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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 applica‐
       tion 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  dif‐
       ferent  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 CUR‐
	      LOPT_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 actu‐
	      ally 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 prevent the CURLOPT_PRO‐
	      GRESSFUNCTION 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 functions that cause  signals  to
	      be  sent	to  the	 process.  This option is mainly here to allow
	      multi-threaded unix applications to still	 set/use  all  timeout
	      options etc, without risking getting signals.  (Added in 7.10)

	      If  this option is set and libcurl has been built with the stan‐
	      dard name resolver, timeouts  will  not  occur  while  the  name
	      resolve takes place.  Consider building libcurl with c-ares sup‐
	      port to enable asynchronous  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 otherwise are sent by the  sys‐
	      tem  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 sig‐
	      nal to be raised.

       CURLOPT_WILDCARDMATCH
	      Set  this	 option	 to  1	if you want to transfer multiple files
	      according to a file name pattern. The pattern 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	imple‐
	      mentation.  You  can  provide  your own matching 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 meaning	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  con‐
		     structed:

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

       (This was added in 7.21.0)

CALLBACK OPTIONS
       CURLOPT_WRITEFUNCTION
	      Pass  a  pointer to a function that matches the following proto‐
	      type: 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 connection to become paused. See
	      curl_easy_pause(3) for further details.

	      This  function  may be called with zero bytes data if the trans‐
	      ferred 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  stdout  if  this	option
	      hasn't been set.

	      If  you're  using	 libcurl as a win32 DLL, you MUST use the CUR‐
	      LOPT_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
	      Pass a pointer to a function that matches the  following	proto‐
	      type:  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 connection 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_READ‐
	      DATA.

       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  internal  read function, this data must be a valid
	      readable FILE *.

	      If you're using libcurl as a win32 DLL,  you  MUST  use  a  CUR‐
	      LOPT_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
	      Pass a pointer to a function that matches the  following	proto‐
	      type: curlioerr function(CURL *handle, int cmd, void *clientp);.
	      This function 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 neces‐
	      sary when doing a HTTP PUT or POST with a multi-pass authentica‐
	      tion 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_IOCTL‐
	      FUNCTION.	 (Option added in 7.12.3)

       CURLOPT_SEEKFUNCTION
	      Pass  a  pointer to a function that matches the following proto‐
	      type: int function(void *instream, curl_off_t offset,  int  ori‐
	      gin);  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 lat‐
	      ter  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 seek 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
	      Pass  a  pointer to a function that matches the following proto‐
	      type: int function(void *clientp,	 curl_socket_t	curlfd,	 curl‐
	      socktype	purpose);.  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 particu‐
	      lar socket:

	      CURLSOCKTYPE_IPCXN for actively  created	connections  or	 since
	      7.28.0 CURLSOCKTYPE_ACCEPT for FTP when the connection was setup
	      with PORT/EPSV (in earlier versions these sockets weren't passed
	      to this callback).

	      Future  versions of libcurl may support more purposes. It passes
	      the newly created socket descriptor 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	 func‐
	      tion to signal an unrecoverable error to the library and it will
	      close the	 socket	 and  return  CURLE_COULDNT_CONNECT.   (Option
	      added in 7.16.0)

	      Added  in	 7.21.5,  the  callback function may return CURL_SOCK‐
	      OPT_ALREADY_CONNECTED, which tells libcurl that the socket is in
	      fact already connected and then libcurl will not attempt to con‐
	      nect it.

       CURLOPT_SOCKOPTDATA
	      Pass a pointer that will be untouched by libcurl and  passed  as
	      the  first  argument  in	the  sockopt  callback	set  with CUR‐
	      LOPT_SOCKOPTFUNCTION.  (Option added in 7.16.0)

       CURLOPT_OPENSOCKETFUNCTION
	      Pass a pointer to a function that matches the  following	proto‐
	      type:  curl_socket_t  function(void  *clientp, curlsocktype pur‐
	      pose, struct curl_sockaddr *address);. This function gets called
	      by libcurl instead of the socket(2) call. The callback's purpose
	      argument	identifies  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 could be established or another error	was  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 blacklisting.  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 CUR‐
	      LOPT_OPENSOCKETFUNCTION.	(Option added in 7.17.1.)

       CURLOPT_CLOSESOCKETFUNCTION
	      Pass a pointer to a function that matches the  following	proto‐
	      type:  int  function(void	 *clientp,  curl_socket_t item);. This
	      function gets called by libcurl instead of the close(3) or clos‐
	      esocket(3)  call when sockets are closed (not for any other file
	      descriptors). This is  pretty  much  the	reverse	 to  the  CUR‐
	      LOPT_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 closesocket callback set with CUR‐
	      LOPT_CLOSESOCKETFUNCTION.	 (Option added in 7.21.7)

       CURLOPT_PROGRESSFUNCTION
	      Pass a pointer to a function that matches the  following	proto‐
	      type:  int function(void *clientp, double dltotal, double dlnow,
	      double ultotal, double ulnow); . 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  transferred 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 idleness  unless  you  call
	      the appropriate libcurl function that performs transfers.

	      CURLOPT_NOPROGRESS  must be set to 0 to make this function actu‐
	      ally get called.

       CURLOPT_PROGRESSDATA
	      Pass a pointer that will be untouched by libcurl and  passed  as
	      the  first  argument  in	the  progress  callback	 set with CUR‐
	      LOPT_PROGRESSFUNCTION.

       CURLOPT_HEADERFUNCTION
	      Pass a pointer to a function that matches the  following	proto‐
	      type:  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 termi‐
	      nated! 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  dif‐
	      fers  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 HTTP 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  CUR‐
	      LOPT_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 CUR‐
	      LOPT_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 regular response-headers mention
	      what header(s) to expect in the trailer.

	      For non-HTTP protocols like FTP, POP3, IMAP and SMTP this	 func‐
	      tion  will  get called with the server responses to the commands
	      that libcurl sends.

       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
	      Pass a pointer to a function that matches the  following	proto‐
	      type:  int  curl_debug_callback  (CURL *, curl_infotype, char *,
	      size_t, void *);	CURLOPT_DEBUGFUNCTION  replaces	 the  standard
	      debug  function  used  when  CURLOPT_VERBOSE  is in effect. This
	      callback receives	 debug	information,  as  specified  with  the
	      curl_infotype  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  CUR‐
	      LOPT_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 function‐
	      ality is absent.

	      Pass a pointer to a function that matches the  following	proto‐
	      type:  CURLcode sslctxfun(CURL *curl, void *sslctx, void *parm);
	      This function gets called by libcurl just before the initializa‐
	      tion  of	a  SSL connection after having processed all other SSL
	      related options to give a last chance to an application to  mod‐
	      ify  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 example, using this function
	      allows you to use openssl callbacks to add additional validation
	      code  for	 certificates,	and even to change the actual URI of a
	      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
	      Pass a pointer to a function that matches the  following	proto‐
	      type: 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_NET‐
	      WORK_FUNCTION  convert between the host encoding and the network
	      encoding.	 They  are  used  when	commands  or  ASCII  data  are
	      sent/received over the network.

	      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	 call‐
	      back   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  differ‐
	      ent on your system.

       CURLOPT_INTERLEAVEFUNCTION
	      Pass  a  pointer to a function that matches the following proto‐
	      type: 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 interleaved 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	inter‐
	      leaved  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 RFC2326 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 challenges for	 the  client  applica‐
	      tion.  Since the stream data is sharing the RTSP control connec‐
	      tion, it is critical to service the RTP in a timely fashion.  If
	      the  RTP	data  is not handled quickly, subsequent response pro‐
	      cessing 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 CUR‐
	      LOPT_INTERLEAVEFUNCTION when interleaved RTP data	 is  received.
	      (Added in 7.20.0)

       CURLOPT_CHUNK_BGN_FUNCTION
	      Pass  a  pointer to a function that matches the following proto‐
	      type: 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_WILDCARD‐
	      MATCH 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  CURLOPT_CHUNK_DATA. The parameter remains
	      contains number of chunks remaining per  the  transfer.  If  the
	      feature 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
	      Pass a pointer to a function that matches the  following	proto‐
	      type:  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
	      Pass  a  pointer to a function that matches the following proto‐
	      type: int function(void *ptr, const char	*pattern,  const  char
	      *string)	prototype (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 read‐
	      able  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  (probably
	      undefined)  contents of the buffer is NOT copied by the library.
	      You must keep the associated storage 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 contents 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  immedi‐
	      ately afterwards.

NETWORK OPTIONS
       CURLOPT_URL
	      Pass  in a pointer to 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 RFC3986.

	      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 sup‐
	      ported, 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	repre‐
	      sented 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:password@www.example.com

	      ftp://user:password@ftp.example.com

	      pop3://user:password@mail.example.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 exam‐
	      ples show how to specify the port:

	      http://www.example.com:8080/ - This will connect to a web server
	      using port 8080 rather than 80.

	      smtp://mail.example.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 con‐
	      figuration.

	      http://www.example.com  -	 This  gets the main page from the web
	      server.

	      http://www.example.com/index.html - This returns the  main  page
	      by explicitly requesting it.

	      http://www.example.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 speci‐
	      fied. If the directory is omitted then the directory listing for
	      the root / home directory will be returned.

	      ftp://ftp.example.com - This retrieves the directory listing for
	      the root directory.

	      ftp://ftp.example.com/readme.txt	 -  This  downloads  the  file
	      readme.txt from the root directory.

	      ftp://ftp.example.com/libcurl/readme.txt	 -   This    downloads
	      readme.txt from the libcurl directory.

	      ftp://user:password@ftp.example.com/readme.txt  - This retrieves
	      the readme.txt file from the user's home directory. When a user‐
	      name  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 underneath
	      the root directory then the absolute path must be	 specified  by
	      prepending  an  additional forward slash to the beginning of the
	      path.

	      ftp://user:password@ftp.example.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  com‐
	      puter's host name. However, this may not return the fully quali‐
	      fied domain name that is required by some mail servers and spec‐
	      ifying  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 getad‐
	      drinfo.

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

	      smtp://mail.example.com/client.example.com  -  This  will	  send
	      client.example.com in the HELO / EHLO command to the mail server
	      at example.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:password@mail.example.com - This lists the available
	      messages	  pop3://user:password@mail.example.com/1    -	  This
	      retrieves the first message

	      SCP

	      The path part of a 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_USER‐
	      PWD or CURLOPT_USERNAME option.

	      scp://user@example.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 a 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 speci‐
	      fied.   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:password@example.com/etc/issue  - This specifies the
	      file /etc/issue

	      sftp://user@example.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	direc‐
	      tory

	      LDAP

	      The path part of a LDAP request can be used to specify the: Dis‐
	      tinguished Name, Attributes, Scope, Filter and Extension	for  a
	      LDAP search. Each field is separated by a question mark and when
	      that field is not required an empty  string  with	 the  question
	      mark separator should be included.

	      ldap://ldap.example.com/o=My%20Organisation  - This will perform
	      a LDAP search with the DN as My Organisation.

	      ldap://ldap.example.com/o=My%20Organisation?postalAddress - This
	      will  perform the same search but will only return postalAddress
	      attributes.

	      ldap://ldap.example.com/?rootDomainNamingContext -  This	speci‐
	      fies  an empty DN and requests information about the rootDomain‐
	      NamingContext attribute for an Active Directory server.

	      For more information about the individual components of  a  LDAP
	      URL please see RFC4516.

	      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  protocols 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_PROTO‐
	      COLS. (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_FOLLOWLO‐
	      CATION  is  enabled. This allows you to limit specific transfers
	      to only be allowed to use a subset of protocols in redirections.
	      By  default libcurl will allow all protocols except for FILE and
	      SCP. This is a difference compared 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 sepa‐
	      rate option. If not specified, libcurl  will  default  to	 using
	      port 1080 for proxies.  CURLOPT_PROXYPORT.

	      When  you	 tell  the  library  to use a 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 CUR‐
	      LOPT_PROXY option does however override any possibly  set	 envi‐
	      ronment 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 vari‐
	      ables can be specified the exact same way as the	proxy  can  be
	      set  with	 CURLOPT_PROXY,	 include protocol prefix (http://) and
	      embedded user + password.

	      Since 7.21.7, the proxy string may be specified  with  a	proto‐
	      col://  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 7.10), CURLPROXY_SOCKS5,
	      CURLPROXY_SOCKS4A (added in 7.18.0)  and	CURLPROXY_SOCKS5_HOST‐
	      NAME  (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  con‐
	      trolled with CURLOPT_HTTP_VERSION.

       CURLOPT_NOPROXY
	      Pass  a pointer to a zero terminated string. The string consists
	      of a comma separated list of host names that do  not  require  a
	      proxy  to get reached, even if one is specified.	The only wild‐
	      card available 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,	example.com  would match exam‐
	      ple.com,	 example.com:80,   and	 www.example.com,   but	   not
	      www.notanexample.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 ref‐
	      erence implementation does not.  If enabled, this option	allows
	      the  unprotected	exchange  of  the protection mode negotiation.
	      (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 syn‐
	      chronously.   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 exist‐
	      ing 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	 combination with CUR‐
	      LOPT_INTERFACE and you are recommended to use  CURLOPT_LOCALPOR‐
	      TRANGE  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 will make to
	      find  a working local port number. It starts with the given CUR‐
	      LOPT_LOCALPORT and adds one to the number for each  retry.  Set‐
	      ting  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 fail‐
	      ures. (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 forever. 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  CUR‐
	      LOPT_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 is	to  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 pur‐
	      pose of this algorithm is to try to minimize the number of small
	      packets on the network (where "small packets" means TCP segments
	      less than the Maximum Segment Size (MSS) for the network).

	      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  conges‐
	      tion 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)

       CURLOPT_TCP_KEEPALIVE
	      Pass a long. If set to 1, TCP keepalive probes will be sent. The
	      delay  and  frequency  of	 these probes can be controlled by the
	      CURLOPT_TCP_KEEPIDLE and CURLOPT_TCP_KEEPINTVL options, provided
	      the  operating system supports them. Set to 0 (default behavior)
	      to disable keepalive probes (Added in 7.25.0).

       CURLOPT_TCP_KEEPIDLE
	      Pass a long. Sets the delay, in seconds, that the operating sys‐
	      tem  will	 wait  while  the  connection  is  idle before sending
	      keepalive probes. Not all operating systems support this option.
	      (Added in 7.25.0)

       CURLOPT_TCP_KEEPINTVL
	      Pass  a  long. Sets the interval, in seconds, that the operating
	      system will wait between sending keepalive probes. Not all oper‐
	      ating systems support this option. (Added in 7.25.0)

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 informa‐
		     tion 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 specified 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	infor‐
		     mation 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 supported).

       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 cur‐
	      rent user's home directory. (Added in 7.10.9)

       CURLOPT_USERPWD
	      Pass a char * as parameter, which should be  [user  name]:[pass‐
	      word]  to use for the connection. Use CURLOPT_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:password".  Some  HTTP servers (on Windows) support
	      this style even for Basic authentication.

	      When using HTTP and CURLOPT_FOLLOWLOCATION, libcurl  might  per‐
	      form  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 acciden‐
	      tal information leakage.

       CURLOPT_PROXYUSERPWD
	      Pass a char * as parameter, which should be  [user  name]:[pass‐
	      word]  to	 use  for  the connection to the HTTP proxy.  Use CUR‐
	      LOPT_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	  CUR‐
	      LOPT_PROXYUSERPWD	 the CURLOPT_PROXYUSERNAME allows the username
	      to  contain  a   colon,	like   in   the	  following   example:
	      "sip:user@example.com".  The  CURLOPT_PROXYUSERNAME option is an
	      alternative way to set the user name while connecting to	Proxy.
	      There  is	 no  meaning to use it together with the CURLOPT_PROX‐
	      YUSERPWD option.

	      In order to specify the password to be used in conjunction  with
	      the  user	 name use the CURLOPT_PROXYPASSWORD 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  sup‐
		     ported 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 authen‐
		     tication  over public networks than the regular old-fash‐
		     ioned 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 sim‐
		     ply 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 challenge-response and
		     hash concept similar to Digest, to prevent	 the  password
		     from being eavesdropped.

		     You  need to build libcurl with either OpenSSL, GnuTLS or
		     NSS support for this option to work, or build libcurl  on
		     Windows.

	      CURLAUTH_NTLM_WB
		     NTLM delegating to winbind helper. Authentication is per‐
		     formed 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  complete,  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 applica‐
		     tion.  In	particular,  the application must not uncondi‐
		     tionally call wait() in its  SIGCHLD  signal  handler  to
		     avoid  being  subject to a race condition.	 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 sin‐
		     gle specific auth value to force libcurl to probe for un-
		     restricted	 auth  and if not, only that single auth algo‐
		     rithm 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  authenti‐
		     cation  for TLS is defined in RFC5054 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 ter‐
	      minated username to use for the TLS authentication method speci‐
	      fied  with  the  CURLOPT_TLSAUTH_TYPE  option. Requires that the
	      CURLOPT_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  ter‐
	      minated password to use for the TLS authentication method speci‐
	      fied with the CURLOPT_TLSAUTH_TYPE  option.  Requires  that  the
	      CURLOPT_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 a  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 spe‐
	      cial 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 response sent using a compressed Transfer-
	      Encoding	that  will be automatically uncompressed by libcurl on
	      reception.

	      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 a 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 automati‐
	      cally  follow.  The  accepted  protocols	are  set   with	  CUR‐
	      LOPT_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  following locations, even
	      when hostname changed. This option is meaningful only when  set‐
	      ting CURLOPT_FOLLOWLOCATION.

       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, 302 or 303	response  back.	  A  parameter
	      with  bit 0 set (value CURL_REDIR_POST_301) tells the library to
	      respect RFC2616/10.3.2 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   whilst   setting   bit   2	(value
	      CURL_REDIR_POST_303) makes libcurl maintain the  request	method
	      after  a 303 redirect. The value CURL_REDIR_POST_ALL is a conve‐
	      nience define that sets all three 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 CUR‐
	      LOPT_FOLLOWLOCATION.  (Added in 7.17.1) (This option  was	 known
	      as  CURLOPT_POST301  up  to  7.19.0 as it only supported the 301
	      then)

       CURLOPT_PUT
	      A parameter set to 1 tells the library to use HTTP PUT to trans‐
	      fer  data. The data should be set with CURLOPT_READDATA and CUR‐
	      LOPT_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 CURLOPT_POSTFIELDSIZE or CUR‐
	      LOPT_POSTFIELDSIZE_LARGE to set the data size.

	      Optionally, you can provide data to POST using the CURLOPT_READ‐
	      FUNCTION	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 chun‐
	      ked 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 set‐
	      ting your own with CURLOPT_HTTPHEADER.

	      Using POST with HTTP 1.1 implies the use of a "Expect:  100-con‐
	      tinue"  header.	You can disable this header with CURLOPT_HTTP‐
	      HEADER 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 CUR‐
	      LOPT_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 a 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	conse‐
	      quence,  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  CURLOPT_POST.  Using  CURLOPT_POSTFIELDS
	      implies CURLOPT_POST.

	      If you want to do	 a  zero-byte  POST,  you  need	 to  set  CUR‐
	      LOPT_POSTFIELDSIZE  explicitly  to  zero, as simply setting CUR‐
	      LOPT_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-con‐
	      tinue"  header.	You can disable this header with CURLOPT_HTTP‐
	      HEADER 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 ver‐
	      sion 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	a HTTP POST operation. It behaves as the CURLOPT_POST‐
	      FIELDS option, but the original data are copied by the  library,
	      allowing	the  application  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_POSTFIELDSIZE  or  CUR‐
	      LOPT_POSTFIELDSIZE_LARGE: If the size has not been set prior  to
	      CURLOPT_COPYPOSTFIELDS,  the data are assumed to be a NUL-termi‐
	      nated 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	  CUR‐
	      LOPT_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-con‐
	      tinue" header.  You can disable this header  with	 CURLOPT_HTTP‐
	      HEADER as usual.

	      When  setting  CURLOPT_HTTPPOST,	it will automatically set CUR‐
	      LOPT_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_HTTP‐
	      HEADER.

       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	inter‐
	      nally,  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  CUR‐
	      LOPT_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=content1; 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  han‐
	      dle,  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 cookies 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  CUR‐
	      LOPT_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, indepen‐
	      dent if they are session cookies or  not.	 Session  cookies  are
	      cookies  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  Net‐
	      scape  /	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 speci‐
	      fied by CURLOPT_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  versions.	 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. This
	      should be used to specify the sender's email address when	 send‐
	      ing SMTP mail with libcurl.

	      An  originator  email  address  should  be specified with angled
	      brackets (<>) around it, which if not specified, will  be	 added
	      by  libcurl from version 7.21.4 onwards. Failing to provide such
	      brackets may cause the server to reject the email.

	      If this parameter is not specified then an empty address will be
	      sent  to the mail server which may or may not cause the email to
	      be rejected.

	      (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 should be	specified  within  a  pair  of	angled
	      brackets	(<>), however, should you not use an angled bracket as
	      the first character libcurl will assume you  provided  a	single
	      email address and enclose that address within brackets for you.

	      (Added in 7.20.0)

       CURLOPT_MAIL_AUTH
	      Pass  a  pointer	to a zero terminated string as parameter. This
	      will be used to specify the authentication address (identity) of
	      a submitted message that is being relayed to another server.

	      This  optional parameter allows co-operating agents in a trusted
	      environment to communicate the authentication of individual mes‐
	      sages  and should only be used by the application program, using
	      libcurl, if the application is itself a mail  server  acting  in
	      such an environment. If the application is operating as such and
	      the AUTH address is not known  or	 is  invalid,  then  an	 empty
	      string should be used for this parameter.

	      Unlike  CURLOPT_MAIL_FROM	 and  CURLOPT_MAIL_RCPT,  the  address
	      should not be specified within a pair of angled  brackets	 (<>).
	      However, if an empty string is used then a pair of brackets will
	      be sent by libcurl as required by RFC2554.

	      (Added in 7.25.0)

TFTP OPTIONS
       CURLOPT_TFTP_BLKSIZE
	      Specify block size to use	 for  TFTP  data  transmission.	 Valid
	      range  as per RFC2348 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 instruc‐
	      tion. 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,  option‐
	      ally  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 avail‐
	      able, libcurl will report CURLE_FTP_PORT_FAILED for the  handle.
	      Invalid  port/range  settings  are ignored.  IPv6 addresses fol‐
	      lowed 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 com‐
	      mand 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 speaking to a FTP (or SFTP since
	      7.24.0) server, prefix the command with an asterisk (*) to  make
	      libcurl continue 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 operation 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 version 7.16.0, 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	neces‐
	      sary.

	      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 downloads 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 simultaneous 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 arguments.

	      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	recom‐
	      mended that if used in conjunction with CURLOPT_TIMEOUT, you set
	      CURLOPT_FTP_RESPONSE_TIMEOUT  to	a  value  smaller  than	  CUR‐
	      LOPT_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 connecting 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	 unen‐
	      crypted.	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  com‐
		     mands.  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 multi‐
		     cwd 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 responsible 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  CURLOPT_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  descrip‐
		     tion  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 a 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 calling setup. If no session ID  is  cur‐
		     rently  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  con‐
		     nections.	(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/parame‐
		     ters header on all non-empty requests unless a custom one
		     is set. GET_PARAMETER acts just like a 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 a HTTP PUT or POST. An applica‐
		     tion may either use CURLOPT_UPLOAD with  CURLOPT_READDATA
		     like  a HTTP PUT, or it may use CURLOPT_POSTFIELDS like a
		     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 CUR‐
		     LOPT_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	 func‐
		     tion  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 exam‐
	      ple,     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  passing '*' 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 resuming a previously bro‐
	      ken 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 simi‐
	      lar.

	      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  per‐
	      forms 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  a  HTTP  proxy, by appending ;type=a or ;type=i to the URL.
	      Without this setting, 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 transfers. 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 format "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 multi‐
	      ple  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 RFC2326 Sec‐
	      tion 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  con‐
	      tinue 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  can
	      be  used to specify the request instead of GET or HEAD when per‐
	      forming HTTP based requests, instead of LIST and NLST when  per‐
	      forming FTP directory listings and instead of LIST and RETR when
	      issuing POP3 based commands. This is  particularly  useful,  for
	      example,	for  performing	 a  HTTP DELETE request or a POP3 DELE
	      command.

	      Please don't perform this at will, on HTTP  based	 requests,  by
	      making  sure  your  server  supports the command you are sending
	      first.

	      When you change the request method by setting  CURLOPT_CUSTOMRE‐
	      QUEST  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:

	      With  the	 HTTP  protocol	 when  you  tell  libcurl to do a HEAD
	      request, but then specify a GET though a custom request  libcurl
	      will  still act as if it sent a HEAD. To switch to a proper HEAD
	      use CURLOPT_NOBODY, to switch to a proper POST use  CURLOPT_POST
	      or  CURLOPT_POSTFIELDS  and  to  switch to a proper GET use CUR‐
	      LOPT_HTTPGET.

	      With the POP3 protocol when you tell libcurl  to	use  a	custom
	      request  it  will	 behave	 like  a LIST or RETR command was sent
	      where it expects data to be returned by the server. As such CUR‐
	      LOPT_NOBODY should be used when specifying commands such as DELE
	      and NOOP for example.

	      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 multiple headers and POST con‐
	      tents. 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 CURLOPT_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.

	      (Support for POP3 added in 7.26.0)

       CURLOPT_FILETIME
	      Pass a long. If it is 1, libcurl will attempt to get the modifi‐
	      cation date of the  remote  document  in	this  operation.  This
	      requires	that  the remote server sends the time or replies to a
	      time querying command. 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_INFILE‐
	      SIZE_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 CURLOPT_INFILESIZE  or  CURLOPT_INFILE‐
	      SIZE_LARGE options are also interesting for uploads. If the pro‐
	      tocol 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-con‐
	      tinue" header.  You can disable this header  with	 CURLOPT_HTTP‐
	      HEADER 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: chunked" 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 transfers.

       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_FILESIZE_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 transfers.

       CURLOPT_TIMECONDITION
	      Pass a long as parameter. This defines how the CURLOPT_TIMEVALUE
	      time value is treated. You can set this parameter to  CURL_TIME‐
	      COND_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_get‐
	      info(3)  with  the  CURLINFO_CONDITION_UNMET  option can be used
	      after a transfer to learn if a zero-byte	successful  "transfer"
	      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 opera‐
	      tions 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.

	      Default timeout is 0 (zero) which means it never times out.

       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 resolu‐
	      tion 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  CUR‐
	      LOPT_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 CURLOPT_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 cumulative 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 cumulative 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 simul‐
	      taneously 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 persistent connections.

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

	      If  you  already have performed transfers with this curl handle,
	      setting a smaller MAXCONNECTS than before may cause open connec‐
	      tions 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  connec‐
	      tions 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  lim‐
	      its  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 CURLOPT_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  authentication  and  connection
	      setup,  but  no  data  transfer.	This option is implemented for
	      HTTP, SMTP and POP3.

	      The option can be used to simply test a connection to a  server,
	      but is more useful when used with the CURLINFO_LASTSOCKET option
	      to curl_easy_getinfo(3) as 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 for‐
	      mat 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	opera‐
	      tions  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  pre‐
	      fixed  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 certificate. 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 certificate. Supported  for‐
	      mats 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 private 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  for‐
	      mats 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 identi‐
	      fier  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 con‐
	      figurations 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.  (Added in 7.9.2)

	      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.x

	      CURL_SSLVERSION_SSLv2
		     Force SSLv2

	      CURL_SSLVERSION_SSLv3
		     Force SSLv3

	      CURL_SSLVERSION_TLSv1_0
		     Force TLSv1.0 (Added in 7.34.0)

	      CURL_SSLVERSION_TLSv1_1
		     Force TLSv1.1 (Added in 7.34.0)

	      CURL_SSLVERSION_TLSv1_2
		     Force TLSv1.2 (Added in 7.34.0)

       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 a SSL connection, the server sends  a  certifi‐
	      cate  indicating	its  identity.	Curl verifies whether the cer‐
	      tificate is authentic, i.e. that you can trust that  the	server
	      is  who  the  certificate	 says it is.  This trust is based on a
	      chain of digital signatures, rooted in  certification  authority
	      (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  verifica‐
	      tion 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 CUR‐
	      LOPT_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_VERI‐
	      FYPEER  option.	If  CURLOPT_SSL_VERIFYPEER   is	  zero,	  CUR‐
	      LOPT_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.

	      If  curl	is  built  against  the	 NSS  SSL library, the NSS PEM
	      PKCS#11 module (libnsspem.so) needs to  be  available  for  this
	      option to work properly.

       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	 addi‐
	      tional 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  cer‐
	      tificate 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  ses‐
	      sion  has	 failed due to a mismatch with the issuer of peer cer‐
	      tificate (CURLOPT_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_CAP‐
	      ATH need not even indicate an accessible path.  The CURLOPT_CAP‐
	      ATH 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 cer‐
	      tificate 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 verifi‐
	      cation 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  certifi‐
	      cate 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 con‐
	      nect.

	      When the value is 1, libcurl will return a failure. It was  pre‐
	      viously  (in  7.28.0  and earlier) a debug option of some sorts,
	      but it is no longer supported due to frequently leading to  pro‐
	      grammer mistakes.

	      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_VERIFYPEER   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 connection. The list must  be
	      syntactically correct, it consists of one or more cipher strings
	      separated by colons. Commas or spaces are also acceptable	 sepa‐
	      rators  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://git.fedora‐
	      hosted.org/cgit/mod_nss.git/plain/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_SSL_OPTIONS
	      Pass  a  long  with a bitmask to tell libcurl about specific SSL
	      behaviors.

	      CURLSSLOPT_ALLOW_BEAST is the only supported bit and by  setting
	      this  the user will tell libcurl to not attempt to use any work‐
	      arounds for a security flaw in the SSL3  and  TLS1.0  protocols.
	      If this option isn't used or this bit is set to 0, the SSL layer
	      libcurl uses may use a work-around for  this  flaw  although  it
	      might  cause  interoperability  problems	with  some (older) SSL
	      implementations. WARNING: avoiding this work-around loosens  the
	      security,	 and  by  setting this option to 1 you ask for exactly
	      that. (Added in 7.25.0)

       CURLOPT_KRBLEVEL
	      Pass a char * as parameter. Set the kerberos security level  for
	      FTP;  this  also	enables kerberos awareness.  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	uncon‐
	      ditional	GSSAPI	credential delegation.	The delegation is dis‐
	      abled by default since 7.21.7.  Set the  parameter  to  CURLGSS‐
	      API_DELEGATION_POLICY_FLAG  to  delegate only if the OK-AS-DELE‐
	      GATE 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 and CURLSSH_AUTH_AGENT.
	      Set CURLSSH_AUTH_ANY to let libcurl pick a  suitable  one.  Cur‐
	      rently  CURLSSH_AUTH_HOST	 has  no  effect. (Added in 7.16.1) If
	      CURLSSH_AUTH_AGENT is used, libcurl attempts to connect to  ssh-
	      agent  or	 pageant and let the agent attempt the authentication.
	      (Added in 7.28.0)

       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  cur‐
	      rent  directory  if  HOME	 is  not set.  (Added in 7.16.1) If an
	      empty string is passed, libcurl will pass no public key to  lib‐
	      ssh2  which  then tries to compute it from the private key, this
	      is known to work when libssh2 1.4.0+ is linked against  OpenSSL.
	      (Added in 7.26.0)

       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-pro‐
	      tected,  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 appli‐
	      cation to act and decide for libcurl how to proceed.  The	 call‐
	      back 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 CURLOPT_SSH_KEYDATA). It MUST return one of  the  fol‐
	      lowing 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  connec‐
		     tion.  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 replacing 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  connec‐
		     tion 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  CURLOPT_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_PRI‐
	      VATE 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 handles
	      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  han‐
	      dle  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 permis‐
	      sions that will be assigned to newly created 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 permis‐
	      sions that will be assigned to newly created 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)
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