CGI.pm - a Perl5 CGI Library

WARNING: As threatened, the import() routine has been changed for compatibility with the standard perl module usage. Please use import_names() to copy CGI variables into your name space. The dependence on the SelfLoader has also been removed by popular demand.

Abstract

Everything is done through a ``CGI'' object. When you create one of these objects it examines the environment for a query string, parses it, and stores the results. You can then ask the CGI object to return or modify the query values. CGI objects handle POST and GET methods correctly, and correctly distinguish between scripts called from <ISINDEX> documents and form-based documents. In fact you can debug your script from the command line without worrying about setting up environment variables.

A script to create a fill-out form that remembers its state each time it's invoked is very easy to write with CGI.pm:

#!/usr/local/bin/perl

use CGI qw(:standard);

print header;
print start_html('A Simple Example'),
    h1('A Simple Example'),
    start_form,
    "What's your name? ",textfield('name'),
    p,
    "What's the combination?",
    p,
    checkbox_group(-name=>'words',
		   -values=>['eenie','meenie','minie','moe'],
		   -defaults=>['eenie','minie']),
    p,
    "What's your favorite color? ",
    popup_menu(-name=>'color',
	       -values=>['red','green','blue','chartreuse']),
    p,
    submit,
    end_form,
    hr;

if (param()) {
    print 
	"Your name is",em(param('name')),
	p,
	"The keywords are: ",em(join(", ",param('words'))),
	p,
	"Your favorite color is ",em(param('color')),
	hr;
}
print a({href=>'../cgi_docs.html'},'Go to the documentation');

(Users of CGI.pm before version 2.20 will notice that the syntax has changed a in this example from previous examples. Don't worry, the object-oriented syntax is still accepted. Read importing CGI methods for an explanation.)

Contents

• Download full package (gzip tar archive)
• Download full package (pkzip archive)
• Download full package (Macintosh stuffit archive)
• Download just the CGI module (uncompressed)

This package requires perl 5.001m or higher. (Perl 5.003 is highly recommended because of a security hole in earlier versions of perl.) You also must have the SelfLoader module installed. To use CGI.pm simply install it in your perl library directory. On most systems this will be /usr/local/lib/perl5, but check with the administrator of your system to be sure. If you know the location of the directory, you can move the module directly:

    cp CGI.pm /usr/local/lib/perl5/

In most cases, though, you should have perl do the installation for you. Move to the directory containing CGI.pm and type the following commands:

   % perl Makefile.PL
   % make
   % make install

This will create two new files in your Perl library. CGI.pm is the main library file. Carp.pm (in the subdirectory "CGI") contains some optional utility routines for writing nicely formatted error messages into your server logs. See the Carp.pm man page for more details.

If you get error messages when you try to install, then you are either:

1. Running a Windows NT port of Perl (or another port) that doesn't have the current MakeMaker program built into it.
2. Have an old version of perl. In particular, version 5.000 will complain that (nonexistent) .c and .o files are missing.

If you do not have sufficient privileges to install into /usr/local/lib/perl5, you can still use CGI.pm. Place it in some convenient place, for example, in /usr/local/etc/httpd/cgi-bin and preface your CGI scripts with a preamble something like the following:

use lib '/usr/local/etc/httpd/cgi-bin';
use CGI;

BEGIN {
     unshift(@INC,'/usr/local/etc/httpd/cgi-bin');
}
use CGI;

Notes on using CGI.pm in NT and other non-Unix platforms

    use CGI;
    $query = new CGI;

An alternative form of the new() method allows you to read script parameters from a previously-opened file handle:

    $query = new CGI(FILEHANDLE)

open (IN,"test.out") || die;
while (!eof(IN)) {
    my $q = new CGI(IN);
    push(@queries,$q);
}

    my $q = new CGI(\*IN);

You can initialize a CGI object from an associative-array reference. Values can be either single- or multivalued:

$query = new CGI({'dinosaur'=>'barney',
                  'song'=>'I love you',
                  'friends'=>[qw/Jessica George Nancy/]});

$query = new CGI('dinosaur=barney&color=purple');

$empty_query = new CGI('');

    @keywords = $query->keywords

    @names = $query->param

   @values = $query->param('foo');
             -or-
   $value = $query->param('foo');

As of version 1.50 of this library, the array of parameter names returned will be in the same order in which the browser sent them. Although this is not guaranteed to be identical to the order in which the parameters were defined in the fill-out form, this is usually the case.

Setting The Value(s) Of A Named Parameter

   $query->param('foo','an','array','of','values');
                   -or-
   $query->param(-name=>'foo',-values=>['an','array','of','values']);

The second example shows an alternative "named parameter" style of function call that is accepted by most of the CGI methods. See Calling CGI functions that Take Multiple Arguments for an explanation of this style.

Appending a Parameter

   $query->append(-name=>'foo',-values=>['yet','more','values']);

   $query->delete('foo');

   $query->delete_all();

   $query->import_names('R');
   print "Your name is $R::name\n"
   print "Your favorite colors are @R::colors\n";

If you don't specify a name space, this method assumes namespace "Q".

Warning: do not import into namespace 'main'. This represents a major security risk, as evil people could then use this feature to redefine central variables such as @INC. CGI.pm will exit with an error if you try to do this.

Note: this method used to be called import(). As of version 2.20 import() has been changed to be consistent with other Perl modules. Please change all occurrences of import() to import_names().

Table of contents

   $query->save(FILEHANDLE)

See advanced techniques for more information.

Saving the State in a Self-Referencing URL

   $my_url=$query->self_url

If you'd like to get the URL without the entire query string appended to it, use the url() method:

   $my_self=$query->url

Calling CGI Functions that Take Multiple Arguments

   $field = $query->radio_group(-name=>'OS',
                                -values=>[Unix,Windows,Macintosh],
                                -default=>'Unix');

   $field = $query->textfield(-name=>'State',
                              -default=>'gaseous',
                              -justification=>'RIGHT');

   <INPUT TYPE="textfield" NAME="State" VALUE="gaseous"
          JUSTIFICATION="RIGHT">

   $query = new CGI;
   $query->use_named_parameters(1);
   $field = $query->radio_group('name'=>'OS',
                                'values'=>['Unix','Windows','Macintosh'],
                                'default'=>'Unix');

Table of contents

Creating the HTTP Header

Creating the Standard Header for a Virtual Document

   print $query->header('image/gif');

An extended form of this method allows you to specify a status code and a message to pass back to the browser:

   print $query->header(-type=>'image/gif',
                        -status=>'204 No Response');

Several other named parameters are recognized. Here's a contrived example that uses them all:

   print $query->header(-type=>'image/gif',
                        -status=>'402 Payment Required',
                        -expires=>'+3d',
                        -cookie=>$my_cookie,
                        -Cost=>'$0.02');

-expires

	+30s                              30 seconds from now
	+10m                              ten minutes from now
	+1h	                          one hour from now
        -1d                               yesterday (i.e. "ASAP!")
	now                               immediately
	+3M                               in three months
        +10y                              in ten years time
	Thursday, 25-Apr-96 00:40:33 GMT  at the indicated time & date

CGI::expires() is the static function call used internally that turns relative time intervals into HTTP dates. You can call it directly if you wish.

-cookie

-nph

print $query->header(-nph=>1,
                        -status=>'200 OK',
                        -type=>'text/html');

1. You are using Microsoft Internet Information Server.
2. If you need to create unbuffered output, for example for use in a "server push" script.
3. To take advantage of HTTP extensions not supported by your server.

Other header fields

   Cost: $0.02

   print $query->redirect('http://somewhere.else/in/the/world');

You can add your own headers to this as in the header() method.

You should always use absolute or full URLs in redirection requests. Relative URLs will not work correctly.

An alternative syntax for redirect() is:

print $query->redirect(-uri=>'http://somewhere.else/',
                          -nph=>1);

Creating an HTML Header

   named parameter style
   print $query->start_html(-title=>'Secrets of the Pyramids',
                            -author=>'fred@capricorn.org',
                            -base=>'true',
			    -meta=>{'keywords'=>'pharoah secret mummy',
                                    'copyright'=>'copyright 1996 King Tut'},
                            -BGCOLOR=>'blue');

   old style
   print $query->start_html('Secrets of the Pyramids',
                            'fred@capricorn.org','true');

• The title (-title)
• The author's e-mail address (will create a <LINK REV="MADE"> tag if present (-author)
• A true flag if you want to include a <BASE> tag in the header (-base). This helps resolve relative addresses to absolute ones when the document is moved, but makes the document hierarchy non-portable. Use with care!
• A -xbase parameter, if you want to include a <BASE> tag that points to some external location. Example:

        print $query->start_html(-title=>'Secrets of the Pyramids',
                                 -xbase=>'http://www.nile.eg/pyramid.html');
        

• A -script parameter to define Netscape JavaScript functions to incorporate into the HTML page. This is the preferred way to define a library of JavaScript functions that will be called from elsewhere within the page. CGI.pm will attempt to format the JavaScript code in such a way that non-Netscape browsers won't try to display the JavaScript code. Unfortunately some browsers get confused nevertheless. Here's an example of how to create a JavaScript library and incorporating it into the HTML code header:

        $query = new CGI;
        print $query->header;
        
        $JSCRIPT=<<END;
        // Ask a silly question
        function riddle_me_this() {
           var r = prompt("What walks on four legs in the morning, " +
                         "two legs in the afternoon, " +
                         "and three legs in the evening?");
           response(r);
        }
        // Get a silly answer
        function response(answer) {
           if (answer == "man")
              alert("Right you are!");
           else
              alert("Wrong!  Guess again.");
        }
        END
        
        print $query->start_html(-title=>'The Riddle of the Sphinx',
                                 -script=>$JSCRIPT);
        

• A -meta parameter to define one or more <META> tags. Pass this parameter a reference to an associative array containing key/value pairs. Each pair becomes a <META> tag in a format similar to this one.

        <META NAME="keywords" CONTENT="pharoah secret mummy">
        <META NAME="description" CONTENT="copyright 1996 King Tut">
        

  There is no support for the HTTP-EQUIV type of <META> tag. This is because you can modify the HTTP header directly with the header method.
• -onLoad and -onUnload parameters to register JavaScript event handlers to be executed when the page generated by your script is opened and closed respectively. Example:

        print $query->start_html(-title=>'The Riddle of the Sphinx',
                                    -script=>$JSCRIPT,
                                    -onLoad=>'riddle_me_this()');
        

  See JavaScripting for more details.
• Any additional attributes you want to incorporate into the <BODY> tag (as many as you like). This is a good way to incorporate other Netscape extensions, such as background color and wallpaper pattern. (The example above sets the page background to a vibrant blue.) You can use this feature to take advantage of new HTML features without waiting for a CGI.pm release.

Ending an HTML Document

  print $query->end_html

Other HTML Tags

Unpaired Tags

   print $query->hr;

Paired Tags

   print $query->em("What a silly art exhibit!");

You can pass as many text arguments as you like: they'll be concatenated together with spaces. This allows you to create nested tags easily:

   print $query->h3("The",$query->em("silly"),"art exhibit");

   <h3>The <em>silly</em> art exhibit</h3>

When used in conjunction with the import facility, the HTML shortcuts can make CGI scripts easier to read. For example:

   use CGI ':standard';
   print h1("Road Guide"),
         ol(
          li(a {href=>"start.html"},"The beginning"),
          li(a {href=>"middle.html"},"The middle"),
          li(a {href=>"end.html"},"The end")
         );

Most HTML tags are represented as lowercase function calls. There are a couple of exceptions:

1. The <tr> tag used to start a new table row conflicts with the perl translate function tr(). Use TR() instead.
2. The <param> tag used to pass parameters to an applet conflicts with CGI's own param() method. Use PARAM() instead.

Tags with Attributes

   use CGI shortcuts;
   print a({href=>"bad_art.html"},"Jump to the silly exhibit");

Table of contents

General note 2. The default values that you specify for the forms are only used the first time the script is invoked. If there are already values present in the query string, they are used, even if blank.

If you want to change the value of a field from its previous value, you have two choices:

1. call the param() method to set it.
2. use the -override (alias -force) parameter. (This is a new feature in 2.15) This forces the default value to be used, regardless of the previous value of the field:

          print $query->textfield(-name=>'favorite_color',
                                  -default=>'red',
   			       -override=>1);
          

1. Create a special defaults button using the defaults() method.
2. Create a hypertext link that calls your script without any parameters.

General note 4. By popular demand, the text and labels that you provide for form elements are escaped according to HTML rules. This means that you can safely use "<CLICK ME>" as the label for a button. However, this behavior may interfere with your ability to incorporate special HTML character sequences, such as &Aacute; (Á) into your fields. If you wish to turn of automatic escaping, call the autoEscape() method with a false value immediately after creating the CGI object:

     $query = new CGI;
     $query->autoEscape(undef);

Form Elements

   print $query->isindex($action);

   print $query->startform($method,$action,$encoding);
     ...various form stuff...
   print $query->endform;

The form encoding is a new feature introduced in version 1.57 in order to support the "file upload" feature of Netscape 2.0. The form encoding tells the browser how to package up the contents of the form in order to transmit it across the Internet. There are two types of encoding that you can specify:

application/x-www-form-urlencoded

This is the type of encoding used by all browsers prior to Netscape 2.0. It is compatible with many CGI scripts and is suitable for short fields containing text data. For your convenience, CGI.pm stores the name of this encoding type in $CGI::URL_ENCODED.

multipart/form-data

This is the newer type of encoding introduced by Netscape 2.0. It is suitable for forms that contain very large fields or that are intended for transferring binary data. Most importantly, it enables the "file upload" feature of Netscape 2.0 forms. For your convenience, CGI.pm stores the name of this encoding type in $CGI::MULTIPART

Forms that use this type of encoding are not easily interpreted by CGI scripts unless they use CGI.pm or another library that knows how to handle them. Unless you are using the file upload feature, there's no particular reason to use this type of encoding.

If you plan to make use of the JavaScript features of Netscape 2.0, you can provide startform() with the optional -name and/or -onSubmit parameters. -name has no effect on the display of the form, but can be used to give the form an identifier so that it can be manipulated by JavaScript functions. Provide the -onSubmit parameter in order to register some JavaScript code to be performed just before the form is submitted. This is useful for checking the validity of a form before submitting it. Your JavaScript code should return a value of "true" to let Netscape know that it can go ahead and submit the form, and "false" to abort the submission.

Starting a Form that Uses the Netscape 2.0 "File Upload" Feature

   print $query->start_multipart_form($method,$action,$encoding);
     ...various form stuff...
   print $query->endform;

  Named parameter style
  print $query->textfield(-name=>'field_name',
	                    -default=>'starting value',
	                    -size=>50,
	                    -maxlength=>80);

   Old style
  print $query->textfield('foo','starting value',50,80);

• The first parameter (-name) is the required name for the field.
• The optional second parameter (-default) is the starting value for the field contents.
• The optional third parameter (-size) is the size of the field in characters.
• The optional fourth parameter (-maxlength) is the maximum number of characters the field will accomodate.

When the form is processed, the value of the text field can be retrieved with:

      $value = $query->param('foo');

JavaScripting: You can also provide -onChange, -onFocus, -onBlur and -onSelect parameters to register JavaScript event handlers.

Creating A Big Text Field

   Named parameter style
   print $query->textarea(-name=>'foo',
	 		  -default=>'starting value',
	                  -rows=>10,
	                  -columns=>50);

   Old style
   print $query->textarea('foo','starting value',10,50);

JavaScripting: Like textfield(), you can provide -onChange, -onFocus, -onBlur and -onSelect parameters to register JavaScript event handlers.

Creating A Password Field

   Named parameter style
   print $query->password_field(-name=>'secret',
				-value=>'starting value',
				-size=>50,
				-maxlength=>80);

   Old style
   print $query->password_field('secret','starting value',50,80);

    Named parameters style
    print $query->filefield(-name=>'uploaded_file',
	                    -default=>'starting value',
	                    -size=>50,
	 		    -maxlength=>80);

    Old style
    print $query->filefield('uploaded_file','starting value',50,80);

• The first parameter (-name) is the required name for the field.
• The optional second parameter (-default) is the starting value for the file name. This field is currently ignored by Netscape 2.0, but there's always hope!
• The optional third parameter (-size) is the size of the field in characters.
• The optional fourth parameter (-maxlength) is the maximum number of characters the field will accomodate.

In order to take full advantage of the file upload facility you must use the new multipart form encoding scheme. You can do this either by calling startform() and specify an encoding type of $CGI::MULTIPART or by using the new start_multipart_form() method. If you don't use multipart encoding, then you'll be able to retreive the name of the file selected by the remote user, but you won't be able to access its contents.

When the form is processed, you can retrieve the entered filename by calling param().

       $filename = $query->param('uploaded_file');

	/path/to/the/file

	C:\PATH\TO\THE\FILE.MSW

	HD 40:Desktop Folder:Sort Through:Reminders

The filename returned is also a file handle. You can read the contents of the file using standard Perl file reading calls:

	# Read a text file and print it out
	while (<$filename>) {
	   print;
        }

        # Copy a binary file to somewhere safe
        open (OUTFILE,">>/usr/local/web/users/feedback");
	while ($bytesread=read($filename,$buffer,1024)) {
	   print OUTFILE $buffer;
        }
       close $filename;

When processing an uploaded file, CGI.pm creates a temporary file on your hard disk and passes you a file handle to that file. After you are finished with the file handle, CGI.pm unlinks (deletes) the temporary file. If you need to you can access the temporary file directly. Its name is stored inside the CGI object's "private" data, and you can access it by passing the file name to the tmpFileName() method:

       $filename = $query->param('uploaded_file');
       $tmpfilename = $query->tmpFileName($filename);

The temporary file will be deleted automatically when your program exits unless you manually rename it. On some operating systems (such as Windows NT), you will need to close the temporary file's filehandle before your program exits. Otherwise the attempt to delete the temporary file will fail.

JavaScripting: Like textfield(), filefield() accepts -onChange, -onFocus, -onBlur and -onSelect parameters to register JavaScript event handlers. Caveats and potential problems in the file upload feature.

Creating A Popup Menu

  Named parameter style
  print $query->popup_menu(-name=>'menu_name',
			    -values=>['eenie','meenie','minie'],
	                    -default=>'meenie',
	                    -labels=>{'eenie'=>'one','meenie'=>'two',
                                      'minie'=>'three'});
  
  Old style
  print $query->popup_menu('menu_name',
                              ['eenie','meenie','minie'],'meenie',
                              {'eenie'=>'one','meenie'=>'two','minie'=>'three'});

• The required first argument (-name) is the menu's name.
• The required second argument (-values) is an array reference containing the list of menu items in the menu. You can pass the method an anonymous array, as shown in the example, or a reference to a named array, such as \@foo
• The optional third parameter (-default) is the name of the default menu choice. If not specified, the first item will be the default. The value of the previous choice will be maintained across queries.
• The optional fourth parameter (-labels) allows you to pass a reference to an associative array containing user-visible labels for one or more of the menu items. You can use this when you want the user to see one menu string, but have the browser return your program a different one. If you don't specify this, the value string will be used instead ("eenie", "meenie" and "minie" in this example).

     $popup_menu_value = $query->param('menu_name');

   Named parameter style
   print $query->scrolling_list(-name=>'list_name',
                                -values=>['eenie','meenie','minie','moe'],
                                -default=>['eenie','moe'],
	                        -size=>5,
	                        -multiple=>'true',
                                -labels=>\%labels);

   Old style
   print $query->scrolling_list('list_name',
                                ['eenie','meenie','minie','moe'],
                                ['eenie','moe'],5,'true',
                                \%labels);

• The first and second arguments (-name, -values)are the list name and values, respectively. As in the popup menu, the second argument should be an array reference.
• The optional third argument (-default)can be either a reference to a list containing the values to be selected by default, or can be a single value to select. If this argument is missing or undefined, then nothing is selected when the list first appears.
• The optional fourth argument (-size) is the display size of the list.
• The optional fifth argument (-multiple) can be set to true to allow multiple simultaneous selections.
• The option sixth argument (-labels) can be used to assign user-visible labels to the list items different from the ones used for the values as above. In this example we assume that an associative array %labels has already been created.

     @selected = $query->param('list_name');

   Named parameter style
   print $query->checkbox_group(-name=>'group_name',
                                -values=>['eenie','meenie','minie','moe'],
                                -default=>['eenie','moe'],
	                        -linebreak=>'true',
	                        -labels=>\%labels);

   Old Style
   print $query->checkbox_group('group_name',
                                ['eenie','meenie','minie','moe'],
                                ['eenie','moe'],'true',\%labels);

   HTML3 Browsers Only
   print $query->checkbox_group(-name=>'group_name',
                                -values=>['eenie','meenie','minie','moe'],
                                -rows=>2,-columns=>2);

• The first and second arguments (-name, -values) are the checkbox name and values, respectively. As in the popup menu, the second argument should be an array reference. These values are used for the user-readable labels printed next to the checkboxes as well as for the values passed to your script in the query string.
• The optional third argument (-default) can be either a reference to a list containing the values to be checked by default, or can be a single value to checked. If this argument is missing or undefined, then nothing is selected when the list first appears.
• The optional fourth argument (-linebreak) can be set to true to place line breaks between the checkboxes so that they appear as a vertical list. Otherwise, they will be strung together on a horizontal line. When the form is procesed, all checked boxes will be returned as a list under the parameter name 'group_name'. The values of the "on" checkboxes can be retrieved with:
• The optional fifth argument (-labels) is a reference to an associative array of checkbox labels. This allows you to use different strings for the user-visible button labels and the values sent to your script. In this example we assume that an associative array %labels has previously been created.
• The optional parameter -nolabels can be used to suppress the printing of labels next to the button. This is useful if you want to capture the button elements individually and use them inside labeled HTML3 tables.
• Browsers that understand HTML3 tables (such as Netscape) can take advantage of the optional parameters -rows, and -columns. These parameters cause checkbox_group() to return an HTML3 compatible table containing the checkbox group formatted with the specified number of rows and columns. You can provide just the -columns parameter if you wish; checkbox_group will calculate the correct number of rows for you.

  To include row and column headings in the returned table, you can use the -rowheaders and -colheaders parameters. Both of these accept a pointer to an array of headings to use. The headings are just decorative. They don't reorganize the interpetation of the checkboxes -- they're still a single named unit.

  When viewed with browsers that don't understand HTML3 tables, the -rows and -columns parameters will leave you with a group of buttons that may be awkwardly formatted but still useable. However, if you add row and/or column headings, the resulting text will be very hard to read.

     @turned_on = $query->param('group_name');

       @h = $query->checkbox_group(-name=>'choice',
                                    -value=>['fee','fie','foe'],
                                    -nolabels=>1);
       create_nice_table(@h);

   Named parameter list
   print $query->checkbox(-name=>'checkbox_name',
			   -checked=>'checked',
		           -value=>'TURNED ON',
		           -label=>'Turn me on');

   Old style
   print $query->checkbox('checkbox_name',1,'TURNED ON','Turn me on');

• The first parameter (-nameis the required name for the checkbox. It will also be used for the user-readable label printed next to the checkbox.
• The optional second parameter (-checkedspecifies that the checkbox is turned on by default. Aliases for this parameter are -selected and -on.
• The optional third parameter (-valuespecifies the value of the checkbox when it is checked. If not provided, the word "on" is assumed.
• The optional fourth parameter (-labelassigns a user-visible label to the button. If not provided, the checkbox's name will be used.

     $turned_on = $query->param('checkbox_name');

   Named parameter style
   print $query->radio_group(-name=>'group_name',
			     -values=>['eenie','meenie','minie'],
                             -default=>'meenie',
			     -linebreak=>'true',
			     -labels=>\%labels);

   Old style
   print $query->radio_group('group_name',['eenie','meenie','minie'],
                                          'meenie','true',\%labels);

   HTML3-compatible browsers only
   print $query->radio_group(-name=>'group_name',
                                -values=>['eenie','meenie','minie','moe'],
	                        -rows=2,-columns=>2);

• The first argument (-nameis the name of the group and is required.
• The second argument (-valuesis the list of values for the radio buttons. The values and the labels that appear on the page are identical. Pass an array reference in the second argument, either using an anonymous array, as shown, or by referencing a named array as in \@foo.
• The optional third parameter (-defaultis the value of the default button to turn on. If not specified, the first item will be the default. Specify some nonexistent value, such as "-" if you don't want any button to be turned on.
• The optional fourth parameter (-linebreakcan be set to 'true' to put line breaks between the buttons, creating a vertical list.
• The optional fifth parameter (-labelsspecifies an associative array containing labels to be printed next to each the button. If not provided the button value will be used instead. This example assumes that the associative array %labels has already been defined.
• The optional parameter -nolabels can be used to suppress the printing of labels next to the button. This is useful if you want to capture the button elements individually and use them inside labeled HTML3 tables.
• Browsers that understand HTML3 tables (such as Netscape) can take advantage of the optional parameters -rows, and -columns. These parameters cause radio_group() to return an HTML3 compatible table containing the radio cluster formatted with the specified number of rows and columns. You can provide just the -columns parameter if you wish; radio_group will calculate the correct number of rows for you.

  To include row and column headings in the returned table, you can use the -rowheader and -colheader parameters. Both of these accept a pointer to an array of headings to use. The headings are just decorative. They don't reorganize the interpetation of the radio buttons -- they're still a single named unit.

  When viewed with browsers that don't understand HTML3 tables, the -rows and -columns parameters will leave you with a group of buttons that may be awkwardly formatted but still useable. However, if you add row and/or column headings, the resulting text will be very hard to read.

       $which_radio_button = $query->param('group_name');

       @h = $query->radio_group(-name=>'choice',
                                 -value=>['fee','fie','foe'],
                                 -nolabels=>1);
       create_nice_table(@h);

JavaScripting: You can provide an -onClick parameter to register some JavaScript code to be performed every time the user clicks on any of the buttons in the group.

Creating A Submit Button

   Named parameter style
   print $query->submit(-name=>'button_name',
		        -value=>'value');

  Old style
  print $query->submit('button_name','value');

• The first argument (-nameis optional. You can give the button a name if you have several submission buttons in your form and you want to distinguish between them.
• The second argument (-valueis also optional. This gives the button a value that will be passed to your script in the query string, and will also appear as the user-visible label.

  You can figure out which of several buttons was pressed by using different values for each one:

      $which_one = $query->param('button_name');
  

• You can use -label as an alias for -value. I always get confused about which of -name and -value changes the user-visible label on the button.

  print $query->reset

  print $query->defaults('button_label')

   Named parameter style
   print $query->hidden(-name=>'hidden_name',
                        -default=>['value1','value2'...]);

   Old style
   print $query->hidden('hidden_name','value1','value2'...);

• The first argument (-name) is required and specifies the name of this field.
• The second and subsequent arguments specify the value for the hidden field. This is a quick and dirty way of passing perl arrays through forms. If you use the named parameter style, you must provide the parameter -default and an array reference here.

As of version 2.0 I have changed the behavior of hidden fields once again. Read this if you use hidden fields.

Hidden fields used to behave differently from all other fields: the provided default values always overrode the "sticky" values. This was the behavior people seemed to expect, however it turns out to make it harder to write state-maintaining forms such as shopping cart programs. Therefore I have made the behavior consistent with other fields.

Just like all the other form elements, the value of a hidden field is "sticky". If you want to replace a hidden field with some other values after the script has been called once you'll have to do it manually before writing out the form element:

     $query->param('hidden_name','new','values','here');
     print $query->hidden('hidden_name');

    $hidden_value = $query->param('hidden_name');
            -or (for values created with arrays)-
    @hidden_values = $query->param('hidden_name');

   Named parameter style
   print $query->image_button(-name=>'button_name',
                              -src=>'/images/NYNY.gif',
                              -align=>'MIDDLE');	

   Old style
   print $query->image_button('button_name','/source/URL','MIDDLE');

• The first argument(-name is required and specifies the name of this field.
• The second argument (-srcspecifies the URL of the image to display. It must be one of the types supported by inline images (e.g. GIF), but can be any local or remote URL.
• The third argument (-alignis anything you might want to use in the ALIGN attribute, such as TOP, BOTTOM, LEFT, RIGHT or MIDDLE. This field is optional.

    $x = $query->param('button_name.x');
    $y = $query->param('button_name.y');

   Named parameter style
   print $query->button(-name=>'button1',
                           -value=>'Click Me',
                           -onClick=>'doButton(this)');	

   Old style
   print $query->image_button('button1','Click Me','doButton(this)');

• The first argument(-name is required and specifies the name of this field.
• The second argument (-value gives the button a value, and will be used as the user-visible label on the button.
• The third argument (-onClick is any valid JavaScript code. It's usually a call to a JavaScript function defined somewhere else (see the start_html() method), but can be any JavaScript you like. Multiple lines are allowed, but you must be careful not to include any double quotes in the JavaScript text.

Controlling HTML Autoescaping

Use

    $query->autoEscape(undef);

    $query->autoEscape('true');

use CGI qw(:standard);

use CGI;
$dinner = $query->param('entree');

use CGI qw(:standard);
$dinner = param('entree');

print $query->start_form,
      "Check here if you're happy: ",
      $query->checkbox(-name=>'happy',-value=>'Y',-checked=>1),
      "
",
      $query->submit,
      $query->end_form;

print start_form,
      "Check here if you're happy: ",
      checkbox(-name=>'happy',-value=>'Y',-checked=>1),
      p,
      submit,
      end_form;

$CGI::Q;

The use CGI statement is used to import method names into the current name space. There is a slight overhead for each name you import, but ordinarily is nothing to worry about. You can import selected method names like this:

   use CGI qw(header start_html end_html);

use CGI qw(:cgi :html2);

:cgi

These are all the tags that support one feature or another of the CGI protocol, including param(), path_info(), cookie(), request_method(), header() and the like.

:form

These are all the form element-generating methods, including start_form(), textfield(), etc.

:html2

These are HTML2-defined shortcuts such as br(), p() and head(). It also includes such things as start_html() and end_html() that aren't exactly HTML2, but are close enough.

:html3

These are a few HTML3 extensions that are in common enough usage to be worth including.

:netscape

These are Netscape extensions not included in the HTML3 category, including frameset(), blink() and center().

:html

These are all the HTML generating shortcuts, comprising the union of html2, html3, and netscape.

:standard

This is the union of html2, form, and :cgi (everything except the HTML3 and Netscape extensions).

:all

This imports all the public methods into your namespace!

use CGI qw(:any :all);
$q=new CGI;
print $q->gradient({speed=>'fast',start=>'red',end=>'blue'});

   my_script.pl keyword1 keyword2 keyword3

   my_script.pl keyword1+keyword2+keyword3

   my_script.pl name1=value1 name2=value2

   my_script.pl name1=value1&name2=value2

   % my_script.pl
   first_name=fred
   last_name=flintstone
   occupation='granite miner'
   ^D

When debugging, you can use quotation marks and the backslash character to escape spaces and other funny characters in exactly the way you would in the shell (which isn't surprising since CGI.pm uses "shellwords.pl" internally). This lets you do this sort of thing:

    my_script.pl "'name 1'='I am a long value'" "'name 2'=two\ words"

   print $query->dump

   <UL>
   <LI>name1
       <UL>
       <LI>value1
       <LI>value2
       </UL>
   <LI>name2
       <UL>
       <LI>value1
       </UL>
   </UL>

   print "<H2>Current Contents:</H2>\n$query\n";

accept()

Return a list of MIME types that the remote browser accepts. If you give this method a single argument corresponding to a MIME type, as in $query->accept('text/html'), it will return a floating point value corresponding to the browser's preference for this type from 0.0 (don't want) to 1.0. Glob types (e.g. text/*) in the browser's accept list are handled correctly.

auth_type()

Return the authorization type, if protection is active. Example "Basic".

raw_cookie()

Returns the "magic cookie" maintained by Netscape 1.1 and higher in a raw state. You'll probably want to use cookie() instead, which gives you a high-level interface to the cookie functions.

path_info()

Returns additional path information from the script URL. E.G. fetching /cgi-bin/your_script/additional/stuff will result in $query->path_info() returning "/additional/stuff"

path_translated()

As per path_info() but returns the additional path information translated into a physical path, e.g. "/usr/local/etc/httpd/htdocs/additional/stuff".

query_string()

Returns a query string suitable for maintaining state.

referer()

Return the URL of the page the browser was viewing prior to fetching your script. Not available for all browsers.

remote_addr()

Return the dotted IP address of the remote host.

remote_ident()

Return the identity-checking information from the remote host. Only available if the remote host has the identd daemon turned on.

remote_host()

Returns either the remote host name or IP address. if the former is unavailable.

remote_user()

Return the name given by the remote user during password authorization.

request_method()

Return the HTTP method used to request your script's URL, usually one of GET, POST, or HEAD.

script_name()

Return the script name as a partial URL, for self-refering scripts.

server_name()

Return the name of the WWW server the script is running under.

server_port()

Return the communications port the server is using.

user_agent()

Returns the identity of the remote user's browser software, e.g. "Mozilla/1.1N (Macintosh; I; 68K)"

user_name()

Attempts to obtain the remote user's name, using a variety of environment variables. This only works with older browsers such as Mosaic. Netscape does not reliably report the user name!

A cookie is a name=value pair much like the named parameters in a CGI query string. CGI scripts create one or more cookies and send them to the browser in the HTTP header. The browser maintains a list of cookies that belong to a particular Web server, and returns them to the CGI script during subsequent interactions.

In addition to the required name=value pair, each cookie has several optional attributes:

an expiration time

This is a time/date string (in a special GMT format) that indicates when a cookie expires. The cookie will be saved and returned to your script until this expiration date is reached if the user exits Netscape and restarts it. If an expiration date isn't specified, the cookie will remain active until the user quits Netscape.

a domain

This is a partial or complete domain name for which the cookie is valid. The browser will return the cookie to any host that matches the partial domain name. For example, if you specify a domain name of ".capricorn.com", then Netscape will return the cookie to Web servers running on any of the machines "www.capricorn.com", "www2.capricorn.com", "feckless.capricorn.com", etc. Domain names must contain at least two periods to prevent attempts to match on top level domains like ".edu". If no domain is specified, then the browser will only return the cookie to servers on the host the cookie originated from.

a path

If you provide a cookie path attribute, the browser will check it against your script's URL before returning the cookie. For example, if you specify the path "/cgi-bin", then the cookie will be returned to each of the scripts "/cgi-bin/tally.pl", "/cgi-bin/order.pl", and "/cgi-bin/customer_service/complain.pl", but not to the script "/cgi-private/site_admin.pl". By default, path is set to "/", which causes the cookie to be sent to any CGI script on your site.

a "secure" flag

If the "secure" attribute is set, the cookie will only be sent to your script if the CGI request is occurring on a secure channel, such as SSL.

    $cookie = $query->cookie(-name=>'sessionID',
			     -value=>'xyzzy',
			     -expires=>'+1h',
			     -path=>'/cgi-bin/database',
			     -domain=>'.capricorn.org',
			     -secure=>1);
    print $query->header(-cookie=>$cookie);

-name

The name of the cookie (required). This can be any string at all. Although Netscape limits its cookie names to non-whitespace alphanumeric characters, CGI.pm removes this restriction by escaping and unescaping cookies behind the scenes.

-value

The value of the cookie. This can be any scalar value, array reference, or even associative array reference. For example, you can store an entire associative array into a cookie this way:

	$cookie=$query->cookie(-name=>'family information',
                               -value=>\%childrens_ages);

-path

The optional partial path for which this cookie will be valid, as described above.

-domain

The optional partial domain for which this cookie will be valid, as described above.

-expires

The optional expiration date for this cookie. The format is as described in the section on the B method:

	"+1h"  one hour from now
      

-secure

If set to true, this cookie will only be used within a secure SSL session.

	print $query->header(-cookie=>$my_cookie);

	$cookie1 = $query->cookie(-name=>'riddle_name',
                                  -value=>"The Sphynx's Question");
        $cookie2 = $query->cookie(-name=>'answers',
                                  -value=>\%answers);
        print $query->header(-cookie=>[$cookie1,$cookie2]);

	use CGI;
	$query = new CGI;
	%answers = $query->cookie('answers');
	# $query->cookie(-name=>'answers') works too!

The cookie and CGI namespaces are separate. If you have a parameter named 'answers' and a cookie named 'answers', the values retrieved by param() and cookie() are independent of each other. However, it's simple to turn a CGI parameter into a cookie, and vice-versa:

   # turn a CGI parameter into a cookie
   $c=$q->cookie(-name=>'answers',-value=>[$q->param('answers')]);
   # vice-versa
   $q->param(-name=>'answers',-value=>[$q->cookie('answers')]);

See the cookie.cgi example script for some ideas on how to use cookies effectively.

NOTE: There appear to be some (undocumented) restrictions on Netscape cookies. In Netscape 2.01, at least, I haven't been able to set more than three cookies at a time. There may also be limits on the length of cookies. If you need to store a lot of information, it's probably better to create a unique session ID, store it in a cookie, and use the session ID to locate an external file/database saved on the server's side of the connection.

Table of contents

1. You can direct the output of a script into a new window or into a preexisting named frame by providing the name of the frame as a -target argument in the header method. For example, the following code will pop up a new Netscape window and display the script's output:

         $query = new CGI;
         print $query->header(-target=>'_blank');
         

2. You can provide the name of a new or preexisting frame in the startform() and start_multipart_form() methods using the -target parameter. When the form is submitted, the output will be redirected to the indicated frame:

         print $query->start_form(-target=>'result_frame');
         

The examples directory contains a script called popup.cgi that demonstrates a simple popup window. frameset.cgi provides a skeleton script for creating side-by-side query/result frame sets.

You'll need to know JavaScript in order to use it. The Netscape JavaScript manual contains a good tutorial and reference guide to the JavaScript programming language.

The usual way to use JavaScript is to define a set of functions in a <SCRIPT> block inside the HTML header and then to register event handlers in the various elements of the page. Events include such things as the mouse passing over a form element, a button being clicked, the contents of a text field changing, or a form being submitted. When an event occurs that involves an element that has registered an event handler, its associated JavaScript code gets called.

The elements that can register event handlers include the <BODY> of an HTML document, hypertext links, all the various elements of a fill-out form, and the form itself. There are a large number of events, and each applies only to the elements for which it is relevant:

onLoad

The browser is loading the current document. Valid in:

• The HTML <BODY> section only.

onUnload

The browser is closing the current page or frame. Valid for:

• The HTML <BODY> section only.

onSubmit

The user has pressed the submit button of a form. This event happens just before the form is submitted, and your function can return a value of false in order to abort the submission. Valid for:

• Forms only.

onClick

The mouse has clicked on an item in a fill-out form. Valid for:

• Buttons (including submit, reset, and image buttons)
• Checkboxes
• Radio buttons

onChange

The user has changed the contents of a field. Valid for:

• Text fields
• Text areas
• Password fields
• File fields
• Popup Menus
• Scrolling lists

onFocus

The user has selected a field to work with. Valid for:

• Text fields
• Text areas
• Password fields
• File fields
• Popup Menus
• Scrolling lists

onBlur

The user has deselected a field (gone to work somewhere else). Valid for:

• Text fields
• Text areas
• Password fields
• File fields
• Popup Menus
• Scrolling lists

onSelect

The user has changed the part of a text field that is selected. Valid for:

• Text fields
• Text areas
• Password fields
• File fields

   print $q->textfield(-name=>'age',-onChange=>"validateAge(this)");

Similarly, you can create a form that checks itself over for consistency and alerts the user if some essential value is missing by creating it this way:

   print $q->startform(-onSubmit=>"validateMe(this)");

Table of contents

Servers use a variety of conventions for designating CGI scripts as NPH. Many Unix servers look at the beginning of the script's name for the prefix "nph-". The Macintosh WebSTAR server and Microsoft's Internet Information Server, in contrast, try to decide whether a program is an NPH script by examining the first line of script output.

CGI.pm supports NPH scripts with a special NPH mode. When in this mode, CGI.pm will output the necessary extra header information when the header() and redirect() methods are called.

Important: If you use the Microsoft Internet Information Server, you must designate your script as an NPH script. Otherwise many of CGI.pm's features, such as redirection and the ability to output non-HTML files, will fail.

There are a number of ways to put CGI.pm into NPH mode:

In the use statement:

Simply add ":nph" to the list of symbols to be imported into your script:

      use CGI qw(:standard :nph)
      

By calling the nph() method:

Call nph() with a non-zero parameter at any point after using CGI.pm in your program.

      CGI->nph(1)
      

By using -nph parameters in the header() and redirect() statements:

      print $q->header(-nph=>1);
      

A Script that Saves Some Information to a File and Restores It

#!/usr/local/bin/perl

use CGI;
$query = new CGI;

print $query->header;
print $query->start_html("Save and Restore Example");
print "<H1>Save and Restore Example</H1>\n";

# Here's where we take action on the previous request
&save_parameters($query)              if $query->param('action') eq 'save';
$query = &restore_parameters($query)  if $query->param('action') eq 'restore';

# Here's where we create the form
print $query->startform;
print "Popup 1: ",$query->popup_menu('popup1',['eenie','meenie','minie']),"\n";
print "Popup 2: ",$query->popup_menu('popup2',['et','lux','perpetua']),"\n";
print "<P>";
print "Save/restore state from file: ",$query->textfield('savefile','state.sav'),"\n";
print "<P>";
print $query->submit('action','save'),$query->submit('action','restore');
print $query->submit('action','usual query');
print $query->endform;

# Here we print out a bit at the end
print $query->end_html;

sub save_parameters {
    local($query) = @_;
    local($filename) = &clean_name($query->param('savefile'));
    if (open(FILE,">$filename")) {
	$query->save(FILE);
	close FILE;
	print "<STRONG>State has been saved to file $filename</STRONG>\n";
    } else {
	print "<STRONG>Error:</STRONG> couldn't write to file $filename: $!\n";
    }
}

sub restore_parameters {
    local($query) = @_;
    local($filename) = &clean_name($query->param('savefile'));
    if (open(FILE,$filename)) {
	$query = new CGI(FILE);  # Throw out the old query, replace it with a new one
	close FILE;
	print "<STRONG>State has been restored from file $filename</STRONG>\n";
    } else {
	print "<STRONG>Error:</STRONG> couldn't restore file $filename: $!\n";
    }
    return $query;
}


# Very important subroutine -- get rid of all the naughty
# metacharacters from the file name. If there are, we
# complain bitterly and die.
sub clean_name {
   local($name) = @_;
   unless ($name=~/^[\w\._-]+$/) {
      print "<STRONG>$name has naughty characters.  Only ";
      print "alphanumerics are allowed.  You can't use absolute names.</STRONG>";
      die "Attempt to use naughty characters";
   }
   return $name;
}

http://www.genome.wi.mit.edu/genome_software/other/boulder.html

A Script that Uses Self-Referencing URLs to Jump to Internal Links

Many people have experienced problems with internal links on pages that have forms. Jumping around within the document causes the state of the form to be reset. A partial solution is to use the self_url() method to generate a link that preserves state information. This script illustrates how this works.

#!/usr/local/bin/perl

use CGI;
$query = new CGI;

# We generate a regular HTML file containing a very long list
# and a popup menu that does nothing except to show that we
# don't lose the state information.
print $query->header;
print $query->start_html("Internal Links Example");
print "<H1>Internal Links Example</H1>\n";

print "<A NAME=\"start\"></A>\n"; # an anchor point at the top

# pick a default starting value;
$query->param('amenu','FOO1') unless $query->param('amenu');

print $query->startform;
print $query->popup_menu('amenu',[('FOO1'..'FOO9')]);
print $query->submit,$query->endform;

# We create a long boring list for the purposes of illustration.
$myself = $query->self_url;
print "<OL>\n";
for (1..100) {
    print qq{<LI>List item #$_<A HREF="$myself#start">Jump to top</A>\n};
}
print "</OL>\n";

print $query->end_html;

Multiple forms on the same page

There is, however, a problem with maintaining the states of multiple forms. Because the browser only sends your script the parameters from the form in which the submit button was pressed, the state of all the other forms will be lost. One way to get around this, suggested in this example, is to use hidden fields to pass as much information as possible regardless of which form the user submits.

#!/usr/local/bin/perl
use CGI;

$query=new CGI;
print $query->header;
print $query->start_html('Multiple forms');
print "<H1>Multiple forms</H1>\n";

# form 1
print "<HR>\n";
print $query->startform;
print $query->textfield('text1'),$query->submit('submit1');
print $query->hidden('text2');  # pass information from the other form
print $query->endform;
print "<HR>\n";

# form 2
print $query->startform;
print $query->textfield('text2'),$query->submit('submit2');
print $query->hidden('text1');  # pass information from the other form
print $query->endform;
print "<HR>\n";
print $query->end_html;

Table of contents

Using CGI.pm with mod_perl and FastCGI

FastCGI

FastCGI modules are available for the Apache and NCSA servers as well as for OpenMarket's own server. In order to use FastCGI with Perl you have to run a specially-modified version of the Perl interpreter. Precompiled Binaries and a patch kit are all available on OpenMarket's FastCGI web site.

To use FastCGI with CGI.pm, change your scripts as follows:

Old Script

#!/usr/local/bin/perl
use CGI qw(:standard);
print header,
      start_html("CGI Script"),
      h1("CGI Script"),
      "Not much to see here",
      hr,
      address(a({href=>'/'},"home page"),  
      end_html;

New Script

#!/usr/local/fcgi/bin/perl
use Fast::CGI qw(:standard);

# Do time-consuming initialization up here.
while (new CGI::Fast) {
   print header,
      start_html("CGI Script"),
      h1("CGI Script"),
      "Not much to see here",
      hr,
      address(a({href=>'/'},"home page"),  
      end_html;
}

mod_perl

1. Server launches a new Perl interpreter every time it needs to interpret a Perl script. This speeds CGI scripts somewhat because there's no overhead for launching a new Perl process.
2. A "fast" mode in which the server launches your script at initialization time. You can load all your favorite modules at initialization time, greatly speeding things up.

#!/usr/local/bin/perl
use CGI qw(:standard);
print header,
      start_html("CGI Script"),
      h1("CGI Script"),
      "Not much to see here",
      hr,
      address(a({href=>'/'},"home page"),  
      end_html;

New Script

#!/usr/bin/perl
use Apache::CGI qw(:standard);

# Do time-consuming initialization up here.
put header,
    start_html("CGI Script"),
    h1("CGI Script"),
    "Not much to see here",
    hr,
    address(a({href=>'/'},"home page"),  
    end_html;
}

I haven't yet experimented with the "fast" mode. There's a bit of work on the programmer's interface that needs doing.

Table of contents

Migrating from cgi-lib.pl

When you call ReadParse(), CGI.pm creates an associative array named %in that contains the named CGI parameters. Multi-valued parameters are separated by "\0" characters in exactly the same way cgi-lib.pl does it. To port an old script to CGI.pm, you have to make just two changes:

Old Script

    require "cgi-lib.pl";
    &ReadParse;
    print "The price of your purchase is $in{price}.\n";

New Script

    use CGI qw(:cgi-lib);
    &ReadParse;
    print "The price of your purchase is $in{price}.\n";

   ReadParse(*Q);
   @partners = split("\0",$Q{'golf_partners'});

The associative array created by CGI::ReadParse() contains a special key 'CGI', which returns the CGI query object itself:

    ReadParse;
    $q = $in{CGI};
    print $q->textfield(-name=>'wow',
                        -value=>'does this really work?');

This allows you to add the more interesting features of CGI.pm to your old scripts without rewriting them completely. As an added benefit, the %in variable is actually tie()'d to the CGI object. Changing the CGI object using param() will dynamically change %in, and vice-versa.

cgi-lib.pl's @in and $in variables are not supported. In addition, the extended version of ReadParse() that allows you to spool uploaded files to disk is not available. You are strongly encouraged to use CGI.pm's file upload interface instead.

See cgi-lib_porting.html for more details on porting cgi-lib.pl scripts to CGI.pm.

Using the File Upload Feature

Known problems include:

1. Large file uploads may fail when using SSL on the Netscape servers (all platforms). This is a documented bug in the Netscape implementation of SSL and not a problem with CGI.pm.
2. If you try to upload a directory path with Unix Netscape, the browser will hang until you hit the "stop" button. I haven't tried to figure this one out since I think it's dumb of Netscape to allow this to happen at all.
3. If you create the CGI object in one package (e.g. "main") and then obtain the filehandle in a different package (e.g. "foo"), the filehandle will be accessible through "main" but not "foo". In order to use the filehandle, try the following contortion:

         $file = $query->param('file to upload');
         $file = "main::$file";
             ...
         

   I haven't found a way to determine the correct caller in this situation. I might add a readFile() method to CGI if this problem bothers enough people.

Frequent Problems

You can't retrieve the name of the uploaded file using the param() method

When you accidentally try to upload a directory name, the browser hangs

You can read the name of the uploaded file, but can't retrieve the data

If you're on a non-Unix system you may need to modify CGI.pm to point at a suitable temporary directory. This directory must be writable by the user ID under which the server runs (usually "nobody") and must have sufficient capacity to handle large file uploads. Open up CGI.pm, and find the line:

      package TempFile;
      foreach ('/usr/tmp','/tmp') {
         do {$TMPDIRECTORY = $_; last} if -w $_;
      }

On Windows Systems, the temporary file is never deleted, but hangs around in \temp, taking up space.

When you press the "back" button, the same page is loaded, not the previous one.

The workaround for this is to use additional path information to trick Netscape into thinking that the form and the response have different URLs. I recommend giving each form a sequence number and bumping the sequence up by one each time the form is accessed:

   my($s) = $query->path_info=~/(\d+)/; # get sequence
   $s++;                                #bump it up
   # Trick Netscape into thinking it's loading a new script:
   print $q->start_multipart_form(-action=>$q->script_name . '/$s');

You can't find the temporary file that CGI.pm creates

Using CGI.pm on non-Unix Platforms

There are a number of differences in file name and text processing conventions on different platforms. By default, CGI.pm is set up to work properly on a Unix (or Linux) system. To run it in other operating systems find the section of code near the top that looks like this:

   # CHANGE THIS VARIABLE FOR YOUR OPERATING SYSTEM
   $OS = 'UNIX';
   # $OS = 'MACINTOSH';
   # $OS = 'WINDOWS';
   # $OS = 'NT';
   # $OS = 'VMS';

Other notes follow:

Windows NT

http://www.perl.hip.com/

For best results with the Microsoft IIS server, put CGI.pm into NPH mode. This is because IIS assumes that a script will either produce all the required HTTP headers, or will produce none of them. Without NPH mode, certain scripts, such as those using redirect() will mysteriously fail.

WebSite uses a slightly different cgi-bin directory structure than the standard. For this server, place the scripts in the cgi-shl directory. CGI.pm appears to work correctly in both the Windows95 and WindowsNT versions of WebSite.

Old Netscape Communications Server technical notes recommended placing perl.exe in cgi-bin. This a very bad idea because it opens up a gaping security hole. Put a C .exe wrapper around the perl script until such time as Netscape recognizes NT file manager associations, or provides a Perl-compatible DLL library for its servers.

If you find that binary files get slightly larger when uploaded but that text files remain the same, then binary made is not correctly activated. Be sure to set the $OS variable to 'NT' or 'WINDOWS'. If you continue to have problems, make sure you're calling binmode() on the filehandle that you use to write the uploaded file to disk.

VMS

Macintosh

ftp://err.ethz.ch/pub/neeri/MacPerl/

1. The perl compiler will object to the use of -values in named parameters. Put single quotes around this parameter ('-values') or use the singular form ('-value') instead.
2. File upload isn't working in my hands (Perl goes into an endless loop). Other people have gotten it to work.

The current version of CGI.pm can be found at:

  
http://www-genome.wi.mit.edu/ftp/pub/software/WWW/

You are encouraged to look at these other Web-related modules:

HTML.pm

A module that simplifies the creation of HTML documents programatically.

CGI::Base,CGI::Form,CGI::MiniSrv,CGI::Request and CGI::URI::URL

Modules for parsing script input, manipulating URLs, creating forms and even launching a miniature Web server.

libwww-perl

Modules for fetching Web resources from within Perl, writing Web robots, and much more.

GD.html

A module for creating GIF images on the fly, using Tom Boutell's gd graphics library.

qd.pl

A library for creating Macintosh PICT files on the fly (which can be converted to GIF or JPEG using NetPBM).

For a collection of CGI scripts of various levels of complexity, see the companion pages for my book How to Set Up and Maintain a World Wide Web Site

Bug Reports

Up to table of contents

Revision History

Version 2.29

1. Fixed cookie bugs
2. Fixed problems that cropped up when useNamedParameters was set to 1.
3. Prevent CGI::Carp::fatalsToBrowser() from crapping out when encountering a die() within an eval().
4. Fixed problems with filehandle initializers.

Version 2.28

1. Added support for NPH scripts; also fixes problems with Microsoft IIS.
2. Fixed a problem with checkbox() values not being correctly saved and restored.
3. Fixed a bug in which CGI objects created with empty string initializers took on default values from earlier CGI objects.
4. Documentation fixes.

Version 2.27

1. Small but important bug fix: the automatic capitalization of tag attributes was accidentally capitalizing the VALUES as well as the ATTRIBUTE names (oops).

Version 2.26

1. Changed behavior of scrolling_list(), checkbox() and checkbox_group() methods so that defaults are honored correctly. The "fix" causes endform() to generate additional <INPUT TYPE="HIDDEN"> tags -- don't be surpised.
2. Fixed bug involving the detection of the SSL protocol.
3. Fixed documentation error in position of the -meta argument in start_html().
4. HTML shortcuts now generate tags in ALL UPPERCASE.
5. start_html() now generates correct SGML header:

         <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
         

6. CGI::Carp no longer fails "use strict refs" pragma.

Version 2.25

1. Fixed bug that caused bad redirection on destination URLs with arguments.
2. Fixed bug involving use_named_parameters() followed by start_multipart_form()
3. Fixed bug that caused incorrect determination of binmode for Macintosh.
4. Spelling fixes on documentation.

Version 2.24

1. Fixed bug that caused generation of lousy HTML for some form elements
2. Fixed uploading bug in Windows NT
3. Some code cleanup (not enough)

Version 2.23

1. Fixed an obscure bug that caused scripts to fail mysteriously.
2. Fixed auto-caching bug.
3. Fixed bug that prevented HTML shortcuts from passing taint checks.
4. Fixed some -w warning problems.

Version 2.22

1. New CGI::Fast module for use with FastCGI protocol. See pod documentation for details.
2. Fixed problems with inheritance and autoloading.
3. Added TR() (<tr>) and PARAM() (<param>) methods to list of exported HTML tag-generating functions.
4. Moved all CGI-related I/O to a bottleneck method so that this can be overridden more easily in mod_perl (thanks to Doug MacEachern).
5. put() method as substitute for print() for use in mod_perl.
6. Fixed crash in tmpFileName() method.
7. Added tmpFileName(), startform() and endform() to export list.
8. Fixed problems with attributes in HTML shortcuts.
9. Functions that don't actually need access to the CGI object now no longer generate a default one. May speed things up slightly.
10. Aesthetic improvements in generated HTML.
11. New examples.

Version 2.21

1. Added the -meta argument to start_html().
2. Fixed hidden fields (again).
3. Radio_group() and checkbox_group() now return an appropriate scalar value when called in a scalar context, rather than returning a numeric value!
4. Cleaned up the formatting of form elements to avoid unesthetic extra spaces within the attributes.
5. HTML elements now correctly include the closing tag when parameters are present but null: em('')
6. Added password_field() to the export list.

Version 2.20

1. Dumped the SelfLoader because of problems with running with taint checks and rolled my own. Performance is now significantly improved.
2. Added HTML shortcuts.
3. import() now adheres to the Perl module conventions, allowing CGI.pm to import any or all method names into the user's name space.
4. Added the ability to initialize CGI objects from strings and associative arrays.
5. Made it possible to initialize CGI objects with filehandle references rather than filehandle strings.
6. Added the delete_all() and append() methods.
7. CGI objects correctly initialize from filehandles on NT/95 systems now.
8. Fixed the problem with binary file uploads on NT/95 systems.
9. Fixed bug in redirect().
10. Added '-Window-target' parameter to redirect().
11. Fixed import_names() so that parameter names containing funny characters work.
12. Broke the unfortunate connection between cookie and CGI parameter name space.
13. Fixed problems with hidden fields whose values are 0.
14. Cleaned up the documentation somewhat.

Version 2.19

1. Added cookie() support routines.
2. Added -expires parameter to header().
3. Added cgi-lib.pl compatability mode.
4. Made the module more configurable for different operating systems.
5. Fixed a dumb bug in JavaScript button() method.

Version 2.18

1. Fixed a bug that corrects a hang that occurs on some platforms when processing file uploads. Unfortunately this disables the check for bad Netscape uploads.
2. Fixed bizarre problem involving the inability to process uploaded files that begin with a non alphabetic character in the file name.
3. Fixed a bug in the hidden fields involving the -override directive being ignored when scalar defaults were passed.
4. Added documentation on how to disable the SelfLoader features.

Version 2.17

1. Added support for the SelfLoader module.
2. Added oodles of JavaScript support routines.
3. Fixed bad bug in query_string() method that caused some parameters to be silently dropped.
4. Robustified file upload code to handle premature termination by the client.
5. Exported temporary file names on file upload.
6. Removed spurious "uninitialized variable" warnings that appeared when running under 5.002.
7. Added the Carp.pm library to the standard distribution.
8. Fixed a number of errors in this documentation, and probably added a few more.
9. Checkbox_group() and radio_group() now return the buttons as arrays, so that you can incorporate the individual buttons into specialized tables.
10. Added the '-nolabels' option to checkbox_group() and radio_group(). Probably should be added to all the other HTML-generating routines.
11. Added the url() method to recover the URL without the entire query string appended.
12. Added request_method() to list of environment variables available.
13. Would you believe it? Fixed hidden fields again!

Version 2.16

1. Fixed hidden fields yet again.
2. Fixed subtle problems in the file upload method that caused intermittent failures (thanks to Keven Hendrick for this one).
3. Made file upload more robust in the face of bizarre behavior by the Macintosh and Windows Netscape clients.
4. Moved the POD documentation to the bottom of the module at the request of Stephen Dahmen.
5. Added the -xbase parameter to the start_html() method, also at the request of Stephen Dahmen.
6. Added JavaScript form buttons at Stephen's request. I'm not sure how to use this Netscape extension correctly, however, so for now the form() method is in the module as an undocumented feature. Use at your own risk!

Version 2.15

1. Added the -override parameter to all field-generating methods.
2. Documented the user_name() and remote_user() methods.
3. Fixed bugs that prevented empty strings from being recognized as valid textfield contents.
4. Documented the use of framesets and added a frameset example.

Version 2.14

Version 2.13

1. Fixed a bug that interfered with the value "0" being entered into text fields.

Version 2.01

1. Added -rows and -columns to the radio and checkbox groups. No doubt this will cause much grief because it seems to promise a level of meta-organization that it doesn't actually provide.
2. Fixed a bug in the redirect() method -- it was not truly HTTP/1.0 compliant.

Version 2.0

1. Support for named parameter style method calls. This turns out to be a big win for extending CGI.pm when Netscape adds new HTML "features".
2. Changed behavior of hidden fields back to the correct "sticky" behavior. This is going to break some programs, but it is for the best in the long run.
3. Netscape 2.0b2 broke the file upload feature. CGI.pm now handles both 2.0b1 and 2.0b2-style uploading. It will probably break again in 2.0b3.
4. There were still problems with library being unable to distinguish between a form being loaded for the first time, and a subsequent loading with all fields blank. We now forcibly create a default name for the Submit button (if not provided) so that there's always at least one parameter.
5. More workarounds to prevent annoying spurious warning messages when run under the -w switch. -w is seriously broken in perl 5.001!

Version 1.57

1. Support for the Netscape 2.0 "File upload" field.
2. The handling of defaults for selected items in scrolling lists and multiple checkboxes is now consistent.

Version 1.56

1. Created true "pod" documentation for the module.
2. Cleaned up the code to avoid many of the spurious "use of uninitialized variable" warnings when running with the -w switch.
3. Added the autoEscape() method.
4. Added string interpolation of the CGI object.
5. Added the ability to pass additional parameters to the <BODY> tag.
6. Added the ability to specify the status code in the HTTP header.

Bug fixes in version 1.55

1. Every time self_url() was called, the parameter list would grow. This was a bad "feature".
2. Documented the fact that you can pass "-" to radio_group() in order to prevent any button from being highlighted by default.

Bug fixes in version 1.54

1. The user_agent() method is now documented;
2. A potential security hole in import() is now plugged.
3. Changed name of import() to import_names() for compatability with CGI:: modules.

Bug fixes in version 1.53

1. Fixed several typos in the code that were causing the following subroutines to fail in some circumstances
   1. checkbox()
   2. hidden()
2. No features added

New features added in version 1.52

1. Added backslashing, quotation marks, and other shell-style escape sequences to the parameters passed in during debugging off-line.
2. Changed the way that the hidden() method works so that the default value always overrides the current one.
3. Improved the handling of sticky values in forms. It's now less likely that sticky values will get stuck.
4. If you call server_name(), script_name() and several other methods when running offline, the methods now create "dummy" values to work with.

Bugs fixed in version 1.51

1. param() when called without arguments was returning an array of length 1 even when there were no parameters to be had. Bad bug! Bad!
2. The HTML code generated would break if input fields contained the forbidden characters ">< or &. You can now use these characters freely.

New features added in version 1.50

1. import() method allows all the parameters to be imported into a namespace in one fell swoop.
2. Parameters are now returned in the same order in which they were defined.

Bugs fixed in version 1.45

1. delete() method didn't work correctly. This is now fixed.
2. reset() method didn't allow you to set the name of the button. Fixed.

Bugs fixed in version 1.44

1. self_url() didn't include the path information. This is now fixed.

New features added in version 1.43

1. Added the delete() method.

New features added in version 1.42

1. The image_button() method to create clickable images.
2. A few bug fixes involving forms embedded in <PRE> blocks.

New features added in version 1.4

1. New header shortcut methods
   • redirect() to create HTTP redirection messages.
   • start_html() to create the HTML title, complete with the recommended <LINK> tag that no one ever remembers to include.
   • end_html() for completeness' sake.
2. A new save() method that allows you to write out the state of an script to a file or pipe.
3. An improved version of the new() method that allows you to restore the state of a script from a file or pipe. With (2) this gives you dump and restore capabilities! (Wow, you can put a "121,931 customers served" banner at the bottom of your pages!)
4. A self_url() method that allows you to create state-maintaining hypertext links. In addition to allowing you to maintain the state of your scripts between invocations, this lets you work around a problem that some browsers have when jumping to internal links in a document that contains a form -- the form information gets lost.
5. The user-visible labels in checkboxes, radio buttons, popup menus and scrolling lists have now been decoupled from the values sent to your CGI script. Your script can know a checkbox by the name of "cb1" while the user knows it by a more descriptive name. I've also added some parameters that were missing from the text fields, such as MAXLENGTH.
6. A whole bunch of methods have been added to get at environment variables involved in user verification and other obscure features.

Bug fixes

1. The problems with the hidden fields have (I hope at last) been fixed.
2. You can create multiple query objects and they will all be initialized correctly. This simplifies the creation of multiple forms on one page.
3. The URL unescaping code works correctly now.

Last modified: Mon Dec 9 14:38:39 EST 1996