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 = new CGI; # create new CGI object
print $q->header, # create the HTTP header
$q->starthtml('hello world'), # start the HTML
$q->h1('hello world'), # level 1 header
$q->endhtml; # 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 differ-
ences 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
starthtml('hello world'), # start the HTML
h1('hello world'), # level 1 header
endhtml; # end the HTML
The examples in this document mainly use the object-oriented style.
See HOW TO IMPORT FUNCTIONS for important information on function-ori-
ented programming in CGI.pm
CCAALLLLIINNGG CCGGII..PPMM RROOUUTTIINNEESS
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:
Each argument name is preceded by a dash. Neither case nor order mat-
ters 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 subse-
quent 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:
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('some','contents');
some contents
h1({-align=>left});
h1({-align=>left},'contents');
contents
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 brack-
ets. 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 exam-
If you use the -ww 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 exam-
ple, -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',
-annoyancelevel => 'high',
-complaintsto => '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 transla-
tion.
This feature allows you to keep up with the rapidly changing HTTP and
HTML "standards".
CCRREEAATTIINNGG AA NNEEWW QQUUEERRYY OOBBJJEECCTT ((OOBBJJEECCTT-OORRIIEENNTTEEDD SSTTYYLLEE))::
$query = new CGI;
This will parse the input (from both POST and GET methods) and store it
into a perl5 object called $query.
CCRREEAATTIINNGG AA NNEEWW QQUUEERRYY OOBBJJEECCTT FFRROOMM AANN IINNPPUUTT FFIILLEE
$query = new CGI(INPUTFILE);
If you provide a file handle to the new() method, it will read parame-
ters 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 refer-
ences to file handles, or even references to filehandle globs, which is
the "official" way to pass a filehandle:
$query = new CGI(\*STDIN);
You can also initialize the CGI object with a FileHandle or IO::File
object.
If you are using the function-oriented interface and want to initialize
CGI state from a file handle, the way to do this is with rreessttoorreeppaarraamm-
eetteerrss(()). This will (re)initialize the default CGI object from the
indicated file handle.
open (IN,"test.in") || die;
restoreparameters(IN);
close IN;
You can also initialize the query object from an associative array ref-
erence:
$query = new CGI( {'dinosaur'=>'barney',
'song'=>'I love you',
'friends'=>[qw/Jessica George Nancy/]}
);
or from a properly formatted, URL-escaped query string:
$query = new CGI('dinosaur=barney&color=purple');
or from a previously existing CGI object (currently this clones the
parameter list, but none of the other object-specific fields, such as
autoescaping):
$oldquery = new CGI;
$newquery = new CGI($oldquery);
To create an empty query, initialize it from an empty string or hash:
$emptyquery = new CGI("");
-or-
$emptyquery = new CGI({});
FFEETTCCHHIINNGG AA LLIISSTT OOFF KKEEYYWWOORRDDSS FFRROOMM TTHHEE QQUUEERRYY::
@keywords = $query->keywords
If the script was invoked as the result of an 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
script and contains a string without ampersands (e.g.
"value1+value2+value3") , there will be a single parameter named "key-
words" 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 guaran-
teed).
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. Oth-
erwise the method will return a single value.
If a value is not given in the query string, as in the queries
"name1=&name2=" or "name1&name2", it will be returned as an empty
string. This feature is new in 2.63.
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 val-
ues. 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:
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. Other-
wise the parameter is created. Note that this method only recognizes
the named argument calling syntax.
IMPORTING ALL PARAMETERS INTO A NAMESPACE:
$query->importnames('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'. WARN-
ING: 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 under-
scores. 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 iimmppoorrtt(()). As of ver-
sion 2.20, this name has been removed completely to avoid conflict with
the built-in Perl module iimmppoorrtt operator.
DDEELLEETTIINNGG AA PPAARRAAMMEETTEERR CCOOMMPPLLEETTEELLYY::
$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.
DDEELLEETTIINNGG AALLLL PPAARRAAMMEETTEERRSS::
$query->deleteall();
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 Deleteall() instead if you are using the function call interface.
If you need access to the parameter list in a way that isn't covered by
the methods above, you can obtain a direct reference to it by calling
the ppaarraammffeettcchh(()) method with the name of the . This will return an
array reference to the named parameters, which you then can manipulate
in any way you like.
You can also use a named argument style using the -nnaammee argument.
FFEETTCCHHIINNGG TTHHEE PPAARRAAMMEETTEERR LLIISSTT AASS AA HHAASSHH::
$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 conven-
tion 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).
SSAAVVIINNGG TTHHEE SSTTAATTEE OOFF TTHHEE SSCCRRIIPPTT TTOO AA FFIILLEE::
$query->save(\*FILEHANDLE)
This will write the current state of the form to the provided filehan-
dle. 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 sin-
gle = symbol. You can write out multiple records and read them back in
with several calls to nneeww. You can do this across several sessions by
opening the file in append mode, allowing you to create primitive guest
books, or to keep a history of users' queries. Here's a short example
of creating multiple session records:
use CGI;
open (OUT,">>test.out") || die;
$records = 5;
foreach (0..$records) {
my $q = new CGI;
$q->param(-name=>'counter',-value=>$);
$q->save(\*OUT);
}
close OUT;
# reopen for reading
open (IN,"test.out") || die;
while (!eof(IN)) {
my $q = new CGI(\*IN);
print $q->param('counter'),"\n";
}
The file format used for save/restore is identical to that used by the
Whitehead Genome Center's data exchange format "Boulderio", and can be
manipulated and even databased using Boulderio utilities. See
http://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 ssaavveeppaarraammeetteerrss(()).
RREETTRRIIEEVVIINNGG CCGGII EERRRROORRSS
Errors can occur while processing user input, particularly when pro-
cessing uploaded files. When these errors occur, CGI will stop pro-
cessing and return an empty parameter list. You can test for the exis-
tence and nature of errors using the cgierror() 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 = $q->cgierror;
if ($error) {
print $q->header(-status=>$error),
$q->starthtml('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!
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 ;
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 ppaarraamm(()) and hheeaaddeerr(()) 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 ":" charac-
ter as in ":html3" (for tags defined in the HTML 3 standard).
Here is a list of the function sets you can import:
::ccggii
Import all CGI-handling methods, such as ppaarraamm(()), ppaatthhiinnffoo(()) and
the like.
::ffoorrmm
Import all fill-out form generating methods, such as tteexxttffiieelldd(()).
::hhttmmll22
Import all methods that generate HTML 2.0 standard elements.
::hhttmmll33
Import all methods that generate HTML 3.0 elements (such as ble>, and ).
::hhttmmll44
Import all methods that generate HTML 4 elements (such as ,
and ).
::nneettssccaappee
Import all methods that generate Netscape-specific HTML extensions.
::hhttmmll
Import all HTML-generating shortcuts (i.e. 'html2' + 'html3' +
'netscape')...
::ssttaannddaarrdd
Import "standard" features, 'html2', 'html3', 'html4', 'form' and
'cgi'.
::aallll
Import all the available methods. For the full list, see the
CGI.pm code, where the variable %EXPORTTAGS 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 subrou-
tine. 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 (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 nnoott 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 meth-
ods, 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 ppaarraamm(()), tteexxttffiieelldd(()), ssuubbmmiitt(()) and the like.
(If you need direct access to the CGI object, you can find it in the
global variable $$CCGGII::::QQ). By importing CGI.pm methods, you can create
visually elegant scripts:
use CGI qw/:standard/;
print
header,
starthtml('Simple Script'),
h1('Simple Script'),
startform,
"What's your name? ",textfield('name'),p,
"What's the combination?",
checkboxgroup(-name=>'words',
-values=>['eenie','meenie','minie','moe'],
-defaults=>['eenie','moe']),p,
"What's your favorite color?",
popupmenu(-name=>'color',
-values=>['red','green','blue','chartreuse']),p,
submit,
endform,
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 endhtml;
PPRRAAGGMMAASS
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 Netscape or Microsoft HTML
extension. This lets you go wild with new and unsupported tags:
Since using any 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 modperl,
and for those destined to be crunched by Malcom Beattie's Perl com-
piler. 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 com-
pile() method instead:
use CGI();
CGI->compile();
This is particularly useful in a modperl environment, in which you
might want to precompile all CGI routines in a startup script, and
then import the functions individually in each modperl 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 val-
ues will interrogate param() to see if similarly-named parameters
are present in the query string. If they find a like-named parame-
ter, they will use it to set their default values.
Sometimes this isn't what you want. The -nnoossttiicckkyy 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.
-noundefparams
This keeps CGI.pm from including undef params in the parameter
list.
-noxhtml
By default, CGI.pm versions 2.69 and higher emit XHTML
(http://www.w3.org/TR/xhtml1/). The -noxhtml pragma disables this
feature. Thanks to Michalis Kabrianis for
this feature.
If starthtml()'s -dtd parameter specifies an HTML 2.0 or 3.2 DTD,
XHTML will automatically be disabled without needing to use this
pragma.
-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.
-newstyleurls
Separate the name=value pairs in CGI parameter query strings with
semicolons rather than ampersands. For example:
?name=fred;age=24;favoritecolor=3
Semicolon-delimited query strings are always accepted, but will not
be emitted by selfurl() and querystring() unless the -new-
styleurls pragma is specified.
This became the default in version 2.64.
-oldstyleurls
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 evalua-
tion. This allows you to use all the CGI.pm functions without
adding them to your symbol table, which is of concern for modperl
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 some-
thing like use subs qw/hr p header/ to the top of your script.
-nodebug
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(-nodebug :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.
-privatetempfiles
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 -privatetempfiles pragma will cause the tempo-
rary 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 the current user (e.g. "nobody") has a directory named
"tmp" in its home directory, use that (Unix systems only).
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 \WWWROOT.
Each of these locations is checked that it is a directory and is
writable. If not, the algorithm tries the next choice.
Many of the methods generate HTML tags. As described below, tag func-
tions automatically generate both the opening and closing tags. For
example:
print h1('Level 1 Header');
produces
Level 1 Header
There will be some times when you want to produce the start and end
tags yourself. In this case, you can use the form starttagname and
endtagname, as in:
print starth1,'Level 1 Header',endh1;
With a few exceptions (described below), starttagname and
endtagname 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, alter-
natively, requesting either "starttagname" or "endtagname" in the
import list.
Example:
use CGI qw/:standard *table startul/;
In this example, the following functions are generated in addition to
the standard ones:
1. starttable() (generates a
Most of CGI.pm's functions deal with creating documents on the fly.
Generally you will produce the HTTP header first, followed by the docu-
ment 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.
CCRREEAATTIINNGG AA SSTTAANNDDAARRDD HHTTTTPP HHEEAADDEERR::
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 manip-
ulated 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-read-
able message. For example, you can specify 204, "No response" to cre-
ate a script that tells the browser to do nothing at all.
The last example shows the named argument style for passing arguments
to the CGI methods using named parameters. Recognized parameters are
-ttyyppee, -ssttaattuuss, -eexxppiirreess, and -ccooookkiiee. 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 under-
scores will be turned into hyphens:
print header(-Contentlength=>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 -eexxppiirreess 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 -ccooookkiiee parameter generates a header that tells the browser to pro-
vide a "magic cookie" during all subsequent transactions with your
script. Netscape cookies have a special format that includes interest-
ing attributes such as expiration time. Use the cookie() method to
create and retrieve session cookies.
The -nnpphh 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 -cchhaarrsseett 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 -aattttaacchhmmeenntt parameter can be used to turn the page into an attach-
ment. 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 -ttyyppee to "application/octet-stream".
The -pp33pp 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"
GGEENNEERRAATTIINNGG AA RREEDDIIRREECCTTIIOONN HHEEAADDEERR
print redirect('http://somewhere.else/in/movie/land');
Sometimes you don't want to produce a document yourself, but simply re-
direct the browser elsewhere, perhaps choosing a URL based on the time
of day or the identity of the user.
The redirect() function redirects the browser to a different URL. If
you use redirection like this, you should nnoott 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:
The -nnpphh 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 -ssttaattuuss 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.
CCRREEAATTIINNGG TTHHEE HHTTMMLL DDOOCCUUMMEENNTT HHEEAADDEERR
print starthtml(-title=>'Secrets of the Pyramids',
-author=>'fred@capricorn.org',
-base=>'true',
-target=>'blank',
-meta=>{'keywords'=>'pharaoh secret mummy',
'copyright'=>'copyright 1996 King Tut'},
-style=>{'src'=>'/styles/style1.css'},
-BGCOLOR=>'blue');
After creating the HTTP header, most CGI scripts will start writing out
an HTML document. The starthtml() 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 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 pro-
vide, such as the Netscape unofficial BGCOLOR attribute, are added to
the tag. Additional parameters must be proceeded by a hyphen.
The argument -xxbbaassee allows you to provide an HREF for the 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 -ttaarrggeett allows you to provide a default target frame for
all the links and fill-out forms on the page. TThhiiss iiss aa nnoonn-ssttaannddaarrdd
HHTTTTPP ffeeaattuurree wwhhiicchh oonnllyy wwoorrkkss wwiitthh NNeettssccaappee bbrroowwsseerrss!! See the Netscape
documentation on frames for details of how to manipulate this.
-target=>"answerwindow"
All relative links will be interpreted relative to this tag. You add
arbitrary meta information to the header with the -mmeettaa argument. This
argument expects a reference to an associative array containing
name/value pairs of meta information. These will be turned into a
series of header tags that look something like this:
To create an HTTP-EQUIV type of tag, use -hheeaadd, described below.
The -ssttyyllee argument is used to incorporate cascading stylesheets into
your code. See the section on CASCADING STYLESHEETS for more informa-
tion.
The -llaanngg argument is used to incorporate a language attribute into the
tag. For example:
print $q->starthtml(-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 -eennccooddiinngg argument can be used to specify the character set for
XHTML. It defaults to iso-8859-1 if not specified.
The -ddeeccllaarreexxmmll argument, when used in conjunction with XHTML, will
put a declaration at the top of the HTML header. The sole pur-
pose of this declaration is to declare the character set encoding. In
the absence of -declarexml, the output HTML will contain a tag
that specifies the encoding, allowing the HTML to pass most validators.
The default for -declarexml is false.
You can place other arbitrary HTML elements to the section with
the -hheeaadd tag. For example, to place the rarely-used element in
the head section, use this:
print starthtml(-head=>Link({-rel=>'next',
-href=>'http://www.capricorn.com/s2.html'}));
To incorporate multiple HTML elements into the section, just
pass an array reference: