lib:CGI
See the current Perl documentation for lib:CGI.
Here is our local, out-dated (pre-5.6) version:
CGI - Simple Common Gateway Interface Class
use CGI qw/:standard/;
print header,
start_html('A Simple Example'),
h1('A Simple Example'),
start_form,
# ...
There are two styles of programming with CGI.pm, an object-oriented style and a function-oriented style. In the object-oriented style you create one or more
CGI objects and then use object methods to create the various elements of the page. Each
CGI object starts out with the list of named parameters that were passed to your
CGI script by the server. You can modify the objects, save them to a file or database and recreate them. Because each object corresponds to the ``state'' of the
CGI script, and because each object's parameter list is independent of the others, this allows you to save the state of the script and restore it later.
For example, using the object oriented style, here is now you create a simple ``Hello World''
HTML page:
#!/usr/local/bin/perl
use CGI; # load CGI routines
$q = new CGI; # create new CGI object
print $q->header, # create the HTTP header
$q->start_html('hello world'), # start the HTML
$q->h1('hello world'), # level 1 header
$q->end_html; # end the HTML
In the function-oriented style, there is one default
CGI object that you rarely deal with directly. Instead you just call functions to retrieve
CGI parameters, create
HTML tags, manage cookies, and so on. This provides you with a cleaner programming interface, but limits you to using one
CGI object at a time. The following example prints the same page, but uses the function-oriented interface. The main differences are that we now need to import a set of functions into our name space (usually the ``standard'' functions), and we don't need to create the
CGI object.
#!/usr/local/bin/pelr
use CGI qw/:standard/; # load standard CGI routines
print header, # create the HTTP header
start_html('hello world'), # start the HTML
h1('hello world'), # level 1 header
end_html; # end the HTML
The examples in this document mainly use the object-oriented style. See
HOW
TO
IMPORT
FUNCTIONS for important information on function-oriented programming in CGI.pm
Most CGI.pm routines accept several arguments, sometimes as many as 20
optional ones! To simplify this interface, all routines use a named
argument calling style that looks like this:
print $q->header(-type=>'image/gif',-expires=>'+3d');
Each argument name is preceded by a dash. Neither case nor order matters in the argument list. -type, -Type, and
-TYPE are all acceptable. In fact, only the first argument needs to begin with a dash. If a dash is present in the first argument, CGI.pm assumes dashes for the subsequent ones.
You don't have to use the hyphen at allif 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');
Several routines are commonly called with just one argument. In the case of these routines you can provide the single argument without an argument name.
header() happens to be one of these routines. In this case, the single argument is the document type.
print $q->header('text/html');
Other such routines are documented below.
Sometimes named arguments expect a scalar, sometimes a reference to an array, and sometimes a reference to a hash. Often, you can pass any type of argument and the routine will do whatever is most appropriate. For example, the
param() routine is used to set a
CGI parameter to a single or a multi-valued value. The two cases are shown below:
$q->param(-name=>'veggie',-value=>'tomato');
$q->param(-name=>'veggie',-value=>'[tomato','tomahto','potato','potahto']);
A large number of routines in CGI.pm actually aren't specifically defined in the module, but are generated automatically as needed. These are the
``HTML shortcuts,'' routines that generate
HTML tags for use in dynamically-generated pages.
HTML tags have both attributes (the attribute=``value'' pairs within the tag itself) and contents (the part between the opening and closing pairs.) To distinguish between attributes and contents, CGI.pm uses the convention of passing
HTML attributes as a hash reference as the first argument, and the contents, if any, as any subsequent arguments. It works out like this:
Code Generated HTML
---- --------------
h1() <H1>
h1('some','contents'); <H1>some contents</H1>
h1({-align=>left}); <H1 ALIGN="LEFT">
h1({-align=>left},'contents'); <H1 ALIGN="LEFT">contents</H1>
HTML tags are described in more detail later.
Many newcomers to CGI.pm are puzzled by the difference between the calling conventions for the
HTML shortcuts, which require curly braces around the
HTML tag attributes, and the calling conventions for other routines, which manage to generate attributes without the curly brackets. Don't be confused. As a convenience the curly braces are optional in all but the
HTML shortcuts. If you like, you can use curly braces when calling any routine that takes named arguments. For example:
print $q->header( {-type=>'image/gif',-expires=>'+3d'} );
If you use the -w switch, you will be warned that some CGI.pm argument names conflict with
built-in Perl functions. The most frequent of these is the -values
argument, used to create multi-valued menus, radio button clusters and the
like. To get around this warning, you have several choices:
- Use another name for the argument, if one is available. For
example, -value is an alias for -values.
- Change the capitalization, e.g. -Values
- Put quotes around the argument name, e.g. '-values'
Many routines will do something useful with a named argument that it doesn't recognize. For example, you can produce non-standard
HTTP header fields by providing them as named arguments:
print $q->header(-type => 'text/html',
-cost => 'Three smackers',
-annoyance_level => 'high',
-complaints_to => 'bit bucket');
This will produce the following nonstandard
HTTP header:
HTTP/1.0 200 OK
Cost: Three smackers
Annoyance-level: high
Complaints-to: bit bucket
Content-type: text/html
Notice the way that underscores are translated automatically into hyphens.
HTML-generating routines perform a different type of translation.
This feature allows you to keep up with the rapidly changing
HTTP and
HTML ``standards''.
$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
CGI object with a FileHandle or IO::File object.
If you are using the function-oriented interface and want to initialize
CGI state from a file handle, the way to do this is
with
restore_parameters(). This will (re)initialize the default
CGI object from the indicated file handle.
open (IN,"test.in") || die;
restore_parameters(IN);
close IN;
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');
or from a previously existing
CGI object (currently this clones the parameter list,
but none of the other object-specific fields, such as autoescaping):
$old_query = new CGI;
$new_query = new CGI($old_query);
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.
If you are using the function call interface, use ``Delete()'' instead to
avoid conflicts with Perl's built-in delete operator.
$query->delete_all();
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.
Use
Delete_all() instead if
you are using the function call interface.
$q->param_fetch('address')->[1] = '1313 Mockingbird Lane';
unshift @{$q->param_fetch(-name=>'address')},'George Munster';
If you need access to the parameter list in a way that isn't covered by the
methods above, you can obtain a direct reference to it by calling the param_fetch() method with the name of the . This will return an array reference to the
named parameters, which you then can manipulate in any way you like.
You can also use a named argument style using the -name argument.
$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.
If you wish to use this method from the function-oriented (non-OO)
interface, the exported name for this method is save_parameters().
To use the function-oriented interface, you must specify which CGI.pm
routines or sets of routines to import into your script's namespace. There
is a small overhead associated with this importation, but it isn't much.
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');
More frequently, you'll import common sets of functions by referring to the gropus by name. All function sets are preceded with a ``:'' character as in ``:html3'' (for tags defined in the
HTML 3 standard).
Here is a list of the function sets you can import:
- :cgi
-
Import all CGI-handling methods, such as param(), path_info()
and the like.
- :form
-
Import all fill-out form generating methods, such as textfield().
- :html2
-
Import all methods that generate
HTML 2.0 standard elements.
- :html3
-
Import all methods that generate
HTML 3.0 proposed elements (such as <table>,
<super> and <sub>).
- :netscape
-
Import all methods that generate Netscape-specific
HTML extensions.
- :html
-
Import all HTML-generating shortcuts (i.e. 'html2' + 'html3' +
'netscape')...
- :standard
-
Import ``standard'' features, 'html2', 'html3', 'form' and 'cgi'.
- :all
-
Import all the available methods. For the full list, see the CGI.pm code,
where the variable
%TAGS is defined.
If you import a function name that is not part of CGI.pm, the module will treat it as a new
HTML tag and generate the appropriate subroutine. You can then use it like any other
HTML tag. This is to provide for the rapidly-evolving
HTML ``standard.'' For example, say Microsoft comes out with a new tag called
<GRADIENT> (which causes the user's desktop to be flooded with a rotating gradient fill until his machine reboots). You don't need to wait for a new version of CGI.pm to start using it immeidately:
use CGI qw/:standard :html3 gradient/;
print gradient({-start=>'red',-end=>'blue'});
Note that in the interests of execution speed CGI.pm does not use the standard Exporter syntax for specifying load symbols. This may change in the future.
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 qw/:standard/;
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;
In addition to the function sets, there are a number of pragmas that you can import. Pragmas, which are always preceded by a hyphen, change the way that CGI.pm functions in various ways. Pragmas, function sets, and individual functions can all be imported in the same
use() line. For example, the following use statement imports the standard set of functions and disables debugging mode (pragma -no_debug):
use CGI qw/:standard -no_debug/;
The current list of pragmas is as follows:
- -any
-
When you use CGI -any, then any method that the query object doesn't recognize will be interpreted as a new
HTML tag. This allows you to support the next
ad hoc Netscape or Microsoft
HTML extension. This lets you go wild with new and
unsupported tags:
use CGI qw(-any);
$q=new CGI;
print $q->gradient({speed=>'fast',start=>'red',end=>'blue'});
Since using <cite>any</cite> causes any mistyped method name to be interpreted as an
HTML tag, use it with care or not at all.
- -compile
-
This causes the indicated autoloaded methods to be compiled up front,
rather than deferred to later. This is useful for scripts that run for an
extended period of time under FastCGI or mod_perl, and for those destined
to be crunched by Malcom Beattie's Perl compiler. Use it in conjunction
with the methods or method familes you plan to use.
use CGI qw(-compile :standard :html3);
or even
use CGI qw(-compile :all);
Note that using the -compile pragma in this way will always have the effect of importing the compiled functions into the current namespace. If you want to compile without importing use the
compile() method instead (see below).
- -nph
-
This makes CGI.pm produce a header appropriate for an
NPH (no parsed header) script. You may need to do other things as well to tell the server that the script is
NPH. See the discussion of
NPH scripts below.
- -autoload
-
This overrides the autoloader so that any function in your program that is
not recognized is referred to CGI.pm for possible evaluation. This allows
you to use all the CGI.pm functions without adding them to your symbol
table, which is of concern for mod_perl users who are worried about memory
consumption. Warning: when
-autoload is in effect, you cannot use ``poetry mode'' (functions without the
parenthesis). Use hr() rather than hr, or add something like use subs qw/hr p header/
to the top of your script.
- -no_debug
-
This turns off the command-line processing features. If you want to run a CGI.pm script from the command line to produce
HTML, and you don't want it pausing to request
CGI parameters from standard input or the command line, then use this pragma:
use CGI qw(-no_debug :standard);
If you'd like to process the command-line parameters but not standard
input, this should work:
use CGI qw(-no_debug :standard);
restore_parameters(join('&',@ARGV));
See the section on debugging for more details.
- -private_tempfiles
-
CGI.pm can process uploaded file. Ordinarily it spools the uploaded file to a temporary directory, then deletes the file when done. However, this opens the risk of eavesdropping as described in the file upload section. Another
CGI script author could peek at this data during the upload, even if it is confidential information. On Unix systems, the -private_tempfiles pragma will cause the temporary file to be unlinked as soon as it is opened and before any data is written into it, eliminating the risk of eavesdropping. n =back
Most of CGI.pm's functions deal with creating documents on the fly. Generally you will produce the
HTTP header first, followed by the document itself. CGI.pm provides functions for generating
HTTP headers of various types as well as for generating
HTML. For creating
GIF images, see the GD.pm module.
Each of these functions produces a fragment of
HTML or
HTTP which you can print out directly so that it displays in the browser window, append to a string, or save to a file for later use.
Normally the first thing you will do in any
CGI script is print out an
HTTP header. This tells the browser what type of document to expect, and gives other optional information, such as the language, expiration date, and whether to cache the document. The header can also be manipulated for special purposes, such as server push and pay per view pages.
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.
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 named parameters will be stripped of their initial hyphens and turned into header fields, allowing you to specify any
HTTP header you desire. Internal underscores will be turned into hyphens:
print $query->header(-Content_length=>3002);
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-1999 00:40:33 GMT at the indicated time & date
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');
Sometimes you don't want to produce a document yourself, but simply redirect the browser elsewhere, perhaps choosing a
URL based on the time of day or the identity of the user.
The
redirect() function redirects the browser to a different
URL. 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 also use named arguments:
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');
After creating the
HTTP header, most
CGI scripts will start writing out an
HTML document. The
start_html() routine creates the top of the page, along with a lot of optional information that controls the page's appearance and behavior.
This method returns 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. Additional parameters must be proceeded by a hyphen.
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->start_html(-head=>Link({-rel=>'next',
-href=>'s2'}));
To incorporate multiple
HTML elements into the
<HEAD> section, just pass an array reference:
print $q->start_html(-head=>[
Link({-rel=>'next',
-href=>'s2'}),
Link({-rel=>'previous',
-href=>'s1'})
]
);
JAVASCRIPTING: The -script, -noScript, -onLoad,
-onMouseOver, -onMouseOut 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;"'
);
A final feature allows you to incorporate multiple
<SCRIPT> sections into the header. Just pass the list of script sections as an array reference. this allows you to specify different source files for different dialects of JavaScript. Example:
print $q->start_html(-title=>'The Riddle of the Sphinx',
-script=>[
{ -language => 'JavaScript1.0',
-src => '/javascript/utilities10.js'
},
{ -language => 'JavaScript1.1',
-src => '/javascript/utilities11.js'
},
{ -language => 'JavaScript1.2',
-src => '/javascript/utilities12.js'
},
{ -language => 'JavaScript28.2',
-src => '/javascript/utilities219.js'
}
]
);
</pre>
If this looks a bit extreme, take my advice and stick with straight
CGI scripting.
See
http://home.netscape.com/eng/mozilla/2.0/handbook/javascript/
for more information about JavaScript.
The old-style positional parameters are as follows:
- Parameters:
-
- .
The title
- .
The author's e-mail address (will create a
<LINK
REV=``MADE''> tag if present
- .
A 'true' flag if you want to include a
<BASE> tag in the header. This helps resolve relative addresses to absolute ones when the document is moved, but makes the document hierarchy non-portable. Use with care!
- , 5, 6...
Any other parameters you want to include in the
<BODY> tag. This is a good place to put Netscape
extensions, such as colors and wallpaper patterns.
print $query->end_html
This ends an
HTML document by printing the
</BODY></HTML> tags.
$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 want more control over what's returned, using the url()
method instead.
You can also retrieve the unprocessed query string with
query_string():
$the_string = $query->query_string;
$full_url = $query->url();
$full_url = $query->url(-full=>1); #alternative syntax
$relative_url = $query->url(-relative=>1);
$absolute_url = $query->url(-absolute=>1);
$url_with_path = $query->url(-path_info=>1);
$url_with_path_and_query = $query->url(-path_info=>1,-query=>1);
url() returns the script's
URL in a variety of formats. Called without any arguments, it returns the full form of the
URL, including host name and port number
http://your.host.com/path/to/script.cgi
You can modify this format with the following named arguments:
- -absolute
-
If true, produce an absolute
URL, e.g.
/path/to/script.cgi
- -relative
-
Produce a relative
URL. This is useful if you want to reinvoke your
script with different parameters. For example:
script.cgi
- -full
-
Produce the full
URL, exactly as if called without any arguments. This
overrides the -relative and -absolute arguments.
- -path (-path_info)
-
Append the additional path information to the
URL. This can be combined with -full, -absolute or -relative. -path_info
is provided as a synonym.
- -query (-query_string)
-
Append the query string to the
URL. This can be combined with
-full, -absolute or -relative. -query_string is provided as a synonym.
CGI.pm defines general
HTML shortcut methods for most, if not all of the
HTML 3 and
HTML 4 tags.
HTML shortcuts are named after a single
HTML element and return a fragment of
HTML text that you can then print or manipulate as you like. Each shortcut returns a fragment of
HTML code that you can append to a string, save to a file, or, most commonly, print out so that it displays in the browser window.
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 ':standard';
print blockquote(
"Many years ago on the island of",
a({href=>"http://crete.org/";},"Crete"),
"there lived a minotaur named",
strong("Fred."),
),
hr;
The
HTML methods will accept zero, one or multiple
arguments. If you provide no arguments, you get a single tag:
print hr; # <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"); # <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");
<A HREF="fred.html",TARGET="_new">Open a new frame</A>
You may dispense with the dashes in front of the attribute names if
you prefer:
print img {src=>'fred.gif',align=>'LEFT'};
<IMG ALIGN="LEFT" SRC="fred.gif">
Sometimes an
HTML tag attribute has no argument. For example, ordered lists can be marked as
COMPACT. The syntax for this is an argument that that points to an undef string:
print ol({compact=>undef},li('one'),li('two'),li('three'));
Prior to CGI.pm version 2.41, providing an empty ('') string as an attribute argument was the same as providing undef. However, this has changed in order to accomodate those who want to create tags of the form
<IMG
ALT=``''>. The difference is shown in these two pieces of code:
CODE
RESULT
img({alt=>undef})
<IMG
ALT>
img({alt=>''})
<IMT
ALT=``''>
One of the cool features of the
HTML shortcuts is that they are distributive. If you
give them an argument consisting of a
reference to a list, the tag will be distributed across each element of the list. For
example, here's one way to make an ordered list:
print ul(
li({-type=>'disc'},['Sneezy','Doc','Sleepy','Happy']);
);
This example will result in
HTML output that looks like this:
<UL>
<LI TYPE="disc">Sneezy</LI>
<LI TYPE="disc">Doc</LI>
<LI TYPE="disc">Sleepy</LI>
<LI TYPE="disc">Happy</LI>
</UL>
This is extremely useful for creating tables. For example:
print table({-border=>undef},
caption('When Should You Eat Your Vegetables?'),
Tr({-align=>CENTER,-valign=>TOP},
[
th(['Vegetable', 'Breakfast','Lunch','Dinner']),
td(['Tomatoes' , 'no', 'yes', 'yes']),
td(['Broccoli' , 'no', 'no', 'yes']),
td(['Onions' , 'yes','yes', 'yes'])
]
)
);
Consider this bit of code:
print blockquote(em('Hi'),'mom!'));
It will ordinarily return the string that you probably expect, namely:
<BLOCKQUOTE><EM>Hi</EM> mom!</BLOCKQUOTE>
Note the space between the element ``Hi'' and the element ``mom!''. CGI.pm
puts the extra space there using array interpolation, which is controlled
by the magic $`` variable. Sometimes this extra space is not what you want,
for example, when you are trying to align a series of images. In this case,
you can simply change the value of $'' to an empty string.
{
local($") = '';
print blockquote(em('Hi'),'mom!'));
}
I suggest you put the code in a block as shown here.
Otherwise the change to $`` will affect all subsequent code until you
explicitly reset it.
A few
HTML tags don't follow the standard pattern for various reasons.
comment() generates an
HTML comment (<!-- comment -->). Call it like
print comment('here is my comment');
Because of conflicts with built-in Perl functions, the following functions
begin with initial caps:
Select
Tr
Link
Delete
In addition,
start_html(),
end_html(),
start_form(),
end_form(),
start_multipart_form() and all the fill-out form tags are special. See their respective sections.
General note The various form-creating methods all return strings to the caller,
containing the tag or tags that will create the requested form element. You
are responsible for actually printing out these strings. It's set up this
way so that you can place formatting tags around the form elements.
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:
- application/x-www-form-urlencoded
-
This is the older 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
designed to handle them.
For compatibility, the
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.
- Parameters
-
- .
The first parameter is the required name for the field (-name).
- .
The optional second parameter is the default starting value for the field
contents (-default).
- .
The optional third parameter is the size of the field in characters
(-size).
- .
The optional fourth parameter is the maximum number of characters the field
will accept (-maxlength).
As with all these methods, the field will be initialized with its previous
contents from earlier invocations of the script. When the form is
processed, the value of the text field can be retrieved with:
$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, -onMouseOver, -onMouseOut 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 ,
-onMouseOver, -onMouseOut, 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,
-onMouseOver, -onMouseOut and -onSelect parameters are recognized. See
textfield().
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