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NAME
CGI - Handle Common Gateway Interface requests and responses
SYNOPSIS
use CGI;
my $q = CGI->new;
# Process an HTTP request
@values = $q->param('form_field');
$fh = $q->upload('file_field');
$riddle = $query->cookie('riddle_name');
%answers = $query->cookie('answers');
# Prepare various HTTP responses
print $q->header();
print $q->header('application/json');
$cookie1 = $q->cookie(-name=>'riddle_name', -value=>"The Sphynx's Question");
$cookie2 = $q->cookie(-name=>'answers', -value=>\%answers);
print $q->header(
-type => 'image/gif',
-expires => '+3d',
-cookie => [$cookie1,$cookie2]
);
print $q->redirect('http://somewhere.else/in/movie/land');
DESCRIPTION
CGI.pm is a stable, complete and mature solution for processing and preparing HTTP
requests and responses. Major features including processing form submissions, file
uploads, reading and writing cookies, query string generation and manipulation, and
processing and preparing HTTP headers. Some HTML generation utilities are included as
well.
CGI.pm performs very well in in a vanilla CGI.pm environment and also comes with built-in
support for mod_perl and mod_perl2 as well as FastCGI.
It has the benefit of having developed and refined over 10 years with input from dozens of
contributors and being deployed on thousands of websites. CGI.pm has been included in the
Perl distribution since Perl 5.4, and has become a de-facto standard.
PROGRAMMING STYLE
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 how you create a simple "Hello
World" HTML page:
#!/usr/local/bin/perl -w
use CGI; # load CGI routines
$q = CGI->new; # 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/perl
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
CALLING CGI.PM ROUTINES
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.
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:
1. Use another name for the argument, if one is available. For example, -value is an
alias for -values.
2. Change the capitalization, e.g. -Values
3. 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".
CREATING A NEW QUERY OBJECT (OBJECT-ORIENTED STYLE):
$query = CGI->new;
This will parse the input (from POST, GET and DELETE methods) and store it into a perl5
object called $query.
Any filehandles from file uploads will have their position reset to the beginning of the
file.
CREATING A NEW QUERY OBJECT FROM AN INPUT FILE
$query = CGI->new(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 = CGI->new(\*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 a hash reference:
$query = CGI->new( {'dinosaur'=>'barney',
'song'=>'I love you',
'friends'=>[qw/Jessica George Nancy/]}
);
or from a properly formatted, URL-escaped query string:
$query = CGI->new('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 = CGI->new;
$new_query = CGI->new($old_query);
To create an empty query, initialize it from an empty string or hash:
$empty_query = CGI->new("");
-or-
$empty_query = CGI->new({});
FETCHING A LIST OF KEYWORDS FROM THE QUERY:
@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.
FETCHING THE NAMES OF ALL THE PARAMETERS PASSED TO YOUR SCRIPT:
@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 and contains a string
without ampersands (e.g. "value1+value2+value3") , there will be a single parameter named
"keywords" containing the "+"-delimited 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).
FETCHING THE VALUE OR VALUES OF A SINGLE NAMED PARAMETER:
@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.
If a value is not given in the query string, as in the queries "name1=&name2=", it will be
returned as an empty string.
If the parameter does not exist at all, then param() will return undef in a scalar
context, and the empty list in a list context.
SETTING THE VALUE(S) OF A NAMED PARAMETER:
$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');
APPENDING ADDITIONAL VALUES TO A NAMED PARAMETER:
$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.
IMPORTING ALL PARAMETERS INTO A NAMESPACE:
$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!!!!
NOTE 1: Variable names are transformed as necessary into legal Perl variable names. All
non-legal characters are transformed into underscores. If you need to keep the original
names, you should use the param() method instead to access CGI variables by name.
NOTE 2: 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.
DELETING A PARAMETER COMPLETELY:
$query->delete('foo','bar','baz');
This completely clears a list of parameters. 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.
DELETING ALL PARAMETERS:
$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.
HANDLING NON-URLENCODED ARGUMENTS
If POSTed data is not of type application/x-www-form-urlencoded or multipart/form-data,
then the POSTed data will not be processed, but instead be returned as-is in a parameter
named POSTDATA. To retrieve it, use code like this:
my $data = $query->param('POSTDATA');
Likewise if PUTed data can be retrieved with code like this:
my $data = $query->param('PUTDATA');
(If you don't know what the preceding means, don't worry about it. It only affects people
trying to use CGI for XML processing and other specialized tasks.)
DIRECT ACCESS TO THE PARAMETER LIST:
$q->param_fetch('address')->[1] = '1313 Mockingbird Lane';
unshift @{$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 given
in the previous sections, you can obtain a direct reference to it by calling the
param_fetch() method with the name of the parameter. This will return an array reference
to the named parameter, which you then can manipulate in any way you like.
You can also use a named argument style using the -name argument.
FETCHING THE PARAMETER LIST AS A HASH:
$params = $q->Vars;
print $params->{'address'};
@foo = split("\0",$params->{'foo'});
%params = $q->Vars;
use CGI ':cgi-lib';
$params = Vars;
Many people want to fetch the entire parameter list as a hash in which the keys are the
names of the CGI parameters, and the values are the parameters' values. The Vars() method
does this. Called in a scalar context, it returns the parameter list as a tied hash
reference. Changing a key changes the value of the parameter in the underlying CGI
parameter list. Called in a list context, it returns the parameter list as an ordinary
hash. This allows you to read the contents of the parameter list, but not to change it.
When using this, the thing you must watch out for are multivalued CGI parameters. Because
a hash cannot distinguish between scalar and list context, multivalued parameters will be
returned as a packed string, separated by the "\0" (null) character. You must split this
packed string in order to get at the individual values. This is the convention introduced
long ago by Steve Brenner in his cgi-lib.pl module for Perl version 4.
If you wish to use Vars() as a function, import the :cgi-lib set of function calls (also
see the section on CGI-LIB compatibility).
SAVING THE STATE OF THE SCRIPT TO A FILE:
$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;
$records = 5;
for (0..$records) {
my $q = CGI->new;
$q->param(-name=>'counter',-value=>$_);
$q->save(\*OUT);
}
close OUT;
# reopen for reading
open (IN,'<','test.out') || die;
while (!eof(IN)) {
my $q = CGI->new(\*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://stein.cshl.org/boulder/
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().
RETRIEVING CGI ERRORS
Errors can occur while processing user input, particularly when processing uploaded files.
When these errors occur, CGI will stop processing and return an empty parameter list. You
can test for the existence and nature of errors using the cgi_error() function. The error
messages are formatted as HTTP status codes. You can either incorporate the error text
into an HTML page, or use it as the value of the HTTP status:
my $error = $q->cgi_error;
if ($error) {
print $q->header(-status=>$error),
$q->start_html('Problems'),
$q->h2('Request not processed'),
$q->strong($error);
exit 0;
}
When using the function-oriented interface (see the next section), errors may only occur
the first time you call param(). Be ready for this!
USING THE FUNCTION-ORIENTED INTERFACE
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 groups 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 elements (such as <table>, <super> and
<sub>).
:html4
Import all methods that generate HTML 4 elements (such as <abbrev>, <acronym> and
<thead>).
:netscape
Import the <blink>, <fontsize> and <center> tags.
:html
Import all HTML-generating shortcuts (i.e. 'html2', 'html3', 'html4' and 'netscape')
:standard
Import "standard" features, 'html2', 'html3', 'html4', 'form' and 'cgi'.
:all
Import all the available methods. For the full list, see the CGI.pm code, where the
variable %EXPORT_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 immediately:
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;
PRAGMAS
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 enables debugging mode (pragma -debug):
use CGI qw/:standard -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 HTML
extension. This lets you go wild with new and unsupported tags:
use CGI qw(-any);
$q=CGI->new;
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 Malcolm Beattie's
Perl compiler. Use it in conjunction with the methods or method families 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:
use CGI();
CGI->compile();
This is particularly useful in a mod_perl environment, in which you might want to
precompile all CGI routines in a startup script, and then import the functions
individually in each mod_perl script.
-nosticky
By default the CGI module implements a state-preserving behavior called "sticky"
fields. The way this works is that if you are regenerating a form, the methods that
generate the form field values will interrogate param() to see if similarly-named
parameters are present in the query string. If they find a like-named parameter, they
will use it to set their default values.
Sometimes this isn't what you want. The -nosticky pragma prevents this behavior. You
can also selectively change the sticky behavior in each element that you generate.
-tabindex
Automatically add tab index attributes to each form field. With this option turned
off, you can still add tab indexes manually by passing a -tabindex option to each
field-generating method.
-no_undef_params
This keeps CGI.pm from including undef params in the parameter list.
-no_xhtml
By default, CGI.pm versions 2.69 and higher emit XHTML (http://www.w3.org/TR/xhtml1/).
The -no_xhtml pragma disables this feature. Thanks to Michalis Kabrianis
<kabrianis@hellug.gr> for this feature.
If start_html()'s -dtd parameter specifies an HTML 2.0, 3.2, 4.0 or 4.01 DTD, XHTML
will automatically be disabled without needing to use this pragma.
-utf8
This makes CGI.pm treat all parameters as UTF-8 strings. Use this with care, as it
will interfere with the processing of binary uploads. It is better to manually select
which fields are expected to return utf-8 strings and convert them using code like
this:
use Encode;
my $arg = decode utf8=>param('foo');
-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.
-newstyle_urls
Separate the name=value pairs in CGI parameter query strings with semicolons rather
than ampersands. For example:
?name=fred;age=24;favorite_color=3
Semicolon-delimited query strings are always accepted, and will be emitted by
self_url() and query_string(). newstyle_urls became the default in version 2.64.
-oldstyle_urls
Separate the name=value pairs in CGI parameter query strings with ampersands rather
than semicolons. This is no longer the default.
-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 to read CGI
parameters from the command line or STDIN, then use this pragma:
use CGI qw(-no_debug :standard);
-debug
This turns on full debugging. In addition to reading CGI arguments from the command-
line processing, CGI.pm will pause and try to read arguments from STDIN, producing the
message "(offline mode: enter name=value pairs on standard input)" features.
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, reducing, but
not eliminating the risk of eavesdropping (there is still a potential race condition).
To make life harder for the attacker, the program chooses tempfile names by
calculating a 32 bit checksum of the incoming HTTP headers.
To ensure that the temporary file cannot be read by other CGI scripts, use suEXEC or a
CGI wrapper program to run your script. The temporary file is created with mode 0600
(neither world nor group readable).
The temporary directory is selected using the following algorithm:
1. if $CGITempFile::TMPDIRECTORY is already set, use that
2. if the environment variable TMPDIR exists, use the location
indicated.
3. Otherwise try the locations /usr/tmp, /var/tmp, C:\temp,
/tmp, /temp, ::Temporary Items, and \WWW_ROOT.
Each of these locations is checked that it is a directory and is writable. If not,
the algorithm tries the next choice.
SPECIAL FORMS FOR IMPORTING HTML-TAG FUNCTIONS
Many of the methods generate HTML tags. As described below, tag functions automatically
generate both the opening and closing tags. For example:
print h1('Level 1 Header');
produces
<h1>Level 1 Header</h1>
There will be some times when you want to produce the start and end tags yourself. In
this case, you can use the form start_tag_name and end_tag_name, as in:
print start_h1,'Level 1 Header',end_h1;
With a few exceptions (described below), start_tag_name and end_tag_name functions are not
generated automatically when you use CGI. However, you can specify the tags you want to
generate start/end functions for by putting an asterisk in front of their name, or,
alternatively, requesting either "start_tag_name" or "end_tag_name" in the import list.
Example:
use CGI qw/:standard *table start_ul/;
In this example, the following functions are generated in addition to the standard ones:
1. start_table() (generates a <table> tag)
2. end_table() (generates a </table> tag)
3. start_ul() (generates a <ul> tag)
4. end_ul() (generates a </ul> tag)
GENERATING DYNAMIC DOCUMENTS
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.
CREATING A STANDARD HTTP HEADER:
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 header;
-or-
print header('image/gif');
-or-
print header('text/html','204 No response');
-or-
print header(-type=>'image/gif',
-nph=>1,
-status=>'402 Payment required',
-expires=>'+3d',
-cookie=>$cookie,
-charset=>'utf-7',
-attachment=>'foo.gif',
-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. Note that RFC 2616 expects
the human-readable phase to be there as well as the numeric status code.
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 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. Some 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 that expect
all their scripts to be NPH.
The -charset parameter can be used to control the character set sent to the browser. If
not provided, defaults to ISO-8859-1. As a side effect, this sets the charset() method as
well.
The -attachment parameter can be used to turn the page into an attachment. Instead of
displaying the page, some browsers will prompt the user to save it to disk. The value of
the argument is the suggested name for the saved file. In order for this to work, you may
have to set the -type to "application/octet-stream".
The -p3p parameter will add a P3P tag to the outgoing header. The parameter can be an
arrayref or a space-delimited string of P3P tags. For example:
print header(-p3p=>[qw(CAO DSP LAW CURa)]);
print header(-p3p=>'CAO DSP LAW CURa');
In either case, the outgoing header will be formatted as:
P3P: policyref="/w3c/p3p.xml" cp="CAO DSP LAW CURa"
CGI.pm will accept valid multi-line headers when each line is separated with a CRLF value
("\r\n" on most platforms) followed by at least one space. For example:
print header( -ingredients => "ham\r\n\seggs\r\n\sbacon" );
Invalid multi-line header input will trigger in an exception. When multi-line headers are
received, CGI.pm will always output them back as a single line, according to the folding
rules of RFC 2616: the newlines will be removed, while the white space remains.
GENERATING A REDIRECTION HEADER
print $q->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() method redirects the browser to a different URL. If you use redirection
like this, you should not print out a header as well.
You should always use full URLs (including the http: or ftp: part) in redirection
requests. Relative URLs will not work correctly.
You can also use named arguments:
print $q->redirect(
-uri=>'http://somewhere.else/in/movie/land',
-nph=>1,
-status=>'301 Moved Permanently');
All names arguments recognized by header() are also recognized by redirect(). However,
most HTTP headers, including those generated by -cookie and -target, are ignored by the
browser.
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 IIS, which expect all their scripts to be NPH.
The -status parameter will set the status of the redirect. HTTP defines three different
possible redirection status codes:
301 Moved Permanently
302 Found
303 See Other
The default if not specified is 302, which means "moved temporarily." You may change the
status to another status code if you wish. Be advised that changing the status to
anything other than 301, 302 or 303 will probably break redirection.
Note that the human-readable phrase is also expected to be present to conform with RFC
2616, section 6.1.
CREATING THE HTML DOCUMENT HEADER
print 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');
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, -dtd, -lang and -target (see below for the explanation). Any additional
parameters you provide, such as the 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. This is a non-standard HTTP feature which only works with
some browsers!
-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 a
hash 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">
To create an HTTP-EQUIV type of <meta> tag, use -head, described below.
The -style argument is used to incorporate cascading stylesheets into your code. See the
section on CASCADING STYLESHEETS for more information.
The -lang argument is used to incorporate a language attribute into the <html> tag. For
example:
print $q->start_html(-lang=>'fr-CA');
The default if not specified is "en-US" for US English, unless the -dtd parameter
specifies an HTML 2.0 or 3.2 DTD, in which case the lang attribute is left off. You can
force the lang attribute to left off in other cases by passing an empty string
(-lang=>'').
The -encoding argument can be used to specify the character set for XHTML. It defaults to
iso-8859-1 if not specified.
The -dtd argument can be used to specify a public DTD identifier string. For example:
-dtd => '-//W3C//DTD HTML 4.01 Transitional//EN')
Alternatively, it can take public and system DTD identifiers as an array:
dtd => [ '-//W3C//DTD HTML 4.01 Transitional//EN', 'http://www.w3.org/TR/html4/loose.dtd' ]
For the public DTD identifier to be considered, it must be valid. Otherwise it will be
replaced by the default DTD. If the public DTD contains 'XHTML', CGI.pm will emit XML.
The -declare_xml argument, when used in conjunction with XHTML, will put a <?xml>
declaration at the top of the HTML header. The sole purpose of this declaration is to
declare the character set encoding. In the absence of -declare_xml, the output HTML will
contain a <meta> tag that specifies the encoding, allowing the HTML to pass most
validators. The default for -declare_xml is false.
You can place other arbitrary HTML elements to the <head> section with the -head tag. For
example, to place a <link> element in the head section, use this:
print start_html(-head=>Link({-rel=>'shortcut icon',
-href=>'favicon.ico'}));
To incorporate multiple HTML elements into the <head> section, just pass an array
reference:
print start_html(-head=>[
Link({-rel=>'next',
-href=>'http://www.capricorn.com/s2.html'}),
Link({-rel=>'previous',
-href=>'http://www.capricorn.com/s1.html'})
]
);
And here's how to create an HTTP-EQUIV <meta> tag:
print start_html(-head=>meta({-http_equiv => 'Content-Type',
-content => 'text/html'}))
JAVASCRIPTING: The -script, -noScript, -onLoad, -onMouseOver, -onMouseOut and -onUnload
parameters are used to add 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 = CGI->new;
print header;
$JSCRIPT=<<END;
// Ask a silly question
function riddle_me_this() {
var r = prompt("What walks on four legs in the morning, " +
"two legs in the afternoon, " +
"and three legs in the evening?");
response(r);
}
// Get a silly answer
function response(answer) {
if (answer == "man")
alert("Right you are!");
else
alert("Wrong! Guess again.");
}
END
print start_html(-title=>'The Riddle of the Sphinx',
-script=>$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).
The <script> tag, has several attributes including "type", "charset" and "src". "src"
allows you to keep JavaScript code in an external file. To use these attributes pass a
HASH reference in the -script parameter containing one or more of -type, -src, or -code:
print $q->start_html(-title=>'The Riddle of the Sphinx',
-script=>{-type=>'JAVASCRIPT',
-src=>'/javascript/sphinx.js'}
);
print $q->(-title=>'The Riddle of the Sphinx',
-script=>{-type=>'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=>[
{ -type => 'text/javascript',
-src => '/javascript/utilities10.js'
},
{ -type => 'text/javascript',
-src => '/javascript/utilities11.js'
},
{ -type => 'text/jscript',
-src => '/javascript/utilities12.js'
},
{ -type => 'text/ecmascript',
-src => '/javascript/utilities219.js'
}
]
);
The option "-language" is a synonym for -type, and is supported for backwards
compatibility.
The old-style positional parameters are as follows:
Parameters:
1. The title
2. The author's e-mail address (will create a <link rev="MADE"> tag if present
3. 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!
4, 5, 6...
Any other parameters you want to include in the <body> tag. This is a good place to
put HTML extensions, such as colors and wallpaper patterns.
ENDING THE HTML DOCUMENT:
print $q->end_html;
This ends an HTML document by printing the </body></html> tags.
CREATING A SELF-REFERENCING URL THAT PRESERVES STATE INFORMATION:
$myself = $q->self_url;
print q(<a href="$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 = $q->self_url;
print "<a href=\"$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 = $q->query_string();
The behavior of calling query_string is currently undefined when the HTTP method is
something other than GET.
OBTAINING THE SCRIPT'S URL
$full_url = url();
$full_url = url(-full=>1); #alternative syntax
$relative_url = url(-relative=>1);
$absolute_url = url(-absolute=>1);
$url_with_path = url(-path_info=>1);
$url_with_path_and_query = url(-path_info=>1,-query=>1);
$netloc = url(-base => 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.
-base
Generate just the protocol and net location, as in http://www.foo.com:8000
-rewrite
If Apache's mod_rewrite is turned on, then the script name and path info probably
won't match the request that the user sent. Set -rewrite=>1 (default) to return URLs
that match what the user sent (the original request URI). Set -rewrite=>0 to return
URLs that match the URL after mod_rewrite's rules have run.
MIXING POST AND URL PARAMETERS
$color = url_param('color');
It is possible for a script to receive CGI parameters in the URL as well as in the fill-
out form by creating a form that POSTs to a URL containing a query string (a "?" mark
followed by arguments). The param() method will always return the contents of the POSTed
fill-out form, ignoring the URL's query string. To retrieve URL parameters, call the
url_param() method. Use it in the same way as param(). The main difference is that it
allows you to read the parameters, but not set them.
Under no circumstances will the contents of the URL query string interfere with similarly-
named CGI parameters in POSTed forms. If you try to mix a URL query string with a form
submitted with the GET method, the results will not be what you expect.
CREATING STANDARD HTML ELEMENTS:
CGI.pm defines general HTML shortcut methods for many HTML tags. HTML shortcuts are named
after a single HTML element and return a fragment of HTML text. Example:
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;
PROVIDING ARGUMENTS TO HTML SHORTCUTS
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 a hash reference, then the keys and values of the hash 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 accommodate 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=>''}) <img alt="">
THE DISTRIBUTIVE PROPERTY OF HTML SHORTCUTS
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'])
]
)
);
HTML SHORTCUTS AND LIST INTERPOLATION
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.
NON-STANDARD HTML SHORTCUTS
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
Accept
Sub
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.
AUTOESCAPING HTML
By default, all HTML that is emitted by the form-generating functions is passed through a
function called escapeHTML():
$escaped_string = escapeHTML("unescaped string");
Escape HTML formatting characters in a string.
Provided that you have specified a character set of ISO-8859-1 (the default), the standard
HTML escaping rules will be used. The "<" character becomes "<", ">" becomes ">",
"&" becomes "&", and the quote character becomes """. In addition, the
hexadecimal 0x8b and 0x9b characters, which some browsers incorrectly interpret as the
left and right angle-bracket characters, are replaced by their numeric character entities
("‹" and "›"). If you manually change the charset, either by calling the
charset() method explicitly or by passing a -charset argument to header(), then all
characters will be replaced by their numeric entities, since CGI.pm has no lookup table
for all the possible encodings.
"escapeHTML()" expects the supplied string to be a character string. This means you should
Encode::decode data received from "outside" and Encode::encode your strings before sending
them back outside. If your source code UTF-8 encoded and you want to upgrade string
literals in your source to character strings, you can use "use utf8". See perlunitut,
perlunifaq and perlunicode for more information on how Perl handles the difference between
bytes and characters.
The automatic escaping does not apply to other shortcuts, such as h1(). You should call
escapeHTML() yourself on untrusted data in order to protect your pages against nasty
tricks that people may enter into guestbooks, etc.. To change the character set, use
charset(). To turn autoescaping off completely, use autoEscape(0):
$charset = charset([$charset]);
Get or set the current character set.
$flag = autoEscape([$flag]);
Get or set the value of the autoescape flag.
PRETTY-PRINTING HTML
By default, all the HTML produced by these functions comes out as one long line without
carriage returns or indentation. This is yuck, but it does reduce the size of the
documents by 10-20%. To get pretty-printed output, please use CGI::Pretty, a subclass
contributed by Brian Paulsen.
CREATING FILL-OUT FORMS:
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 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 = CGI->new;
$query->autoEscape(0);
Note that autoEscape() is exclusively used to effect the behavior of how some CGI.pm HTML
generation functions handle escaping. Calling escapeHTML() explicitly will always escape
the HTML.
A Lurking Trap! Some of the form-element generating methods return multiple tags. In a
scalar context, the tags will be concatenated together with spaces, or whatever is the
current value of the $" global. In a list context, the methods will return a list of
elements, allowing you to modify them if you wish. Usually you will not notice this
behavior, but beware of this:
printf("%s\n",end_form())
end_form() produces several tags, and only the first of them will be printed because the
format only expects one value.
<p>
CREATING AN ISINDEX TAG
print isindex(-action=>$action);
-or-
print isindex($action);
Prints out an <isindex> tag. Not very exciting. The parameter -action specifies the URL
of the script to process the query. The default is to process the query with the current
script.
STARTING AND ENDING A FORM
print start_form(-method=>$method,
-action=>$action,
-enctype=>$encoding);
<... various form stuff ...>
print end_form;
-or-
print start_form($method,$action,$encoding);
<... various form stuff ...>
print end_form;
start_form() will return a <form> tag with the optional method, action and form encoding
that you specify. The defaults are:
method: POST
action: this script
enctype: application/x-www-form-urlencoded for non-XHTML
multipart/form-data for XHTML, see multipart/form-data below.
end_form() returns the closing </form> tag.
Start_form()'s enctype argument tells the browser how to package the various fields of the
form before sending the form to the server. Two values are possible:
Note: These methods were previously named startform() and endform(). These methods are
now DEPRECATED. Please use start_form() and end_form() instead.
application/x-www-form-urlencoded
This is the older type of encoding. 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. 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. 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.
If XHTML is activated (the default), then forms will be automatically created using
this type of encoding.
The start_form() method uses the older form of encoding by default unless XHTML is
requested. If you want to use the newer form of encoding by default, you can call
start_multipart_form() instead of start_form(). The method end_multipart_form() is an
alias to end_form().
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.
FORM ELEMENTS
After starting a form, you will typically create one or more textfields, popup menus,
radio groups and other form elements. Each of these elements takes a standard set of
named arguments. Some elements also have optional arguments. The standard arguments are
as follows:
-name
The name of the field. After submission this name can be used to retrieve the field's
value using the param() method.
-value, -values
The initial value of the field which will be returned to the script after form
submission. Some form elements, such as text fields, take a single scalar -value
argument. Others, such as popup menus, take a reference to an array of values. The two
arguments are synonyms.
-tabindex
A numeric value that sets the order in which the form element receives focus when the
user presses the tab key. Elements with lower values receive focus first.
-id A string identifier that can be used to identify this element to JavaScript and DHTML.
-override
A boolean, which, if true, forces the element to take on the value specified by
-value, overriding the sticky behavior described earlier for the -nosticky pragma.
-onChange, -onFocus, -onBlur, -onMouseOver, -onMouseOut, -onSelect
These are used to assign JavaScript event handlers. See the JavaScripting section for
more details.
Other common arguments are described in the next section. In addition to these, all
attributes described in the HTML specifications are supported.
CREATING A TEXT FIELD
print textfield(-name=>'field_name',
-value=>'starting value',
-size=>50,
-maxlength=>80);
-or-
print textfield('field_name','starting value',50,80);
textfield() will return a text input field.
Parameters
1. The first parameter is the required name for the field (-name).
2. The optional second parameter is the default starting value for the field contents
(-value, formerly known as -default).
3. The optional third parameter is the size of the field in
characters (-size).
4. 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 = 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:
param('foo',"I'm taking over this value!");
CREATING A BIG TEXT FIELD
print textarea(-name=>'foo',
-default=>'starting value',
-rows=>10,
-columns=>50);
-or
print 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.
CREATING A PASSWORD FIELD
print password_field(-name=>'secret',
-value=>'starting value',
-size=>50,
-maxlength=>80);
-or-
print 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.
CREATING A FILE UPLOAD FIELD
print filefield(-name=>'uploaded_file',
-default=>'starting value',
-size=>50,
-maxlength=>80);
-or-
print filefield('uploaded_file','starting value',50,80);
filefield() will return a file upload field. 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 start_form() with an encoding type of &CGI::MULTIPART, or by calling the new
method start_multipart_form() instead of vanilla start_form().
Parameters
1. The first parameter is the required name for the field (-name).
2. The optional second parameter is the starting value for the field contents to be used
as the default file name (-default).
For security reasons, browsers don'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 some browser will eventually provide support for
it.
3. The optional third parameter is the size of the field in characters (-size).
4. The optional fourth parameter is the maximum number of characters the field will
accept (-maxlength).
JAVASCRIPTING: The -onChange, -onFocus, -onBlur, -onMouseOver, -onMouseOut and -onSelect
parameters are recognized. See textfield() for details.
PROCESSING A FILE UPLOAD FIELD
Basics
When the form is processed, you can retrieve an IO::Handle compatible handle for a file
upload field like this:
$lightweight_fh = $q->upload('field_name');
# undef may be returned if it's not a valid file handle
if (defined $lightweight_fh) {
# Upgrade the handle to one compatible with IO::Handle:
my $io_handle = $lightweight_fh->handle;
open (OUTFILE,'>>','/usr/local/web/users/feedback');
while ($bytesread = $io_handle->read($buffer,1024)) {
print OUTFILE $buffer;
}
}
In a list context, upload() will return an array of filehandles. This makes it possible
to process forms that use the same name for multiple upload fields.
If you want the entered file name for the file, you can just call param():
$filename = $q->param('field_name');
Different browsers will return slightly different things for the name. Some browsers
return the filename only. Others return the full path to the file, using the path
conventions of the user's machine. Regardless, the name returned is always the name of
the file on the user's machine, and is unrelated to the name of the temporary file that
CGI.pm creates during upload spooling (see below).
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. To
retrieve this information, call uploadInfo(). It returns a reference to a hash containing
all the document headers.
$filename = $q->param('uploaded_file');
$type = $q->uploadInfo($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.
Accessing the temp files directly
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. You can access the temp file for a file upload 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.
Handling interrupted file uploads
There are occasionally problems involving parsing the uploaded file. This usually happens
when the user presses "Stop" before the upload is finished. In this case, CGI.pm will
return undef for the name of the uploaded file and set cgi_error() to the string "400 Bad
request (malformed multipart POST)". This error message is designed so that you can
incorporate it into a status code to be sent to the browser. Example:
$file = $q->upload('uploaded_file');
if (!$file && $q->cgi_error) {
print $q->header(-status=>$q->cgi_error);
exit 0;
}
You are free to create a custom HTML page to complain about the error, if you wish.
Progress bars for file uploads and avoiding temp files
CGI.pm gives you low-level access to file upload management through a file upload hook.
You can use this feature to completely turn off the temp file storage of file uploads, or
potentially write your own file upload progress meter.
This is much like the UPLOAD_HOOK facility available in Apache::Request, with the
exception that the first argument to the callback is an Apache::Upload object, here it's
the remote filename.
$q = CGI->new(\&hook [,$data [,$use_tempfile]]);
sub hook {
my ($filename, $buffer, $bytes_read, $data) = @_;
print "Read $bytes_read bytes of $filename\n";
}
The $data field is optional; it lets you pass configuration information (e.g. a database
handle) to your hook callback.
The $use_tempfile field is a flag that lets you turn on and off CGI.pm's use of a
temporary disk-based file during file upload. If you set this to a FALSE value (default
true) then $q->param('uploaded_file') will no longer work, and the only way to get at the
uploaded data is via the hook you provide.
If using the function-oriented interface, call the CGI::upload_hook() method before
calling param() or any other CGI functions:
CGI::upload_hook(\&hook [,$data [,$use_tempfile]]);
This method is not exported by default. You will have to import it explicitly if you wish
to use it without the CGI:: prefix.
Troubleshooting file uploads on Windows
If you are using CGI.pm on a Windows platform and find that binary files get slightly
larger when uploaded but that text files remain the same, then you have forgotten to
activate binary mode on the output filehandle. Be sure to call binmode() on any handle
that you create to write the uploaded file to disk.
Older ways to process file uploads
( This section is here for completeness. if you are building a new application with
CGI.pm, you can skip it. )
The original way to process file uploads with CGI.pm was to use param(). The value it
returns has a dual nature as both a file name and a lightweight filehandle. This dual
nature is problematic if you following the recommended practice of having "use strict" in
your code. Perl will complain when you try to use a string as a filehandle. More
seriously, it is possible for the remote user to type garbage into the upload field, in
which case what you get from param() is not a filehandle at all, but a string.
To solve this problem the upload() method was added, which always returns a lightweight
filehandle. This generally works well, but will have trouble interoperating with some
other modules because the file handle is not derived from IO::Handle. So that brings us to
current recommendation given above, which is to call the handle() method on the file
handle returned by upload(). That upgrades the handle to an IO::Handle. It's a big win
for compatibility for a small penalty of loading IO::Handle the first time you call it.
CREATING A POPUP MENU
print popup_menu('menu_name',
['eenie','meenie','minie'],
'meenie');
-or-
%labels = ('eenie'=>'your first choice',
'meenie'=>'your second choice',
'minie'=>'your third choice');
%attributes = ('eenie'=>{'class'=>'class of first choice'});
print popup_menu('menu_name',
['eenie','meenie','minie'],
'meenie',\%labels,\%attributes);
-or (named parameter style)-
print popup_menu(-name=>'menu_name',
-values=>['eenie','meenie','minie'],
-default=>['meenie','minie'],
-labels=>\%labels,
-attributes=>\%attributes);
popup_menu() creates a menu.
1. The required first argument is the menu's name (-name).
2. 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".
3. The optional third parameter (-default) is the name of the default menu choice. If
not specified, the first item will be the default. The values of the previous choice
will be maintained across queries. Pass an array reference to select multiple
defaults.
4. The optional fourth parameter (-labels) is provided for people who want to use
different values for the user-visible label inside the popup menu and the value
returned to your script. It's a pointer to an hash relating menu values to user-
visible labels. If you leave this parameter blank, the menu values will be displayed
by default. (You can also leave a label undefined if you want to).
5. The optional fifth parameter (-attributes) is provided to assign any of the common
HTML attributes to an individual menu item. It's a pointer to a hash relating menu
values to another hash with the attribute's name as the key and the attribute's value
as the value.
When the form is processed, the selected value of the popup menu can be retrieved using:
$popup_menu_value = param('menu_name');
CREATING AN OPTION GROUP
Named parameter style
print popup_menu(-name=>'menu_name',
-values=>[qw/eenie meenie minie/,
optgroup(-name=>'optgroup_name',
-values => ['moe','catch'],
-attributes=>{'catch'=>{'class'=>'red'}})],
-labels=>{'eenie'=>'one',
'meenie'=>'two',
'minie'=>'three'},
-default=>'meenie');
Old style
print popup_menu('menu_name',
['eenie','meenie','minie',
optgroup('optgroup_name', ['moe', 'catch'],
{'catch'=>{'class'=>'red'}})],'meenie',
{'eenie'=>'one','meenie'=>'two','minie'=>'three'});
optgroup() creates an option group within a popup menu.
1. The required first argument (-name) is the label attribute of the optgroup and is not
inserted in the parameter list of the query.
2. 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. If you pass a HASH
reference, the keys will be used for the menu values, and the values will be used for
the menu labels (see -labels below).
3. The optional third parameter (-labels) allows you to pass a reference to a hash
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). This is equivalent to using
a hash reference for the -values parameter.
4. An optional fourth parameter (-labeled) can be set to a true value and indicates that
the values should be used as the label attribute for each option element within the
optgroup.
5. An optional fifth parameter (-novals) can be set to a true value and indicates to
suppress the val attribute in each option element within the optgroup.
See the discussion on optgroup at W3C
(http://www.w3.org/TR/REC-html40/interact/forms.html#edef-OPTGROUP) for details.
6. An optional sixth parameter (-attributes) is provided to assign any of the common HTML
attributes to an individual menu item. It's a pointer to a hash relating menu values
to another hash with the attribute's name as the key and the attribute's value as the
value.
CREATING A SCROLLING LIST
print scrolling_list('list_name',
['eenie','meenie','minie','moe'],
['eenie','moe'],5,'true',{'moe'=>{'class'=>'red'}});
-or-
print scrolling_list('list_name',
['eenie','meenie','minie','moe'],
['eenie','moe'],5,'true',
\%labels,%attributes);
-or-
print scrolling_list(-name=>'list_name',
-values=>['eenie','meenie','minie','moe'],
-default=>['eenie','moe'],
-size=>5,
-multiple=>'true',
-labels=>\%labels,
-attributes=>\%attributes);
scrolling_list() creates a scrolling list.
Parameters:
1. The first and second arguments are the list name (-name) and values (-values). As in
the popup menu, the second argument should be an array reference.
2. 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. In the named parameter version, you can use the synonym "-defaults" for this
parameter.
3. The optional fourth argument is the size of the list (-size).
4. The optional fifth argument can be set to true to allow multiple simultaneous
selections (-multiple). Otherwise only one selection will be allowed at a time.
5. The optional sixth argument is a pointer to a hash containing long user-visible labels
for the list items (-labels). If not provided, the values will be displayed.
6. The optional sixth parameter (-attributes) is provided to assign any of the common
HTML attributes to an individual menu item. It's a pointer to a hash relating menu
values to another hash with the attribute's name as the key and the attribute's value
as the value.
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 = param('list_name');
CREATING A GROUP OF RELATED CHECKBOXES
print checkbox_group(-name=>'group_name',
-values=>['eenie','meenie','minie','moe'],
-default=>['eenie','moe'],
-linebreak=>'true',
-disabled => ['moe'],
-labels=>\%labels,
-attributes=>\%attributes);
print checkbox_group('group_name',
['eenie','meenie','minie','moe'],
['eenie','moe'],'true',\%labels,
{'moe'=>{'class'=>'red'}});
HTML3-COMPATIBLE BROWSERS ONLY:
print 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.
Parameters:
1. The first and second arguments are the checkbox name and values, respectively (-name
and -values). 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.
2. 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.
3. 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.
The optional -labels argument is a pointer to a hash relating the checkbox values to the
user-visible labels that will be printed next to them. If not provided, the values will
be used as the default.
The optional parameters -rows, and -columns 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.
The option -disabled takes an array of checkbox values and disables them by greying them
out (this may not be supported by all browsers).
The optional -attributes argument is provided to assign any of the common HTML attributes
to an individual menu item. It's a pointer to a hash relating menu values to another hash
with the attribute's name as the key and the attribute's value as the value.
The optional -tabindex argument can be used to control the order in which radio buttons
receive focus when the user presses the tab button. If passed a scalar numeric value, the
first element in the group will receive this tab index and subsequent elements will be
incremented by one. If given a reference to an array of radio button values, then the
indexes will be jiggered so that the order specified in the array will correspond to the
tab order. You can also pass a reference to a hash in which the hash keys are the radio
button values and the values are the tab indexes of each button. Examples:
-tabindex => 100 # this group starts at index 100 and counts up
-tabindex => ['moe','minie','eenie','meenie'] # tab in this order
-tabindex => {meenie=>100,moe=>101,minie=>102,eenie=>200} # tab in this order
The optional -labelattributes argument will contain attributes attached to the <label>
element that surrounds each button.
When the form is processed, 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:
@turned_on = 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 = checkbox_group(-name=>'group_name',-values=>\@values);
&use_in_creative_way(@h);
CREATING A STANDALONE CHECKBOX
print checkbox(-name=>'checkbox_name',
-checked=>1,
-value=>'ON',
-label=>'CLICK ME');
-or-
print checkbox('checkbox_name','checked','ON','CLICK ME');
checkbox() is used to create an isolated checkbox that isn't logically related to any
others.
Parameters:
1. The first parameter is the required name for the checkbox (-name). It will also be
used for the user-readable label printed next to the checkbox.
2. The optional second parameter (-checked) specifies that the checkbox is turned on by
default. Synonyms are -selected and -on.
3. The optional third parameter (-value) specifies the value of the checkbox when it is
checked. If not provided, the word "on" is assumed.
4. The optional fourth parameter (-label) is the user-readable label to be attached to
the checkbox. If not provided, the checkbox name is used.
The value of the checkbox can be retrieved using:
$turned_on = param('checkbox_name');
CREATING A RADIO BUTTON GROUP
print radio_group(-name=>'group_name',
-values=>['eenie','meenie','minie'],
-default=>'meenie',
-linebreak=>'true',
-labels=>\%labels,
-attributes=>\%attributes);
-or-
print radio_group('group_name',['eenie','meenie','minie'],
'meenie','true',\%labels,\%attributes);
HTML3-COMPATIBLE BROWSERS ONLY:
print 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)
Parameters:
1. The first argument is the name of the group and is required (-name).
2. The second argument (-values) is 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".
3. The optional third parameter (-default) is the name of the default button to turn on.
If not specified, the first item will be the default. You can provide a nonexistent
button name, such as "-" to start up with no buttons selected.
4. The optional fourth parameter (-linebreak) can be set to 'true' to put line breaks
between the buttons, creating a vertical list.
5. The optional fifth parameter (-labels) is a pointer to an associative array relating
the radio button values to user-visible labels to be used in the display. If not
provided, the values themselves are displayed.
All modern browsers can take advantage of the optional parameters -rows, and -columns.
These parameters cause 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 -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 interpretation of the radio
buttons -- they're still a single named unit.
The optional -tabindex argument can be used to control the order in which radio buttons
receive focus when the user presses the tab button. If passed a scalar numeric value, the
first element in the group will receive this tab index and subsequent elements will be
incremented by one. If given a reference to an array of radio button values, then the
indexes will be jiggered so that the order specified in the array will correspond to the
tab order. You can also pass a reference to a hash in which the hash keys are the radio
button values and the values are the tab indexes of each button. Examples:
-tabindex => 100 # this group starts at index 100 and counts up
-tabindex => ['moe','minie','eenie','meenie'] # tab in this order
-tabindex => {meenie=>100,moe=>101,minie=>102,eenie=>200} # tab in this order
The optional -attributes argument is provided to assign any of the common HTML attributes
to an individual menu item. It's a pointer to a hash relating menu values to another hash
with the attribute's name as the key and the attribute's value as the value.
The optional -labelattributes argument will contain attributes attached to the <label>
element that surrounds each button.
When the form is processed, the selected radio button can be retrieved using:
$which_radio_button = 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 = radio_group(-name=>'group_name',-values=>\@values);
&use_in_creative_way(@h);
CREATING A SUBMIT BUTTON
print submit(-name=>'button_name',
-value=>'value');
-or-
print submit('button_name','value');
submit() will create the query submission button. Every form should have one of these.
Parameters:
1. The first argument (-name) is optional. You can give the button a name if you have
several submission buttons in your form and you want to distinguish between them.
2. The second argument (-value) is also optional. This gives the button a value that
will be passed to your script in the query string. The name will also be used as the
user-visible label.
3. 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.
You can figure out which button was pressed by using different values for each one:
$which_one = param('button_name');
CREATING A RESET BUTTON
print 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.
Note that this conflicts with the Perl reset() built-in. Use CORE::reset() to get the
original reset function.
CREATING A DEFAULT BUTTON
print 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.
CREATING A HIDDEN FIELD
print hidden(-name=>'hidden_name',
-default=>['value1','value2'...]);
-or-
print 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.
Parameters:
1. The first argument is required and specifies the name of this field (-name).
2. The second argument is also required and specifies its value (-default). In the named
parameter style of calling, you can provide a single value here or a reference to a
whole list
Fetch the value of a hidden field this way:
$hidden_value = 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:
param('hidden_name','new','values','here');
CREATING A CLICKABLE IMAGE BUTTON
print image_button(-name=>'button_name',
-src=>'/source/URL',
-align=>'MIDDLE');
-or-
print 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.
Parameters:
1. The first argument (-name) is required and specifies the name of this field.
2. The second argument (-src) is also required and specifies the URL
3. The third option (-align, optional) is an alignment type, and may be TOP, BOTTOM or
MIDDLE
Fetch the value of the button this way:
$x = param('button_name.x');
$y = param('button_name.y');
CREATING A JAVASCRIPT ACTION BUTTON
print button(-name=>'button_name',
-value=>'user visible label',
-onClick=>"do_something()");
-or-
print button('button_name',"user visible value","do_something()");
button() produces an "<input>" tag with "type="button"". When it's pressed the fragment
of JavaScript code pointed to by the -onClick parameter will be executed.
HTTP COOKIES
Browsers support a so-called "cookie" designed to help maintain state within a browser
session. CGI.pm has several methods that support cookies.
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:
1. 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 the browser and restarts it. If an expiration date
isn't specified, the cookie will remain active until the user quits the browser.
2. 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 the browser 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.
3. 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.
4. 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.
The interface to HTTP cookies is the cookie() method:
$cookie = cookie(-name=>'sessionID',
-value=>'xyzzy',
-expires=>'+1h',
-path=>'/cgi-bin/database',
-domain=>'.capricorn.org',
-secure=>1);
print header(-cookie=>$cookie);
cookie() creates a new cookie. Its parameters include:
-name
The name of the cookie (required). This can be any string at all. Although browsers
limit their 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 hash
reference. For example, you can store an entire hash into a cookie this way:
$cookie=cookie(-name=>'family information',
-value=>\%childrens_ages);
-path
The optional partial path for which this cookie will be valid, as described above.
-domain
The optional partial domain for which this cookie will be valid, as described above.
-expires
The optional expiration date for this cookie. The format is as described in the
section on the header() method:
"+1h" one hour from now
-secure
If set to true, this cookie will only be used within a secure SSL session.
The cookie created by cookie() must be incorporated into the HTTP header within the string
returned by the header() method:
use CGI ':standard';
print header(-cookie=>$my_cookie);
To create multiple cookies, give header() an array reference:
$cookie1 = cookie(-name=>'riddle_name',
-value=>"The Sphynx's Question");
$cookie2 = cookie(-name=>'answers',
-value=>\%answers);
print header(-cookie=>[$cookie1,$cookie2]);
To retrieve a cookie, request it by name by calling cookie() method without the -value
parameter. This example uses the object-oriented form:
use CGI;
$query = CGI->new;
$riddle = $query->cookie('riddle_name');
%answers = $query->cookie('answers');
Cookies created with a single scalar value, such as the "riddle_name" cookie, will be
returned in that form. Cookies with array and hash values can also be retrieved.
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=cookie(-name=>'answers',-value=>[param('answers')]);
# vice-versa
param(-name=>'answers',-value=>[cookie('answers')]);
If you call cookie() without any parameters, it will return a list of the names of all
cookies passed to your script:
@cookies = cookie();
See the cookie.cgi example script for some ideas on how to use cookies effectively.
WORKING WITH FRAMES
It's possible for CGI.pm scripts to write into several browser panels and windows using
the HTML 4 frame mechanism. There are three techniques for defining new frames
programmatically:
1. Create a <Frameset> document
After writing out the HTTP header, instead of creating a standard HTML document using
the 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.
2. Specify the destination for the document in the HTTP header
You may provide a -target parameter to the header() method:
print header(-target=>'ResultsWindow');
This will tell the browser to load the output of your script into the frame named
"ResultsWindow". If a frame of that name doesn't already exist, the browser 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 HTML "<frame>" documentation for
details.
3. Specify the destination for the document in the <form> tag
You can specify the frame to load in the FORM tag itself. With CGI.pm it looks like
this:
print start_form(-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.
The script "frameset.cgi" in the examples directory shows one way to create pages in which
the fill-out form and the response live in side-by-side frames.
SUPPORT FOR JAVASCRIPT
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. Here is a partial list:
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
onMouseOver
The mouse has moved over an element.
+ Text fields
+ Text areas
+ Password fields
+ File fields
+ Popup Menus
+ Scrolling lists
onMouseOut
The mouse has moved off an element.
+ Text fields
+ Text areas
+ Password fields
+ File fields
+ Popup Menus
+ Scrolling lists
In order to register a JavaScript event handler with an HTML element, just use the event
name as a parameter when you call the corresponding CGI method. For example, to have your
validateAge() JavaScript code executed every time the textfield named "age" changes,
generate the field like this:
print textfield(-name=>'age',-onChange=>"validateAge(this)");
This example assumes that you've already declared the validateAge() function by
incorporating it into a <SCRIPT> block. The CGI.pm start_html() method provides a
convenient way to create this section.
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 start_form(-onSubmit=>"validateMe(this)");
See the javascript.cgi script for a demonstration of how this all works.
LIMITED SUPPORT FOR CASCADING STYLE SHEETS
CGI.pm has limited support for HTML3's cascading style sheets (css). To incorporate a
stylesheet into your document, pass the start_html() method a -style parameter. The value
of this parameter may be a scalar, in which case it is treated as the source URL for the
stylesheet, 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."
You may also specify the type of the stylesheet by adding the optional -type parameter to
the hash pointed to by -style. If not specified, the style defaults to 'text/css'.
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/Style/CSS/ 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;
Pass an array reference to -code or -src in order to incorporate multiple stylesheets into
your document.
Should you wish to incorporate a verbatim stylesheet that includes arbitrary formatting in
the header, you may pass a -verbatim tag to the -style hash, as follows:
print start_html (-style => {-verbatim => '@import
url("/server-common/css/'.$cssFile.'");',
-src => '/server-common/css/core.css'});
This will generate an HTML header that contains this:
<link rel="stylesheet" type="text/css" href="/server-common/css/core.css">
<style type="text/css">
@import url("/server-common/css/main.css");
</style>
Any additional arguments passed in the -style value will be incorporated into the <link>
tag. For example:
start_html(-style=>{-src=>['/styles/print.css','/styles/layout.css'],
-media => 'all'});
This will give:
<link rel="stylesheet" type="text/css" href="/styles/print.css" media="all"/>
<link rel="stylesheet" type="text/css" href="/styles/layout.css" media="all"/>
<p>
To make more complicated <link> tags, use the Link() function and pass it to start_html()
in the -head argument, as in:
@h = (Link({-rel=>'stylesheet',-type=>'text/css',-src=>'/ss/ss.css',-media=>'all'}),
Link({-rel=>'stylesheet',-type=>'text/css',-src=>'/ss/fred.css',-media=>'paper'}));
print start_html({-head=>\@h})
To create primary and "alternate" stylesheet, use the -alternate option:
start_html(-style=>{-src=>[
{-src=>'/styles/print.css'},
{-src=>'/styles/alt.css',-alternate=>1}
]
});
DEBUGGING
If you are running the script from the command line or in the perl debugger, you can pass
the script a list of keywords or parameter=value pairs on the command line or from
standard input (you don't have to worry about tricking your script into reading from
environment variables). You can pass keywords like this:
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
To turn off this feature, use the -no_debug pragma.
To test the POST method, you may enable full debugging with the -debug pragma. This will
allow you to feed newline-delimited name=value pairs to the script 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"
Finally, you can set the path info for the script by prefixing the first name/value
parameter with the path followed by a question mark (?):
your_script.pl /your/path/here?name1=value1&name2=value2
DUMPING OUT ALL THE NAME/VALUE PAIRS
The 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 Dump
Produces something that looks like:
<ul>
<li>name1
<ul>
<li>value1
<li>value2
</ul>
<li>name2
<ul>
<li>value1
</ul>
</ul>
As a shortcut, you can interpolate the entire CGI object into a string and it will be
replaced with the a nice HTML dump shown above:
$query=CGI->new;
print "<h2>Current Values</h2> $query\n";
FETCHING ENVIRONMENT VARIABLES
Some of the more useful environment variables can be fetched through this interface. The
methods are as follows:
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 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.
Note that the capitalization changed between version 2.43 and 2.44 in order to avoid
conflict with Perl's accept() function.
raw_cookie()
Returns the HTTP_COOKIE variable. Cookies have a special format, and this method call
just returns the raw form (?cookie dough). See cookie() for ways of setting and
retrieving cooked cookies.
Called with no parameters, raw_cookie() returns the packed cookie structure. You can
separate it into individual cookies by splitting on the character sequence "; ".
Called with the name of a cookie, retrieves the unescaped form of the cookie. You can
use the regular cookie() method to get the names, or use the raw_fetch() method from
the CGI::Cookie module.
user_agent()
Returns the HTTP_USER_AGENT variable. If you give this method a single argument, it
will attempt to pattern match on it, allowing you to do something like
user_agent(Mozilla);
path_info()
Returns additional path information from the script URL. E.G. fetching
/cgi-bin/your_script/additional/stuff will result in path_info() returning
"/additional/stuff".
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_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".
The Microsoft IIS is broken with respect to the translated path as well.
remote_host()
Returns either the remote host name or IP address. if the former is unavailable.
remote_addr()
Returns the remote host IP address, or 127.0.0.1 if the address is unavailable.
script_name() Return the script name as a partial URL, for self-referring scripts.
referer()
Return the URL of the page the browser was viewing prior to fetching your script. Not
available for all browsers.
auth_type ()
Return the authorization/verification method in use for this script, if any.
server_name ()
Returns the name of the server, usually the machine's host name.
virtual_host ()
When using virtual hosts, returns the name of the host that the browser attempted to
contact
server_port ()
Return the port that the server is listening on.
virtual_port ()
Like server_port() except that it takes virtual hosts into account. Use this when
running with virtual hosts.
server_software ()
Returns the server software and version number.
remote_user ()
Return the authorization/verification name used for user verification, if this script
is protected.
user_name ()
Attempt to obtain the remote user's name, using a variety of different techniques.
This only works with older browsers such as Mosaic. Newer browsers do not report the
user name for privacy reasons!
request_method()
Returns the method used to access your script, usually one of 'POST', 'GET' or 'HEAD'.
content_type()
Returns the content_type of data submitted in a POST, generally multipart/form-data or
application/x-www-form-urlencoded
http()
Called with no arguments returns the list of HTTP environment variables, including
such things as HTTP_USER_AGENT, HTTP_ACCEPT_LANGUAGE, and HTTP_ACCEPT_CHARSET,
corresponding to the like-named HTTP header fields in the request. Called with the
name of an HTTP header field, returns its value. Capitalization and the use of
hyphens versus underscores are not significant.
For example, all three of these examples are equivalent:
$requested_language = http('Accept-language');
$requested_language = http('Accept_language');
$requested_language = http('HTTP_ACCEPT_LANGUAGE');
https()
The same as http(), but operates on the HTTPS environment variables present when the
SSL protocol is in effect. Can be used to determine whether SSL is turned on.
USING NPH SCRIPTS
NPH, or "no-parsed-header", scripts bypass the server completely by sending the complete
HTTP header directly to the browser. This has slight performance benefits, but is of most
use for taking advantage of HTTP extensions that are not directly supported by your
server, such as server push and PICS headers.
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.
However, note that if you have applied Service Pack 6, much of the functionality of NPH
scripts, including the ability to redirect while setting a cookie, do not work at all on
IIS without a special patch from Microsoft. See
http://web.archive.org/web/20010812012030/http://support.microsoft.com/support/kb/articles/Q280/3/41.ASP
Non-Parsed Headers Stripped From CGI Applications That Have nph- Prefix in Name.
In the use statement
Simply add the "-nph" pragma 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 header(-nph=>1);
Server Push
CGI.pm provides four simple functions for producing multipart documents of the type needed
to implement server push. These functions were graciously provided by Ed Jordan
<ed@fidalgo.net>. To import these into your namespace, you must import the ":push" set.
You are also advised to put the script into NPH mode and to set $| to 1 to avoid buffering
problems.
Here is a simple script that demonstrates server push:
#!/usr/local/bin/perl
use CGI qw/:push -nph/;
$| = 1;
print multipart_init(-boundary=>'----here we go!');
for (0 .. 4) {
print multipart_start(-type=>'text/plain'),
"The current time is ",scalar(localtime),"\n";
if ($_ < 4) {
print multipart_end;
} else {
print multipart_final;
}
sleep 1;
}
This script initializes server push by calling multipart_init(). It then enters a loop in
which it begins a new multipart section by calling multipart_start(), prints the current
local time, and ends a multipart section with multipart_end(). It then sleeps a second,
and begins again. On the final iteration, it ends the multipart section with
multipart_final() rather than with multipart_end().
multipart_init()
multipart_init(-boundary=>$boundary);
Initialize the multipart system. The -boundary argument specifies what MIME boundary
string to use to separate parts of the document. If not provided, CGI.pm chooses a
reasonable boundary for you.
multipart_start()
multipart_start(-type=>$type)
Start a new part of the multipart document using the specified MIME type. If not
specified, text/html is assumed.
multipart_end()
multipart_end()
End a part. You must remember to call multipart_end() once for each
multipart_start(), except at the end of the last part of the multipart document when
multipart_final() should be called instead of multipart_end().
multipart_final()
multipart_final()
End all parts. You should call multipart_final() rather than multipart_end() at the
end of the last part of the multipart document.
Users interested in server push applications should also have a look at the CGI::Push
module.
Avoiding Denial of Service Attacks
A potential problem with CGI.pm is that, by default, it attempts to process form POSTings
no matter how large they are. A wily hacker could attack your site by sending a CGI
script a huge POST of many megabytes. CGI.pm will attempt to read the entire POST into a
variable, growing hugely in size until it runs out of memory. While the script attempts
to allocate the memory the system may slow down dramatically. This is a form of denial of
service attack.
Another possible attack is for the remote user to force CGI.pm to accept a huge file
upload. CGI.pm will accept the upload and store it in a temporary directory even if your
script doesn't expect to receive an uploaded file. CGI.pm will delete the file
automatically when it terminates, but in the meantime the remote user may have filled up
the server's disk space, causing problems for other programs.
The best way to avoid denial of service attacks is to limit the amount of memory, CPU time
and disk space that CGI scripts can use. Some Web servers come with built-in facilities
to accomplish this. In other cases, you can use the shell limit or ulimit commands to put
ceilings on CGI resource usage.
CGI.pm also has some simple built-in protections against denial of service attacks, but
you must activate them before you can use them. These take the form of two global
variables in the CGI name space:
$CGI::POST_MAX
If set to a non-negative integer, this variable puts a ceiling on the size of
POSTings, in bytes. If CGI.pm detects a POST that is greater than the ceiling, it
will immediately exit with an error message. This value will affect both ordinary
POSTs and multipart POSTs, meaning that it limits the maximum size of file uploads as
well. You should set this to a reasonably high value, such as 1 megabyte.
$CGI::DISABLE_UPLOADS
If set to a non-zero value, this will disable file uploads completely. Other fill-out
form values will work as usual.
You can use these variables in either of two ways.
1. On a script-by-script basis
Set the variable at the top of the script, right after the "use" statement:
use CGI qw/:standard/;
use CGI::Carp 'fatalsToBrowser';
$CGI::POST_MAX=1024 * 100; # max 100K posts
$CGI::DISABLE_UPLOADS = 1; # no uploads
2. Globally for all scripts
Open up CGI.pm, find the definitions for $POST_MAX and $DISABLE_UPLOADS, and set them
to the desired values. You'll find them towards the top of the file in a subroutine
named initialize_globals().
An attempt to send a POST larger than $POST_MAX bytes will cause param() to return an
empty CGI parameter list. You can test for this event by checking cgi_error(), either
after you create the CGI object or, if you are using the function-oriented interface, call
<param()> for the first time. If the POST was intercepted, then cgi_error() will return
the message "413 POST too large".
This error message is actually defined by the HTTP protocol, and is designed to be
returned to the browser as the CGI script's status
code. For example:
$uploaded_file = param('upload');
if (!$uploaded_file && cgi_error()) {
print header(-status=>cgi_error());
exit 0;
}
However it isn't clear that any browser currently knows what to do with this status code.
It might be better just to create an HTML page that warns the user of the problem.
COMPATIBILITY WITH CGI-LIB.PL
To make it easier to port existing programs that use cgi-lib.pl the compatibility routine
"ReadParse" is provided. Porting is simple:
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.
An even simpler way to mix cgi-lib calls with CGI.pm calls is to import both the
":cgi-lib" and ":standard" method:
use CGI qw(:cgi-lib :standard);
&ReadParse;
print "The price of your purchase is $in{price}.\n";
print textfield(-name=>'price', -default=>'$1.99');
Cgi-lib functions that are available in CGI.pm
In compatibility mode, the following cgi-lib.pl functions are available for your use:
ReadParse()
PrintHeader()
HtmlTop()
HtmlBot()
SplitParam()
MethGet()
MethPost()
Cgi-lib functions that are not available in CGI.pm
* Extended form of ReadParse()
The extended form of ReadParse() that provides for file upload
spooling, is not available.
* MyBaseURL()
This function is not available. Use CGI.pm's url() method instead.
* MyFullURL()
This function is not available. Use CGI.pm's self_url() method
instead.
* CgiError(), CgiDie()
These functions are not supported. Look at CGI::Carp for the way I
prefer to handle error messages.
* PrintVariables()
This function is not available. To achieve the same effect,
just print out the CGI object:
use CGI qw(:standard);
$q = CGI->new;
print h1("The Variables Are"),$q;
* PrintEnv()
This function is not available. You'll have to roll your own if you really need it.
AUTHOR INFORMATION
The CGI.pm distribution is copyright 1995-2007, Lincoln D. Stein. It is distributed under
GPL and the Artistic License 2.0. It is currently maintained by Mark Stosberg with help
from many contributors.
Address bug reports and comments to:
https://rt.cpan.org/Public/Dist/Display.html?Queue=CGI.pm When sending bug reports, please
provide the version of CGI.pm, the version of Perl, the name and version of your Web
server, and the name and version of the operating system you are using. If the problem is
even remotely browser dependent, please provide information about the affected browsers as
well.
CREDITS
Thanks very much to:
Matt Heffron (heffron@falstaff.css.beckman.com)
James Taylor (james.taylor@srs.gov)
Scott Anguish <sanguish@digifix.com>
Mike Jewell (mlj3u@virginia.edu)
Timothy Shimmin (tes@kbs.citri.edu.au)
Joergen Haegg (jh@axis.se)
Laurent Delfosse (delfosse@delfosse.com)
Richard Resnick (applepi1@aol.com)
Craig Bishop (csb@barwonwater.vic.gov.au)
Tony Curtis (tc@vcpc.univie.ac.at)
Tim Bunce (Tim.Bunce@ig.co.uk)
Tom Christiansen (tchrist@convex.com)
Andreas Koenig (k@franz.ww.TU-Berlin.DE)
Tim MacKenzie (Tim.MacKenzie@fulcrum.com.au)
Kevin B. Hendricks (kbhend@dogwood.tyler.wm.edu)
Stephen Dahmen (joyfire@inxpress.net)
Ed Jordan (ed@fidalgo.net)
David Alan Pisoni (david@cnation.com)
Doug MacEachern (dougm@opengroup.org)
Robin Houston (robin@oneworld.org)
...and many many more...
for suggestions and bug fixes.
A COMPLETE EXAMPLE OF A SIMPLE FORM-BASED SCRIPT
#!/usr/local/bin/perl
use CGI ':standard';
print header;
print start_html("Example CGI.pm Form");
print "<h1> Example CGI.pm Form</h1>\n";
print_prompt();
do_work();
print_tail();
print end_html;
sub print_prompt {
print start_form;
print "<em>What's your name?</em><br>";
print textfield('name');
print checkbox('Not my real name');
print "<p><em>Where can you find English Sparrows?</em><br>";
print 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>",
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 popup_menu(-name=>'Color',
-values=>['black','brown','red','yellow'],
-default=>'red');
print hidden('Reference','Monty Python and the Holy Grail');
print "<p><em>What have you got there?</em><br>";
print 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 textarea(-name=>'Comments',
-rows=>10,
-columns=>50);
print "<p>",reset;
print submit('Action','Shout');
print submit('Action','Scream');
print end_form;
print "<hr>\n";
}
sub do_work {
print "<h2>Here are the current settings in this form</h2>";
for my $key (param) {
print "<strong>$key</strong> -> ";
my @values = 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
}
BUGS
Please report them.
SEE ALSO
CGI::Carp - provides a Carp implementation tailored to the CGI environment.
CGI::Fast - supports running CGI applications under FastCGI
CGI::Pretty - pretty prints HTML generated by CGI.pm (with a performance penalty)
POD ERRORS
Hey! The above document had some coding errors, which are explained below:
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