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-'\"
-'\" Copyright (c) 1995-1997 Sun Microsystems, Inc.
-'\"
-'\" See the file "license.terms" for information on usage and redistribution
-'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
-'\"
-'\" RCS: @(#) $Id: http.n,v 1.3 1999/04/16 00:46:35 stanton Exp $
-'\"
-.so man.macros
-.TH "Http" n 8.0 Tcl "Tcl Built-In Commands"
-.BS
-'\" Note: do not modify the .SH NAME line immediately below!
-.SH NAME
-Http \- Client-side implementation of the HTTP/1.0 protocol.
-.SH SYNOPSIS
-\fBpackage require http ?2.0?\fP
-.sp
-\fB::http::config \fI?options?\fR
-.sp
-\fB::http::geturl \fIurl ?options?\fR
-.sp
-\fB::http::formatQuery \fIlist\fR
-.sp
-\fB::http::reset \fItoken\fR
-.sp
-\fB::http::wait \fItoken\fR
-.sp
-\fB::http::status \fItoken\fR
-.sp
-\fB::http::size \fItoken\fR
-.sp
-\fB::http::code \fItoken\fR
-.sp
-\fB::http::data \fItoken\fR
-.BE
-
-.SH DESCRIPTION
-.PP
-The \fBhttp\fR 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 \fBSafesock\fR security
-policy, so it can be used by untrusted applets to do URL fetching from
-a restricted set of hosts.
-.PP
-The \fB::http::geturl\fR procedure does a HTTP transaction.
-Its \fIoptions \fR determine whether a GET, POST, or HEAD transaction
-is performed.
-The return value of \fB::http::geturl\fR is a token for the transaction.
-The value is also the name of an array in the ::http namespace
- that contains state
-information about the transaction. The elements of this array are
-described in the STATE ARRAY section.
-.PP
-If the \fB-command\fP option is specified, then
-the HTTP operation is done in the background.
-\fB::http::geturl\fR returns immediately after generating the
-HTTP request and the callback is invoked
-when the transaction completes. 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 \fB::http::wait\fR after calling
-\fB::http::geturl\fR to start the event loop.
-.SH COMMANDS
-.TP
-\fB::http::config\fP ?\fIoptions\fR?
-The \fB::http::config\fR 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:
-.RS
-.TP
-\fB\-accept\fP \fImimetypes\fP
-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 example, "image/gif, image/jpeg, text/*".
-.TP
-\fB\-proxyhost\fP \fIhostname\fP
-The name of the proxy host, if any. If this value is the
-empty string, the URL host is contacted directly.
-.TP
-\fB\-proxyport\fP \fInumber\fP
-The proxy port number.
-.TP
-\fB\-proxyfilter\fP \fIcommand\fP
-The command is a callback that is made during
-\fB::http::geturl\fR
-to determine if a proxy is required for a given host. One argument, a
-host name, is added to \fIcommand\fR 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
-\fB\-proxyhost\fR and \fB\-proxyport\fR settings if they are
-non-empty.
-.TP
-\fB\-useragent\fP \fIstring\fP
-The value of the User-Agent header in the HTTP request. The default
-is \fB"Tcl http client package 2.0."\fR
-.RE
-.TP
-\fB::http::geturl\fP \fIurl\fP ?\fIoptions\fP?
-The \fB::http::geturl \fR command is the main procedure in the package.
-The \fB\-query\fR option causes a POST operation and
-the \fB\-validate\fR option causes a HEAD operation;
-otherwise, a GET operation is performed. The \fB::http::geturl\fR command
-returns a \fItoken\fR value that can be used to get
-information about the transaction. See the STATE ARRAY section for
-details. The \fB::http::geturl\fR command blocks until the operation
-completes, unless the \fB\-command\fR option specifies a callback
-that is invoked when the HTTP transaction completes.
-\fB::http::geturl\fR takes several options:
-.RS
-.TP
-\fB\-blocksize\fP \fIsize\fP
-The blocksize used when reading the URL.
-At most
-\fIsize\fR
-bytes are read at once. After each block, a call to the
-\fB\-progress\fR
-callback is made.
-.TP
-\fB\-channel\fP \fIname\fP
-Copy the URL contents to channel \fIname\fR instead of saving it in
-\fBstate(body)\fR.
-.TP
-\fB\-command\fP \fIcallback\fP
-Invoke \fIcallback\fP after the HTTP transaction completes.
-This option causes \fB::http::geturl\fP to return immediately.
-The \fIcallback\fP gets an additional argument that is the \fItoken\fR returned
-from \fB::http::geturl\fR. This token is the name of an array that is
-described in the STATE ARRAY section. Here is a template for the
-callback:
-.RS
-.CS
-proc httpCallback {token} {
- upvar #0 $token state
- # Access state as a Tcl array
-}
-.CE
-.RE
-.TP
-\fB\-handler\fP \fIcallback\fP
-Invoke \fIcallback\fP 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 \fItoken\fR returned from
-\fB::http::geturl\fR. The token is the name of a global array that is described
-in the STATE ARRAY section. The procedure is expected to return the number
-of bytes read from the socket. Here is a template for the callback:
-.RS
-.CS
-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
-}
-.CE
-.RE
-.TP
-\fB\-headers\fP \fIkeyvaluelist\fP
-This option is used to add extra headers to the HTTP request. The
-\fIkeyvaluelist\fR argument must be a list with an even number of
-elements that alternate between keys and values. The keys become
-header field names. Newlines are stripped from the values so the
-header cannot be corrupted. For example, if \fIkeyvaluelist\fR is
-\fBPragma no-cache\fR then the following header is included in the
-HTTP request:
-.CS
-Pragma: no-cache
-.CE
-.TP
-\fB\-progress\fP \fIcallback\fP
-The \fIcallback\fR is made after each transfer of data from the URL.
-The callback gets three additional arguments: the \fItoken\fR from
-\fB::http::geturl\fR, the expected total size of the contents from the
-\fBContent-Length\fR meta-data, and the current 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:
-.RS
-.CS
-proc httpProgress {token total current} {
- upvar #0 $token state
-}
-.CE
-.RE
-.TP
-\fB\-query\fP \fIquery\fP
-This flag causes \fB::http::geturl\fR to do a POST request that passes the
-\fIquery\fR to the server. The \fIquery\fR must be a x-url-encoding
-formatted query. The \fB::http::formatQuery\fR procedure can be used to
-do the formatting.
-.TP
-\fB\-timeout\fP \fImilliseconds\fP
-If \fImilliseconds\fR is non-zero, then \fB::http::geturl\fR sets up a timeout
-to occur after the specified number of milliseconds.
-A timeout results in a call to \fB::http::reset\fP and to
-the \fB-command\fP callback, if specified.
-The return value of \fB::http::status\fP is \fBtimeout\fP
-after a timeout has occurred.
-.TP
-\fB\-validate\fP \fIboolean\fP
-If \fIboolean\fR is non-zero, then \fB::http::geturl\fR 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
-\fBstate(meta) \fR variable after the transaction. See the STATE
-ARRAY section for details.
-.RE
-.TP
-\fB::http::formatQuery\fP \fIkey value\fP ?\fIkey value\fP ...?
-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
-\fB\-query\fR value passed to \fB::http::geturl\fR.
-.TP
-\fB::http::reset\fP \fItoken\fP ?\fIwhy\fP?
-This command resets the HTTP transaction identified by \fItoken\fR, if
-any. This sets the \fBstate(status)\fP value to \fIwhy\fP, which defaults to \fBreset\fR, and then calls the registered \fB\-command\fR callback.
-.TP
-\fB::http::wait\fP \fItoken\fP
-This is a convenience procedure that blocks and waits for the
-transaction to complete. This only works in trusted code because it
-uses \fBvwait\fR.
-.TP
-\fB::http::data\fP \fItoken\fP
-This is a convenience procedure that returns the \fBbody\fP element
-(i.e., the URL data) of the state array.
-.TP
-\fB::http::status\fP \fItoken\fP
-This is a convenience procedure that returns the \fBstatus\fP element of
-the state array.
-.TP
-\fB::http::code\fP \fItoken\fP
-This is a convenience procedure that returns the \fBhttp\fP element of the
-state array.
-.TP
-\fB::http::size\fP \fItoken\fP
-This is a convenience procedure that returns the \fBcurrentsize\fP
-element of the state array.
-.SH "STATE ARRAY"
-The \fB::http::geturl\fR procedure returns a \fItoken\fR 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:
-.CS
-upvar #0 $token state
-.CE
-Once the data associated with the url is no longer needed, the state
-array should be unset to free up storage. The following elements of
-the array are supported:
-.RS
-.TP
-\fBbody\fR
-The contents of the URL. This will be empty if the \fB\-channel\fR
-option has been specified. This value is returned by the \fB::http::data\fP command.
-.TP
-\fBcurrentsize\fR
-The current number of bytes fetched from the URL.
-This value is returned by the \fB::http::size\fP command.
-.TP
-\fBerror\fR
-If defined, this is the error string seen when the HTTP transaction
-was aborted.
-.TP
-\fBhttp\fR
-The HTTP status reply from the server. This value
-is returned by the \fB::http::code\fP command. The format of this value is:
-.RS
-.CS
-\fIcode string\fP
-.CE
-The \fIcode\fR 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
-\fBLocation\fR meta-data specifies a new URL that contains the
-requested information.
-.RE
-.TP
-\fBmeta\fR
-The HTTP protocol returns meta-data that describes the URL contents.
-The \fBmeta\fR 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 contains the meta-data:
-.RS
-.CS
-array set meta $state(meta)
-.CE
-Some of the meta-data keys are listed below, but the HTTP standard defines
-more, and servers are free to add their own.
-.TP
-\fBContent-Type\fR
-The type of the URL contents. Examples include \fBtext/html\fR,
-\fBimage/gif,\fR \fBapplication/postscript\fR and
-\fBapplication/x-tcl\fR.
-.TP
-\fBContent-Length\fR
-The advertised size of the contents. The actual size obtained by
-\fB::http::geturl\fR is available as \fBstate(size)\fR.
-.TP
-\fBLocation\fR
-An alternate URL that contains the requested data.
-.RE
-.TP
-\fBstatus\fR
-Either \fBok\fR, for successful completion, \fBreset\fR for
-user-reset, or \fBerror\fR for an error condition. During the
-transaction this value is the empty string.
-.TP
-\fBtotalsize\fR
-A copy of the \fBContent-Length\fR meta-data value.
-.TP
-\fBtype\fR
-A copy of the \fBContent-Type\fR meta-data value.
-.TP
-\fBurl\fR
-The requested URL.
-.RE
-.SH EXAMPLE
-.DS
-# Copy a URL to a file and print meta-data
-proc ::http::copy { url file {chunk 4096} } {
- set out [open $file w]
- set token [geturl $url -channel $out -progress ::http::Progress \\
- -blocksize $chunk]
- close $out
- # This ends the line started by http::Progress
- 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 [copy [string trim $value] $file $chunk]
- }
- }
- incr max
- foreach {name value} $state(meta) {
- puts [format "%-*s %s" $max $name: $value]
- }
-
- return $token
-}
-proc ::http::Progress {args} {
- puts -nonewline stderr . ; flush stderr
-}
-
-.DE
-.SH "SEE ALSO"
-safe(n), socket(n), safesock(n)
-.SH KEYWORDS
-security policy, socket
-
-