HEAD VI

Owning Palette: HTTP Client VIs

Requires: Base Development System

Sends a Web request that returns headers from a server, Web page, or Web service. This VI uses the HEAD HTTP method. This VI does not submit any data to the server or receive body data. The minimal data exchange makes the HEAD VI useful for testing the validity of a URL.

You can assign a client handle to add authentication credentials, HTTP headers, or a cookie to Web requests made by the HEAD VI. Use the OpenHandle VI to open a client handle and establish credentials. Use the AddHeader VI to add header lines to Web requests made by the HEAD VI.

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	client handle specifies the client handle to associate with the Web request. Use client handles to wire together multiple HTTP Client VIs while preserving authentication credentials, HTTP headers, and cookies. Client handles are not required when making independent Web requests without persistent data such as headers or credentials.
	URL specifies the URL of the server, Web page, or Web service which this VI sends the Web request.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	timeout specifies the amount of time in milliseconds to wait for a response from the server before the Web request times out. The default value is 10000 ms. A value of -1 defers timeout monitoring to the operating system.
	client handle out returns the client handle associated with the Web request. Use client handles to wire together multiple HTTP Client VIs while preserving authentication credentials, HTTP headers, and cookies. Client handles are not required when making independent Web requests without persistent data such as headers or credentials.
	headers returns the header fields returned by the server. Refer to the World Wide Web Consortium website at www.w3.org for more information about header field definitions including available headers, descriptions, and syntax.
	error out contains error information. This output provides standard error out functionality.

HEAD Details

Refer to the World Wide Web Consortium website at www.w3.org for more information about HTTP method definitions, including the HEAD method.