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FreeBSD/Linux/UNIX General Commands Manual
Hypertext Man Pages
http
 
http(n) 		     Tcl Bundled Packages		       http(n)



NAME
       http - Client-side implementation of the HTTP/1.0 protocol.

SYNOPSIS
       package require http ?2.5?

       ::http::config ?options?

       ::http::geturl url ?options?

       ::http::formatQuery key value ?key value ...?

       ::http::reset token ?why?

       ::http::wait token

       ::http::status token

       ::http::size token

       ::http::code token

       ::http::ncode token

       ::http::data token

       ::http::error token

       ::http::cleanup token

       ::http::register proto port command

       ::http::unregister proto


DESCRIPTION
       The  http  package  provides  the client side of the HTTP/1.0 protocol.
       The package implements the GET, POST, and HEAD operations of  HTTP/1.0.
       It  allows configuration of a proxy host to get through firewalls.  The
       package is compatible with the Safesock security policy, so it  can  be
       used  by  untrusted applets to do URL fetching from a restricted set of
       hosts. This package can be extended to support additional  HTTP	trans-
       port  protocols,  such  as HTTPS, by providing a custom socket command,
       via ::http::register.

       The ::http::geturl procedure does  a  HTTP  transaction.   Its  options
       determine  whether  a GET, POST, or HEAD transaction is performed.  The
       return value of ::http::geturl is a token  for  the  transaction.   The
       value  is  also	the name of an array in the ::http namespace that con-
       tains state information about the transaction.  The  elements  of  this
       array are described in the STATE ARRAY section.

       If the -command option is specified, then the HTTP operation is done in
       the background.	::http::geturl returns	immediately  after  generating
       the  HTTP request and the callback is invoked when the transaction com-
       pletes.	For this to work, the Tcl event loop must be  active.	In  Tk
       applications  this  is  always  true.   For  pure-Tcl applications, the
       caller can use ::http::wait after calling ::http::geturl to  start  the
       event loop.

COMMANDS
       ::http::config ?options?
	      The  ::http::config command is used to set and query the name of
	      the proxy server and port, and the User-Agent name used  in  the
	      HTTP  requests.	If  no options are specified, then the current
	      configuration is returned.  If a single argument	is  specified,
	      then  it	should	be  one of the flags described below.  In this
	      case the current value of that setting is returned.   Otherwise,
	      the  options should be a set of flags and values that define the
	      configuration:

	      -accept mimetypes
		     The Accept header of the request.	The  default  is  */*,
		     which  means  that  all  types of documents are accepted.
		     Otherwise you can supply a comma-separated list  of  mime
		     type patterns that you are willing to receive.  For exam-
		     ple, "image/gif, image/jpeg, text/*".

	      -proxyhost hostname
		     The name of the proxy host, if any.  If this value is the
		     empty string, the URL host is contacted directly.

	      -proxyport number
		     The proxy port number.

	      -proxyfilter command
		     The   command   is   a   callback	that  is  made	during
		     ::http::geturl to determine if a proxy is required for  a
		     given  host.  One argument, a host name, is added to com-
		     mand when it is invoked.  If a  proxy  is	required,  the
		     callback  should return a two-element list containing the
		     proxy server and proxy port.  Otherwise the filter should
		     return  an  empty	list.	The default filter returns the
		     values of the -proxyhost and -proxyport settings if  they
		     are non-empty.

	      -urlencoding encoding
		     The  encoding  used  for  creating the x-url-encoded URLs
		     with ::http::formatQuery.	The default is utf-8, as spec-
		     ified  by	RFC 2718.  Prior to http 2.5 this was unspeci-
		     fied, and that behavior can be returned by specifying the
		     empty  string  ({}), although iso8859-1 is recommended to
		     restore similar behavior but without the  ::http::format-
		     Query  throwing  an  error processing non-latin-1 charac-
		     ters.

	      -useragent string
		     The value of the User-Agent header in the	HTTP  request.
		     The default is "Tcl http client package 2.4."

       ::http::geturl url ?options?
	      The ::http::geturl command is the main procedure in the package.
	      The -query option causes a  POST	operation  and	the  -validate
	      option  causes  a  HEAD operation; otherwise, a GET operation is
	      performed.  The ::http::geturl command  returns  a  token  value
	      that  can be used to get information about the transaction.  See
	      the  STATE  ARRAY  and  ERRORS   section	 for   details.    The
	      ::http::geturl  command  blocks  until  the operation completes,
	      unless the -command option specifies a callback that is  invoked
	      when  the HTTP transaction completes.  ::http::geturl takes sev-
	      eral options:

	      -binary boolean
		     Specifies whether to force interpreting the URL  data  as
		     binary.   Normally  this  is  auto-detected (anything not
		     beginning with a  text  content  type  or	whose  content
		     encoding  is gzip or compress is considered binary data).

	      -blocksize size
		     The block size used when reading the URL.	At  most  size
		     bytes  are read at once.  After each block, a call to the
		     -progress callback is made (if that option is specified).

	      -channel name
		     Copy  the	URL contents to channel name instead of saving
		     it in state(body).

	      -command callback
		     Invoke callback after  the  HTTP  transaction  completes.
		     This  option causes ::http::geturl to return immediately.
		     The callback gets an  additional  argument  that  is  the
		     token  returned  from  ::http::geturl.  This token is the
		     name of an array that is described  in  the  STATE  ARRAY
		     section.  Here is a template for the callback:
		     proc httpCallback {token} {
			 upvar #0 $token state
			 # Access state as a Tcl array }

	      -handler callback
		     Invoke  callback  whenever  HTTP  data  is  available; if
		     present, nothing else will be done with  the  HTTP  data.
		     This  procedure gets two additional arguments: the socket
		     for  the  HTTP  data  and	 the   token   returned   from
		     ::http::geturl.   The token is the name of a global array
		     that is described in the STATE ARRAY section.  The proce-
		     dure  is expected to return the number of bytes read from
		     the socket.  Here is a template for the callback:
		     proc httpHandlerCallback {socket token} {
			 upvar #0 $token state
			 # Access socket, and state as a Tcl array
			 ...
			 (example: set data  [read  $socket  1000];set	nbytes
		     [string length $data])
			 ...
			 return nbytes }

	      -headers keyvaluelist
		     This  option  is  used  to  add extra headers to the HTTP
		     request.  The keyvaluelist argument must be a  list  with
		     an  even  number  of elements that alternate between keys
		     and values.  The keys become header  field  names.   New-
		     lines  are  stripped from the values so the header cannot
		     be corrupted.  For example, if keyvaluelist is Pragma no-
		     cache  then  the following header is included in the HTTP
		     request: Pragma: no-cache

	      -progress callback
		     The callback is made after each transfer of data from the
		     URL.   The  callback gets three additional arguments: the
		     token from ::http::geturl, the expected total size of the
		     contents  from the Content-Length meta-data, and the cur-
		     rent number of bytes transferred so  far.	 The  expected
		     total  size  may be unknown, in which case zero is passed
		     to the callback.  Here is a  template  for  the  progress
		     callback:
		     proc httpProgress {token total current} {
			 upvar #0 $token state }

	      -query query
		     This flag causes ::http::geturl to do a POST request that
		     passes the query to the server. The query must be	an  x-
		     url-encoding  formatted  query.   The ::http::formatQuery
		     procedure can be used to do the formatting.

	      -queryblocksize size
		     The block size used when posting query data to  the  URL.
		     At  most  size  bytes  are  written  at once.  After each
		     block, a call to the -queryprogress callback is made  (if
		     that option is specified).

	      -querychannel channelID
		     This flag causes ::http::geturl to do a POST request that
		     passes the data contained in channelID to the server. The
		     data  contained  in  channelID  must be an x-url-encoding
		     formatted query unless the -type option  below  is  used.
		     If  a  Content-Length  header  is	not  specified via the
		     -headers options, ::http::geturl  attempts  to  determine
		     the size of the post data in order to create that header.
		     If it is unable to determine  the	size,  it  returns  an
		     error.

	      -queryprogress callback
		     The  callback  is made after each transfer of data to the
		     URL (i.e. POST)  and  acts  exactly  like	the  -progress
		     option (the callback format is the same).

	      -timeout milliseconds
		     If  milliseconds is non-zero, then ::http::geturl sets up
		     a timeout to occur after the  specified  number  of  mil-
		     liseconds.   A timeout results in a call to ::http::reset
		     and to the -command callback, if specified.   The	return
		     value  of	::http::status	is timeout after a timeout has
		     occurred.

	      -type mime-type
		     Use mime-type as the Content-Type value, instead  of  the
		     default  value (application/x-www-form-urlencoded) during
		     a POST operation.

	      -validate boolean
		     If boolean is non-zero, then ::http::geturl does an  HTTP
		     HEAD  request.   This  request  returns  meta information
		     about the URL, but the contents are  not  returned.   The
		     meta  information	is available in the state(meta)  vari-
		     able after the transaction.  See the STATE ARRAY  section
		     for details.

       ::http::formatQuery key value ?key value ...?
	      This  procedure  does x-url-encoding of query data.  It takes an
	      even number of arguments that are the keys  and  values  of  the
	      query.  It encodes the keys and values, and generates one string
	      that has the proper & and = separators.  The result is  suitable
	      for the -query value passed to ::http::geturl.

       ::http::reset token ?why?
	      This command resets the HTTP transaction identified by token, if
	      any.  This sets the state(status) value to why,  which  defaults
	      to reset, and then calls the registered -command callback.

       ::http::wait token
	      This  is	a  convenience procedure that blocks and waits for the
	      transaction to  complete.   This	only  works  in  trusted  code
	      because it uses vwait.  Also, it's not useful for the case where
	      ::http::geturl is called without the -command option because  in
	      this  case the ::http::geturl call doesn't return until the HTTP
	      transaction is complete, and thus there's nothing to wait for.

       ::http::data token
	      This is a convenience procedure that returns  the  body  element
	      (i.e., the URL data) of the state array.

       ::http::error token
	      This  is	a convenience procedure that returns the error element
	      of the state array.

       ::http::status token
	      This is a convenience procedure that returns the status  element
	      of the state array.

       ::http::code token
	      This is a convenience procedure that returns the http element of
	      the state array.

       ::http::ncode token
	      This is a convenience procedure that returns  just  the  numeric
	      return  code (200, 404, etc.) from the http element of the state
	      array.

       ::http::size token
	      This is a convenience procedure  that  returns  the  currentsize
	      element of the state array, which represents the number of bytes
	      received from the URL in the ::http::geturl call.

       ::http::cleanup token
	      This procedure cleans up the state associated with  the  connec-
	      tion  identified by token.  After this call, the procedures like
	      ::http::data cannot be used to get information about the	opera-
	      tion.   It  is  strongly recommended that you call this function
	      after you're done with a given HTTP request.  Not doing so  will
	      result  in  memory  not  being  freed,  and  if  your  app calls
	      ::http::geturl enough times, the memory leak could cause a  per-
	      formance hit...or worse.

       ::http::register proto port command
	      This procedure allows one to provide custom HTTP transport types
	      such as HTTPS, by registering a prefix, the  default  port,  and
	      the command to execute to create the Tcl channel. E.g.:
	      package require http package require tls

	      ::http::register https 443 ::tls::socket

	      set token [::http::geturl https://my.secure.site/]

       ::http::unregister proto
	      This  procedure  unregisters  a protocol handler that was previ-
	      ously registered via ::http::register.


ERRORS
       The ::http::geturl procedure will raise errors in the following	cases:
       invalid	command  line options, an invalid URL, a URL on a non-existent
       host, or a URL at a bad port on an existing host.   These  errors  mean
       that  it cannot even start the network transaction.  It will also raise
       an error if it gets an I/O error while writing  out  the  HTTP  request
       header.	 For  synchronous  ::http::geturl calls (where -command is not
       specified), it will raise an error if it gets an I/O error while  read-
       ing  the  HTTP  reply  headers or data.	Because ::http::geturl doesn't
       return a token in these cases, it does all  the	required  cleanup  and
       there's no issue of your app having to call ::http::cleanup.

       For  asynchronous  ::http::geturl  calls, all of the above error situa-
       tions apply, except that if there's any error while  reading  the  HTTP
       reply  headers  or data, no exception is thrown.  This is because after
       writing the HTTP headers, ::http::geturl returns, and the rest  of  the
       HTTP  transaction  occurs  in the background.  The command callback can
       check if any error occurred during the read by  calling	::http::status
       to  check the status and if its error, calling ::http::error to get the
       error message.

       Alternatively, if the main program flow reaches a point where it  needs
       to  know  the  result  of  the  asynchronous  HTTP request, it can call
       ::http::wait and then check status and  error,  just  as  the  callback
       does.

       In  any	case,  you must still call ::http::cleanup to delete the state
       array when you're done.

       There are other possible results of the HTTP transaction determined  by
       examining the status from ::http::status.  These are described below.

       ok     If  the HTTP transaction completes entirely, then status will be
	      ok.  However, you should still check the ::http::code  value  to
	      get  the HTTP status.  The ::http::ncode procedure provides just
	      the numeric error (e.g., 200, 404 or 500) while the ::http::code
	      procedure returns a value like "HTTP 404 File not found".

       eof    If  the server closes the socket without replying, then no error
	      is raised, but the status of the transaction will be eof.

       error  The error message will also be stored in the error status  array
	      element, accessible via ::http::error.

       Another error possibility is that ::http::geturl is unable to write all
       the post query data to the server before the server responds and closes
       the  socket.   The error message is saved in the posterror status array
       element and then  ::http::geturl attempts to complete the  transaction.
       If  it can read the server's response it will end up with an ok status,
       otherwise it will have an eof status.


STATE ARRAY
       The ::http::geturl procedure returns a token that can be used to get to
       the state of the HTTP transaction in the form of a Tcl array.  Use this
       construct to create an easy-to-use  array  variable:  upvar  #0	$token
       state  Once  the  data associated with the URL is no longer needed, the
       state array should be unset to free up  storage.   The  ::http::cleanup
       procedure  is provided for that purpose.  The following elements of the
       array are supported:

	      body   The contents of the URL.	This  will  be	empty  if  the
		     -channel  option  has  been  specified.   This  value  is
		     returned by the ::http::data command.

	      charset
		     The value of the charset attribute from the  Content-Type
		     meta-data value.  If none was specified, this defaults to
		     the   RFC	 standard   iso8859-1,	 or   the   value   of
		     $::http::defaultCharset.	Incoming  text	data  will  be
		     automatically converted from this charset to utf-8.

	      coding A copy of the Content-Encoding meta-data value.

	      currentsize
		     The current number of bytes fetched from the  URL.   This
		     value is returned by the ::http::size command.

	      error  If  defined,  this is the error string seen when the HTTP
		     transaction was aborted.

	      http   The HTTP status reply from the  server.   This  value  is
		     returned by the ::http::code command.  The format of this
		     value is:
		     HTTP/1.0 code string The code  is	a  three-digit	number
		     defined  in  the  HTTP  standard.	 A  code of 200 is OK.
		     Codes beginning with  4  or  5  indicate  errors.	 Codes
		     beginning	with  3  are redirection errors.  In this case
		     the Location meta-data specifies a new URL that  contains
		     the requested information.

	      meta   The  HTTP	protocol  returns meta-data that describes the
		     URL contents.  The meta element of the state array  is  a
		     list of the keys and values of the meta-data.  This is in
		     a format useful for initializing an array that just  con-
		     tains the meta-data:
		     array  set  meta  $state(meta) Some of the meta-data keys
		     are listed below, but the HTTP standard defines more, and
		     servers are free to add their own.

		     Content-Type
			    The  type  of  the URL contents.  Examples include
			    text/html, image/gif,  application/postscript  and
			    application/x-tcl.

		     Content-Length
			    The  advertised  size of the contents.  The actual
			    size obtained by ::http::geturl  is  available  as
			    state(size).

		     Location
			    An alternate URL that contains the requested data.

	      posterror
		     The error, if any, that occurred while writing  the  post
		     query data to the server.

	      status Either  ok,  for  successful  completion, reset for user-
		     reset, timeout if a timeout occurred before the  transac-
		     tion  could  complete,  or  error for an error condition.
		     During the transaction this value is the empty string.

	      totalsize
		     A copy of the Content-Length meta-data value.

	      type   A copy of the Content-Type meta-data value.

	      url    The requested URL.

EXAMPLE
       # Copy a URL to a file and print meta-data proc	httpcopy  {  url  file
       {chunk 4096} } {
	  set out [open $file w]
	  set token [::http::geturl $url -channel $out \
		 -progress httpCopyProgress -blocksize $chunk]
	  close $out

	  # This ends the line started by httpCopyProgress
	  puts stderr ""

	  upvar #0 $token state
	  set max 0
	  foreach {name value} $state(meta) {
	     if {[string length $name] > $max} {
		set max [string length $name]
	     }
	     if {[regexp -nocase ^location$ $name]} {
		# Handle URL redirects
		puts stderr "Location:$value"
		return [httpcopy [string trim $value] $file $chunk]
	     }
	  }
	  incr max
	  foreach {name value} $state(meta) {
	     puts [format "%-*s %s" $max $name: $value]
	  }

	  return $token } proc httpCopyProgress {args} {
	  puts -nonewline stderr .
	  flush stderr }


SEE ALSO
       safe(n), socket(n), safesock(n)


KEYWORDS
       security policy, socket



http				      2.5			       http(n)
=208861
+315
(80)