Groundwork: Form Processing

Form Processing

Forms can be submitted using POST or GET methods and can be application/x-www-form-urlencoded or sent as multipart/form-data. The cgi class automatically detects form submission method and encoding and parses the data into form entries and file entries if the page sent files.

Form entries are name/value pairs and file entries are name/filename/tempfilename/mimetype tuples.

The following web page sends several name/value pairs and a file using the POST method. Note the action attribute of the form tag.

<html>
<body>

Enter your personal information:

<form method="post" action="mycgi.cgi">
Name: <input name="name" type="text" value=""><br>
Address: <input name="address" type="text" value=""><br>
City: <input name="city" type="text" value=""><br>
State: <input name="state" type="text" value=""><br>
Zip: <input name="zip" type="text" value=""><br>
Phone: <input name="phone" type="text" value=""><br>
<input name="submit" type="submit" value="Submit">
</form>

</body>
</html>

The following web page sends several name/value pairs using the GET method. Note the action attribute of the form tag.

<html>
<body>

Enter your personal information:

<form method="get" action="mycgi.cgi">
Name: <input name="name" type="text" value=""><br>
Address: <input name="address" type="text" value=""><br>
City: <input name="city" type="text" value=""><br>
State: <input name="state" type="text" value=""><br>
Zip: <input name="zip" type="text" value=""><br>
Phone: <input name="phone" type="text" value=""><br>
<input name="submit" type="submit" value="Submit">
</form>

</body>
</html>

The following web page sends several name/value pairs using an anchor with a get string.

<html>
<body>

<a href="mycgi.cgi?name=David+Muse&address=1234+My+Street&city=Atlanta&state=Georgia&zip=12345&phone=555-444-3333">Submit Information</a>

</body>
</html>

The following web page sends a file and several name/value pairs. Note the enctype attribute of the form tag. When a file-input tag is used in a form, the enctype of the form must be "multipart/form-data".

<html>
<body>

Enter your personal information:

<form method="post" action="mycgi.cgi" enctype="multipart/form-data">
Name: <input name="name" type="text" value=""><br>
Address: <input name="address" type="text" value=""><br>
City: <input name="city" type="text" value=""><br>
State: <input name="state" type="text" value=""><br>
Zip: <input name="zip" type="text" value=""><br>
Phone: <input name="phone" type="text" value=""><br>
Upload a File: <input name="file" type="file" value=""<br>
<input name="submit" type="submit" value="Submit">
</form>

</body>
</html>

Using the cgi class, the following program reads the form and file entries passed in from the previous page and writes them back out to the browser.

#include <groundwork/cgi.h>
#include <groundwork/cgimodule.h>
#include <iostream.h>
#include <fstream.h>
#include <unistd.h>

MAIN {

        cgi     *c=new cgi(APISTRUCT);

        // send a standard http header
        c->sendHeader();

        // get the form entries
        char    *name=c->formEntry("name");
        char    *address=c->formEntry("address");
        char    *city=c->formEntry("city");
        char    *state=c->formEntry("state");
        char    *zip=c->formEntry("zip");
        char    *phone=c->formEntry("phone");

        // get the file entry
        char    *originalfilename=c->fileEntryFilename("file");
        char    *tempfilename=c->fileEntryTempFilename("file");
        char    *mimetype=c->fileEntryMimeType("file");

        // write the form entries back out to the browser
        cout << "The following values were passed in from the previous page:<br>" << endl;

        cout << "Name: " << name << "<br>" << endl;
        cout << "Address: " << address << "<br>" << endl;
        cout << "City: " << city << "<br>" << endl;
        cout << "State: " << state << "<br>" << endl;
        cout << "Zip: " << zip << "<br>" << endl;
        cout << "Phone: " << phone << "<br>" << endl;

        cout << "<br><br>" << endl;

        // write the file metadata back out to the browser
        cout << "The following file was uploaded as well:<br>" << endl;

        cout << "<br><br>" << endl;

        cout << "Filename: " << originalfilename << "<br>" << endl;
        cout << "Mime Type: " << mimetype << "<br>" << endl;
        cout << "File Content: <br>" << endl;

        cout << "<br><br>" << endl;

        // write the file itself back out to the browser
        ifstream        tempfile(tempfilename);
        cout << tempfile.rdbuf() << endl;

        // remove the temporary file
        unlink(tempfilename);

        delete c;
}