File Upload with Rivet

Example 4. File Upload

The upload command endows Rivet with an interface to access files transferred over http as parts of a multipart form. The following HTML in one file, say, upload.html creates a form with a text input entry. By clicking the file chooser button the file browser shows up and the user selects the file to be uploaded (the file path will appear in the text input). In order to make sure you're uploading the whole file you must combine the action of the enctype and method attributes of the form tag in the way shown in the example. Failure to do so would result in the client sending only the file's path, rather than the actual contents.

<form action="foo.rvt" enctype="multipart/form-data" method="post">
    <input type="file" name="MyUpload"></input>
    <input type="submit" value="Send File"></input>

In the script invoked by the form (upload.rvt) upload ?argument ...? commands can be used to manipulate the various files uploaded.

upload save MyUpload /tmp/uploadfiles/file1
puts "Saved file [upload filename MyUpload] \
        ([upload size MyUpload] bytes) to server"

Don't forget that the apache server must have write access to the directory where files are being created. The Rivet Apache directives have a substantial impact on the upload process, you have to carefully read the docs in order to set the appropriate directives values that would match your requirements.

It is also important to understand that some upload commands are effective only when used in a mutually exclusive way. Apache stores the data in temporary files which are read by the upload save ?upload name? ?filename? or by the upload data ?upload name? command. Subsequent calls to these 2 commands using the same ?upload name? argument will return no data on the second call. Likewise upload channel ?upload name? will return a Tcl file channel that you can use in regular Tcl scripts only if you haven't already read the data, for example with a call to the upload data ?upload name? command.

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