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use CGI; # the rest is too complicated for a synopsis; keep reading
The current version of CGI.pm is available at
http://www.genome.wi.mit.edu/ftp/pub/software/WWW/cgi_docs.html ftp://ftp-genome.wi.mit.edu/pub/software/WWW/
To install this package, just change to the directory in which this file is found and type the following:
perl Makefile.PL
make
make install
This will copy CGI.pm to your perl library directory for use by all perl scripts. You probably must be root to do this. Now you can load the CGI routines in your Perl scripts with the line:
use CGI;
If you don't have sufficient privileges to install CGI.pm in the Perl library directory, you can put CGI.pm into some convenient spot, such as your home directory, or in cgi-bin itself and prefix all Perl scripts that call it with something along the lines of the following preamble:
use lib '/home/davis/lib';
use CGI;
If you are using a version of perl earlier than 5.002 (such as NT perl), use this instead:
BEGIN {
unshift(@INC,'/home/davis/lib');
}
use CGI;
The CGI distribution also comes with a cute module called Carp. It redefines the die(), warn(),
confess() and croak() error routines so that they
write nicely formatted error messages into the server's error log (or to
the output stream of your choice). This avoids long hours of groping
through the error and access logs, trying to figure out which CGI script is
generating error messages. If you choose, you can even have fatal error
messages echoed to the browser to avoid the annoying and uninformative
``Server Error'' message.
$query = new CGI;
This will parse the input (from both POST and GET methods) and store it into a perl5 object called $query.
$query = new CGI(INPUTFILE);
If you provide a file handle to the new() method, it will read
parameters from the file (or STDIN, or whatever). The file can be in any of
the forms describing below under debugging (i.e. a series of newline
delimited TAG=VALUE pairs will work). Conveniently, this type of file is
created by the save() method (see below). Multiple records can
be saved and restored.
Perl purists will be pleased to know that this syntax accepts references to file handles, or even references to filehandle globs, which is the ``official'' way to pass a filehandle:
$query = new CGI(\*STDIN);
You can also initialize the query object from an associative array reference:
$query = new CGI( {'dinosaur'=>'barney',
'song'=>'I love you',
'friends'=>[qw/Jessica George Nancy/]}
);
or from a properly formatted, URL-escaped query string:
$query = new CGI('dinosaur=barney&color=purple');
To create an empty query, initialize it from an empty string or hash:
$empty_query = new CGI("");
-or-
$empty_query = new CGI({});
@keywords = $query->keywords
If the script was invoked as the result of an <ISINDEX> search, the
parsed keywords can be obtained as an array using the
keywords() method.
@names = $query->param
If the script was invoked with a parameter list (e.g.
``name1=value1&name2=value2&name3=value3''), the
param() method will return the parameter names as a list. If
the script was invoked as an <ISINDEX> script, there will be a single
parameter named 'keywords'.
NOTE: As of version 1.5, the array of parameter names returned will be in the same order as they were submitted by the browser. Usually this order is the same as the order in which the parameters are defined in the form (however, this isn't part of the spec, and so isn't guaranteed).
@values = $query->param('foo');
-or-
$value = $query->param('foo');
Pass the param() method a single argument to fetch the value
of the named parameter. If the parameter is multivalued (e.g. from multiple
selections in a scrolling list), you can ask to receive an array. Otherwise
the method will return a single value.
$query->param('foo','an','array','of','values');
This sets the value for the named parameter 'foo' to an array of values. This is one way to change the value of a field AFTER the script has been invoked once before. (Another way is with the -override parameter accepted by all methods that generate form elements.)
param() also recognizes a named parameter style of calling
described in more detail later:
$query->param(-name=>'foo',-values=>['an','array','of','values']);
-or-
$query->param(-name=>'foo',-value=>'the value');
$query->append(-name=>;'foo',-values=>['yet','more','values']);
This adds a value or list of values to the named parameter. The values are appended to the end of the parameter if it already exists. Otherwise the parameter is created. Note that this method only recognizes the named argument calling syntax.
$query->import_names('R');
This creates a series of variables in the 'R' namespace. For example, $R::foo, @R:foo. For keyword lists, a variable @R::keywords will appear. If no namespace is given, this method will assume 'Q'. WARNING: don't import anything into 'main'; this is a major security risk!!!!
In older versions, this method was called import(). As of version 2.20, this name has been removed completely to avoid conflict with the built-in Perl module import operator.
$query->delete('foo');
This completely clears a parameter. It sometimes useful for resetting parameters that you don't want passed down between script invocations.
This clears the CGI object completely. It might be useful to ensure that all the defaults are taken when you create a fill-out form.
$query->save(FILEHANDLE)
This will write the current state of the form to the provided filehandle.
You can read it back in by providing a filehandle to the new()
method. Note that the filehandle can be a file, a pipe, or whatever!
The format of the saved file is:
NAME1=VALUE1
NAME1=VALUE1'
NAME2=VALUE2
NAME3=VALUE3
=
Both name and value are URL escaped. Multi-valued CGI parameters are represented as repeated names. A session record is delimited by a single = symbol. You can write out multiple records and read them back in with several calls to new. You can do this across several sessions by opening the file in append mode, allowing you to create primitive guest books, or to keep a history of users' queries. Here's a short example of creating multiple session records:
use CGI;
open (OUT,">>test.out") || die;
$records = 5;
foreach (0..$records) {
my $q = new CGI;
$q->param(-name=>'counter',-value=>$_);
$q->save(OUT);
}
close OUT;
# reopen for reading
open (IN,"test.out") || die;
while (!eof(IN)) {
my $q = new CGI(IN);
print $q->param('counter'),"\n";
}
The file format used for save/restore is identical to that used by the Whitehead Genome Center's data exchange format ``Boulderio'', and can be manipulated and even databased using Boulderio utilities. See http://www.genome.wi.mit.edu/genome_software/other/boulder.html
for further details.
$myself = $query->self_url;
print "<A HREF=$myself>I'm talking to myself.</A>";
self_url() will return a URL, that, when selected, will
reinvoke this script with all its state information intact. This is most
useful when you want to jump around within the document using internal
anchors but you don't want to disrupt the current contents of the
form(s). Something like this will do the trick.
$myself = $query->self_url;
print "<A HREF=$myself#table1>See table 1</A>";
print "<A HREF=$myself#table2>See table 2</A>";
print "<A HREF=$myself#yourself>See for yourself</A>";
If you don't want to get the whole query string, call the method
url() to return just the URL for the script:
$myself = $query->url;
print "<A HREF=$myself>No query string in this baby!</A>\n";
You can also retrieve the unprocessed query string with
query_string():
$the_string = $query->query_string;
OLD VERSION require ``cgi-lib.pl''; &ReadParse; print ``The value of the antique is $in{antique}.\n'';
NEW VERSION use CGI; CGI::ReadParse print ``The value of the antique is $in{antique}.\n'';
CGI.pm's ReadParse() routine creates a tied variable named
%in, which can be accessed to obtain the query variables. Like ReadParse,
you can also provide your own variable. Infrequently used features of
ReadParse, such as the creation of @in and $in
variables, are not supported.
Once you use ReadParse, you can retrieve the query object itself this way:
$q = $in{CGI};
print $q->textfield(-name=>'wow',
-value=>'does this really work?');
This allows you to start using the more interesting features of CGI.pm without rewriting your old scripts from scratch.
$field = $query->radio_group(-name=>'OS',
-values=>[Unix,Windows,Macintosh],
-default=>'Unix');
The advantages of this style are that you don't have to remember the exact order of the arguments, and if you leave out a parameter, in most cases it will default to some reasonable value. If you provide a parameter that the method doesn't recognize, it will usually do something useful with it, such as incorporating it into the HTML form tag. For example if Netscape decides next week to add a new JUSTIFICATION parameter to the text field tags, you can start using the feature without waiting for a new version of CGI.pm:
$field = $query->textfield(-name=>'State',
-default=>'gaseous',
-justification=>'RIGHT');
This will result in an HTML tag that looks like this:
<INPUT TYPE="textfield" NAME="State" VALUE="gaseous"
JUSTIFICATION="RIGHT">
Parameter names are case insensitive: you can use -name, or -Name or -NAME. You don't have to use the hyphen if you don't want to. After creating a CGI object, call the use_named_parameters() method with a nonzero value. This will tell CGI.pm that you intend to use named parameters exclusively:
$query = new CGI;
$query->use_named_parameters(1);
$field = $query->radio_group('name'=>'OS',
'values'=>['Unix','Windows','Macintosh'],
'default'=>'Unix');
Actually, CGI.pm only looks for a hyphen in the first parameter. So you can leave it off subsequent parameters if you like. Something to be wary of is the potential that a string constant like ``values'' will collide with a keyword (and in fact it does!) While Perl usually figures out when you're referring to a function and when you're referring to a string, you probably should put quotation marks around all string constants just to play it safe.
print $query->header;
-or-
print $query->header('image/gif');
-or-
print $query->header('text/html','204 No response');
-or-
print $query->header(-type=>'image/gif',
-nph=>1,
-status=>'402 Payment required',
-expires=>'+3d',
-cookie=>$cookie,
-Cost=>'$2.00');
header() returns the Content-type: header. You can provide
your own MIME type if you choose, otherwise it defaults to text/html. An
optional second parameter specifies the status code and a human-readable
message. For example, you can specify 204, ``No response'' to create a
script that tells the browser to do nothing at all. If you want to add
additional fields to the header, just tack them on to the end:
print $query->header('text/html','200 OK','Content-Length: 3002');
The last example shows the named argument style for passing arguments to the CGI methods using named parameters. Recognized parameters are -type, -status, -expires, and -cookie. Any other parameters will be stripped of their initial hyphens and turned into header fields, allowing you to specify any HTTP header you desire.
Most browsers will not cache the output from CGI scripts. Every time the browser reloads the page, the script is invoked anew. You can change this behavior with the -expires parameter. When you specify an absolute or relative expiration interval with this parameter, some browsers and proxy servers will cache the script's output until the indicated expiration date. The following forms are all valid for the -expires field:
+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.)
The -cookie parameter generates a header that tells the browser to provide a ``magic
cookie'' during all subsequent transactions with your script. Netscape
cookies have a special format that includes interesting attributes such as
expiration time. Use the cookie() method to create and
retrieve session cookies.
The -nph parameter, if set to a true value, will issue the correct headers to work with a NPH (no-parse-header) script. This is important to use with certain servers, such as Microsoft Internet Explorer, which expect all their scripts to be NPH.
print $query->redirect('http://somewhere.else/in/movie/land');
redirects the browser elsewhere. If you use redirection like this, you should not print out a header as well. As of version 2.0, we produce both the unofficial Location: header and the official URI: header. This should satisfy most servers and browsers.
One hint I can offer is that relative links may not work correctly when you generate a redirection to another document on your site. This is due to a well-intentioned optimization that some servers use. The solution to this is to use the full URL (including the http: part) of the document you are redirecting to.
You can use named parameters:
print $query->redirect(-uri=>'http://somewhere.else/in/movie/land',
-nph=>1);
The -nph parameter, if set to a true value, will issue the correct headers to work with a NPH (no-parse-header) script. This is important to use with certain servers, such as Microsoft Internet Explorer, which expect all their scripts to be NPH.
print $query->start_html(-title=>'Secrets of the Pyramids',
-author=>'fred@capricorn.org',
-base=>'true',
-target=>'_blank',
-meta=>{'keywords'=>'pharaoh secret mummy',
'copyright'=>'copyright 1996 King Tut'},
-style=>{'src'=>'/styles/style1.css'},
-BGCOLOR=>'blue');
-or-
print $query->start_html('Secrets of the Pyramids',
'fred@capricorn.org','true',
'BGCOLOR="blue"');
This will return a canned HTML header and the opening <BODY> tag. All parameters are optional. In the named parameter form, recognized parameters are -title, -author, -base, -xbase and -target (see below for the explanation). Any additional parameters you provide, such as the Netscape unofficial BGCOLOR attribute, are added to the <BODY> tag.
The argument -xbase allows you to provide an HREF for the <BASE> tag different from the current location, as in
-xbase=>"http://home.mcom.com/";
All relative links will be interpreted relative to this tag.
The argument -target allows you to provide a default target frame for all the links and fill-out forms on the page. See the Netscape documentation on frames for details of how to manipulate this.
-target=>"answer_window"
All relative links will be interpreted relative to this tag. You add arbitrary meta information to the header with the -meta argument. This argument expects a reference to an associative array containing name/value pairs of meta information. These will be turned into a series of header <META> tags that look something like this:
<META NAME="keywords" CONTENT="pharaoh 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. For example, if you want to send the Refresh: header, do it in the
header() method:
print $q->header(-Refresh=>'10; URL=http://www.capricorn.com');
The -style tag is used to incorporate cascading stylesheets into your code. See the section on CASCADING STYLESHEETS for more information.
You can place other arbitrary HTML elements to the <HEAD> section with the -head tag. For example, to place the rarely-used <LINK> element in the head section, use this:
print $q->header(-head=>link({-rel=>'next',
-href=>'http://www.capricorn.com/s2.html'}));
To incorporate multiple HTML elements into the <HEAD> section, just pass an array reference:
print $q->header(-head=>[ link({-rel=>'next',
-href=>'http://www.capricorn.com/s2.html'}),
link({-rel=>'previous',
-href=>'http://www.capricorn.com/s1.html'})
]
);
JAVASCRIPTING: The -script, -noScript, -onLoad and -onUnload parameters are used to add Netscape JavaScript calls to your pages. -script should point to a block of text containing JavaScript function definitions. This block will be placed within a <SCRIPT> block inside the HTML (not HTTP) header. The block is placed in the header in order to give your page a fighting chance of having all its JavaScript functions in place even if the user presses the stop button before the page has loaded completely. CGI.pm attempts to format the script in such a way that JavaScript-naive browsers will not choke on the code: unfortunately there are some browsers, such as Chimera for Unix, that get confused by it nevertheless.
The -onLoad and -onUnload parameters point to fragments of JavaScript code to execute when the page is respectively opened and closed by the browser. Usually these parameters are calls to functions defined in the -script field:
$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);
Use the -noScript parameter to pass some HTML text that will be displayed on browsers that do not have JavaScript (or browsers where JavaScript is turned off).
Netscape 3.0 recognizes several attributes of the <SCRIPT> tag, including LANGUAGE and SRC. The latter is particularly interesting, as it allows you to keep the JavaScript code in a file or CGI script rather than cluttering up each page with the source. To use these attributes pass a HASH reference in the -script parameter containing one or more of -language, -src, or -code:
print $q->start_html(-title=>'The Riddle of the Sphinx',
-script=>{-language=>'JAVASCRIPT',
-src=>'/javascript/sphinx.js'}
);
print $q->(-title=>'The Riddle of the Sphinx',
-script=>{-language=>'PERLSCRIPT'},
-code=>'print "hello world!\n;"'
);
See
http://home.netscape.com/eng/mozilla/2.0/handbook/javascript/
for more information about JavaScript.
The old-style positional parameters are as follows:
print $query->end_html
This ends an HTML document by printing the </BODY></HTML> tags.
Another note The default values that you specify for the forms are only used the first time the script is invoked (when there is no query string). On subsequent invocations of the script (when there is a query string), the former values are used even if they are 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 (a new feature in version 2.15). This forces the default value to be used, regardless of the previous value:
print $query->textfield(-name=>'field_name',
-default=>'starting value',
-override=>1,
-size=>50,
-maxlength=>80);
Yet another note By default, the text and labels of form elements are escaped according to
HTML rules. This means that you can safely use ``<CLICK ME>'' as the
label for a button. However, it also interferes with your ability to
incorporate special HTML character sequences, such as Á, into
your fields. If you wish to turn off automatic escaping, call the
autoEscape() method with a false value immediately after
creating the CGI object:
$query = new CGI;
$query->autoEscape(undef);
print $query->isindex(-action=>$action);
-or-
print $query->isindex($action);
Prints out an <ISINDEX> tag. Not very exciting. The parameter -action specifies the URL of the script to process the query. The default is to process the query with the current script.
print $query->startform(-method=>$method,
-action=>$action,
-encoding=>$encoding);
<... various form stuff ...>
print $query->endform;
-or-
print $query->startform($method,$action,$encoding);
<... various form stuff ...>
print $query->endform;
startform() will return a <FORM> tag with the optional
method, action and form encoding that you specify. The defaults are:
method: POST action: this script encoding:
application/x-www-form-urlencoded
endform() returns the closing </FORM> tag.
Startform()'s encoding method tells the browser how to package
the various fields of the form before sending the form to the server. Two
values are possible:
Forms that use this type of encoding are not easily interpreted by CGI scripts unless they use CGI.pm or another library designed to handle them.
startform() method uses the older form
of encoding by default. If you want to use the newer form of encoding by
default, you can call start_multipart_form() instead of
startform().
JAVASCRIPTING: The -name and -onSubmit parameters are provided for use with JavaScript. The -name parameter gives the form a name so that it can be identified and manipulated by JavaScript functions. -onSubmit should point to a JavaScript function that will be executed just before the form is submitted to your server. You can use this opportunity to check the contents of the form for consistency and completeness. If you find something wrong, you can put up an alert box or maybe fix things up yourself. You can abort the submission by returning false from this function.
Usually the bulk of JavaScript functions are defined in a <SCRIPT>
block in the HTML header and -onSubmit points to one of these function
call. See start_html() for details.
print $query->textfield(-name=>'field_name',
-default=>'starting value',
-size=>50,
-maxlength=>80);
-or-
print $query->textfield('field_name','starting value',50,80);
textfield() will return a text input field.
$value = $query->param('foo');
If you want to reset it from its initial value after the script has been called once, you can do so like this:
$query->param('foo',"I'm taking over this value!");
NEW AS OF VERSION 2.15: If you don't want the field to take on its previous value, you can force its current value by using the -override (alias -force) parameter:
print $query->textfield(-name=>'field_name',
-default=>'starting value',
-override=>1,
-size=>50,
-maxlength=>80);
JAVASCRIPTING: You can also provide -onChange, -onFocus, -onBlur and -onSelect parameters to register JavaScript event handlers. The onChange handler will be called whenever the user changes the contents of the text field. You can do text validation if you like. onFocus and onBlur are called respectively when the insertion point moves into and out of the text field. onSelect is called when the user changes the portion of the text that is selected.
print $query->textarea(-name=>'foo',
-default=>'starting value',
-rows=>10,
-columns=>50);
-or
print $query->textarea('foo','starting value',10,50);
textarea() is just like textfield, but it allows you to
specify rows and columns for a multiline text entry box. You can provide a
starting value for the field, which can be long and contain multiple lines.
JAVASCRIPTING: The -onChange, -onFocus, -onBlur
and -onSelect parameters are recognized. See textfield().
print $query->password_field(-name=>'secret',
-value=>'starting value',
-size=>50,
-maxlength=>80);
-or-
print $query->password_field('secret','starting value',50,80);
password_field() is identical to textfield(),
except that its contents will be starred out on the web page.
JAVASCRIPTING: The -onChange, -onFocus, -onBlur
and -onSelect parameters are recognized. See textfield().
print $query->filefield(-name=>'uploaded_file',
-default=>'starting value',
-size=>50,
-maxlength=>80);
-or-
print $query->filefield('uploaded_file','starting value',50,80);
filefield() will return a file upload field for Netscape 2.0
browsers. In order to take full advantage of this you must use the new
multipart encoding scheme for the form. You can do this either by calling startform() with an encoding type of $CGI::MULTIPART, or by calling the new method start_multipart_form() instead of vanilla startform().
The beta2 version of Netscape 2.0 currently doesn't pay any attention to this field, and so the starting value will always be blank. Worse, the field loses its ``sticky'' behavior and forgets its previous contents. The starting value field is called for in the HTML specification, however, and possibly later versions of Netscape will honor it.
param().
$filename = $query->param('uploaded_file');
In Netscape Gold, the filename that gets returned is the full local filename on the remote user's machine. If the remote user is on a Unix machine, the filename will follow Unix conventions:
/path/to/the/file
On an MS-DOS/Windows and OS/2 machines, the filename will follow DOS conventions:
C:\PATH\TO\THE\FILE.MSW
On a Macintosh machine, the filename will follow Mac conventions:
HD 40:Desktop Folder:Sort Through:Reminders
The filename returned is also a file handle. You can read the contents of the file using standard Perl file reading calls:
# Read a text file and print it out
while (<$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;
}
When a file is uploaded the browser usually sends along some information
along with it in the format of headers. The information usually includes
the MIME content type. Future browsers may send other information as well
(such as modification date and size). To retrieve this information, call
uploadInfo(). It returns a reference to an associative array
containing all the document headers.
$filename = $query->param('uploaded_file');
$type = $query->uploadInfo($filename)->{'Content-Type'};
unless ($type eq 'text/html') {
die "HTML FILES ONLY!";
}
If you are using a machine that recognizes ``text'' and ``binary'' data modes, be sure to understand when and how to use them (see the Camel book). Otherwise you may find that binary files are corrupted during file uploads.
JAVASCRIPTING: The -onChange, -onFocus, -onBlur
and -onSelect parameters are recognized. See textfield() for details.
print $query->popup_menu('menu_name',
['eenie','meenie','minie'],
'meenie');
-or-
%labels = ('eenie'=>'your first choice',
'meenie'=>'your second choice',
'minie'=>'your third choice');
print $query->popup_menu('menu_name',
['eenie','meenie','minie'],
'meenie',\%labels);
-or (named parameter style)-
print $query->popup_menu(-name=>'menu_name',
-values=>['eenie','meenie','minie'],
-default=>'meenie',
-labels=>\%labels);
popup_menu() creates a menu.
$popup_menu_value = $query->param('menu_name');
JAVASCRIPTING: popup_menu() recognizes the following event
handlers:
-onChange, -onFocus, and -onBlur. See the textfield() section for details on when these
handlers are called.
print $query->scrolling_list('list_name',
['eenie','meenie','minie','moe'],
['eenie','moe'],5,'true');
-or-
print $query->scrolling_list('list_name',
['eenie','meenie','minie','moe'],
['eenie','moe'],5,'true',
\%labels);
-or-
print $query->scrolling_list(-name=>'list_name',
-values=>['eenie','meenie','minie','moe'],
-default=>['eenie','moe'],
-size=>5,
-multiple=>'true',
-labels=>\%labels);
scrolling_list() creates a scrolling list.
When this form is processed, all selected list items will be returned as a list under the parameter name 'list_name'. The values of the selected items can be retrieved with:
@selected = $query->param('list_name');
scrolling_list() recognizes the following event
handlers:
-onChange, -onFocus, and -onBlur. See textfield() for the description of when these handlers
are called.
print $query->checkbox_group(-name=>'group_name',
-values=>['eenie','meenie','minie','moe'],
-default=>['eenie','moe'],
-linebreak=>'true',
-labels=>\%labels);
print $query->checkbox_group('group_name',
['eenie','meenie','minie','moe'],
['eenie','moe'],'true',\%labels);
HTML3-COMPATIBLE BROWSERS ONLY:
print $query->checkbox_group(-name=>'group_name',
-values=>['eenie','meenie','minie','moe'],
-rows=2,-columns=>2);
checkbox_group() creates a list of checkboxes that are related
by the same name.
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 -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 interpretation of the checkboxes -- they're still a single named unit.
@turned_on = $query->param('group_name');
The value returned by checkbox_group() is actually an array of
button elements. You can capture them and use them within tables, lists, or
in other creative ways:
@h = $query->checkbox_group(-name=>'group_name',-values=>\@values);
&use_in_creative_way(@h);
JAVASCRIPTING: checkbox_group() recognizes the -onClick
parameter. This specifies a JavaScript code fragment or function call to be
executed every time the user clicks on any of the buttons in the group. You
can retrieve the identity of the particular button clicked on using the
``this'' variable.
print $query->checkbox(-name=>'checkbox_name',
-checked=>'checked',
-value=>'ON',
-label=>'CLICK ME');
-or-
print $query->checkbox('checkbox_name','checked','ON','CLICK ME');
checkbox() is used to create an isolated checkbox that isn't
logically related to any others.
$turned_on = $query->param('checkbox_name');
JAVASCRIPTING: checkbox() recognizes the -onClick
parameter. See checkbox_group() for further details.
print $query->radio_group(-name=>'group_name',
-values=>['eenie','meenie','minie'],
-default=>'meenie',
-linebreak=>'true',
-labels=>\%labels);
-or-
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);
radio_group() creates a set of logically-related radio buttons
(turning one member of the group on turns the others off)
radio_group() to return an HTML3
compatible table containing the radio group 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.
$which_radio_button = $query->param('group_name');
The value returned by radio_group() is actually an array of
button elements. You can capture them and use them within tables, lists, or
in other creative ways:
@h = $query->radio_group(-name=>'group_name',-values=>\@values);
&use_in_creative_way(@h);
print $query->submit(-name=>'button_name',
-value=>'value');
-or-
print $query->submit('button_name','value');
submit() will create the query submission button. Every form
should have one of these.
$which_one = $query->param('button_name');
JAVASCRIPTING: radio_group() recognizes the -onClick
parameter. See checkbox_group() for further details.
print $query->reset
reset() creates the ``reset'' button. Note that it restores
the form to its value from the last time the script was called, NOT
necessarily to the defaults.
print $query->defaults('button_label')
defaults() creates a button that, when invoked, will cause the
form to be completely reset to its defaults, wiping out all the changes the
user ever made.
print $query->hidden(-name=>'hidden_name',
-default=>['value1','value2'...]);
-or-
print $query->hidden('hidden_name','value1','value2'...);
hidden() produces a text field that can't be seen by the user.
It is useful for passing state variable information from one invocation of
the script to the next.
$hidden_value = $query->param('hidden_name');
Note, that 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:
$query->param('hidden_name','new','values','here');
print $query->image_button(-name=>'button_name',
-src=>'/source/URL',
-align=>'MIDDLE');
-or-
print $query->image_button('button_name','/source/URL','MIDDLE');
image_button() produces a clickable image. When it's clicked
on the position of the click is returned to your script as
``button_name.x'' and ``button_name.y'', where ``button_name'' is the name
you've assigned to it.
JAVASCRIPTING: image_button() recognizes the -onClick
parameter. See checkbox_group() for further details.
$x =
$query->param('button_name.x'); $y =
$query->param('button_name.y');
print $query->button(-name=>'button_name',
-value=>'user visible label',
-onClick=>"do_something()");
-or-
print $query->button('button_name',"do_something()");
button() produces a button that is compatible with Netscape
2.0's JavaScript. When it's pressed the fragment of JavaScript code pointed
to by the -onClick parameter will be executed. On non-Netscape browsers this form element will
probably not even display.
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:
$cookie = $query->cookie(-name=>'sessionID',
-value=>'xyzzy',
-expires=>'+1h',
-path=>'/cgi-bin/database',
-domain=>'.capricorn.org',
-secure=>1);
print $query->header(-cookie=>$cookie);
cookie() creates a new cookie. Its parameters include:
$cookie=$query->cookie(-name=>'family information',
-value=>\%childrens_ages);
"+1h" one hour from now
cookie() must be incorporated into the
HTTP header within the string returned by the header() method:
print $query->header(-cookie=>$my_cookie);
To create multiple cookies, give header() an array reference:
$cookie1 = $query->cookie(-name=>'riddle_name',
-value=>"The Sphynx's Question");
$cookie2 = $query->cookie(-name=>'answers',
-value=>\%answers);
print $query->header(-cookie=>[$cookie1,$cookie2]);
To retrieve a cookie, request it by name by calling cookie()
method without the -value parameter:
use CGI;
$query = new CGI;
%answers = $query->cookie(-name=>'answers');
# $query->cookie('answers') will work 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.
start_html() call, create a
<FRAMESET> document that defines the frames on the page. Specify your
script(s) (with appropriate parameters) as the SRC for each of
the frames.
There is no specific support for creating <FRAMESET> sections in CGI.pm, but the HTML is very simple to write. See the frame documentation in Netscape's home pages for details
http://home.netscape.com/assist/net_sites/frames.html
header() method: print
$q->header(-target=>'ResultsWindow');
This will tell Netscape to load the output of your script into the frame named ``ResultsWindow''. If a frame of that name doesn't already exist, Netscape will pop up a new window and load your script's document into that. There are a number of magic names that you can use for targets. See the frame documents on Netscape's home pages for details.
print $q->startform(-target=>'ResultsWindow');
When your script is reinvoked by the form, its output will be loaded into the frame named ``ResultsWindow''. If one doesn't already exist a new window will be created.
start_html() method a -style parameter. The value of this parameter may be a scalar, in which case it is
incorporated directly into a <STYLE> section, or it may be a hash reference. In the latter case you
should provide the hash with one or more of -src or
-code. -src points to a URL where an externally-defined stylesheet can be found. -code points to a scalar value to be incorporated into a <STYLE> section. Style definitions in -code
override similarly-named ones in -src, hence the name ``cascading.''
To refer to a style within the body of your document, add the -class parameter to any HTML element:
print h1({-class=>'Fancy'},'Welcome to the Party');
Or define styles on the fly with the -style parameter:
print h1({-style=>'Color: red;'},'Welcome to Hell');
You may also use the new span() element to apply a style to a section of text:
print span({-style=>'Color: red;'},
h1('Welcome to Hell'),
"Where did that handbasket get to?"
);
Note that you must import the ``:html3'' definitions to have the span() method available. Here's a quick and dirty example of using CSS's. See the CSS specification at http://www.w3.org/pub/WWW/TR/Wd-css-1.html for more information.
use CGI qw/:standard :html3/;
#here's a stylesheet incorporated directly into the page
$newStyle=<<END;
<!--
P.Tip {
margin-right: 50pt;
margin-left: 50pt;
color: red;
}
P.Alert {
font-size: 30pt;
font-family: sans-serif;
color: red;
}
-->
END
print header();
print start_html( -title=>'CGI with Style',
-style=>{-src=>'http://www.capricorn.com/style/st1.css',
-code=>$newStyle}
);
print h1('CGI with Style'),
p({-class=>'Tip'},
"Better read the cascading style sheet spec before playing with this!"),
span({-style=>'color: magenta'},
"Look Mom, no hands!",
p(),
"Whooo wee!"
);
print end_html;
your_script.pl keyword1 keyword2 keyword3
or this:
your_script.pl keyword1+keyword2+keyword3
or this:
your_script.pl name1=value1 name2=value2
or this:
your_script.pl name1=value1&name2=value2
or even as newline-delimited parameters on standard input.
When debugging, you can use quotes and backslashes to escape characters in the familiar shell manner, letting you place spaces and other funny characters in your parameter=value pairs:
your_script.pl "name1='I am a long value'" "name2=two\ words"
dump() method produces a string consisting of all the
query's name/value pairs formatted nicely as a nested list. This is useful
for debugging purposes:
print $query->dump
Produces something that looks like:
<UL>
<LI>name1
<UL>
<LI>value1
<LI>value2
</UL>
<LI>name2
<UL>
<LI>value1
</UL>
</UL>
You can pass a value of 'true' to dump() in order to get it to
print the results out as plain text, suitable for incorporating into a
<PRE> section.
As a shortcut, as of version 1.56 you can interpolate the entire CGI object into a string and it will be replaced with the a nice HTML dump shown above:
$query=new CGI;
print "<H2>Current Values</H2> $query\n";
cookie() for ways of setting and retrieving cooked cookies.
NOTE: The Microsoft Internet Information Server is broken with respect to additional path information. If you use the Perl DLL library, the IIS server will attempt to execute the additional path information as a Perl script. If you use the ordinary file associations mapping, the path information will be present in the environment, but incorrect. The best thing to do is to avoid using additional path information in CGI scripts destined for use with IIS.
path_info() but returns the additional path information
translated into a physical path, e.g.
``/usr/local/etc/httpd/htdocs/additional/stuff''.
The Microsoft IIS is broken with respect to the translated path as well.
This example shows how to use the HTML methods:
$q = new CGI;
print $q->blockquote(
"Many years ago on the island of",
$q->a({href=>"http://crete.org/";},"Crete"),
"there lived a minotaur named",
$q->strong("Fred."),
),
$q->hr;
This results in the following HTML code (extra newlines have been added for readability):
<blockquote>
Many years ago on the island of
<a HREF="http://crete.org/";>Crete</a> there lived
a minotaur named <strong>Fred.</strong>
</blockquote>
<hr>
If you find the syntax for calling the HTML shortcuts awkward, you can import them into your namespace and dispense with the object syntax completely (see the next section for more details):
use CGI shortcuts; # IMPORT HTML SHORTCUTS
print blockquote(
"Many years ago on the island of",
a({href=>"http://crete.org/";},"Crete"),
"there lived a minotaur named",
strong("Fred."),
),
hr;
print hr;
# gives "<hr>"
If you provide one or more string arguments, they are concatenated together with spaces and placed between opening and closing tags:
print h1("Chapter","1");
# gives "<h1>Chapter 1</h1>"
If the first argument is an associative array reference, then the keys and values of the associative array become the HTML tag's attributes:
print a({href=>'fred.html',target=>'_new'},
"Open a new frame");
# gives <a href="fred.html",target="_new">Open a new frame</a>
You are free to use CGI.pm-style dashes in front of the attribute names if you prefer:
print img {-src=>'fred.gif',-align=>'LEFT'};
# gives <img ALIGN="LEFT" SRC="fred.gif">
use CGI shortcuts,winkin,blinkin,nod;
Now, in addition to the standard CGI shortcuts, you've created HTML tags named ``winkin'', ``blinkin'' and ``nod''. You can use them like this:
print blinkin {color=>'blue',rate=>'fast'},"Yahoo!";
# <blinkin COLOR="blue" RATE="fast">Yahoo!</blinkin>
use CGI <list of methods>;
The listed methods will be imported into the current package; you can call them directly without creating a CGI object first. This example shows how to import the param() and header() methods, and then use them directly:
use CGI param,header;
print header('text/plain');
$zipcode = param('zipcode');
You can import groups of methods by referring to a number of special names:
%TAGS is defined.
If you import any of the state-maintaining CGI or form-generating methods, a default CGI object will be created and initialized automatically the first time you use any of the methods that require one to be present. This includes param(), textfield(), submit() and the like. (If you need direct access to the CGI object, you can find it in the global variable $CGI::Q). By importing CGI.pm methods, you can create visually elegant scripts:
use CGI standard,html2;
print
header,
start_html('Simple Script'),
h1('Simple Script'),
start_form,
"What's your name? ",textfield('name'),p,
"What's the combination?",
checkbox_group(-name=>'words',
-values=>['eenie','meenie','minie','moe'],
-defaults=>['eenie','moe']),p,
"What's your favorite color?",
popup_menu(-name=>'color',
-values=>['red','green','blue','chartreuse']),p,
submit,
end_form,
hr,"\n";
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')),".\n";
}
print end_html;
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.
The Microsoft Internet Information Server requires NPH mode. As of version 2.30, CGI.pm will automatically detect when the script is running under IIS and put itself into this mode. You do not need to do this manually, although it won't hurt anything if you do.
There are a number of ways to put CGI.pm into NPH mode:
use CGI qw(:standard :nph)
CGI->nph(1)
print $q->header(-nph=>1);
Address bug reports and comments to: lstein@genome.wi.mit.edu
#!/usr/local/bin/perl
use CGI;
$query = new CGI;
print $query->header;
print $query->start_html("Example CGI.pm Form");
print "<H1> Example CGI.pm Form</H1>\n";
&print_prompt($query);
&do_work($query);
&print_tail;
print $query->end_html;
sub print_prompt {
my($query) = @_;
print $query->startform;
print "<EM>What's your name?</EM><BR>";
print $query->textfield('name');
print $query->checkbox('Not my real name');
print "<P><EM>Where can you find English Sparrows?</EM><BR>";
print $query->checkbox_group(
-name=>'Sparrow locations',
-values=>[England,France,Spain,Asia,Hoboken],
-linebreak=>'yes',
-defaults=>[England,Asia]);
print "<P><EM>How far can they fly?</EM><BR>",
$query->radio_group(
-name=>'how far',
-values=>['10 ft','1 mile','10 miles','real far'],
-default=>'1 mile');
print "<P><EM>What's your favorite color?</EM> ";
print $query->popup_menu(-name=>'Color',
-values=>['black','brown','red','yellow'],
-default=>'red');
print $query->hidden('Reference','Monty Python and the Holy Grail');
print "<P><EM>What have you got there?</EM><BR>";
print $query->scrolling_list(
-name=>'possessions',
-values=>['A Coconut','A Grail','An Icon',
'A Sword','A Ticket'],
-size=>5,
-multiple=>'true');
print "<P><EM>Any parting comments?</EM><BR>";
print $query->textarea(-name=>'Comments',
-rows=>10,
-columns=>50);
print "<P>",$query->reset;
print $query->submit('Action','Shout');
print $query->submit('Action','Scream');
print $query->endform;
print "<HR>\n";
}
sub do_work {
my($query) = @_;
my(@values,$key);
print "<H2>Here are the current settings in this form</H2>";
foreach $key ($query->param) {
print "<STRONG>$key</STRONG> -> ";
@values = $query->param($key);
print join(", ",@values),"<BR>\n";
}
}
sub print_tail {
print <<END;
<HR>
<ADDRESS>Lincoln D. Stein</ADDRESS><BR>
<A HREF="/">Home Page</A>
END
}
Note that the code is truly contorted in order to avoid spurious warnings when programs are run with the -w switch.