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  RudeCGI CGI File Upload Tutorial - Part 1


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CGI File Upload Tutorial - part 1

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HTML Source Code for File Uploads

As far as the HTML code is concerned, there are 3 things you need to do to enable file uploads.

  1. Make sure the form's METHOD is set to POST
    The GET method is limited to a certain number of characters. If you submit large amounts of data, they will be truncated if they exceed the maximum bytes allowed for the GET Method. Furthermore, the next item in this list requires the POST method in order to work.
  2. Add the parameter enctype='multipart/form-data' to the FORM tag
    This forces the browser to encode the form in a special manner - pretty much identical to the format used by MIME (email). The browser sends the data in sections, where each section has a header that describes the data that the section contains. Each section is delimited by some large random string. You don't need to know anything about this to get this to work, unless you build your own CGI parser. The RudeCGI™ CGI C++ library library supports this encoding.
  3. Provide one or more file input fields within the form.
    A File input field acts like any other input field: it has a type, a name, and a value. The value is determined when the person filling in the form browses to a particular file. You are probably already familiar with this. The HTML code for a File Input Field looks like this:


    You can use anything in place of "SOMENAME". If you provide more than one file input field, they can each have the same name, or they can each have different names. However, accessing multiple uploaded files can be a bit tricky on the CGI end if they all have the same name. When possible, use different names for each file input field.

Example 1

Here is the HTML source code for a simple file upload form. It is as simple as it gets. Make sure the ACTION parameter points to your CGI script.

<form action="'" method=POST enctype="multipart/form-data">
      <input type="file" name="userfile"/>
      <input type="submit"/>

Example 2

Here is the HTML source for a more complex form that accepts three files for upload, plus some other information:

<form action="" method="POST" enctype="multipart/form-data">
      ENTER YOUR NAME: <input type="text" name="customer_name"> <br>
      ENTER YOUR EMAIL ADDRESS: <input type="text" name="customer_email"> <br>
      SELECT FILE NUMBER 1: <input type="file" name="file_1"> <br>
      SELECT FILE NUMBER 2: <input type="file" name="file_2"> <br>
      SELECT FILE NUMBER 3: <input type="file" name="file_3"> <br>
      <input type="submit" value="Upload Files">

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