Multiple argument input to a Perl CGI script

Let us now return to a more complex form example. We previously looked at the Python Quiz form.

Python Quiz:

What is thy name:

What is thy quest:

What is thy favorite color: chartreuse azure puce cornflower olive draub gunmetal indigo2 blanched almond flesh ochre opal amber mustard

What is the weight of a swallow: African Swallow or Continental Swallow

What do you have to say for yourself

Press to submit your query.

The HTML to produce this is:

<H1>Python Quiz: </H1>

<form  method = "post" action = "simple-form.cgi">
What is thy name: <input name="name"><P>
What is thy quest: <input name="quest"><P>

What is thy favorite color:
 <select name="color">
 <option selected>chartreuse
 <option>azure
 <option>puce
 <option>cornflower
 <option>olive draub
 <option>gunmetal
 <option>indigo2
 <option>blanched almond
 <option>flesh
 <option>ochre
 <option>opal
 <option>amber
 <option>mustard
 </select>
<P>

What is the weight of a swallow: <input type="radio" name="swallow"
value="african" checked> African Swallow or
<input type="radio" name="swallow" value="continental"> Continental
Swallow
<P>

What do you have to say for yourself 
<textarea name="text" rows=5 cols=60></textarea>
<P>

Press <input type="submit" value="here"> to submit your query.
</form>

Note: that the Method attribute is set to POST. This desirable since many name/value pairs are sent to the CGI script.

If the method was set to GET instead the call would look something like this:

http://dave.cs.cf.ac.uk/simple-form.cgi?name=Dave&
quest=Find+Holy+Grail&
color=olive+draub&
swallow=continental&
text=I+am+Tired

Also:

• note relevant character substiutions and argument dividors
• this is all one line of a URL

The Post method sends all this dat via standard input which is far neater.

This has several input name/value pairs.

To extract out the relevant value for a given name is straightforward though:

• use &ReadParse(*input)
• extract out the value for a given name using $input{'name'}

It is also useful to process the form input for a Textarea field so that line breaks are inserted - since HTML does not preserve linebreaks and carriage returns will be present in the multiline output.

The Perl commands:

($text = $input{'text'}) =~ s/\n/\n<BR>/g;

does this.

This Perl is a little complex for complete study now. Essentially the following occurs

• The input value to the text name is copied to a $text array.

  ($text = $input{'text'})
  

• All end of lines \n characters are substituted (s/.../ command) by \n<BR>.

   s/\n/\n<BR>/g
  

  The s/old_sting/new_string/ command is commonly used in Perl. The g at the end of the command indicates a global substitution (all instances get replaced) rather than the (default) first found.

So our complete Perl script is as follows:

• Input is read and parsed as usual with cgi-lib.pl routine &ReadParse(*input)
• Values pertaining to names (name, color, quest, swallow and text are sought.
• The text value is processed as above.
• The values are printed out in HTML format.
• cgi-lib.pl subroutines are used to output CGI Header, and HTML Top and bottom.
• Another cgi-lib.pl subroutine, &PrintVariables(*input), is also used to print out all the input name/value pairs.

The complete Perl code is as follows:

#!/usr/local/bin/perl

# Copyright (C) 1994 Steven E. Brenner
# This is a small demonstration script 
# to demonstrate the use of 
# the cgi-lib.pl library

require "cgi-lib.pl";


# Read in all the variables from form
&ReadParse(*input);

# Print the header
print &PrintHeader;
print &HtmlTop ("cgi-lib.pl demo form output");

# Do some processing, and print some output
# add <BR>'s after carriage returns
# to multline input, since HTML does not
# preserve line breaks
($text = $input{'text'}) =~ s/\n/\n<BR>/g; 
                                   
print << ENDOFTEXT; 

You, $input{'name'}, whose favorite color is $input{'color'} are on a
quest which is $input{'quest'}, and are looking for the air speed/velocity of an
$input{'swallow'} swallow.  And this is what you have to say for
yourself:<P> $text<P>

ENDOFTEXT


# If you want, just print out a list of all of the variables.
print "<HR>And here is a list of the variables you entered...<P>";
print &PrintVariables(*input);

# Close the document cleanly.
print &HtmlBot;