WILDCARDMATCH
              Set  this  option to 1 if you want to transfer multiple files according to a file name pattern. The pat-
              tern can be specified as part of the CURLOPT_URL option, using an fnmatch-like  pattern  (Shell  Pattern
              Matching) in the last part of URL (file name).

              By  default, libcurl uses its internal wildcard matching implementation. You can provide your own match-
              ing function by the CURLOPT_FNMATCH_FUNCTION option.

              This feature is only supported by the FTP download for now.

              A brief introduction of its syntax follows:

              * - ASTERISK
                     ftp://example.com/some/path/*.txt (for all txt's from the root directory)

              ? - QUESTION MARK
                     Question mark matches any (exactly one) character.

                     ftp://example.com/some/path/photo?.jpeg

              [ - BRACKET EXPRESSION
                     The left bracket opens a bracket expression. The question mark and asterisk have no special mean-
                     ing  in  a  bracket  expression.  Each  bracket  expression ends by the right bracket and matches
                     exactly one character. Some examples follow:

                     [a-zA-Z0-9] or [f-gF-G] - character interval

                     [abc] - character enumeration

                     [^abc] or [!abc] - negation

                     [[:name:]] class expression. Supported classes  are  alnum,lower,  space,  alpha,  digit,  print,
                     upper, blank, graph, xdigit.

                     [][-!^] - special case - matches only '-', ']', '[', '!' or '^'. These characters have no special
                     purpose.

                     [\[\]\\] - escape syntax. Matches '[', ']' or '\'.

                     Using the rules above, a file name pattern can be constructed:

                     ftp://example.com/some/path/[a-z[:upper:]\\].jpeg

       (This was added in 7.21.0)

CALLBACK OPTIONS
       CURLOPT_WRITEFUNCTION
              Function pointer that should match the following prototype: size_t function(  char  *ptr,  size_t  size,
              size_t  nmemb,  void  *userdata); 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 ptr is size multiplied with  nmemb,  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. This will abort  the  transfer
              and return CURLE_WRITE_ERROR.

              From  7.18.0, the function can return CURL_WRITEFUNC_PAUSE which then will cause writing to this connec-
              tion to become paused. See curl_easy_pause(3) for further details.

              This function may be called with zero bytes data if the transferred file is empty.

              Set this option to NULL to get the internal default function. The internal default function  will  write
              the data to the FILE * given with CURLOPT_WRITEDATA.

              Set the userdata argument with the CURLOPT_WRITEDATA option.

              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 body data that  can
              be  passed  to  the  write callback is defined in the curl.h header file: CURL_MAX_WRITE_SIZE (the usual
              default is 16K). If you however have CURLOPT_HEADER set, which sends header data to the write  callback,
              you can get up to CURL_MAX_HTTP_HEADER bytes of header data passed into it. This usually means 100K.

       CURLOPT_WRITEDATA
              Data  pointer  to  pass to the file write function. If you use the CURLOPT_WRITEFUNCTION 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.

              The  internal CURLOPT_WRITEFUNCTION will write the data to the FILE * given with this option, or to std-
              out if this option hasn't been set.

              If you're using libcurl as a win32 DLL, you MUST use the CURLOPT_WRITEFUNCTION if you set this option or
              you will experience crashes.

              This option is also known with the older name CURLOPT_FILE, the name CURLOPT_WRITEDATA was introduced in
              7.9.7.

       CURLOPT_READFUNCTION
              Function pointer that should match the following prototype: size_t function(  void  *ptr,  size_t  size,
              size_t  nmemb, void *userdata); 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 ptr may be  filled  with  at  most
              size  multiplied  with  nmemb 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.

              If  you stop the current transfer by returning 0 "pre-maturely" (i.e before the server expected it, like
              when you've said 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.

              The read callback may return CURL_READFUNC_ABORT to stop the current operation immediately, resulting in
              a CURLE_ABORTED_BY_CALLBACK error code from the transfer (Added in 7.12.1)

              From 7.18.0, the function can return CURL_READFUNC_PAUSE which then will cause reading from this connec-
              tion to become paused. See curl_easy_pause(3) for further details.

              Bugs:  when  doing TFTP uploads, you must return the exact amount of data that the callback wants, or it
              will be considered the final packet by the server end and the transfer will end there.

              If you set this callback pointer to NULL, or don't set it at all, the  default  internal  read  function
              will be used. It is doing an fread() on the FILE * userdata set with CURLOPT_READDATA.

       CURLOPT_READDATA
              Data  pointer to pass to the file read function. If you use the CURLOPT_READFUNCTION option, this is the
              pointer you'll get as input. If you don't specify a read callback but instead rely on the default inter-
              nal read function, this data must be a valid readable FILE *.

              If you're using libcurl as a win32 DLL, you MUST use a CURLOPT_READFUNCTION if you set this option.

              This option was also known by the older name CURLOPT_INFILE, the name CURLOPT_READDATA was introduced in
              7.9.7.

       CURLOPT_IOCTLFUNCTION
              Function pointer that should match the curl_ioctl_callback prototype found in <curl/curl.h>. This  func-
              tion  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).

              Use CURLOPT_SEEKFUNCTION instead to provide seeking!

       CURLOPT_IOCTLDATA
              Pass a pointer that will be untouched by libcurl and passed as the 3rd argument in  the  ioctl  callback
              set with CURLOPT_IOCTLFUNCTION.  (Option added in 7.12.3)

       CURLOPT_SEEKFUNCTION
              Function pointer that should match the following prototype: int function(void *instream, curl_off_t off-
              set, int origin); This function gets called by libcurl to seek to a certain position in the input stream
              and  can  be used to fast forward a file in a resumed upload (instead of reading all uploaded bytes with
              the normal read function/callback). It is also called to rewind a stream when doing a HTTP PUT  or  POST
              with  a  multi-pass  authentication method. The function shall work like "fseek" or "lseek" and accepted
              SEEK_SET, SEEK_CUR and SEEK_END as argument  for  origin,  although  (in  7.18.0)  libcurl  only  passes
              SEEK_SET.  The callback must return 0 (CURL_SEEKFUNC_OK) on success, 1 (CURL_SEEKFUNC_FAIL) to cause the
              upload operation to fail or 2 (CURL_SEEKFUNC_CANTSEEK) to indicate that while the seek  failed,  libcurl
              is free to work around the problem if possible. The latter can sometimes be done by instead reading from
              the input or similar.

              If you forward the input arguments directly to "fseek" or "lseek", note that the data type for offset is
              not the same as defined for curl_off_t on many systems! (Option added in 7.18.0)

       CURLOPT_SEEKDATA
              Data  pointer to pass to the file read function. If you use the CURLOPT_SEEKFUNCTION option, this is the
              pointer you'll get as input. If you don't specify a seek callback, NULL  is  passed.  (Option  added  in
              7.18.0)

       CURLOPT_SOCKOPTFUNCTION
              Function  pointer  that  should  match  the curl_sockopt_callback prototype found in <curl/curl.h>. This
              function gets called by libcurl after the socket() call but before the connect()  call.  The  callback's
              purpose  argument  identifies the exact purpose for this particular socket, and currently only one value
              is supported: CURLSOCKTYPE_IPCXN 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 descrip-
              tor so additional setsockopt() calls can be done at the user's discretion.  Return  0  (zero)  from  the
              callback on success. Return 1 from the callback function to signal an unrecoverable error to the library
              and it will close the socket and return CURLE_COULDNT_CONNECT.  (Option added in 7.15.6.)

              Added in 7.21.5, the callback function may return CURL_SOCKOPT_ALREADY_CONNECTED,  which  tells  libcurl
              that the socket is in fact already connected and then libcurl will not attempt to connect it.

       CURLOPT_SOCKOPTDATA
              Pass  a  pointer that will be untouched by libcurl and passed as the first argument in the sockopt call-
              back set with CURLOPT_SOCKOPTFUNCTION.  (Option added in 7.15.6.)

       CURLOPT_OPENSOCKETFUNCTION
              Function pointer that should match the curl_opensocket_callback prototype found in  <curl/curl.h>.  This
              function  gets  called by libcurl instead of the socket(2) call. The callback's purpose argument identi-
              fies the exact purpose for this particular socket:  CURLSOCKTYPE_IPCXN  is  for  IP  based  connections.
              Future  versions  of libcurl may support more purposes. It passes the resolved peer address as a address
              argument so the callback can modify the address or refuse to  connect  at  all.  The  callback  function
              should  return  the  socket  or CURL_SOCKET_BAD in case no connection should be established or any error
              detected. Any additional setsockopt(2) calls can be  done  on  the  socket  at  the  user's  discretion.
              CURL_SOCKET_BAD  return  value  from  the  callback  function  will signal an unrecoverable error to the
              library and it will return CURLE_COULDNT_CONNECT.  This return code can be used for  IP  address  black-
              listing.  The default behavior is:
                 return socket(addr->family, addr->socktype, addr->protocol);
              (Option added in 7.17.1.)

       CURLOPT_OPENSOCKETDATA
              Pass  a  pointer  that  will  be untouched by libcurl and passed as the first argument in the opensocket
              callback set with CURLOPT_OPENSOCKETFUNCTION.  (Option added in 7.17.1.)

       CURLOPT_CLOSESOCKETFUNCTION
              Function pointer that should match the curl_closesocket_callback prototype found in <curl/curl.h>.  This
              function  gets  called by libcurl instead of the close(3) or closesocket(3) call when sockets are closed
              (not for any other file descriptors). This is pretty much the reverse to the  CURLOPT_OPENSOCKETFUNCTION
              option. Return 0 to signal success and 1 if there was an error.  (Option added in 7.21.7)

       CURLOPT_CLOSESOCKETDATA
              Pass  a  pointer  that  will  be untouched by libcurl and passed as the first argument in the opensocket
              callback set with CURLOPT_CLOSESOCKETFUNCTION.  (Option added in 7.21.7)

       CURLOPT_PROGRESSFUNCTION
              Function pointer that should match the curl_progress_callback prototype  found  in  <curl/curl.h>.  This
              function  gets  called  by  libcurl  instead  of its internal equivalent with a frequent interval during
              operation (roughly once  per  second  or  sooner)  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 CURLE_ABORTED_BY_CALLBACK.

              If  you transfer data with the multi interface, this function will not be called during periods of idle-
              ness unless you call the appropriate libcurl function that performs transfers.

              CURLOPT_NOPROGRESS must be set to 0 to make this function actually get called.

       CURLOPT_PROGRESSDATA
              Pass a pointer that will be untouched by libcurl and passed as the first argument in the progress  call-
              back set with CURLOPT_PROGRESSFUNCTION.

       CURLOPT_HEADERFUNCTION
              Function  pointer  that  should  match the following prototype: size_t function( void *ptr, size_t size,
              size_t nmemb, void *userdata);. 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 is very easy using this. The size of the data pointed to by  ptr  is
              size  multiplied  with  nmemb.  Do not assume that the header line is zero terminated! The pointer named
              userdata is the one you set with the CURLOPT_WRITEHEADER option. The callback function must  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. This will abort the transfer and return CURL_WRITE_ERROR.

              A complete header that is passed to this function can be up to CURL_MAX_HTTP_HEADER (100K) bytes.

              If this option is not set, or if it is set to NULL, but CURLOPT_HEADERDATA (CURLOPT_WRITEHEADER) is  set
              to  anything  but NULL, the function used to accept response data will be used instead. That is, it will
              be the function specified with CURLOPT_WRITEFUNCTION, or if it is not specified or NULL -  the  default,
              stream-writing function.

              It's important to note that the callback will be invoked for the headers of all responses received after
              initiating a request and not just the final response. This includes all  responses  which  occur  during
              authentication negotiation. If you need to operate on only the headers from the final response, you will
              need to collect headers in the callback yourself and use HTTP status  lines,  for  example,  to  delimit
              response boundaries.

              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  regu-
              lar response-headers mention what header(s) to expect in the trailer.

       CURLOPT_WRITEHEADER
              (This  option is also known as CURLOPT_HEADERDATA) Pass a pointer to be used to write the header part of
              the received data to. If you don't use CURLOPT_WRITEFUNCTION or CURLOPT_HEADERFUNCTION to take  care  of
              the writing, this must be a valid FILE * as the internal default will then be a plain fwrite(). See also
              the CURLOPT_HEADERFUNCTION option above on how to set a custom get-all-headers callback.

       CURLOPT_DEBUGFUNCTION
              Function pointer that should match the following prototype: int curl_debug_callback (CURL *,  curl_info-
              type, char *, size_t, void *); CURLOPT_DEBUGFUNCTION replaces the standard debug function used when CUR-
              LOPT_VERBOSE  is in effect. This callback receives debug information, as specified with  the  curl_info-
              type  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.

              Available curl_infotype values:

              CURLINFO_TEXT
                     The data is informational text.

              CURLINFO_HEADER_IN
                     The data is header (or header-like) data received from the peer.

              CURLINFO_HEADER_OUT
                     The data is header (or header-like) data sent to the peer.

              CURLINFO_DATA_IN
                     The data is protocol data received from the peer.

              CURLINFO_DATA_OUT
                     The data is protocol data sent to the peer.

       CURLOPT_DEBUGDATA
              Pass a pointer to whatever you want passed in to your CURLOPT_DEBUGFUNCTION in the last void * argument.
              This pointer is not used by libcurl, it is only passed to the callback.

       CURLOPT_SSL_CTX_FUNCTION
              This  option does only function for libcurl powered by OpenSSL. If libcurl was built against another SSL
              library, this functionality is absent.

              Function pointer that should match the following prototype: CURLcode sslctxfun(CURL *curl, void *sslctx,
              void  *parm);  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 sslctx parameter is actually a pointer to an openssl
              SSL_CTX. 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  parm  argument with the CUR-
              LOPT_SSL_CTX_DATA option. This option was introduced in 7.11.0.

              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.

              To use this properly, a non-trivial amount of knowledge of the openssl libraries is necessary. For exam-
              ple, using this function allows you to use openssl callbacks to add additional validation code for  cer-
              tificates, 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.

       CURLOPT_SSL_CTX_DATA
              Data pointer to pass to the ssl context callback set by the option CURLOPT_SSL_CTX_FUNCTION, this is the
              pointer you'll get as third parameter, otherwise NULL. (Added in 7.11.0)

       CURLOPT_CONV_TO_NETWORK_FUNCTION

       CURLOPT_CONV_FROM_NETWORK_FUNCTION

       CURLOPT_CONV_FROM_UTF8_FUNCTION
              Function  pointers  that  should  match  the  following  prototype:  CURLcode function(char *ptr, size_t
              length);

              These three options apply to non-ASCII platforms only.  They are available only if CURL_DOES_CONVERSIONS
              was  defined  when  libcurl  was  built.  When  this  is  the case, curl_version_info(3) will return the
              CURL_VERSION_CONV feature bit set.

              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.

              CURLOPT_CONV_TO_NETWORK_FUNCTION  and CURLOPT_CONV_FROM_NETWORK_FUNCTION convert between the host encod-
              ing and the network encoding.  They are used when commands or ASCII data are sent/received over the net-
              work.

              CURLOPT_CONV_FROM_UTF8_FUNCTION  is  called to convert from UTF8 into the host encoding.  It is required
              only for SSL processing.

              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.

              If HAVE_ICONV is defined, CURL_ICONV_CODESET_OF_HOST must also be defined.  For example:

               #define CURL_ICONV_CODESET_OF_HOST "IBM-1047"

              The iconv code in libcurl will default the network and UTF8 codeset names as follows:

               #define CURL_ICONV_CODESET_OF_NETWORK "ISO8859-1"

               #define CURL_ICONV_CODESET_FOR_UTF8   "UTF-8"

              You will need to override these definitions if they are different on your system.

       CURLOPT_INTERLEAVEFUNCTION
              Function pointer that should match the following prototype: size_t function(  void  *ptr,  size_t  size,
              size_t  nmemb,  void  *userdata). This function gets called by libcurl as soon as it has received inter-
              leaved RTP data. This function gets called for each $ block and therefore contains  exactly  one  upper-
              layer  protocol  unit (e.g.  one RTP packet). Curl writes the interleaved header as well as the included
              data for each call. The first byte is always an ASCII dollar sign. The dollar sign is followed by a  one
              byte  channel  identifier  and  then a 2 byte integer length in network byte order. See RFC 2326 Section
              10.12 for more information on how RTP interleaving behaves. If unset or set to NULL, curl will  use  the
              default write function.

              Interleaved  RTP poses some challeneges for the client application. Since the stream data is sharing the
              RTSP control connection, it is critical to service the RTP in a timely fashion. If the RTP data  is  not
              handled  quickly,  subsequent response processing may become unreasonably delayed and the connection may
              close. The application may use CURL_RTSPREQ_RECEIVE to service RTP data when no requests are desired. If
              the  application  makes a request, (e.g.  CURL_RTSPREQ_PAUSE) then the response handler will process any
              pending RTP data before marking the request as finished.  (Added in 7.20.0)

       CURLOPT_INTERLEAVEDATA
              This is the userdata pointer that will be passed to CURLOPT_INTERLEAVEFUNCTION when interleaved RTP data
              is received. (Added in 7.20.0)

       CURLOPT_CHUNK_BGN_FUNCTION
              Function  pointer  that  should match the following prototype: long function (const void *transfer_info,
              void *ptr, int remains). This function gets called by libcurl before a part of the stream is going to be
              transferred (if the transfer supports chunks).

              This callback makes sense only when using the CURLOPT_WILDCARDMATCH option for now.

              The  target of transfer_info parameter is a "feature depended" structure. For the FTP wildcard download,
              the target is curl_fileinfo structure (see curl/curl.h).  The parameter ptr is a pointer given  by  CUR-
              LOPT_CHUNK_DATA. The parameter remains contains number of chunks remaining per the transfer. If the fea-
              ture is not available, the parameter has zero value.

              Return CURL_CHUNK_BGN_FUNC_OK if everything is fine, CURL_CHUNK_BGN_FUNC_SKIP if you want  to  skip  the
              concrete  chunk  or  CURL_CHUNK_BGN_FUNC_FAIL to tell libcurl to stop if some error occurred.  (This was
              added in 7.21.0)

       CURLOPT_CHUNK_END_FUNCTION
              Function pointer that should match the following prototype: long function(void *ptr). This function gets
              called by libcurl as soon as a part of the stream has been transferred (or skipped).

              Return  CURL_CHUNK_END_FUNC_OK if everything is fine or CURL_CHUNK_END_FUNC_FAIL to tell the lib to stop
              if some error occurred.  (This was added in 7.21.0)

       CURLOPT_CHUNK_DATA
              Pass  a  pointer  that  will  be  untouched  by  libcurl  and  passed  as  the  ptr  argument   to   the
              CURL_CHUNK_BGN_FUNTION and CURL_CHUNK_END_FUNTION.  (This was added in 7.21.0)

       CURLOPT_FNMATCH_FUNCTION
              Function pointer that should match int function(void *ptr, const char *pattern, const char *string) pro-
              totype (see curl/curl.h). It is used internally for the wildcard matching feature.

              Return CURL_FNMATCHFUNC_MATCH  if  pattern  matches  the  string,  CURL_FNMATCHFUNC_NOMATCH  if  not  or
              CURL_FNMATCHFUNC_FAIL if an error occurred.  (This was added in 7.21.0)

       CURLOPT_FNMATCH_DATA
              Pass   a   pointer  that  will  be  untouched  by  libcurl  and  passed  as  the  ptr  argument  to  the
              CURL_FNMATCH_FUNCTION. (This was added in 7.21.0)

ERROR OPTIONS
       CURLOPT_ERRORBUFFER
              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 curl_easy_perform. The buffer must be at least CURL_ERROR_SIZE
              big.  Although this argument is a 'char *', it does not describe an input string.  Therefore the (proba-
              bly undefined) contents of the buffer is NOT copied by the library. You should keep the associated stor-
              age available until libcurl no longer needs it. Failing to do so will cause very odd  behavior  or  even
              crashes.  libcurl  will  need it until you call curl_easy_cleanup(3) or you set the same option again to
              use a different pointer.

              Use CURLOPT_VERBOSE and CURLOPT_DEBUGFUNCTION to better debug/trace why errors happen.

              If the library does not return an error, the buffer may not have been touched. Do not rely on  the  con-
              tents in those cases.


       CURLOPT_STDERR
              Pass  a FILE * as parameter. Tell libcurl to use this stream instead of stderr when showing the progress
              meter and displaying CURLOPT_VERBOSE data.

       CURLOPT_FAILONERROR
              A parameter set to 1 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.

              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).

              You might get some amounts of headers transferred  before  this  situation  is  detected,  like  when  a
              "100-continue"  is  received as a response to a POST/PUT and a 401 or 407 is received immediately after-
              wards.

NETWORK OPTIONS
       CURLOPT_URL
              The actual URL to deal with. The parameter should be a char * to a zero terminated string which must  be
              URL-encoded in the following format:

              scheme://host:port/path

              For a greater explanation of the format please see RFC 3986 (http://curl.haxx.se/rfc/rfc3986.txt).

              If  the  given URL lacks the scheme, or protocol, part ("http://" or "ftp://" etc), libcurl will attempt
              to resolve which protocol to use based on the given host mame. If the protocol is not supported, libcurl
              will  return  (CURLE_UNSUPPORTED_PROTOCOL)  when you call curl_easy_perform(3) or curl_multi_perform(3).
              Use curl_version_info(3) for detailed information on which protocols are supported.

              The host part of the URL contains the address of the server that you want to connect to. This can be the
              fully  qualified domain name of the server, the local network name of the machine on your network or the
              IP address of the server or machine represented by either an IPv4 or IPv6 address. For example:

              http://www.example.com/

              http://hostname/

              http://192.168.0.1/

              http://[2001:1890:1112:1::20]/

              It is also possible to specify the user name and password as part of the host, for some protocols,  when
              connecting to servers that require authentication.

              For example the following types of authentication support this:

              http://user:passwordATwww.com         ftp://user:passwordATftp.com         pop3://user:pass-
              wordATmail.com

              The port is optional and when not specified libcurl will use the default port based on the determined or
              specified  protocol:  80  for  http, 21 for ftp and 25 for smtp, etc. The following examples show how to
              specify the port:

              http://www.weirdserver.com:8080/ - This will connect to a web server using port 8080.

              smtp://mail.domain.com:587/ - This will connect to a smtp server on the alternative mail port.

              The path part of the URL is protocol specific and whilst some examples are given below this list is  not
              conclusive:

              HTTP

              The path part of a HTTP request specifies the file to retrieve and from what directory. If the directory
              is not specified then the web server's root directory is used. If the file is omitted then  the  default
              document  will be retrieved for either the directory specified or the root directory. The exact resource
              returned for each URL is entirely dependent on the server's configuration.

              http://www.netscape.com - This gets the main page (index.html  in  this  example)  from  Netscape's  web
              server.

              http://www.netscape.com/index.html  - This returns the main page from Netscape by specifying the page to
              get.

              http://www.netscape.com/contactus/ - This returns the default document from the contactus directory.

              FTP

              The path part of an FTP request specifies the file to retrieve and from what directory. If the file part
              is omitted then libcurl downloads the directory listing for the directory specified. If the directory is
              omitted then the directory listing for the root / home directory will be returned.

              ftp://cool.haxx.se - This retrieves the directory listing for our FTP server.

              ftp://cool.haxx.se/readme.txt - This downloads the file readme.txt from the root directory.

              ftp://cool.haxx.se/libcurl/readme.txt - This downloads readme.txt from the libcurl directory.

              ftp://user:passwordATmy.com/readme.txt - This retrieves the readme.txt file from the user's  home
              directory.  When  a username and password is specified, everything that is specified in the path part is
              relative to the user's home directory. To retrieve files from the root directory or a  directory  under-
              neath  the  root  directory then the absolute path must be specified by prepending an additional forward
              slash to the beginning of the path.

              ftp://user:passwordATmy.com//readme.txt - This retrieves the readme.txt from the  root  directory
              when logging in as a specified user.

              SMTP

              The  path  part  of a SMTP request specifies the host name to present during communication with the mail
              server. If the path is omitted then libcurl will attempt to resolve the local computer's host name. How-
              ever,  this  may  not  return  the fully qualified domain name that is required by some mail servers and
              specifying this path allows you to set an alternative name,  such  as  your  machine's  fully  qualified
              domain name, which you might have obtained from an external function such as gethostname or getaddrinfo.

              smtp://mail.domain.com - This connects to the mail server at domain.com and sends your local  computer's
              host name in the HELO / EHLO command.

              smtp://mail.domain.com/client.domain.com  -  This will send client.domain.com in the HELO / EHLO command
              to the mail server at domain.com.

              POP3

              The path part of a POP3 request specifies the mailbox (message) to retrieve.   If  the  mailbox  is  not
              specified then a list of waiting messages is returned instead.

              pop3://user:passwordATmail.com   -   This   lists   the   available   messages   pop3://user:pass-
              wordATmail.com/1 - This retrieves the first message

              SCP

              The path part of an SCP request specifies the file to retrieve and from what directory.  The  file  part
              may  not  be  omitted.  The  file is taken as an absolute path from the root directory on the server. To
              specify a path relative to the user's home directory on the server, prepend ~/ to the path portion.   If
              the  user  name  is  not embedded in the URL, it can be set with the CURLOPT_USERPWD or CURLOPT_USERNAME
              option.

              scp://userATexample.com/etc/issue - This specifies the file /etc/issue

              scp://example.com/~/my-file - This specifies the file my-file in the user's home directory on the server

              SFTP

              The  path  part  of  an SFTP request specifies the file to retrieve and from what directory. If the file
              part is omitted then libcurl downloads the directory listing for the directory specified.  If  the  path
              ends  in  a  /  then a directory listing is returned instead of a file.  If the path is omitted entirely
              then the directory listing for the root / home directory will be returned.  If  the  user  name  is  not
              embedded in the URL, it can be set with the CURLOPT_USERPWD or CURLOPT_USERNAME option.

              sftp://user:passwordATexample.com/etc/issue - This specifies the file /etc/issue

              sftp://userATexample.com/~/my-file - This specifies the file my-file in the user's home directory

              sftp://ssh.example.com/~/Documents/ - This requests a directory listing of the Documents directory under
              the user's home directory

              NOTES

              Starting with version 7.20.0, the fragment part of the URI will not be sent as part of the  path,  which
              was previously the case.

              CURLOPT_URL is the only option that must be set before curl_easy_perform(3) is called.

              CURLOPT_PROTOCOLS can be used to limit what protocols libcurl will use for this transfer, independent of
              what libcurl has been compiled to support. That may be useful if you accept the  URL  from  an  external
              source and want to limit the accessibility.

       CURLOPT_PROTOCOLS
              Pass  a  long  that  holds a bitmask of CURLPROTO_* defines. If used, this bitmask limits what protocols
              libcurl may use in the transfer. This allows you to have a libcurl built to support a wide range of pro-
              tocols but still limit specific transfers to only be allowed to use a subset of them. By default libcurl
              will accept all protocols it supports. See also CURLOPT_REDIR_PROTOCOLS. (Added in 7.19.4)

       CURLOPT_REDIR_PROTOCOLS
              Pass a long that holds a bitmask of CURLPROTO_* defines. If used, this  bitmask  limits  what  protocols
              libcurl  may  use in a transfer that it follows to in a redirect when CURLOPT_FOLLOWLOCATION is enabled.
              This allows you to limit specific transfers to only be allowed to use a subset of protocols in  redirec-
              tions.  By  default  libcurl will allow all protocols except for FILE and SCP. This is a difference com-
              pared to pre-7.19.4 versions which unconditionally would follow to all protocols  supported.  (Added  in
              7.19.4)

       CURLOPT_PROXY
              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. If not specified, libcurl will
              default to using port 1080 for proxies.  CURLOPT_PROXYPORT.

              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 CURLOPT_QUOTE and similar FTP specifics that don't work unless you tunnel through the
              HTTP proxy. Such tunneling is activated with CURLOPT_HTTPPROXYTUNNEL.

              libcurl respects the environment variables http_proxy, ftp_proxy, all_proxy etc, if  any  of  those  are
              set. The CURLOPT_PROXY option does however override any possibly set environment variables.

              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.

              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 CURLOPT_PROXY, include protocol prefix (http://) and embedded user + pass-
              word.

              Since 7.21.7, the proxy string may be specified with a protocol:// prefix to specify  alternative  proxy
              protocols.  Use socks4://, socks4a://, socks5:// or socks5h:// (the last one to enable socks5 and asking
              the proxy to do the resolving, also known as CURLPROXY_SOCKS5_HOSTNAME type)  to  request  the  specific
              SOCKS version to be used. No protocol specified, http:// and all others will be treated as HTTP proxies.

       CURLOPT_PROXYPORT
              Pass a long with this option to set the proxy port to connect to unless it is  specified  in  the  proxy
              string CURLOPT_PROXY.

       CURLOPT_PROXYTYPE
              Pass  a  long  with this option to set type of the proxy. Available options for this are CURLPROXY_HTTP,
              CURLPROXY_HTTP_1_0  (added  in  7.19.4),   CURLPROXY_SOCKS4   (added   in   7.15.2),   CURLPROXY_SOCKS5,
              CURLPROXY_SOCKS4A  (added  in  7.18.0) and CURLPROXY_SOCKS5_HOSTNAME (added in 7.18.0). The HTTP type is
              default. (Added in 7.10)

              If you set CURLOPT_PROXYTYPE to CURLPROXY_HTTP_1_0, it will only affect how libcurl speaks  to  a  proxy
              when  CONNECT is used. The HTTP version used for "regular" HTTP requests is instead controlled with CUR-
              LOPT_HTTP_VERSION.

       CURLOPT_NOPROXY
              Pass a pointer to a zero terminated string. The should be a comma separated list of hosts which  do  not
              use  a  proxy, if one is specified.  The only wildcard is a single * character, which matches all hosts,
              and effectively disables the proxy. Each name in this list is matched as either a domain which  contains
              the  hostname,  or  the hostname itself. For example, local.com would match local.com, local.com:80, and
              www.local.com, but not www.notlocal.com.  (Added in 7.19.4)

       CURLOPT_HTTPPROXYTUNNEL
              Set the parameter to 1 to make the library 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.

       CURLOPT_SOCKS5_GSSAPI_SERVICE
              Pass a char * as parameter to a string holding the name of the service. The default service name  for  a
              SOCKS5 server is rcmd/server-fqdn. This option allows you to change it. (Added in 7.19.4)

       CURLOPT_SOCKS5_GSSAPI_NEC
              Pass  a  long set to 1 to enable or 0 to disable. As part of the gssapi negotiation a protection mode is
              negotiated. The rfc1961 says in section 4.3/4.4 it should be protected, but the NEC reference  implemen-
              tation does not.  If enabled, this option allows the unprotected exchange of the protection mode negoti-
              ation. (Added in 7.19.4).

       CURLOPT_INTERFACE
              Pass a char * as parameter. This sets the interface name to use as outgoing network interface. The  name
              can be an interface name, an IP address, or a host name.

              Starting  with  7.24.0:  If the parameter starts with "if!" then it is treated as only as interface name
              and no attempt will ever be named to do treat it as an IP address or to do name resolution  on  it.   If
              the  parameter  starts  with "host!" it is treated as either an IP address or a hostname.  Hostnames are
              resolved synchronously.  Using the if! format is highly recommended when using the multi  interfaces  to
              avoid  allowing  the  code to block.  If "if!" is specified but the parameter does not match an existing
              interface, CURLE_INTERFACE_FAILED is returned.

       CURLOPT_LOCALPORT
              Pass a long. This sets the local port number of the socket used for connection. This can be used in com-
              bination  with CURLOPT_INTERFACE and you are recommended to use CURLOPT_LOCALPORTRANGE as well when this
              is set. Valid port numbers are 1 - 65535. (Added in 7.15.2)

       CURLOPT_LOCALPORTRANGE
              Pass a long. This is the number of attempts libcurl should make to find a working local port number.  It
              starts  with the given CURLOPT_LOCALPORT and adds one to the number for each retry. Setting this to 1 or
              below will make libcurl do only one try for the exact port number. Port numbers  by  nature  are  scarce
              resources  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)

       CURLOPT_DNS_CACHE_TIMEOUT
              Pass a long, this sets the timeout in seconds. Name resolves will be kept in memory for this  number  of
              seconds.  Set to zero to completely disable caching, or set to -1 to make the cached entries remain for-
              ever. By default, libcurl caches this info for 60 seconds.

              The name resolve functions of various libc implementations don't re-read name server information  unless
              explicitly told so (for example, by calling res_init(3)). This may cause libcurl to keep using the older
              server even if DHCP has updated the server info, and this may look like a DNS cache issue to the  casual
              libcurl-app user.

       CURLOPT_DNS_USE_GLOBAL_CACHE
              Pass  a  long. If the value is 1, 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.

              WARNING: this option is considered obsolete. Stop using it. Switch over to  using  the  share  interface
              instead! See CURLOPT_SHARE and curl_share_init(3).

       CURLOPT_BUFFERSIZE
              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)

              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.

       CURLOPT_PORT
              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.

       CURLOPT_TCP_NODELAY
              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.

              Setting this option will disable TCP's Nagle algorithm. The purpose of this algorithm is to try to mini-
              mize the number of small packets on the network (where "small packets" means TCP segments less than  the
              Maximum Segment Size (MSS) for the network).

              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 con-
              gestion on the network if overdone.

       CURLOPT_ADDRESS_SCOPE
              Pass a long specifying the scope_id value to use  when  connecting  to  IPv6  link-local  or  site-local
              addresses. (Added in 7.19.0)

NAMES and PASSWORDS OPTIONS (Authentication)
       CURLOPT_NETRC
              This  parameter  controls  the  preference  of  libcurl between using user names and passwords from your
              ~/.netrc file, relative to user names and passwords in the URL supplied with CURLOPT_URL.

              libcurl uses a user name (and supplied or prompted password) supplied with CURLOPT_USERPWD in preference
              to any of the options controlled by this parameter.

              Pass a long, set to one of the values described below.

              CURL_NETRC_OPTIONAL
                     The  use  of  your ~/.netrc file is optional, and information in the URL is to be preferred.  The
                     file will be scanned for the host and user name (to find the password only) or for the host only,
                     to find the first user name and password after that machine, which ever information is not speci-
                     fied in the URL.

                     Undefined values of the option will have this effect.

              CURL_NETRC_IGNORED
                     The library will ignore the file and use only the information in the URL.

                     This is the default.

              CURL_NETRC_REQUIRED
                     This value tells the library that use of the file is required, to ignore the information  in  the
                     URL, and to search the file for the host only.
       Only  machine  name,  user name and password are taken into account (init macros and similar things aren't sup-
       ported).

       libcurl does not verify that the file has the correct properties set (as the standard Unix ftp client does). It
       should only be readable by user.

       CURLOPT_NETRC_FILE
              Pass  a  char  * as parameter, pointing to a zero terminated string containing the full path name to the
              file you want libcurl to use as .netrc file. If this  option  is  omitted,  and  CURLOPT_NETRC  is  set,
              libcurl will attempt to find a .netrc file in the current user's home directory. (Added in 7.10.9)

       CURLOPT_USERPWD
              Pass  a  char * as parameter, which should be [user name]:[password] to use for the connection. Use CUR-
              LOPT_HTTPAUTH to decide the authentication method.

              When using NTLM, you can set the domain by prepending it to the user name and separating the domain  and
              name  with  a forward (/) or backward slash (\). Like this: "domain/user:password" or "domain\user:pass-
              word". Some HTTP servers (on Windows) support this style even for Basic authentication.

              When using HTTP and CURLOPT_FOLLOWLOCATION, libcurl might perform several requests to possibly different
              hosts.  libcurl  will  only send this user and password information to hosts using the initial host name
              (unless CURLOPT_UNRESTRICTED_AUTH is set), so if libcurl follows locations to other hosts  it  will  not
              send the user and password to those. This is enforced to prevent accidental information leakage.

       CURLOPT_PROXYUSERPWD
              Pass a char * as parameter, which should be [user name]:[password] to use for the connection to the HTTP
              proxy.  Use CURLOPT_PROXYAUTH to decide the authentication method.

       CURLOPT_USERNAME
              Pass a char * as parameter, which should be pointing to the zero terminated user name  to  use  for  the
              transfer.

              CURLOPT_USERNAME  sets  the  user  name  to  be used in protocol authentication. You should not use this
              option together with the (older) CURLOPT_USERPWD option.

              In order to specify the password to be used in conjunction with the user name use  the  CURLOPT_PASSWORD
              option.  (Added in 7.19.1)

       CURLOPT_PASSWORD
              Pass  a  char  *  as  parameter, which should be pointing to the zero terminated password to use for the
              transfer.

              The CURLOPT_PASSWORD option should be used in conjunction with the CURLOPT_USERNAME  option.  (Added  in
              7.19.1)

       CURLOPT_PROXYUSERNAME
              Pass  a  char  *  as parameter, which should be pointing to the zero terminated user name to use for the
              transfer while connecting to Proxy.

              The CURLOPT_PROXYUSERNAME option should be used in same way as the  CURLOPT_PROXYUSERPWD  is  used.   In
              comparison  to  CURLOPT_PROXYUSERPWD  the  CURLOPT_PROXYUSERNAME allows the username to contain a colon,
              like in the following example: "sip:userATexample.com". The CURLOPT_PROXYUSERNAME option is  an  alterna-
              tive  way  to  set the user name while connecting to Proxy.  There is no meaning to use it together with
              the CURLOPT_PROXYUSERPWD option.

              In order to specify the password to be used in conjunction with the user name use the CURLOPT_PROXYPASS-
              WORD option.  (Added in 7.19.1)

       CURLOPT_PROXYPASSWORD
              Pass  a  char  *  as  parameter, which should be pointing to the zero terminated password to use for the
              transfer while connecting to Proxy.

              The CURLOPT_PROXYPASSWORD option should be used in conjunction with  the  CURLOPT_PROXYUSERNAME  option.
              (Added in 7.19.1)

       CURLOPT_HTTPAUTH
              Pass  a long as parameter, which is set to a bitmask, to tell libcurl which authentication method(s) you
              want it to use. The available bits are listed below. If more than one bit is  set,  libcurl  will  first
              query  the  site to see which authentication methods it supports and then pick the best one you allow it
              to use. For some methods, this will induce an extra network round-trip. Set the actual name and password
              with  the  CURLOPT_USERPWD option or with the CURLOPT_USERNAME and the CURLOPT_PASSWORD options.  (Added
              in 7.10.6)

              CURLAUTH_BASIC
                     HTTP Basic authentication. This is the default choice, and the only method that is in wide-spread
                     use and supported virtually everywhere. This sends the user name and password over the network in
                     plain text, easily captured by others.

              CURLAUTH_DIGEST
                     HTTP Digest authentication.  Digest authentication is defined in RFC2617 and is a more secure way
                     to do authentication over public networks than the regular old-fashioned Basic method.

              CURLAUTH_DIGEST_IE
                     HTTP Digest authentication with an IE flavor.  Digest authentication is defined in RFC2617 and is
                     a more secure way to do authentication over public networks than the regular old-fashioned  Basic
                     method.  The IE flavor is simply that libcurl will use a special "quirk" that IE is known to have
                     used before version 7 and that some servers require the client to use. (This define was added  in
                     7.19.3)

              CURLAUTH_GSSNEGOTIATE
                     HTTP GSS-Negotiate authentication. The GSS-Negotiate (also known as plain "Negotiate") method was
                     designed by Microsoft and is used in their web applications. It is primarily meant as  a  support
                     for  Kerberos5  authentication  but may also be used along with other authentication methods. For
                     more information see IETF draft draft-brezak-spnego-http-04.txt.

                     You need to build libcurl with a suitable GSS-API library for this to work.

              CURLAUTH_NTLM
                     HTTP NTLM authentication. A proprietary protocol invented and used by Microsoft. It uses a  chal-
                     lenge-response  and  hash  concept  similar  to Digest, to prevent the password from being eaves-
                     dropped.

                     You need to build libcurl with OpenSSL support for this option to work, or build libcurl on  Win-
                     dows.

              CURLAUTH_NTLM_WB
                     NTLM  delegating  to winbind helper. Authentication is performed by a separate binary application
                     that is executed when needed. The name of the application is specified at  compile  time  but  is
                     typically /usr/bin/ntlm_auth (Added in 7.22.0)

                     Note  that  libcurl will fork when necessary to run the winbind application and kill it when com-
                     plete, calling waitpid() to await its exit when done. On POSIX  operating  systems,  killing  the
                     process will cause a SIGCHLD signal to be raised (regardless of whether CURLOPT_NOSIGNAL is set),
                     which must be handled intelligently by the application. In particular, the application  must  not
                     unconditionally call wait() in its SIGCHLD signal handler to avoid being subject to a race condi-
                     tion.  This behavior is subject to change in future versions of libcurl.

              CURLAUTH_ANY
                     This is a convenience macro that sets all bits and thus makes libcurl pick any it finds suitable.
                     libcurl will automatically select the one it finds most secure.

              CURLAUTH_ANYSAFE
                     This  is  a  convenience macro that sets all bits except Basic and thus makes libcurl pick any it
                     finds suitable. libcurl will automatically select the one it finds most secure.

              CURLAUTH_ONLY
                     This is a meta symbol. Or this value together with a single specific auth value to force  libcurl
                     to probe for un-restricted auth and if not, only that single auth algorithm is acceptable. (Added
                     in 7.21.3)

       CURLOPT_TLSAUTH_TYPE
              Pass a long as parameter, which is set to a bitmask, to tell libcurl which authentication method(s)  you
              want it to use for TLS authentication.

              CURLOPT_TLSAUTH_SRP
                     TLS-SRP  authentication. Secure Remote Password authentication for TLS is defined in RFC 5054 and
                     provides mutual authentication if both sides have a shared secret. To use TLS-SRP, you must  also
                     set the CURLOPT_TLSAUTH_USERNAME and CURLOPT_TLSAUTH_PASSWORD options.

                     You need to build libcurl with GnuTLS or OpenSSL with TLS-SRP support for this to work. (Added in
                     7.21.4)

       CURLOPT_TLSAUTH_USERNAME
              Pass a char * as parameter, which should point to the zero  terminated  username  to  use  for  the  TLS
              authentication   method   specified  with  the  CURLOPT_TLSAUTH_TYPE  option.  Requires  that  the  CUR-
              LOPT_TLS_PASSWORD option also be set. (Added in 7.21.4)

       CURLOPT_TLSAUTH_PASSWORD
              Pass a char * as parameter, which should point to the zero  terminated  password  to  use  for  the  TLS
              authentication   method   specified  with  the  CURLOPT_TLSAUTH_TYPE  option.  Requires  that  the  CUR-
              LOPT_TLS_USERNAME option also be set. (Added in 7.21.4)

       CURLOPT_PROXYAUTH
              Pass a long as parameter, which is set to a bitmask, to tell libcurl which authentication method(s)  you
              want it to use for your proxy authentication.  If more than one bit is set, libcurl will first query the
              site to see what authentication methods it supports and then pick the best one you allow it to use.  For
              some  methods,  this  will induce an extra network round-trip. Set the actual name and password with the
              CURLOPT_PROXYUSERPWD option. The bitmask can be constructed by or'ing together the bits listed above for
              the CURLOPT_HTTPAUTH option. As of this writing, only Basic, Digest and NTLM work. (Added in 7.10.7)

HTTP OPTIONS
       CURLOPT_AUTOREFERER
              Pass  a  parameter  set  to  1 to enable this. When enabled, libcurl will automatically set the Referer:
              field in requests where it follows a Location: redirect.

       CURLOPT_ACCEPT_ENCODING
              Sets the contents of the Accept-Encoding: header sent in an HTTP request,  and  enables  decoding  of  a
              response  when  a  Content-Encoding: header is received.  Three encodings are supported: identity, which
              does nothing, deflate which requests the server to compress its response using the zlib  algorithm,  and
              gzip which requests the gzip algorithm.  If a zero-length string is set, then an Accept-Encoding: header
              containing all supported encodings is sent.

              This is a request, not an order; the server may or may not do it.  This option must be set (to any  non-
              NULL  value)  or  else  any  unsolicited  encoding  done  by the server is ignored. See the special file
              lib/README.encoding for details.

              (This option was called CURLOPT_ENCODING before 7.21.6)

       CURLOPT_TRANSFER_ENCODING
              Adds a request for compressed Transfer Encoding in the outgoing HTTP request.  If  the  server  supports
              this and so desires, it can respond with the HTTP resonse sent using a compressed Transfer-Encoding that
              will be automatically uncompressed by libcurl on receival.

              Transfer-Encoding differs slightly from the Content-Encoding you ask for with CURLOPT_ACCEPT_ENCODING in
              that  a  Transfer-Encoding  is strictly meant to be for the transfer and thus MUST be decoded before the
              data arrives in the client. Traditionally, Transfer-Encoding has been much less used  and  supported  by
              both HTTP clients and HTTP servers.

              (Added in 7.21.6)

       CURLOPT_FOLLOWLOCATION
              A  parameter  set to 1 tells the library to follow any Location: header that the server sends as part of
              an HTTP header.

              This means that the library will re-send the same request on the new location and follow  new  Location:
              headers  all the way until no more such headers are returned. CURLOPT_MAXREDIRS can be used to limit the
              number of redirects libcurl will follow.

              Since 7.19.4, libcurl can limit what protocols it will automatically follow. The accepted protocols  are
              set with CURLOPT_REDIR_PROTOCOLS and it excludes the FILE protocol by default.

       CURLOPT_UNRESTRICTED_AUTH
              A  parameter set to 1 tells the library it can continue to send authentication (user+password) when fol-
              lowing locations, even when hostname changed. This option is meaningful only when  setting  CURLOPT_FOL-
              LOWLOCATION.

       CURLOPT_MAXREDIRS
              Pass a long. The set number will be the redirection limit. If that many redirections have been followed,
              the next redirect will cause an error (CURLE_TOO_MANY_REDIRECTS). This option only makes  sense  if  the
              CURLOPT_FOLLOWLOCATION  is  used  at  the  same  time. Added in 7.15.1: Setting the limit to 0 will make
              libcurl refuse any redirect. Set it to -1 for an infinite number of redirects (which is the default)

       CURLOPT_POSTREDIR
              Pass a bitmask to control how libcurl acts on redirects after POSTs that get a 301 or 302 response back.
              A  parameter with bit 0 set (value CURL_REDIR_POST_301) tells the library to respect RFC 2616/10.3.2 and
              not convert POST requests into GET requests when following a  301  redirection.  Setting  bit  1  (value
              CURL_REDIR_POST_302) makes libcurl maintain the request method after a 302 redirect. CURL_REDIR_POST_ALL
              is a convenience define that sets both bits.

              The non-RFC behaviour is ubiquitous in web browsers, so the library does the conversion  by  default  to
              maintain  consistency.  However,  a server may require a POST to remain a POST after such a redirection.
              This option is meaningful only when setting CURLOPT_FOLLOWLOCATION.  (Added in 7.17.1) (This option  was
              known as CURLOPT_POST301 up to 7.19.0 as it only supported the 301 way before then)

       CURLOPT_PUT
              A  parameter  set  to  1 tells the library to use HTTP PUT to transfer data. The data should be set with
              CURLOPT_READDATA and CURLOPT_INFILESIZE.

              This option is deprecated and starting with version 7.12.1 you should instead use CURLOPT_UPLOAD.

       CURLOPT_POST
              A parameter set to 1 tells the library to do a regular HTTP post. This will also make the library use  a
              "Content-Type:  application/x-www-form-urlencoded"  header.  (This is by far the most commonly used POST
              method).

              Use one of CURLOPT_POSTFIELDS or CURLOPT_COPYPOSTFIELDS options to specify what data to  post  and  CUR-
              LOPT_POSTFIELDSIZE or CURLOPT_POSTFIELDSIZE_LARGE to set the data size.

              Optionally, you can provide data to POST using the CURLOPT_READFUNCTION and CURLOPT_READDATA options but
              then you must make sure to not set CURLOPT_POSTFIELDS to anything but NULL. When providing data  with  a
              callback, you must transmit it using chunked transfer-encoding or you must set the size of the data with
              the CURLOPT_POSTFIELDSIZE or CURLOPT_POSTFIELDSIZE_LARGE option. To enable chunked encoding, you  simply
              pass in the appropriate Transfer-Encoding header, see the post-callback.c example.

              You can override the default POST Content-Type: header by setting your own with CURLOPT_HTTPHEADER.

              Using  POST  with  HTTP  1.1  implies  the use of a "Expect: 100-continue" header.  You can disable this
              header with CURLOPT_HTTPHEADER as usual.

              If you use POST to a HTTP 1.1 server, you can send data without knowing the  size  before  starting  the
              POST  if  you use chunked encoding. You enable this by adding a header like "Transfer-Encoding: chunked"
              with CURLOPT_HTTPHEADER. With HTTP 1.0 or without chunked transfer, you must specify  the  size  in  the
              request.

              When setting CURLOPT_POST to 1, it will automatically set CURLOPT_NOBODY to 0 (since 7.14.1).

              If  you issue a POST request and then want to make a HEAD or GET using the same re-used handle, you must
              explicitly set the new request type using CURLOPT_NOBODY or CURLOPT_HTTPGET or similar.

       CURLOPT_POSTFIELDS
              Pass a void * as parameter, which should be the full data to post in an HTTP POST  operation.  You  must
              make sure that the data is formatted the way you want the server to receive it. libcurl will not convert
              or encode it for you. Most web servers will assume this data to be url-encoded.

              The pointed data are NOT copied by the library: as a consequence, they must be preserved by the  calling
              application until the transfer finishes.

              This  POST is a normal application/x-www-form-urlencoded kind (and libcurl will set that Content-Type by
              default when this option is used), which is the most commonly used one by HTML forms. See also the  CUR-
              LOPT_POST. Using CURLOPT_POSTFIELDS implies CURLOPT_POST.

              If  you want to do a zero-byte POST, you need to set CURLOPT_POSTFIELDSIZE explicitly to zero, as simply
              setting CURLOPT_POSTFIELDS to NULL or "" just effectively disables the sending of the specified  string.
              libcurl will instead assume that you'll send the POST data using the read callback!

              Using  POST  with  HTTP  1.1  implies  the use of a "Expect: 100-continue" header.  You can disable this
              header with CURLOPT_HTTPHEADER as usual.

              To make multipart/formdata posts (aka RFC2388-posts), check out the CURLOPT_HTTPPOST option.

       CURLOPT_POSTFIELDSIZE
              If you want to post data to the server without letting libcurl do a strlen() to measure the  data  size,
              this  option  must  be used. When this option is used you can post fully binary data, which otherwise is
              likely to fail. If this size is set to -1, the library will use strlen() to get the size.

       CURLOPT_POSTFIELDSIZE_LARGE
              Pass a curl_off_t as parameter. Use this to set the size  of  the  CURLOPT_POSTFIELDS  data  to  prevent
              libcurl  from  doing  strlen() on the data to figure out the size. This is the large file version of the
              CURLOPT_POSTFIELDSIZE option. (Added in 7.11.1)

       CURLOPT_COPYPOSTFIELDS
              Pass a char * as parameter, which should be the full data to post in an HTTP POST operation. It  behaves
              as the CURLOPT_POSTFIELDS option, but the original data are copied by the library, allowing the applica-
              tion to overwrite the original data after setting this option.

              Because data are copied, care must be taken when using this option  in  conjunction  with  CURLOPT_POST-
              FIELDSIZE  or CURLOPT_POSTFIELDSIZE_LARGE: If the size has not been set prior to CURLOPT_COPYPOSTFIELDS,
              the data are assumed to be a NUL-terminated string; else the stored size informs the library  about  the
              data  byte count to copy. In any case, the size must not be changed after CURLOPT_COPYPOSTFIELDS, unless
              another CURLOPT_POSTFIELDS or CURLOPT_COPYPOSTFIELDS option is issued.  (Added in 7.17.1)

       CURLOPT_HTTPPOST
              Tells libcurl you want a multipart/formdata HTTP POST to be made and you instruct what data to  pass  on
              to  the server.  Pass a pointer to a linked list of curl_httppost structs as parameter.  The easiest way
              to create such a list, is to use curl_formadd(3) as documented. The data in this list must remain intact
              until you close this curl handle again with curl_easy_cleanup(3).

              Using  POST  with  HTTP  1.1  implies  the use of a "Expect: 100-continue" header.  You can disable this
              header with CURLOPT_HTTPHEADER as usual.

              When setting CURLOPT_HTTPPOST, it will automatically set CURLOPT_NOBODY to 0 (since 7.14.1).

       CURLOPT_REFERER
              Pass a pointer to a zero terminated string as parameter. It will be used to set the Referer:  header  in
              the  http  request  sent to the remote server. This can be used to fool servers or scripts. You can also
              set any custom header with CURLOPT_HTTPHEADER.

       CURLOPT_USERAGENT
              Pass a pointer to a zero terminated string as parameter. It will be used to set the  User-Agent:  header
              in the http request sent to the remote server. This can be used to fool servers or scripts. You can also
              set any custom header with CURLOPT_HTTPHEADER.

       CURLOPT_HTTPHEADER
              Pass a pointer to a linked list of HTTP headers to pass to the server in your HTTP request.  The  linked
              list   should   be   a   fully  valid  list  of  struct  curl_slist  structs  properly  filled  in.  Use
              curl_slist_append(3) to create the list and curl_slist_free_all(3) to clean up an entire  list.  If  you
              add  a  header  that  is otherwise generated and used by libcurl internally, your added one will be used
              instead. If you add a header with no content as in 'Accept:' (no data on the right side of  the  colon),
              the  internally  used header will get disabled. Thus, using this option you can add new headers, replace
              internal headers and remove internal headers. To add a header with no content, make the content  be  two
              quotes:  "". The headers included in the linked list must not be CRLF-terminated, because curl adds CRLF
              after each header item. Failure to comply with this will result in strange bugs because the server  will
              most likely ignore part of the headers you specified.

              The first line in a request (containing the method, usually a GET or POST) is not a header and cannot be
              replaced using this option. Only the lines following the request-line are headers.  Adding  this  method
              line in this list of headers will only cause your request to send an invalid header.

              Pass a NULL to this to reset back to no custom headers.

              The most commonly replaced headers have "shortcuts" in the options CURLOPT_COOKIE, CURLOPT_USERAGENT and
              CURLOPT_REFERER.

       CURLOPT_HTTP200ALIASES
              Pass a pointer to a linked list of aliases to be treated as valid  HTTP  200  responses.   Some  servers
              respond with a custom header response line.  For example, IceCast servers respond with "ICY 200 OK".  By
              including this string in your list of aliases, the response will be treated as a valid HTTP header  line
              such as "HTTP/1.0 200 OK". (Added in 7.10.3)

              The  linked  list  should be a fully valid list of struct curl_slist structs, and be properly filled in.
              Use curl_slist_append(3) to create the list and curl_slist_free_all(3) to clean up an entire list.

              The alias itself is not parsed for any version strings. Before libcurl 7.16.3, Libcurl  used  the  value
              set  by  option CURLOPT_HTTP_VERSION, but starting with 7.16.3 the protocol is assumed to match HTTP 1.0
              when an alias matched.

       CURLOPT_COOKIE
              Pass a pointer to a zero terminated string as parameter. It will be used to set a  cookie  in  the  http
              request. The format of the string should be NAME=CONTENTS, where NAME is the cookie name and CONTENTS is
              what the cookie should contain.

              If you need to set multiple cookies, you need to set them all using a single option and thus you need to
              concatenate  them  all  in  one single string. Set multiple cookies in one string like this: "name1=con-
              tent1; name2=content2;" etc.

              This option sets the cookie header explicitly in the outgoing request(s). If multiple requests are  done
              due to authentication, followed redirections or similar, they will all get this cookie passed on.

              Using this option multiple times will only make the latest string override the previous ones.

       CURLOPT_COOKIEFILE
              Pass a pointer to a zero terminated string as parameter. It should contain the name of your file holding
              cookie data to read. The cookie data may be in Netscape / Mozilla cookie data  format  or  just  regular
              HTTP-style headers dumped to a file.

              Given an empty or non-existing file or by passing the empty string (""), this option will enable cookies
              for this curl handle, making it understand and parse received cookies and then use matching  cookies  in
              future requests.

              If  you use this option multiple times, you just add more files to read.  Subsequent files will add more
              cookies.

       CURLOPT_COOKIEJAR
              Pass a file name as char *, zero terminated. This will make libcurl write all internally  known  cookies
              to  the  specified  file  when  curl_easy_cleanup(3) is called. If no cookies are known, no file will be
              created. Specify "-" to instead have the cookies written to stdout. Using this option also enables cook-
              ies  for  this  session,  so if you for example follow a location it will make matching cookies get sent
              accordingly.

              If the cookie jar file can't be created or written to (when the curl_easy_cleanup(3) is called), libcurl
              will  not and cannot report an error for this. Using CURLOPT_VERBOSE or CURLOPT_DEBUGFUNCTION will get a
              warning to display, but that is the only visible feedback you get about this possibly lethal  situation.

       CURLOPT_COOKIESESSION
              Pass a long set to 1 to mark this as a new cookie "session". It will force libcurl to ignore all cookies
              it is about to load that are "session cookies" from the previous session.  By  default,  libcurl  always
              stores  and loads all cookies, independent if they are session cookies or not. Session cookies are cook-
              ies without expiry date and they are meant to be alive and existing for this "session" only.

       CURLOPT_COOKIELIST
              Pass a char * to a cookie string. Cookie can be either in Netscape /  Mozilla  format  or  just  regular
              HTTP-style  header  (Set-Cookie:  ...)  format. If cURL cookie engine was not enabled it will enable its
              cookie engine.  Passing a magic string "ALL" will erase all cookies known by  cURL.  (Added  in  7.14.1)
              Passing  the  special string "SESS" will only erase all session cookies known by cURL. (Added in 7.15.4)
              Passing the special string "FLUSH" will write all cookies known by cURL to the file  specified  by  CUR-
              LOPT_COOKIEJAR.  (Added in 7.17.1)

       CURLOPT_HTTPGET
              Pass  a long. If the long is 1, this forces the HTTP request to get back to GET. Usable if a POST, HEAD,
              PUT, or a custom request has been used previously using the same curl handle.

              When setting CURLOPT_HTTPGET to 1, it will automatically set CURLOPT_NOBODY to 0 (since 7.14.1).

       CURLOPT_HTTP_VERSION
              Pass a long, set to one of the values described below. They force libcurl to use the specific HTTP  ver-
              sions. This is not sensible to do unless you have a good reason.

              CURL_HTTP_VERSION_NONE
                     We don't care about what version the library uses. libcurl will use whatever it thinks fit.

              CURL_HTTP_VERSION_1_0
                     Enforce HTTP 1.0 requests.

              CURL_HTTP_VERSION_1_1
                     Enforce HTTP 1.1 requests.

       CURLOPT_IGNORE_CONTENT_LENGTH
              Ignore  the Content-Length header. This is useful for Apache 1.x (and similar servers) which will report
              incorrect content length for files over 2 gigabytes. If this option is used, curl will not  be  able  to
              accurately  report  progress,  and  will  simply  stop the download when the server ends the connection.
              (added in 7.14.1)

       CURLOPT_HTTP_CONTENT_DECODING
              Pass a long to tell libcurl how to act on content decoding. If set to zero,  content  decoding  will  be
              disabled.  If  set  to  1 it is enabled. Libcurl has no default content decoding but requires you to use
              CURLOPT_ENCODING for that. (added in 7.16.2)

       CURLOPT_HTTP_TRANSFER_DECODING
              Pass a long to tell libcurl how to act on transfer decoding. If set to zero, transfer decoding  will  be
              disabled,  if set to 1 it is enabled (default). libcurl does chunked transfer decoding by default unless
              this option is set to zero. (added in 7.16.2)

SMTP OPTIONS
       CURLOPT_MAIL_FROM
              Pass a pointer to a zero terminated string as parameter. It will be used to specify the  sender  address
              in a mail when sending an SMTP mail with libcurl.

              An originator email address in SMTP lingo is specified within angle brackets (<>) which libcurl will not
              add for you before version 7.21.4. Failing to provide such brackets may cause the server to reject  your
              mail.

              (Added in 7.20.0)

       CURLOPT_MAIL_RCPT
              Pass  a  pointer  to  a  linked list of recipients to pass to the server in your SMTP mail request.  The
              linked list should be a  fully  valid  list  of  struct  curl_slist  structs  properly  filled  in.  Use
              curl_slist_append(3) to create the list and curl_slist_free_all(3) to clean up an entire list.

              Each  recipient  in  SMTP  lingo  is specified with angle brackets (<>), but should you not use an angle
              bracket as first letter libcurl will assume you provide a single email address  only  and  enclose  that
              with angle brackets for you.

              (Added in 7.20.0)

TFTP OPTIONS
       CURLOPT_TFTP_BLKSIZE
              Specify  block size to use for TFTP data transmission. Valid range as per RFC 2348 is 8-65464 bytes. The
              default of 512 bytes will be used if this option is not specified. The specified block size will only be
              used  pending  support  by the remote server. If the server does not return an option acknowledgement or
              returns an option acknowledgement with no blksize, the default of 512 bytes  will  be  used.  (added  in
              7.19.4)

FTP OPTIONS
       CURLOPT_FTPPORT
              Pass  a  pointer  to a zero terminated string as parameter. It will be used to get the IP address to use
              for the FTP PORT instruction. The PORT instruction tells the remote server to connect to  our  specified
              IP  address. The string may be a plain IP address, a host name, a network interface name (under Unix) or
              just a '-' symbol to let the library use your system's default IP address. Default  FTP  operations  are
              passive, and thus won't use PORT.

              The  address  can be followed by a ':' to specify a port, optionally followed by a '-' to specify a port
              range.  If the port specified is 0, the operating system will pick a free port.  If a range is  provided
              and  all ports in the range are not available, libcurl will report CURLE_FTP_PORT_FAILED for the handle.
              Invalid port/range settings are ignored.  IPv6 addresses followed by a port or portrange have to  be  in
              brackets.  IPv6 addresses without port/range specifier can be in brackets.  (added in 7.19.5)

              Examples with specified ports:

                eth0:0
                192.168.1.2:32000-33000
                curl.se:32123
                [::1]:1234-4567

              You disable PORT again and go back to using the passive version by setting this option to NULL.

       CURLOPT_QUOTE
              Pass a pointer to a linked list of FTP or SFTP commands to pass to the server prior to your FTP request.
              This will be done before any other commands are issued (even before the CWD command for FTP). The linked
              list  should  be a fully valid list of 'struct curl_slist' structs properly filled in with text strings.
              Use curl_slist_append(3) to append strings (commands) to the list, and clear the entire list  afterwards
              with  curl_slist_free_all(3). Disable this operation again by setting a NULL to this option. When speak-
              ing to a FTP (or SFTP since 7.24.0) server, prefix the command with an asterisk (*) to make libcurl con-
              tinue even if the command fails as by default libcurl will stop at first failure.

              The set of valid FTP commands depends on the server (see RFC959 for a list of mandatory commands).

              The  valid  SFTP  commands  are:  chgrp,  chmod,  chown, ln, mkdir, pwd, rename, rm, rmdir, symlink (see
              curl(1)) (SFTP support added in 7.16.3)

       CURLOPT_POSTQUOTE
              Pass a pointer to a linked list of FTP or SFTP commands to pass to the server after  your  FTP  transfer
              request.  The  commands  will  only be run if no error occurred. The linked list should be a fully valid
              list of struct curl_slist structs properly filled in as described for CURLOPT_QUOTE. Disable this opera-
              tion again by setting a NULL to this option.

       CURLOPT_PREQUOTE
              Pass  a  pointer  to a linked list of FTP commands to pass to the server after the transfer type is set.
              The linked list should be a fully valid  list  of  struct  curl_slist  structs  properly  filled  in  as
              described  for CURLOPT_QUOTE. Disable this operation again by setting a NULL to this option. Before ver-
              sion 7.15.6, if you also set CURLOPT_NOBODY to 1, this option didn't work.

       CURLOPT_DIRLISTONLY
              A parameter set to 1 tells the library to just list the names of files in a directory, instead of  doing
              a full directory listing that would include file sizes, dates etc. This works for FTP and SFTP URLs.

              This  causes  an  FTP  NLST command to be sent on an FTP server.  Beware that some FTP servers list only
              files in their response to NLST; they might not include subdirectories and symbolic links.

              Setting this option to 1 also implies a directory listing even if the URL  doesn't  end  with  a  slash,
              which otherwise is necessary.

              Do  NOT  use this option if you also use CURLOPT_WILDCARDMATCH as it will effectively break that feature
              then.

              (This option was known as CURLOPT_FTPLISTONLY up to 7.16.4)

       CURLOPT_APPEND
              A parameter set to 1 tells the library to append to the remote file instead of  overwrite  it.  This  is
              only useful when uploading to an FTP site.

              (This option was known as CURLOPT_FTPAPPEND up to 7.16.4)

       CURLOPT_FTP_USE_EPRT
              Pass  a  long. If the value is 1, it tells curl to use the EPRT (and LPRT) command when doing active FTP
              downloads (which is enabled by CURLOPT_FTPPORT). Using EPRT means that it will first attempt to use EPRT
              and  then  LPRT  before  using  PORT, but if you pass zero to this option, it will not try using EPRT or
              LPRT, only plain PORT. (Added in 7.10.5)

              If the server is an IPv6 host, this option will have no effect as of 7.12.3.

       CURLOPT_FTP_USE_EPSV
              Pass a long. If the value is 1, it tells curl to use the EPSV command when doing passive  FTP  downloads
              (which  it always does by default). Using EPSV means that it will first attempt to use EPSV before using
              PASV, but if you pass zero to this option, it will not try using EPSV, only plain PASV.

              If the server is an IPv6 host, this option will have no effect as of 7.12.3.

       CURLOPT_FTP_USE_PRET
              Pass a long. If the value is 1, it tells curl to send a PRET command before PASV (and EPSV). Certain FTP
              servers, mainly drftpd, require this non-standard command for directory listings as well as up and down-
              loads in PASV mode. Has no effect when using the active FTP transfers mode.  (Added in 7.20.0)

       CURLOPT_FTP_CREATE_MISSING_DIRS
              Pass a long. If the value is 1, curl will attempt to create any remote directory that it  fails  to  CWD
              into. CWD is the command that changes working directory. (Added in 7.10.7)

              This  setting  also  applies to SFTP-connections. curl will attempt to create the remote directory if it
              can't obtain a handle to the target-location. The creation will fail if a file of the same name  as  the
              directory to create already exists or lack of permissions prevents creation. (Added in 7.16.3)

              Starting  with  7.19.4,  you can also set this value to 2, which will make libcurl retry the CWD command
              again if the subsequent MKD command fails. This is especially useful if you're  doing  many  simultanoes
              connections  against  the  same server and they all have this option enabled, as then CWD may first fail
              but then another connection does MKD before this connection and thus MKD fails  but  trying  CWD  works!
              7.19.4  also  introduced  the CURLFTP_CREATE_DIR and CURLFTP_CREATE_DIR_RETRY enum names for these argu-
              ments.

              Before version 7.19.4, libcurl will simply ignore arguments set to 2 and act as if 1 was selected.

       CURLOPT_FTP_RESPONSE_TIMEOUT
              Pass a long.  Causes curl to set a timeout period (in seconds) on the amount of time that the server  is
              allowed  to  take in order to generate a response message for a command before the session is considered
              hung.  While curl is waiting for a response, this value overrides  CURLOPT_TIMEOUT.  It  is  recommended
              that  if  used  in  conjunction  with  CURLOPT_TIMEOUT,  you set CURLOPT_FTP_RESPONSE_TIMEOUT to a value
              smaller than CURLOPT_TIMEOUT.  (Added in 7.10.8)

       CURLOPT_FTP_ALTERNATIVE_TO_USER
              Pass a char * as parameter, pointing to a string which will be used to authenticate  if  the  usual  FTP
              "USER user" and "PASS password" negotiation fails. This is currently only known to be required when con-
              necting to Tumbleweed's Secure Transport FTPS  server  using  client  certificates  for  authentication.
              (Added in 7.15.5)

       CURLOPT_FTP_SKIP_PASV_IP
              Pass  a  long.  If  set  to 1, it instructs libcurl to not use the IP address the server suggests in its
              227-response to libcurl's PASV command when libcurl connects the data connection. Instead  libcurl  will
              re-use  the  same IP address it already uses for the control connection. But it will use the port number
              from the 227-response. (Added in 7.14.2)

              This option has no effect if PORT, EPRT or EPSV is used instead of PASV.

       CURLOPT_FTPSSLAUTH
              Pass a long using one of the values from below, to alter how libcurl issues "AUTH  TLS"  or  "AUTH  SSL"
              when FTP over SSL is activated (see CURLOPT_USE_SSL). (Added in 7.12.2)

              CURLFTPAUTH_DEFAULT
                     Allow libcurl to decide.

              CURLFTPAUTH_SSL
                     Try "AUTH SSL" first, and only if that fails try "AUTH TLS".

              CURLFTPAUTH_TLS
                     Try "AUTH TLS" first, and only if that fails try "AUTH SSL".

       CURLOPT_FTP_SSL_CCC
              If  enabled,  this option makes libcurl use CCC (Clear Command Channel). It shuts down the SSL/TLS layer
              after authenticating. The rest of the control channel communication will be unencrypted. This allows NAT
              routers to follow the FTP transaction. Pass a long using one of the values below.  (Added in 7.16.1)

              CURLFTPSSL_CCC_NONE
                     Don't attempt to use CCC.

              CURLFTPSSL_CCC_PASSIVE
                     Do not initiate the shutdown, but wait for the server to do it. Do not send a reply.

              CURLFTPSSL_CCC_ACTIVE
                     Initiate the shutdown and wait for a reply.

       CURLOPT_FTP_ACCOUNT
              Pass  a  pointer  to a zero terminated string (or NULL to disable). When an FTP server asks for "account
              data" after user name and password has been provided, this data is sent  off  using  the  ACCT  command.
              (Added in 7.13.0)

       CURLOPT_FTP_FILEMETHOD
              Pass  a  long  that  should  have  one of the following values. This option controls what method libcurl
              should use to reach a file on a FTP(S) server. The argument should be one of the following alternatives:

              CURLFTPMETHOD_MULTICWD
                     libcurl  does  a  single  CWD operation for each path part in the given URL. For deep hierarchies
                     this means many commands. This is how RFC1738 says it should be done. This is the default but the
                     slowest behavior.

              CURLFTPMETHOD_NOCWD
                     libcurl  does  no  CWD  at  all. libcurl will do SIZE, RETR, STOR etc and give a full path to the
                     server for all these commands. This is the fastest behavior.

              CURLFTPMETHOD_SINGLECWD
                     libcurl does one CWD with the full target directory and then  operates  on  the  file  "normally"
                     (like  in  the multicwd case). This is somewhat more standards compliant than 'nocwd' but without
                     the full penalty of 'multicwd'.
       (Added in 7.15.1)

RTSP OPTIONS
       CURLOPT_RTSP_REQUEST
              Tell libcurl what kind of RTSP request to make. Pass one of the following RTSP enum values. Unless noted
              otherwise, commands require the Session ID to be initialized. (Added in 7.20.0)

              CURL_RTSPREQ_OPTIONS
                     Used  to retrieve the available methods of the server. The application is responsbile for parsing
                     and obeying the response. (The session ID is not needed for this method.)  (Added in 7.20.0)

              CURL_RTSPREQ_DESCRIBE
                     Used to get the low level description of a stream. The application should note  what  formats  it
                     understands  in  the  'Accept:'  header.  Unless set manually, libcurl will automatically fill in
                     'Accept: application/sdp'. Time-condition headers will be added to Describe requests if the  CUR-
                     LOPT_TIMECONDITION  option  is  active. (The session ID is not needed for this method)  (Added in
                     7.20.0)

              CURL_RTSPREQ_ANNOUNCE
                     When sent by a client, this method changes the description of the  session.  For  example,  if  a
                     client  is using the server to record a meeting, the client can use Announce to inform the server
                     of all the meta-information about the session.  ANNOUNCE acts like an HTTP PUT or POST just  like
                     CURL_RTSPREQ_SET_PARAMETER (Added in 7.20.0)

              CURL_RTSPREQ_SETUP
                     Setup  is  used  to  initialize the transport layer for the session. The application must set the
                     desired Transport options for a session by using the CURLOPT_RTSP_TRANSPORT option prior to call-
                     ing  setup.  If no session ID is currently set with CURLOPT_RTSP_SESSION_ID, libcurl will extract
                     and use the session ID in the response to this request. (The session ID is not  needed  for  this
                     method).  (Added in 7.20.0)

              CURL_RTSPREQ_PLAY
                     Send a Play command to the server. Use the CURLOPT_RANGE option to modify the playback time (e.g.
                     'npt=10-15').  (Added in 7.20.0)

              CURL_RTSPREQ_PAUSE
                     Send a Pause command to the server. Use the CURLOPT_RANGE option with a single value to  indicate
                     when the stream should be halted. (e.g. npt='25') (Added in 7.20.0)

              CURL_RTSPREQ_TEARDOWN
                     This  command terminates an RTSP session. Simply closing a connection does not terminate the RTSP
                     session since it is valid to control an RTSP  session  over  different  connections.   (Added  in
                     7.20.0)

              CURL_RTSPREQ_GET_PARAMETER
                     Retrieve  a  parameter from the server. By default, libcurl will automatically include a Content-
                     Type: text/parameters header on all non-empty requests unless a custom one is set.  GET_PARAMETER
                     acts  just  like  an  HTTP PUT or POST (see CURL_RTSPREQ_SET_PARAMETER).  Applications wishing to
                     send a heartbeat message (e.g. in the presence of a server-specified timeout) should send use  an
                     empty GET_PARAMETER request.  (Added in 7.20.0)

              CURL_RTSPREQ_SET_PARAMETER
                     Set  a  parameter  on  the server. By default, libcurl will automatically include a Content-Type:
                     text/parameters header unless a custom one is set. The interaction with SET_PARAMTER is much like
                     an  HTTP  PUT or POST. An application may either use CURLOPT_UPLOAD with CURLOPT_READDATA like an
                     HTTP PUT, or it may use CURLOPT_POSTFIELDS like an HTTP POST. No chunked transfers  are  allowed,
                     so the application must set the CURLOPT_INFILESIZE in the former and CURLOPT_POSTFIELDSIZE in the
                     latter. Also, there is no use of multi-part POSTs within RTSP. (Added in 7.20.0)

              CURL_RTSPREQ_RECORD
                     Used to tell the server to record a session. Use the CURLOPT_RANGE option to  modify  the  record
                     time. (Added in 7.20.0)

              CURL_RTSPREQ_RECEIVE
                     This  is  a  special request because it does not send any data to the server. The application may
                     call this function in order to receive interleaved RTP data. It will return after processing  one
                     read buffer of data in order to give the application a chance to run. (Added in 7.20.0)

       CURLOPT_RTSP_SESSION_ID
              Pass  a char * as a parameter to set the value of the current RTSP Session ID for the handle. Useful for
              resuming an in-progress session. Once this value is set to  any  non-NULL  value,  libcurl  will  return
              CURLE_RTSP_SESSION_ERROR  if  ID  received  from  the  server does not match. If unset (or set to NULL),
              libcurl will automatically set the ID the first time the server sets it in a response. (Added in 7.20.0)

       CURLOPT_RTSP_STREAM_URI
              Set  the stream URI to operate on by passing a char * . For example, a single session may be controlling
              rtsp://foo/twister/audio and rtsp://foo/twister/video and the application can switch to the  appropriate
              stream using this option. If unset, libcurl will default to operating on generic server options by pass-
              ing '*' in the place of the RTSP Stream URI. This option is distinct from CURLOPT_URL. When working with
              RTSP,  the  CURLOPT_STREAM_URI  indicates what URL to send to the server in the request header while the
              CURLOPT_URL indicates where to make the connection to.  (e.g. the CURLOPT_URL  for  the  above  examples
              might be set to rtsp://foo/twister (Added in 7.20.0)

       CURLOPT_RTSP_TRANSPORT
              Pass  a  char  *  to  tell libcurl what to pass for the Transport: header for this RTSP session. This is
              mainly a convenience method to avoid needing to set a custom Transport: header for every SETUP  request.
              The application must set a Transport: header before issuing a SETUP request. (Added in 7.20.0)

       CURLOPT_RTSP_HEADER
              This  option  is  simply an alias for CURLOPT_HTTP_HEADER. Use this to replace the standard headers that
              RTSP and HTTP share. It is also valid to use the shortcuts such as CURLOPT_USERAGENT. (Added in 7.20.0)

       CURLOPT_RTSP_CLIENT_CSEQ
              Manually set the the CSEQ number to issue for the next RTSP request. Useful if the application is resum-
              ing  a  previously broken connection. The CSEQ will increment from this new number henceforth. (Added in
              7.20.0)

       CURLOPT_RTSP_SERVER_CSEQ
              Manually set the CSEQ number to expect for the next RTSP Server->Client request.  At  the  moment,  this
              feature (listening for Server requests) is unimplemented. (Added in 7.20.0)

PROTOCOL OPTIONS
       CURLOPT_TRANSFERTEXT
              A  parameter  set  to  1  tells  the library to use ASCII mode for FTP transfers, instead of the default
              binary transfer. For win32 systems it does not set the stdout to binary mode. This option can be  usable
              when transferring text data between systems with different views on certain characters, such as newlines
              or similar.

              libcurl does not do a complete ASCII conversion when doing ASCII transfers over FTP.  This  is  a  known
              limitation/flaw that nobody has rectified. libcurl simply sets the mode to ASCII and performs a standard
              transfer.

       CURLOPT_PROXY_TRANSFER_MODE
              Pass a long. If the value is set to 1 (one), it tells libcurl to set the transfer mode (binary or ASCII)
              for  FTP transfers done via an HTTP proxy, by appending ;type=a or ;type=i to the URL. Without this set-
              ting, or it being set to 0 (zero, the default), CURLOPT_TRANSFERTEXT has no effect when doing FTP via  a
              proxy. Beware that not all proxies support this feature.  (Added in 7.18.0)

       CURLOPT_CRLF
              Pass  a  long. If the value is set to 1 (one), libcurl converts Unix newlines to CRLF newlines on trans-
              fers. Disable this option again by setting the value to 0 (zero).

       CURLOPT_RANGE
              Pass a char * as parameter, which should contain the specified range you want. It should be in the  for-
              mat  "X-Y",  where X or Y may be left out. HTTP transfers also support several intervals, separated with
              commas as in "X-Y,N-M". Using this kind of multiple intervals will cause the HTTP  server  to  send  the
              response  document  in pieces (using standard MIME separation techniques). For RTSP, the formatting of a
              range should follow RFC 2326 Section 12.29. For RTSP, byte ranges are  not  permitted.  Instead,  ranges
              should be given in npt, utc, or smpte formats.

              Pass a NULL to this option to disable the use of ranges.

              Ranges work on HTTP, FTP, FILE (since 7.18.0), and RTSP (since 7.20.0) transfers only.

       CURLOPT_RESUME_FROM
              Pass  a long as parameter. It contains the offset in number of bytes that you want the transfer to start
              from. Set this option to 0 to make the transfer start from the beginning (effectively disabling resume).
              For  FTP,  set  this  option to -1 to make the transfer start from the end of the target file (useful to
              continue an interrupted upload).

              When doing uploads with FTP, the resume position is where in the local/source file libcurl should try to
              resume the upload from and it will then append the source file to the remote target file.

       CURLOPT_RESUME_FROM_LARGE
              Pass  a curl_off_t as parameter. It contains the offset in number of bytes that you want the transfer to
              start from. (Added in 7.11.0)

       CURLOPT_CUSTOMREQUEST
              Pass a pointer to a zero terminated string as parameter. It will be used instead of  GET  or  HEAD  when
              doing an HTTP request, or instead of LIST or NLST when doing a FTP directory listing. This is useful for
              doing DELETE or other more or less obscure HTTP requests. Don't do this at will, make sure  your  server
              supports the command first.

              When  you  change  the  request method by setting CURLOPT_CUSTOMREQUEST to something, you don't actually
              change how libcurl behaves or acts in regards to the particular request method, it will only change  the
              actual string sent in the request.

              For  example: if you tell libcurl to do a HEAD request, but then change the request to a "GET" with CUR-
              LOPT_CUSTOMREQUEST you'll still see libcurl act as if it sent a HEAD even when it does send a GET.

              To switch to a proper HEAD, use CURLOPT_NOBODY, to switch to a proper POST,  use  CURLOPT_POST  or  CUR-
              LOPT_POSTFIELDS and so on.

              Restore to the internal default by setting this to NULL.

              Many people have wrongly used this option to replace the entire request with their own, including multi-
              ple headers and POST contents. While that might work in many  cases,  it  will  cause  libcurl  to  send
              invalid  requests  and  it  could  possibly  confuse  the remote server badly. Use CURLOPT_POST and CUR-
              LOPT_POSTFIELDS to set POST data. Use CURLOPT_HTTPHEADER to replace or extend the set of headers sent by
              libcurl. Use CURLOPT_HTTP_VERSION to change HTTP version.

       CURLOPT_FILETIME
              Pass  a  long.  If  it is 1, libcurl will attempt to get the modification date of the remote document in
              this operation. This requires that the remote server sends the time or replies to a time  querying  com-
              mand. The curl_easy_getinfo(3) function with the CURLINFO_FILETIME argument can be used after a transfer
              to extract the received time (if any).

       CURLOPT_NOBODY
              A parameter set to 1 tells the library to not include the body-part in the output. This is only relevant
              for  protocols that have separate header and body parts. On HTTP(S) servers, this will make libcurl do a
              HEAD request.

              To change request to GET, you should use CURLOPT_HTTPGET. Change request to POST with CURLOPT_POST  etc.

       CURLOPT_INFILESIZE
              When  uploading  a  file  to a remote site, this option should be used to tell libcurl what the expected
              size of the infile is. This value should be passed as a long. See also CURLOPT_INFILESIZE_LARGE.

              For uploading using SCP, this option or CURLOPT_INFILESIZE_LARGE is mandatory.

              When sending emails using SMTP, this command can be used to specify the optional SIZE parameter for  the
              MAIL FROM command. (Added in 7.23.0)

              This  option  does not limit how much data libcurl will actually send, as that is controlled entirely by
              what the read callback returns.

       CURLOPT_INFILESIZE_LARGE
              When uploading a file to a remote site, this option should be used to tell  libcurl  what  the  expected
              size of the infile is.  This value should be passed as a curl_off_t. (Added in 7.11.0)

              For uploading using SCP, this option or CURLOPT_INFILESIZE is mandatory.

              This  option  does not limit how much data libcurl will actually send, as that is controlled entirely by
              what the read callback returns.

       CURLOPT_UPLOAD
              A parameter set to 1 tells the  library  to  prepare  for  an  upload.  The  CURLOPT_READDATA  and  CUR-
              LOPT_INFILESIZE or CURLOPT_INFILESIZE_LARGE options are also interesting for uploads. If the protocol is
              HTTP, uploading means using the PUT request unless you tell libcurl otherwise.

              Using PUT with HTTP 1.1 implies the use of a "Expect: 100-continue" header.  You can disable this header
              with CURLOPT_HTTPHEADER as usual.

              If  you  use  PUT to a HTTP 1.1 server, you can upload data without knowing the size before starting the
              transfer if you use chunked encoding. You enable this by adding a header like "Transfer-Encoding:  chun-
              ked" with CURLOPT_HTTPHEADER. With HTTP 1.0 or without chunked transfer, you must specify the size.

       CURLOPT_MAXFILESIZE
              Pass  a long as parameter. This allows you to specify the maximum size (in bytes) of a file to download.
              If the file requested is larger than this value, the transfer will not start and CURLE_FILESIZE_EXCEEDED
              will be returned.

              The  file  size is not always known prior to download, and for such files this option has no effect even
              if the file transfer ends up being larger than this given limit. This concerns both FTP and HTTP  trans-
              fers.

       CURLOPT_MAXFILESIZE_LARGE
              Pass  a  curl_off_t  as  parameter.  This allows you to specify the maximum size (in bytes) of a file to
              download. If the file requested is larger than this value, the transfer will not start  and  CURLE_FILE-
              SIZE_EXCEEDED will be returned. (Added in 7.11.0)

              The  file  size is not always known prior to download, and for such files this option has no effect even
              if the file transfer ends up being larger than this given limit. This concerns both FTP and HTTP  trans-
              fers.

       CURLOPT_TIMECONDITION
              Pass a long as parameter. This defines how the CURLOPT_TIMEVALUE time value is treated. You can set this
              parameter to CURL_TIMECOND_IFMODSINCE or CURL_TIMECOND_IFUNMODSINCE. This feature applies to HTTP,  FTP,
              RTSP, and FILE.

              The last modification time of a file is not always known and in such instances this feature will have no
              effect even if the given  time  condition  would  not  have  been  met.  curl_easy_getinfo(3)  with  the
              CURLINFO_CONDITION_UNMET  option can be used after a transfer to learn if a zero-byte successful "trans-
              fer" was due to this condition not matching.

       CURLOPT_TIMEVALUE
              Pass a long as parameter. This should be the time in seconds since 1 Jan 1970, and the time will be used
              in a condition as specified with CURLOPT_TIMECONDITION.

CONNECTION OPTIONS
       CURLOPT_TIMEOUT
              Pass  a  long  as  parameter  containing the maximum time in seconds that you allow the libcurl transfer
              operation to take. Normally, name lookups can take a considerable time and limiting operations  to  less
              than  a  few  minutes  risk aborting perfectly normal operations. This option will cause curl to use the
              SIGALRM to enable time-outing system calls.

              In unix-like systems, this might cause signals to be used unless CURLOPT_NOSIGNAL is set.

       CURLOPT_TIMEOUT_MS
              Like CURLOPT_TIMEOUT but takes number of milliseconds instead. If libcurl is built to use  the  standard
              system  name  resolver,  that portion of the transfer will still use full-second resolution for timeouts
              with a minimum timeout allowed of one second.  (Added in 7.16.2)

       CURLOPT_LOW_SPEED_LIMIT
              Pass a long as parameter. It contains the transfer speed in bytes per second that the transfer should be
              below during CURLOPT_LOW_SPEED_TIME seconds for the library to consider it too slow and abort.

       CURLOPT_LOW_SPEED_TIME
              Pass  a  long  as  parameter. It contains the time in seconds that the transfer should be below the CUR-
              LOPT_LOW_SPEED_LIMIT for the library to consider it too slow and abort.

       CURLOPT_MAX_SEND_SPEED_LARGE
              Pass a curl_off_t as parameter.  If an upload exceeds this speed (counted in bytes per second) on  cumu-
              lative  average during the transfer, the transfer will pause to keep the average rate less than or equal
              to the parameter value.  Defaults to unlimited speed. (Added in 7.15.5)

       CURLOPT_MAX_RECV_SPEED_LARGE
              Pass a curl_off_t as parameter.  If a download exceeds this speed (counted in bytes per second) on cumu-
              lative  average during the transfer, the transfer will pause to keep the average rate less than or equal
              to the parameter value. Defaults to unlimited speed. (Added in 7.15.5)

       CURLOPT_MAXCONNECTS
              Pass a long. The set number will be the persistent connection cache size. The set  amount  will  be  the
              maximum amount of simultaneously open connections that libcurl may cache in this easy handle. Default is
              5, and there isn't much point in changing this value unless you are perfectly aware of  how  this  works
              and  changes libcurl's behaviour. This concerns connections using any of the protocols that support per-
              sistent connections.

              When reaching the maximum limit, curl closes the oldest one in the cache to prevent increasing the  num-
              ber of open connections.

              If you already have performed transfers with this curl handle, setting a smaller MAXCONNECTS than before
              may cause open connections to get closed unnecessarily.

              If you add this easy handle to a multi handle, this setting is not acknowledged, and  you  must  instead
              use curl_multi_setopt(3) and the CURLMOPT_MAXCONNECTS option.

       CURLOPT_CLOSEPOLICY
              (Obsolete) This option does nothing.

       CURLOPT_FRESH_CONNECT
              Pass a long. Set to 1 to make the next transfer use a new (fresh) connection by force. If the connection
              cache is full before this connection, one of the existing connections will be closed as according to the
              selected  or  default policy. This option should be used with caution and only if you understand what it
              does. Set this to 0 to have libcurl attempt re-using an existing connection (default behavior).

       CURLOPT_FORBID_REUSE
              Pass a long. Set to 1 to make the next transfer explicitly close the  connection  when  done.  Normally,
              libcurl  keeps  all  connections alive when done with one transfer in case a succeeding one follows that
              can re-use them.  This option should be used with caution and only if you understand what it  does.  Set
              to 0 to have libcurl keep the connection open for possible later re-use (default behavior).

       CURLOPT_CONNECTTIMEOUT
              Pass  a  long. It should contain the maximum time in seconds that you allow the connection to the server
              to take.  This only limits the connection phase, once it has connected, this option is of no  more  use.
              Set  to  zero  to  switch  to  the  default built-in connection timeout - 300 seconds. See also the CUR-
              LOPT_TIMEOUT option.

              In unix-like systems, this might cause signals to be used unless CURLOPT_NOSIGNAL is set.

       CURLOPT_CONNECTTIMEOUT_MS
              Like CURLOPT_CONNECTTIMEOUT but takes the number of milliseconds instead. If libcurl is built to use the
              standard  system  name  resolver,  that portion of the connect will still use full-second resolution for
              timeouts with a minimum timeout allowed of one second.  (Added in 7.16.2)

       CURLOPT_IPRESOLVE
              Allows an application to select what kind of IP addresses to use when resolving host names. This is only
              interesting  when using host names that resolve addresses using more than one version of IP. The allowed
              values are:

              CURL_IPRESOLVE_WHATEVER
                     Default, resolves addresses to all IP versions that your system allows.

              CURL_IPRESOLVE_V4
                     Resolve to IPv4 addresses.

              CURL_IPRESOLVE_V6
                     Resolve to IPv6 addresses.

       CURLOPT_CONNECT_ONLY
              Pass a long. If the parameter equals 1, it tells the library to perform all the required proxy authenti-
              cation and connection setup, but no data transfer.  This option is useful only on HTTP URLs.

              This  option  is useful with the CURLINFO_LASTSOCKET option to curl_easy_getinfo(3). The library can set
              up the connection and then the application can obtain the most recently used  socket  for  special  data
              transfers. (Added in 7.15.2)

       CURLOPT_USE_SSL
              Pass  a  long  using one of the values from below, to make libcurl use your desired level of SSL for the
              transfer. (Added in 7.11.0)

              This is for enabling SSL/TLS when you use FTP, SMTP, POP3, IMAP etc.

              (This option was known as CURLOPT_FTP_SSL up to 7.16.4, and the constants were known as CURLFTPSSL_*)

              CURLUSESSL_NONE
                     Don't attempt to use SSL.

              CURLUSESSL_TRY
                     Try using SSL, proceed as normal otherwise.

              CURLUSESSL_CONTROL
                     Require SSL for the control connection or fail with CURLE_USE_SSL_FAILED.

              CURLUSESSL_ALL
                     Require SSL for all communication or fail with CURLE_USE_SSL_FAILED.

       CURLOPT_RESOLVE
              Pass a pointer to a linked list of strings with host name resolve information to use for  requests  with
              this  handle.  The linked list should be a fully valid list of struct curl_slist structs properly filled
              in. Use curl_slist_append(3) to create the list and curl_slist_free_all(3) to clean up an entire list.

              Each single name resolve string should be written using the format HOST:PORT:ADDRESS where HOST  is  the
              name  libcurl will try to resolve, PORT is the port number of the service where libcurl wants to connect
              to the HOST and ADDRESS is the numerical IP address. If libcurl is built to support IPv6, ADDRESS can of
              course be either IPv4 or IPv6 style addressing.

              This option effectively pre-populates the DNS cache with entries for the host+port pair so redirects and
              everything that operations against the HOST+PORT will instead use your provided ADDRESS.

              You can remove names from the DNS cache again, to stop providing these fake  resolves,  by  including  a
              string in the linked list that uses the format "-HOST:PORT". The host name must be prefixed with a dash,
              and the host name and port number must exactly match what was already added previously.

              (Added in 7.21.3)

       CURLOPT_DNS_SERVERS
              Set the list of DNS servers to be used instead of the system default.  The format  of  the  dns  servers
              option is:

              host[:port][,host[:port]]...

              For example:

              192.168.1.100,192.168.1.101,3.4.5.6

              This option requires that libcurl was built with a resolver backend that supports this operation. The c-
              ares backend is the only such one.

              (Added in 7.24.0)

       CURLOPT_ACCEPTTIMEOUT_MS
              Pass a long telling libcurl the maximum number of milliseconds to wait for a server to connect  back  to
              libcurl  when an active FTP connection is used. If no timeout is set, the internal default of 60000 will
              be used. (Added in 7.24.0)

SSL and SECURITY OPTIONS
       CURLOPT_SSLCERT
              Pass a pointer to a zero terminated string as parameter. The string should be the file name of your cer-
              tificate. The default format is "PEM" and can be changed with CURLOPT_SSLCERTTYPE.

              With  NSS this can also be the nickname of the certificate you wish to authenticate with. If you want to
              use a file from the current directory, please precede it with "./" prefix, in order to  avoid  confusion
              with a nickname.

       CURLOPT_SSLCERTTYPE
              Pass  a  pointer  to a zero terminated string as parameter. The string should be the format of your cer-
              tificate. Supported formats are "PEM" and "DER".  (Added in 7.9.3)

       CURLOPT_SSLKEY
              Pass a pointer to a zero terminated string as parameter. The string should be the file name of your pri-
              vate key. The default format is "PEM" and can be changed with CURLOPT_SSLKEYTYPE.

       CURLOPT_SSLKEYTYPE
              Pass a pointer to a zero terminated string as parameter. The string should be the format of your private
              key. Supported formats are "PEM", "DER" and "ENG".

              The format "ENG" enables you to load the private key from a crypto engine. In this  case  CURLOPT_SSLKEY
              is used as an identifier passed to the engine. You have to set the crypto engine with CURLOPT_SSLENGINE.
              "DER" format key file currently does not work because of a bug in OpenSSL.

       CURLOPT_KEYPASSWD
              Pass a pointer to a zero terminated string as parameter. It will be used as the password required to use
              the CURLOPT_SSLKEY or CURLOPT_SSH_PRIVATE_KEYFILE private key.  You never needed a pass phrase to load a
              certificate but you need one to load your private key.

              (This option was known as CURLOPT_SSLKEYPASSWD up to 7.16.4 and CURLOPT_SSLCERTPASSWD up to 7.9.2)

       CURLOPT_SSLENGINE
              Pass a pointer to a zero terminated string as parameter. It will be  used  as  the  identifier  for  the
              crypto engine you want to use for your private key.

              If the crypto device cannot be loaded, CURLE_SSL_ENGINE_NOTFOUND is returned.

       CURLOPT_SSLENGINE_DEFAULT
              Sets the actual crypto engine as the default for (asymmetric) crypto operations.

              If the crypto device cannot be set, CURLE_SSL_ENGINE_SETFAILED is returned.

              Even  though  this  option  doesn't need any parameter, in some configurations curl_easy_setopt might be
              defined as a macro taking exactly three arguments. Therefore, it's recommended to pass 1 as parameter to
              this option.

       CURLOPT_SSLVERSION
              Pass  a  long  as parameter to control what version of SSL/TLS to attempt to use.  The available options
              are:

              CURL_SSLVERSION_DEFAULT
                     The default action. This will attempt to figure out the remote SSL protocol version, i.e.  either
                     SSLv3 or TLSv1 (but not SSLv2, which became disabled by default with 7.18.1).

              CURL_SSLVERSION_TLSv1
                     Force TLSv1

              CURL_SSLVERSION_SSLv2
                     Force SSLv2

              CURL_SSLVERSION_SSLv3
                     Force SSLv3

       CURLOPT_SSL_VERIFYPEER
              Pass a long as parameter. By default, curl assumes a value of 1.

              This  option  determines  whether curl verifies the authenticity of the peer's certificate. A value of 1
              means curl verifies; 0 (zero) means it doesn't.

              When negotiating an SSL connection, the server sends a certificate indicating its identity.  Curl  veri-
              fies  whether  the certificate is authentic, i.e. that you can trust that the server is who the certifi-
              cate says it is.  This trust is based on a chain of digital signatures, rooted in certification  author-
              ity  (CA)  certificates you supply.  curl uses a default bundle of CA certificates (the path for that is
              determined at build time) and you can specify alternate certificates with the CURLOPT_CAINFO  option  or
              the CURLOPT_CAPATH option.

              When  CURLOPT_SSL_VERIFYPEER  is  nonzero,  and  the verification fails to prove that the certificate is
              authentic, the connection fails.  When the option is zero, the peer  certificate  verification  succeeds
              regardless.

              Authenticating  the  certificate  is  not  by itself very useful.  You typically want to ensure that the
              server, as authentically identified by its certificate, is the server you mean to be  talking  to.   Use
              CURLOPT_SSL_VERIFYHOST to control that. The check that the host name in the certificate is valid for the
              host name you're connecting to is done independently of the CURLOPT_SSL_VERIFYPEER option.

       CURLOPT_CAINFO
              Pass a char * to a zero terminated string naming a file holding one or more certificates to  verify  the
              peer  with.   This makes sense only when used in combination with the CURLOPT_SSL_VERIFYPEER option.  If
              CURLOPT_SSL_VERIFYPEER is zero, CURLOPT_CAINFO need not even indicate an accessible file.

              This option is by default set to the system path where libcurl's cacert bundle is assumed to be  stored,
              as established at build time.

              When built against NSS, this is the directory that the NSS certificate database resides in.

       CURLOPT_ISSUERCERT
              Pass  a  char * to a zero terminated string naming a file holding a CA certificate in PEM format. If the
              option is set, an additional check against the peer certificate is performed to  verify  the  issuer  is
              indeed  the  one associated with the certificate provided by the option. This additional check is useful
              in multi-level PKI where one needs to enforce that the peer certificate is from a specific branch of the
              tree.

              This option makes sense only when used in combination with the CURLOPT_SSL_VERIFYPEER option. Otherwise,
              the result of the check is not considered as failure.

              A specific error code (CURLE_SSL_ISSUER_ERROR) is defined with the option,  which  is  returned  if  the
              setup  of  the  SSL/TLS  session  has failed due to a mismatch with the issuer of peer certificate (CUR-
              LOPT_SSL_VERIFYPEER has to be set too for the check to fail). (Added in 7.19.0)

       CURLOPT_CAPATH
              Pass a char * to a zero terminated string naming a directory holding multiple CA certificates to  verify
              the peer with. If libcurl is built against OpenSSL, the certificate directory must be prepared using the
              openssl c_rehash utility.  This makes sense only when used in  combination  with  the  CURLOPT_SSL_VERI-
              FYPEER  option.   If CURLOPT_SSL_VERIFYPEER is zero, CURLOPT_CAPATH need not even indicate an accessible
              path.  The CURLOPT_CAPATH function apparently does not  work  in  Windows  due  to  some  limitation  in
              openssl. This option is OpenSSL-specific and does nothing if libcurl is built to use GnuTLS. NSS-powered
              libcurl provides the option only for backward compatibility.

       CURLOPT_CRLFILE
              Pass a char * to a zero terminated string naming a file with the concatenation of CRL (in PEM format) to
              use in the certificate validation that occurs during the SSL exchange.

              When  curl  is built to use NSS or GnuTLS, there is no way to influence the use of CRL passed to help in
              the verification process.  When  libcurl  is  built  with  OpenSSL  support,  X509_V_FLAG_CRL_CHECK  and
              X509_V_FLAG_CRL_CHECK_ALL  are both set, requiring CRL check against all the elements of the certificate
              chain if a CRL file is passed.

              This option makes sense only when used in combination with the CURLOPT_SSL_VERIFYPEER option.

              A specific error code (CURLE_SSL_CRL_BADFILE) is defined with the option. It is returned  when  the  SSL
              exchange  fails  because  the CRL file cannot be loaded.  A failure in certificate verification due to a
              revocation information found in the CRL does not trigger this specific error. (Added in 7.19.0)

       CURLOPT_SSL_VERIFYHOST
              Pass a long as parameter.

              This option determines whether libcurl verifies that the server cert is for the server it is known as.

              When negotiating a SSL connection, the server sends a certificate indicating its identity.

              When CURLOPT_SSL_VERIFYHOST is 2, that certificate must indicate that the server is the server to  which
              you meant to connect, or the connection fails.

              Curl  considers the server the intended one when the Common Name field or a Subject Alternate Name field
              in the certificate matches the host name in the URL to which you told Curl to connect.

              When the value is 1, the certificate must contain a Common Name field, but it doesn't matter  what  name
              it says.  (This is not ordinarily a useful setting).

              When the value is 0, the connection succeeds regardless of the names in the certificate.

              The default value for this option is 2.

              This  option  controls checking the server's certificate's claimed identity.  The server could be lying.
              To control lying, see CURLOPT_SSL_VERIFYPEER.  If libcurl is built  against  NSS  and  CURLOPT_SSL_VERI-
              FYPEER is zero, CURLOPT_SSL_VERIFYHOST is ignored.


       CURLOPT_CERTINFO
              Pass a long set to 1 to enable libcurl's certificate chain info gatherer. With this enabled, libcurl (if
              built with OpenSSL) will extract lots of information and data about the certificates in the  certificate
              chain  used  in  the  SSL  connection.  This  data  is  then  possible to extract after a transfer using
              curl_easy_getinfo(3) and its option CURLINFO_CERTINFO. (Added in 7.19.1)

       CURLOPT_RANDOM_FILE
              Pass a char * to a zero terminated file name. The file will be used to read  from  to  seed  the  random
              engine for SSL. The more random the specified file is, the more secure the SSL connection will become.

       CURLOPT_EGDSOCKET
              Pass  a  char * to the zero terminated path name to the Entropy Gathering Daemon socket. It will be used
              to seed the random engine for SSL.

       CURLOPT_SSL_CIPHER_LIST
              Pass a char *, pointing to a zero terminated string holding the list of ciphers to use for the SSL  con-
              nection.  The list must be syntactically correct, it consists of one or more cipher strings separated by
              colons. Commas or spaces are also acceptable separators but colons are normally used, !, - and + can  be
              used as operators.

              For  OpenSSL  and  GnuTLS  valid  examples  of  cipher  lists include 'RC4-SHA', ?SHA1+DES?, 'TLSv1' and
              'DEFAULT'. The default list is normally set when you compile OpenSSL.

              You'll find more details about cipher lists on this URL: http://www.openssl.org/docs/apps/ciphers.html

              For NSS, valid examples of cipher lists include 'rsa_rc4_128_md5', ?rsa_aes_128_sha?, etc. With NSS  you
              don't  add/remove  ciphers.  If  one uses this option then all known ciphers are disabled and only those
              passed in are enabled.

              You'll find  more  details  about  the  NSS  cipher  lists  on  this  URL:  http://directory.fedora.red-
              hat.com/docs/mod_nss.html#Directives


       CURLOPT_SSL_SESSIONID_CACHE
              Pass  a long set to 0 to disable libcurl's use of SSL session-ID caching. Set this to 1 to enable it. By
              default all transfers are done using the cache. While nothing ever should  get  hurt  by  attempting  to
              reuse  SSL  session-IDs, there seem to be broken SSL implementations in the wild that may require you to
              disable this in order for you to succeed. (Added in 7.16.0)

       CURLOPT_KRBLEVEL
              Pass a char * as parameter. Set the kerberos security level for FTP; this also enables  kerberos  aware-
              ness.  This is a string, 'clear', 'safe', 'confidential' or 'private'.  If the string is set but doesn't
              match one of these, 'private' will be used. Set the string to NULL to disable kerberos support for  FTP.

              (This option was known as CURLOPT_KRB4LEVEL up to 7.16.3)

       CURLOPT_GSSAPI_DELEGATION
              Set  the  parameter  to  CURLGSSAPI_DELEGATION_FLAG to allow unconditional GSSAPI credential delegation.
              The delegation is disabled by default since 7.21.7.  Set  the  parameter  to  CURLGSSAPI_DELEGATION_POL-
              ICY_FLAG  to  delegate only if the OK-AS-DELEGATE flag is set in the service ticket in case this feature
              is supported by the GSSAPI implementation and the definition of GSS_C_DELEG_POLICY_FLAG was available at
              compile-time.  (Added in 7.22.0)

SSH OPTIONS
       CURLOPT_SSH_AUTH_TYPES
              Pass a long set to a bitmask consisting of one or more of CURLSSH_AUTH_PUBLICKEY, CURLSSH_AUTH_PASSWORD,
              CURLSSH_AUTH_HOST, CURLSSH_AUTH_KEYBOARD. Set CURLSSH_AUTH_ANY to  let  libcurl  pick  one.   (Added  in
              7.16.1)

       CURLOPT_SSH_HOST_PUBLIC_KEY_MD5
              Pass  a  char  * pointing to a string containing 32 hexadecimal digits. The string should be the 128 bit
              MD5 checksum of the remote host's public key, and libcurl will reject the connection to the host  unless
              the md5sums match. This option is only for SCP and SFTP transfers. (Added in 7.17.1)

       CURLOPT_SSH_PUBLIC_KEYFILE
              Pass  a  char  *  pointing  to  a  file  name  for  your  public  key.  If not used, libcurl defaults to
              $HOME/.ssh/id_dsa.pub if the HOME environment variable is set, and  just  "id_dsa.pub"  in  the  current
              directory if HOME is not set.  (Added in 7.16.1)

       CURLOPT_SSH_PRIVATE_KEYFILE
              Pass  a  char  *  pointing  to  a  file  name  for  your  private  key. If not used, libcurl defaults to
              $HOME/.ssh/id_dsa if the HOME environment variable is set, and just "id_dsa" in the current directory if
              HOME  is not set.  If the file is password-protected, set the password with CURLOPT_KEYPASSWD. (Added in
              7.16.1)

       CURLOPT_SSH_KNOWNHOSTS
              Pass a pointer to a zero terminated string holding the file name of the known_host  file  to  use.   The
              known_hosts  file should use the OpenSSH file format as supported by libssh2. If this file is specified,
              libcurl will only accept connections with hosts that are known and present in that file, with a matching
              public  key.  Use  CURLOPT_SSH_KEYFUNCTION  to alter the default behavior on host and key (mis)matching.
              (Added in 7.19.6)

       CURLOPT_SSH_KEYFUNCTION
              Pass a pointer to a curl_sshkeycallback function. It gets called when the known_host matching  has  been
              done,  to  allow the application to act and decide for libcurl how to proceed. The callback will only be
              called if CURLOPT_SSH_KNOWNHOSTS is also set.

              The curl_sshkeycallback function gets passed the CURL handle, the key from the known_hosts file, the key
              from  the  remote  site,  info  from  libcurl on the matching status and a custom pointer (set with CUR-
              LOPT_SSH_KEYDATA). It MUST return one of the following return codes to tell libcurl how to act:

              CURLKHSTAT_FINE_ADD_TO_FILE
                     The host+key is accepted and libcurl will append it to the  known_hosts  file  before  continuing
                     with  the connection. This will also add the host+key combo to the known_host pool kept in memory
                     if it wasn't already present there. The adding of data to the file is done by completely  replac-
                     ing the file with a new copy, so the permissions of the file must allow this.

              CURLKHSTAT_FINE
                     The  host+key  is  accepted  libcurl  will  continue  with the connection. This will also add the
                     host+key combo to the known_host pool kept in memory if it wasn't already present there.

              CURLKHSTAT_REJECT
                     The host+key is rejected. libcurl will deny the connection to continue and it will be closed.

              CURLKHSTAT_DEFER
                     The host+key is rejected, but the SSH connection is asked to be kept alive.  This  feature  could
                     be  used  when  the  app  wants to somehow return back and act on the host+key situation and then
                     retry without needing the overhead of setting it up from scratch again.
        (Added in 7.19.6)

       CURLOPT_SSH_KEYDATA
              Pass a void * as parameter. This pointer will be passed along verbatim to the  callback  set  with  CUR-
              LOPT_SSH_KEYFUNCTION. (Added in 7.19.6)

OTHER OPTIONS
       CURLOPT_PRIVATE
              Pass  a  void  *  as  parameter,  pointing to data that should be associated with this curl handle.  The
              pointer can subsequently be retrieved  using  curl_easy_getinfo(3)  with  the  CURLINFO_PRIVATE  option.
              libcurl itself does nothing with this data. (Added in 7.10.3)

       CURLOPT_SHARE
              Pass  a  share  handle  as  a  parameter.  The share handle must have been created by a previous call to
              curl_share_init(3). Setting this option, will make this curl handle use the data from the shared  handle
              instead of keeping the data to itself. This enables several curl handles to share data. If the curl han-
              dles are used simultaneously in multiple threads, you MUST use the locking methods in the share  handle.
              See curl_share_setopt(3) for details.

              If you add a share that is set to share cookies, your easy handle will use that cookie cache and get the
              cookie engine enabled. If you unshare an object that was using cookies (or change to another object that
              doesn't share cookies), the easy handle will get its cookie engine disabled.

              Data  that  the  share  object  is not set to share will be dealt with the usual way, as if no share was
              used.

       CURLOPT_NEW_FILE_PERMS
              Pass a long as a parameter, containing the value of the permissions that will be assigned to newly  cre-
              ated  files on the remote server.  The default value is 0644, but any valid value can be used.  The only
              protocols that can use this are sftp://, scp://, and file://. (Added in 7.16.4)

       CURLOPT_NEW_DIRECTORY_PERMS
              Pass a long as a parameter, containing the value of the permissions that will be assigned to newly  cre-
              ated directories on the remote server.  The default value is 0755, but any valid value can be used.  The
              only protocols that can use this are sftp://, scp://, and file://.  (Added in 7.16.4)

TELNET OPTIONS
       CURLOPT_TELNETOPTIONS
              Provide a pointer to a curl_slist with variables to pass  to  the  telnet  negotiations.  The  variables
              should  be in the format <option=value>. libcurl supports the options 'TTYPE', 'XDISPLOC' and 'NEW_ENV'.
              See the TELNET standard for details.

RETURN VALUE
       CURLE_OK (zero) means that the option was set properly, non-zero  means  an  error  occurred  as  <curl/curl.h>
       defines. See the libcurl-errors(3) man page for the full list with descriptions.

       If  you try to set an option that libcurl doesn't know about, perhaps because the library is too old to support
       it or the option was removed in a recent version, this function will return CURLE_FAILED_INIT.

SEE ALSO
       curl_easy_init(3), curl_easy_cleanup(3), curl_easy_reset(3)



libcurl 7.20.0                    1 Jan 2010               curl_easy_setopt(3)