CGI(3) Perl Programmers Reference Guide CGI(3) NAME CGI - Simple Common Gateway Interface Class SYNOPSIS # CGI script that creates a fill-out form # and echoes back its values. use CGI qw/:standard/; print header, start_html('A Simple Example'), h1('A Simple Example'), start_form, "What's your name? ",textfield('name'),p, "What's the combination?", p, checkbox_group(-name=>'words', -values=>['eenie','meenie','minie','moe'], -defaults=>['eenie','minie']), p, "What's your favorite color? ", popup_menu(-name=>'color', -values=>['red','green','blue','chartreuse']),p, submit, end_form, hr; if(3,n) (param()) { print "Your name is",em(param('name')),p, "The keywords are: ",em(join(1,n)(", ",param('words'))),p, "Your favorite color is ",em(param('color')), hr; } ABSTRACT This perl library uses perl5 objects to make it easy to create Web fill-out forms and parse their contents. This package defines CGI objects, entities that contain the values of the current query string(3,n) and other state variables. Using a CGI object's methods, you can exam- ine keywords and parameters passed to your script, and create forms whose initial values are taken from the current query (thereby preserv- ing state information). The module provides shortcut functions that produce boilerplate HTML, reducing typing and coding errors. It also provides functionality for some of the more advanced features of CGI scripting, including support for file(1,n) uploads, cookies, cascading style sheets, server push, and frames. CGI.pm also provides a simple function-oriented programming style for those who don't need its object-oriented features. The current version(1,3,5) of CGI.pm is available at http://www.genome.wi.mit.edu/ftp/pub/software/WWW/cgi_docs.html ftp://ftp-genome.wi.mit.edu/pub/software/WWW/ DESCRIPTION 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(5,8) parameters that were passed to your CGI script by the server. You can modify the objects, save them to a file(1,n) 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(7,n) CGI routines $q = new CGI; # create new CGI object print $q->header, # create the HTTP header $q->start_html('hello world'), # start the HTML $q->h1('hello world'), # level 1 header $q->end_html; # end the HTML In the function-oriented style, there is one default CGI object that you rarely deal with directly. Instead you just call functions to retrieve CGI parameters, create HTML tags, manage cookies, and so on. This provides you with a cleaner programming interface, but limits you to using one CGI object at a time. The following example prints the same page, but uses the function-oriented interface. The main differ- ences are that we now need to import a set(7,n,1 builtins) 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(7,n) 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(1,8) this document mainly use the object-oriented style. See HOW TO IMPORT FUNCTIONS for important information on function-ori- ented programming in(1,8) CGI.pm CALLING CGI.PM ROUTINES Most CGI.pm routines accept(2,8) several arguments, sometimes as many as 20 optional ones! To simplify this interface, all routines use a named(5,8) 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 mat- ters in(1,8) 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(1,8) 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(5,8) 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(7,n,1 builtins) 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(1,8) CGI.pm actually aren't specifically defined in(1,8) the module, but are generated automatically as needed. These are the "HTML shortcuts," routines that generate HTML tags for use in(1,8) 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(3,n) 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(1,8) 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(1,8) all but the HTML shortcuts. If you like, you can use curly braces when calling any routine that takes named(5,8) arguments. For exam- ple: print $q->header( {-type=>'image/gif',-expires=>'+3d'} ); If you use the -w switch(1,n), 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(3,n) 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(5,8) argument that it doesn't recognize. For example, you can produce non-standard HTTP header fields by providing them as named(5,8) 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 transla- tion. This feature allows you to keep up with the rapidly changing HTTP and HTML "standards". CREATING A NEW QUERY OBJECT (OBJECT-ORIENTED STYLE): $query = new CGI; This will parse the input (from both POST and GET methods) and store it into a perl5 object called $query. CREATING A NEW QUERY OBJECT FROM AN INPUT FILE $query = new CGI(INPUTFILE); If you provide a file(1,n) handle to the new() method, it will read(2,n,1 builtins) parame- ters from the file(1,n) (or STDIN, or whatever). The file(1,n) can be in(1,8) 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(1,n) 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(1,n) 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(1,n) handle, the way to do this is with restore_param- eters(). This will (re)initialize the default CGI object from the indicated file(1,n) handle. open(2,3,n) (IN,"test.in") || die; restore_parameters(IN); close(2,7,n) 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): $old_query = new CGI; $new_query = new CGI($old_query); To create an empty query, initialize it from an empty string(3,n) or hash: $empty_query = new CGI(""); -or- $empty_query = new CGI({}); 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(3,n) without ampersands (e.g. "value1+value2+value3") , there will be a single parameter named(5,8) "key- words" containing the "+"-delimited keywords. NOTE: As of version(1,3,5) 1.5, the array of parameter names returned will be in(1,8) the same order as they were submitted by the browser. Usually this order is the same as the order in(1,8) which the parameters are defined in(1,8) 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(5,8) parameter. If the parameter is multivalued (e.g. from multiple selections in(1,8) 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(1,8) the query string(3,n), as in(1,8) the queries "name1=&name2=" or "name1&name2", it will be returned as an empty string. This feature is new in(1,8) 2.63. If the parameter does not exist at all, then param() will return undef in(1,8) a scalar context, and the empty list in(1,8) 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(5,8) 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(5,8) parameter style of calling described in(1,8) 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(5,8) parameter. The values are appended to the end of the parameter if(3,n) it already exists. Other- wise the parameter is created. Note that this method only recognizes the named(5,8) argument calling syntax. IMPORTING ALL PARAMETERS INTO A NAMESPACE: $query->import_names('R'); This creates a series of variables in(1,8) 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(2,5) CGI variables by name. NOTE 2: In older versions, this method was called import(). As of ver- sion(1,3,5) 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(3,n) you are using the function call interface. 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(2,5) to the parameter list in(1,8) a way that isn't covered by the methods above, you can obtain a direct reference to it by calling the param_fetch() method with the name of the . This will return an array reference to the named(5,8) parameters, which you then can manipulate in(1,8) any way you like. You can also use a named(5,8) argument style using the -name argument. FETCHING THE PARAMETER LIST AS A HASH: $params = $q->Vars; print $params->{'address'}; @foo = split(1,n)("\0",$params->{'foo'}); %params = $q->Vars; use CGI ':cgi-lib'; $params = Vars; Many people want to fetch the entire parameter list as a hash in(1,8) which the keys are the names of the CGI parameters, and the values are the parameters' values. The Vars() method does this. Called in(1,8) a scalar context, it returns the parameter list as a tied hash reference. Changing a key changes the value of the parameter in(1,8) the underlying CGI parameter list. Called in(1,8) a list context, it returns the parameter list as an ordinary hash. This allows you to read(2,n,1 builtins) 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(3,n), separated by the "\0" (null) character. You must split(1,n) this packed string(3,n) in(1,8) order to get at the individual values. This is the conven- tion introduced long ago by Steve Brenner in(1,8) his cgi-lib.pl module for Perl version(1,3,5) 4. If you wish to use Vars() as a function, import the :cgi-lib set(7,n,1 builtins) 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(1,2) the current state of the form to the provided filehan- dle. You can read(2,n,1 builtins) it back in(1,8) by providing a filehandle to the new() method. Note that the filehandle can be a file(1,n), a pipe(2,8), or whatever! The format of the saved file(1,n) 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(1,2) out multiple records and read(2,n,1 builtins) them back in(1,8) with several calls to new. You can do this across several sessions by opening the file(1,n) in(1,8) append mode, allowing you to create primitive guest books, or to keep a history(1,3,n,1 builtins) of users(1,5)' queries. Here's a short example of creating multiple session records: use CGI; open(2,3,n) (OUT,">>test.out") || die; $records = 5; foreach (0..$records) { my $q = new CGI; $q->param(-name=>'counter',-value=>$_); $q->save(OUT); } close(2,7,n) OUT; # reopen for reading open(2,3,n) (IN,"test.out") || die; while (!eof(IN)) { my $q = new CGI(IN); print $q->param('counter'),"\n"; } The file(1,n) 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 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 cgi_error() function. The error(8,n) messages are formatted as HTTP status codes. You can either incorporate the error(8,n) text into an HTML page, or use it as the value of the HTTP status: my $error(8,n) = $q->cgi_error; if(3,n) ($error(8,n)) { print $q->header(-status=>$error(8,n)), $q->start_html('Problems'), $q->h2('Request not processed'), $q->strong($error(8,n)); exit(3,n,1 builtins) 0; } When using the function-oriented interface (see the next section), errors may only occur the first time(1,2,n) 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 ":" charac- ter as in(1,8) ":html3" (for tags defined in(1,8) 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 <ta- ble>, <super> and <sub>). :html4 Import all methods that generate HTML 4 elements (such as <abbrev>, <acronym> and <thead>). :netscape Import all methods that generate Netscape-specific HTML extensions. :html Import all HTML-generating shortcuts (i.e. 'html2' + 'html3' + 'netscape')... :standard Import "standard" features, 'html2', 'html3', '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 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 <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(1,3,5) of CGI.pm to start using it immediately: use CGI qw/:standard :html3 gradient/; print gradient({-start=>'red',-end=>'blue'}); Note that in(1,8) the interests of execution speed CGI.pm does not use the standard Exporter syntax for specifying load(7,n) symbols. This may change in(1,8) 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(1,2,n) 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(2,5) to the CGI object, you can find it in(1,8) 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(3,n) (param) { print "Your name is ",em(param('name')),p, "The keywords are: ",em(join(1,n)(", ",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(1,8) various ways. Pragmas, function sets, and individual functions can all be imported in(1,8) the same use() line. For example, the following use statement imports the standard set(7,n,1 builtins) 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: use CGI qw(-any); $q=new CGI; print $q->gradient({speed=>'fast',start=>'red',end=>'blue'}); Since using <cite>any</cite> causes any mistyped method name to be interpreted as an HTML tag, use it with care or not at all. -compile This causes the indicated autoloaded methods to be compiled up front, rather than deferred to later. This is useful for scripts that run for an extended period of time(1,2,n) under FastCGI or mod_perl, and for those destined to be crunched by Malcom Beattie's Perl com- piler. Use it in(1,8) 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(1,8) 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(1,8) a mod_perl environment, in(1,8) which you might want to precompile all CGI routines in(1,8) a startup script, and then import the functions individually in(1,8) each mod_perl script. -nosticky This makes CGI.pm not generating the hidden fields .submit and .cgifields. It is very useful if(3,n) you don't want to have the hidden fields appear in(1,8) the querystring in(1,8) a GET method. For example, a search script generated this way will have a very nice(1,2) url with search parameters for bookmarking. -no_undef_params This keeps CGI.pm from including undef params in(1,8) 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 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. -newstyle_urls Separate the name=value pairs in(1,8) 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, but will not be emitted by self_url() and query_string() unless the -new- style_urls pragma is specified. This became the default in(1,8) version(1,3,5) 2.64. -oldstyle_urls Separate the name=value pairs in(1,8) 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(1,8) 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 mod_perl users(1,5) who are worried about memory consumption. Warning: when -autoload is in(1,8) 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. -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(2,n,1 builtins) 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(2,n,1 builtins) 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(1,n) to a temporary directory, then deletes the file(1,n) when done. However, this opens the risk of eavesdropping as described in(1,8) the file(1,n) upload section. Another CGI script author could peek at this data during the upload, even if(3,n) it is confidential information. On Unix systems, the -private_tempfiles pragma will cause the tempo- rary file(1,n) 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(1,n) cannot be read(2,n,1 builtins) by other CGI scripts, use suEXEC or a CGI wrapper program to run your script. The temporary file(1,n) is created with mode 0600 (neither world nor group readable). The temporary directory is selected using the following algorithm: 1. if(3,n) the current user (e.g. "nobody") has a directory named(5,8) "tmp" in(1,8) its home directory, use that (Unix systems only). 2. if(3,n) 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 func- tions 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(1,8) front of their name, or, alter- natively, requesting either "start_tag_name" or "end_tag_name" in(1,8) the import list. Example: use CGI qw/:standard *table start_ul/; In this example, the following functions are generated in(1,8) 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 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(1,8) the browser window, append to a string(3,n), or save to a file(1,n) for later use. CREATING A STANDARD HTTP HEADER: Normally the first thing you will do in(1,8) 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 $query->header; -or- print $query->header('image/gif'); -or- print $query->header('text/html','204 No response'); -or- print $query->header(-type=>'image/gif', -nph=>1, -status=>'402 Payment required', -expires=>'+3d', -cookie=>$cookie, -charset=>'utf-7', -attachment=>'foo.gif', -Cost=>'$2.00'); header() returns the Content-type: header. You can provide your own MIME type if(3,n) 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(5,8) argument style for passing arguments to the CGI methods using named(5,8) parameters. Recognized parameters are -type, -status, -expires, and -cookie. Any other named(5,8) 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 $query->header(-Content_length=>3002); Most browsers will not cache the output from CGI scripts. Every time(1,2,n) 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(1,8) three months +10y in(1,8) ten years time(1,2,n) Thursday, 25-Apr-1999 00:40:33 GMT at the indicated time(1,2,n) & date The -cookie parameter generates a header that tells the browser to pro- vide a "magic(4,5) 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 -nph parameter, if(3,n) set(7,n,1 builtins) 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(7,n,1 builtins) 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 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(7,n,1 builtins) 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(3,n) 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" GENERATING A REDIRECTION HEADER print $query->redirect('http://somewhere.else/in(1,8)/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(1,2,n) of day or the identity of the user. The redirect() function redirects the browser to a different URL. If you use redirection like this, you should not print out a header as well. You should always use full URLs (including the http: or ftp: part) in(1,8) redirection requests. Relative URLs will not work correctly. You can also use named(5,8) arguments: print $query->redirect(-uri=>'http://somewhere.else/in(1,8)/movie/land', -nph=>1, -status=>301); The -nph parameter, if(3,n) set(7,n,1 builtins) 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(7,n,1 builtins) the status of the redirect. HTTP defines three different possible redirection status codes: 301 Moved Permanently 302 Found 303 See Other The default if(3,n) not specified is 302, which means "moved temporarily." You may change the status to another status code if(3,n) you wish. Be advised that changing the status to anything other than 301, 302 or 303 will probably break redirection. CREATING THE HTML DOCUMENT HEADER print $query->start_html(-title=>'Secrets of the Pyramids', -author=>'fred@capricorn.org', -base=>'true', -target=>'_blank', -meta=>{'keywords'=>'pharaoh secret mummy', 'copyright'=>'copyright 1996 King Tut'}, -style=>{'src'=>'/styles/style1.css'}, -BGCOLOR=>'blue'); After creating the HTTP header, most CGI scripts will start writing out an HTML document. The start_html() routine creates the top of the page, along with a lot of optional information that controls the page's appearance and behavior. This method returns a canned HTML header and the opening <body> tag. All parameters are optional. In the named(5,8) 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 <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(1,8) -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 Netscape browsers! See the Netscape documentation on frames for details of how to manipulate this. -target=>"answer_window" All relative links will be interpreted relative to this tag. You add arbitrary meta information to the header with the -meta argument. This argument expects a reference to an associative array containing name/value pairs of meta information. These will be turned into a series of header <meta> tags that look(1,8,3 Search::Dict) 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 informa- tion. 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(3,n) not specified is "en-US" for US English, unless the -dtd parameter specifies an HTML 2.0 or 3.2 DTD, in(1,8) which case the lang attribute is left off. You can force the lang attribute to left off in(1,8) other cases by passing an empty string(3,n) (-lang=>''). The -encoding argument can be used to specify the character set(7,n,1 builtins) for XHTML. It defaults to iso-8859-1 if(3,n) not specified. You can place other arbitrary HTML elements to the <head> section with the -head tag. For example, to place the rarely-used <link(1,2)> element in(1,8) the head section, use this: print start_html(-head=>Link({-rel=>'next', -href=>'http://www.capricorn.com/s2.html'})); To incorporate multiple HTML elements into the <head> section, just pass an array reference: print 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, -onMouse- Out and -onUnload parameters are used to add Netscape JavaScript calls to your pages. -script should point to a block of text containing JavaScript function definitions. This block will be placed within a <script> block inside the HTML (not HTTP) header. The block is placed in(1,8) the header in(1,8) order to give your page a fighting chance of having all its JavaScript functions in(1,8) place even if(3,n) the user presses the stop button before the page has loaded completely. CGI.pm attempts to for- mat the script in(1,8) 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(1,8) the -script field: $query = new CGI; print $query->header; $JSCRIPT=<<END; // Ask a silly question function riddle_me_this() { var r = prompt("What walks on four legs in(1,8) the morning, " + "two legs in(1,8) the afternoon, " + "and three legs in(1,8) the evening?"); response(r); } // Get a silly answer function response(answer) { if(3,n) (answer == "man(1,5,7)") alert("Right you are!"); else alert("Wrong! Guess again."); } END print $query->start_html(-title=>'The Riddle of the Sphinx', -script=>$JSCRIPT); Use the -noScript parameter to pass some HTML text that will be dis- played on browsers that do not have JavaScript (or browsers where JavaScript is turned off). Netscape 3.0 recognizes several attributes of the <script> tag, includ- ing LANGUAGE and SRC. The latter is particularly interesting, as it allows you to keep the JavaScript code in(1,8) a file(1,n) or CGI script rather than cluttering up each page with the source. To use these attributes pass a HASH reference in(1,8) the -script parameter containing one or more of -language, -src, or -code: print $q->start_html(-title=>'The Riddle of the Sphinx', -script=>{-language=>'JAVASCRIPT', -src=>'/javascript/sphinx.js'} ); print $q->(-title=>'The Riddle of the Sphinx', -script=>{-language=>'PERLSCRIPT', -code=>'print "hello world!\n;"'} ); A final feature allows you to incorporate multiple <script> sections into the header. Just pass the list of script sections as an array reference. this allows you to specify different source files for dif- ferent dialects of JavaScript. Example: print $q->start_html(-title=>'The Riddle of the Sphinx', -script=>[ { -language => 'JavaScript1.0', -src => '/javascript/utilities10.js' }, { -language => 'JavaScript1.1', -src => '/javascript/utilities11.js' }, { -language => 'JavaScript1.2', -src => '/javascript/utilities12.js' }, { -language => 'JavaScript28.2', -src => '/javascript/utilities219.js' } ] ); If this looks a bit extreme, take my advice and stick with straight CGI scripting. See http://home.netscape.com/eng/mozilla/2.0/handbook/javascript/ for more information about JavaScript. The old-style positional parameters are as follows: Parameters: 1. The title 2. The author's e-mail address (will create a <link(1,2) rev="MADE"> tag if(3,n) present 3. A 'true' flag if(3,n) you want to include a <base> tag in(1,8) 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(1,8) the <body> tag. This is a good place to put Netscape extensions, such as colors and wallpaper patterns. ENDING THE HTML DOCUMENT: print $query->end_html This ends an HTML document by printing the </body></html> tags. CREATING A SELF-REFERENCING URL THAT PRESERVES STATE INFORMATION: $myself = $query->self_url; print q(<a href="$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). Some- thing like this will do the trick. $myself = $query->self_url; print "<a href=\"$myself#table1\">See table 1</a>"; print "<a href=\"$myself#table2\">See table 2</a>"; print "<a href=\"$myself#yourself\">See for yourself</a>"; If you want more control over what's returned, using the url() method instead. You can also retrieve the unprocessed query string(3,n) with query_string(): $the_string = $query->query_string; OBTAINING THE SCRIPT'S URL $full_url = $query->url(); $full_url = $query->url(-full=>1); #alternative syntax $relative_url = $query->url(-relative=>1); $absolute_url = $query->url(-absolute=>1); $url_with_path = $query->url(-path_info=>1); $url_with_path_and_query = $query->url(-path_info=>1,-query=>1); $netloc = $query->url(-base => 1); url() returns the script's URL in(1,8) a variety of formats. Called without any arguments, it returns the full form of the URL, including host(1,5) name and port number http://your.host.com/path/to/script.cgi You can modify this format with the following named(5,8) arguments: -absolute If true, produce an absolute URL, e.g. /path/to/script.cgi -relative Produce a relative URL. This is useful if(3,n) you want to reinvoke your script with different parameters. For example: script.cgi -full Produce the full URL, exactly as if(3,n) 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 pro- vided as a synonym. -query (-query_string) Append the query string(3,n) to the URL. This can be combined with -full, -absolute or -relative. -query_string is provided as a syn- onym. -base Generate just the protocol and net location, as in(1,8) http://www.foo.com:8000 MIXING POST AND URL PARAMETERS $color = $query->url_param('color'); It is possible for a script to receive CGI parameters in(1,8) the URL as well as in(1,8) the fill-out form by creating a form that POSTs to a URL containing a query string(3,n) (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(1,8) the same way as param(). The main difference is that it allows you to read(2,n,1 builtins) the parameters, but not set(7,n,1 builtins) them. Under no circumstances will the contents of the URL query string(3,n) inter- fere with similarly-named CGI parameters in(1,8) POSTed forms. If you try to mix a URL query string(3,n) 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 most, if(3,n) not all of the HTML 3 and HTML 4 tags. HTML shortcuts are named(5,8) after a single HTML element and return a fragment of HTML text that you can then print or manipulate as you like. Each shortcut returns a fragment of HTML code that you can append to a string(3,n), save to a file(1,n), or, most com- monly, print out so that it displays in(1,8) the browser window. This example shows how to use the HTML methods: $q = new CGI; print $q->blockquote( "Many years ago on the island of", $q->a({href=>"http://crete.org/"},"Crete"), "there lived a Minotaur named(5,8)", $q->strong("Fred."), ), $q->hr; This results in(1,8) 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(5,8) <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(5,8)", strong("Fred."), ), hr; PROVIDING ARGUMENTS TO HTML SHORTCUTS The HTML methods will accept(2,8) 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(3,n) arguments, they are concatenated together with spaces and placed between opening and closing tags: print h1("Chapter","1"); # <h1>Chapter 1</h1>" If the first argument is an associative array reference, then the keys and values of the associative array become the HTML tag's attributes: print a({-href=>'fred.html',-target=>'_new'}, "Open a new frame"); <a href="fred.html",target="_new">Open a new frame</a> You may dispense with the dashes in(1,8) front of the attribute names if(3,n) 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(1,3,5) 2.41, providing an empty ('') string(3,n) as an attribute argument was the same as providing undef. However, this has changed in(1,8) order to accommodate those who want to create tags of the form <img alt="">. The difference is shown in(1,8) 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 dis- tributive. 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(1,8) 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(3,n) 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(3,n) the extra space there using array interpolation, which is con- trolled by the magic(4,5) $" 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(1,8) a block as shown here. Otherwise the change to $" will affect all subsequent code until you explicitly reset(1,7,1 tput) 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 func- tions 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(3,n)"); Escape HTML formatting characters in(1,8) a string. Provided that you have specified a character set(7,n,1 builtins) of ISO-8859-1 (the default), the standard HTML escaping rules will be used. The "<" char- acter 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. The automatic escaping does not apply to other shortcuts, such as h1(). You should call escapeHTML() yourself on untrusted data in(1,8) order to protect your pages against nasty tricks that people may enter into guestbooks, etc.. To change the character set(7,n,1 builtins), use charset(). To turn autoescaping off completely, use autoEscape(0): $charset = charset([$charset]); Get or set(7,n,1 builtins) the current character set. $flag = autoEscape([$flag]); Get or set(7,n,1 builtins) 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(7,n,1 builtins) 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(1,2,n) the script is invoked (when there is no query string(3,n)). On subsequent invocations of the script (when there is a query string(3,n)), the former values are used even if(3,n) 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(7,n,1 builtins) it. (2) use the -override (alias -force) parameter (a new feature in(1,8) ver- sion(1,3,5) 2.15). This forces the default value to be used, regardless of the previous value: print $query->textfield(-name=>'field_name', -default=>'starting value', -override=>1, -size=>50, -maxlength=>80); Yet another note By default, the text and labels of form elements are escaped according to HTML rules. This means that you can safely use "<CLICK ME>" as the label for a button. However, it also interferes with your ability to incorporate special HTML character sequences, such as Á, into your fields. If you wish to turn off automatic escaping, call the autoEscape() method with a false value immediately after creating the CGI object: $query = new CGI; $query->autoEscape(undef); A Lurking Trap! Some of the form-element generating methods return mul- tiple tags. In a scalar context, the tags will be concatenated together with spaces, or whatever is the current value of the $" global. In a list context, the methods will return a list of elements, allowing you to modify them if(3,n) you wish. Usually you will not notice this behavior, but beware of this: printf(1,3,1 builtins)("%s\n",$query->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 $query->isindex(-action=>$action); -or- print $query->isindex($action); Prints out an <isindex> tag. Not very exciting. The parameter -action specifies the URL of the script to process the query. The default is to process the query with the current script. STARTING AND ENDING A FORM print $query->start_form(-method=>$method, -action=>$action, -enctype=>$encoding(3,n)); <... various form stuff ...> print $query->endform; -or- print $query->start_form($method,$action,$encoding(3,n)); <... various form stuff ...> print $query->endform; start_form() will return a <form> tag with the optional method, action and form encoding(3,n) that you specify. The defaults are: method: POST action: this script enctype: application/x-www-form-urlencoded endform() 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: This method was previously named(5,8) startform(), and startform() is still recognized as an alias. application/x-www-form-urlencoded This is the older type of encoding(3,n) used by all browsers prior to Netscape 2.0. It is compatible with many CGI scripts and is suit- able for short fields containing text data. For your convenience, CGI.pm stores the name of this encoding(3,n) type in(1,8) &CGI::URL_ENCODED. multipart/form-data This is the newer type of encoding(3,n) introduced by Netscape 2.0. It is suitable for forms that contain very large fields or that are intended for transferring binary data. Most importantly, it enables the "file(1,n) upload" feature of Netscape 2.0 forms. For your convenience, CGI.pm stores the name of this encoding(3,n) type in(1,8) &CGI::MULTIPART Forms that use this type of encoding(3,n) are not easily interpreted by CGI scripts unless they use CGI.pm or another library designed to handle them. For compatibility, the start_form() method uses the older form of encoding(3,n) by default. If you want to use the newer form of encoding(3,n) by default, you can call start_multipart_form() instead of start_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(3,7) the submission by returning false from this function. Usually the bulk of JavaScript functions are defined in(1,8) a <script> block in(1,8) the HTML header and -onSubmit points to one of these function call. See start_html() for details. CREATING A TEXT FIELD print $query->textfield(-name=>'field_name', -default=>'starting value', -size=>50, -maxlength=>80); -or- print $query->textfield('field_name','starting value',50,80); textfield() will return a text input field. Parameters 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 (-default). 3. The optional third parameter is the size of the field in(1,8) characters (-size). 4. The optional fourth parameter is the maximum number of characters the field will accept(2,8) (-maxlength). As with all these methods, the field will be initialized with its pre- vious contents from earlier invocations of the script. When the form is processed, the value of the text field can be retrieved with: $value = $query->param('foo'); If you want to reset(1,7,1 tput) it from its initial value after the script has been called once, you can do so like this: $query->param('foo',"I'm taking over this value!"); NEW AS OF VERSION 2.15: If you don't want the field to take on its pre- vious value, you can force its current value by using the -override (alias -force) parameter: print $query->textfield(-name=>'field_name', -default=>'starting value', -override=>1, -size=>50, -maxlength=>80); JAVASCRIPTING: You can also provide -onChange, -onFocus, -onBlur, -onMouseOver, -onMouseOut and -onSelect parameters to register JavaScript event handlers. The onChange handler will be called when- ever the user changes the contents of the text field. You can do text validation if(3,n) you like. onFocus and onBlur are called respectively when the insertion point moves into and out of the text field. onSe- lect is called when the user changes the portion of the text that is selected. CREATING A BIG TEXT FIELD print $query->textarea(-name=>'foo', -default=>'starting value', -rows=>10, -columns=>50); -or print $query->textarea('foo','starting value',10,50); textarea() is just like textfield, but it allows you to specify rows and columns for a multiline text entry box. You can provide a starting value for the field, which can be long and contain multiple lines. JAVASCRIPTING: The -onChange, -onFocus, -onBlur , -onMouseOver, -onMouseOut, and -onSelect parameters are recognized. See textfield(). CREATING A PASSWORD FIELD print $query->password_field(-name=>'secret', -value=>'starting value', -size=>50, -maxlength=>80); -or- print $query->password_field('secret','starting value',50,80); password_field() is identical to textfield(), except that its contents will be starred out on the web page. JAVASCRIPTING: The -onChange, -onFocus, -onBlur, -onMouseOver, -onMouseOut and -onSelect parameters are recognized. See textfield(). CREATING A FILE UPLOAD FIELD print $query->filefield(-name=>'uploaded_file', -default=>'starting value', -size=>50, -maxlength=>80); -or- print $query->filefield('uploaded_file','starting value',50,80); filefield() will return a file(1,n) upload field for Netscape 2.0 browsers. In order to take full advantage of this you must use the new multipart encoding(3,n) scheme for the form. You can do this either by calling start_form() with an encoding(3,n) 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(1,n) 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 con- tents. The starting value field is called for in(1,8) the HTML specifi- cation, however, and possibly some browser will eventually provide support for it. 3. The optional third parameter is the size of the field in(1,8) characters (-size). 4. The optional fourth parameter is the maximum number of characters the field will accept(2,8) (-maxlength). When the form is processed, you can retrieve the entered filename by calling param(): $filename = $query->param('uploaded_file'); Different browsers will return slightly different things for the name. Some browsers return the filename only. Others return the full path to the file(1,n), using the path conventions of the user's machine. Regard- less(1,3), the name returned is always the name of the file(1,n) on the user's machine, and is unrelated to the name of the temporary file(1,n) that CGI.pm creates during upload spooling (see below). The filename returned is also a file(1,n) handle. You can read(2,n,1 builtins) the contents of the file(1,n) using standard Perl file(1,n) reading calls: # Read a text file(1,n) and print it out while (<$filename>) { print; } # Copy a binary file(1,n) to somewhere safe open(2,3,n) (OUTFILE,">>/usr/local/web/users(1,5)/feedback"); while ($bytesread=read(2,n,1 builtins)($filename,$buffer,1024)) { print OUTFILE $buffer; } However, there are problems with the dual nature of the upload fields. If you "use strict", then Perl will complain when you try to use a string(3,n) as a filehandle. You can get around this by placing the file(1,n) reading code in(1,8) a block containing the "no strict" pragma. More seri- ously, it is possible for the remote user to type garbage into the upload field, in(1,8) which case what you get from param() is not a filehan- dle at all, but a string. To be safe, use the upload() function (new in(1,8) version(1,3,5) 2.47). When called with the name of an upload field, upload() returns a filehandle, or undef if(3,n) the parameter is not a valid filehandle. $fh = $query->upload('uploaded_file'); while (<$fh>) { print; } In an list context, upload() will return an array of filehandles. This makes it possible to create forms that use the same name for multiple upload fields. This is the recommended idiom. When a file(1,n) is uploaded the browser usually sends along some informa- tion along with it in(1,8) the format of headers. The information usually includes the MIME content type. Future browsers may send(2,n) other infor- mation as well (such as modification date and size). To retrieve this information, call uploadInfo(). It returns a reference to an associa- tive array containing all the document headers. $filename = $query->param('uploaded_file'); $type = $query->uploadInfo($filename)->{'Content-Type'}; unless ($type eq 'text/html') { die "HTML FILES ONLY!"; } If you are using a machine that recognizes "text" and "binary" data modes, be sure to understand when and how to use them (see the Camel book). Otherwise you may find that binary files are corrupted during file(1,n) 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(1,n) and set(7,n,1 builtins) cgi_error() to the string(3,n) "400 Bad request (mal- formed multipart POST)". This error(8,n) message is designed so that you can incorporate it into a status code to be sent to the browser. Exam- ple: $file(1,n) = $query->upload('uploaded_file'); if(3,n) (!$file(1,n) && $query->cgi_error) { print $query->header(-status=>$query->cgi_error); exit(3,n,1 builtins) 0; } You are free to create a custom HTML page to complain about the error(8,n), if(3,n) you wish. You can set(7,n,1 builtins) up a callback that will be called whenever a file(1,n) upload is being read(2,n,1 builtins) during the form processing. This is much like the UPLOAD_HOOK facility available in(1,8) 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(); $q->upload_hook(\&hook,$data); sub hook { my ($filename, $buffer, $bytes_read, $data) = @_; print "Read $bytes_read bytes of $filename\n"; } If using the function-oriented interface, call the CGI::upload_hook() method before calling param() or any other CGI functions: CGI::upload_hook(\&hook,$data); This method is not exported by default. You will have to import it explicitly if(3,n) you wish to use it without the CGI:: prefix. 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(1,2) the uploaded file(1,n) to disk. JAVASCRIPTING: The -onChange, -onFocus, -onBlur, -onMouseOver, -onMouseOut and -onSelect parameters are recognized. See textfield() for details. CREATING A POPUP MENU print $query->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 $query->popup_menu('menu_name', ['eenie','meenie','minie'], 'meenie',\%labels,\%attributes); -or (named(5,8) parameter style)- print $query->popup_menu(-name=>'menu_name', -values=>['eenie','meenie','minie'], -default=>'meenie', -labels=>\%labels, -attributes=>\%attributes); popup_menu() creates a menu. 1. The required first argument is the menu(3x,n,n tk_menuSetFocus)'s name (-name). 2. The required second argument (-values) is an array reference con- taining the list of menu(3x,n,n tk_menuSetFocus) items in(1,8) the menu. You can pass the method an anonymous array, as shown in(1,8) the example, or a reference to a named(5,8) array, such as "\@foo". 3. The optional third parameter (-default) is the name of the default menu(3x,n,n tk_menuSetFocus) choice. If not specified, the first item will be the default. The values of the previous choice will be maintained across queries. 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(3x,n,n tk_menuSetFocus) and the value returned to your script. It's a pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to user-visible labels. If you leave this parameter blank, the menu(3x,n,n tk_menuSetFocus) values will be displayed by default. (You can also leave a label undefined if(3,n) you want to). 5. The optional fifth parameter (-attributes) is provided to assign any of the common HTML attributes to an individual menu(3x,n,n tk_menuSetFocus) item. It's a pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to another associative array 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(3x,n,n tk_menuSetFocus) can be retrieved using: $popup_menu_value = $query->param('menu_name'); JAVASCRIPTING: popup_menu() recognizes the following event handlers: -onChange, -onFocus, -onMouseOver, -onMouseOut, and -onBlur. See the textfield() section for details on when these handlers are called. CREATING AN OPTION GROUP Named parameter style print $query->popup_menu(-name=>'menu_name', -values=>[qw/eenie meenie minie/, $q->optgroup(-name=>'optgroup_name', -values ['moe','catch'], -attributes=>{'catch'=>{'class'=>'red'}}), -labels=>{'eenie'=>'one', 'meenie'=>'two', 'minie'=>'three'}, -default=>'meenie'); Old style print $query->popup_menu('menu_name', ['eenie','meenie','minie', $q->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(1,8) the parameter list of the query. 2. The required second argument (-values) is an array reference con- taining the list of menu(3x,n,n tk_menuSetFocus) items in(1,8) the menu. You can pass the method an anonymous array, as shown in(1,8) the example, or a reference to a named(5,8) array, such as \@foo. If you pass a HASH reference, the keys will be used for the menu(3x,n,n tk_menuSetFocus) values, and the values will be used for the menu(3x,n,n tk_menuSetFocus) labels (see -labels below). 3. The optional third parameter (-labels) allows you to pass a refer- ence to an associative array containing user-visible labels for one or more of the menu(3x,n,n tk_menuSetFocus) items. You can use this when you want the user to see one menu(3x,n,n tk_menuSetFocus) string(3,n), but have the browser return your program a different one. If you don't specify this, the value string(3,n) will be used instead ("eenie", "meenie" and "minie" in(1,8) this example). This is equivalent to using a hash reference for the -values parameter. 4. An optional fourth parameter (-labeled) can be set(7,n,1 builtins) 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(7,n,1 builtins) to a true value and indicates to suppress the val attribut in(1,8) 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(3x,n,n tk_menuSetFocus) item. It's a pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to another associative array with the attribute's name as the key and the attribute's value as the value. CREATING A SCROLLING LIST print $query->scrolling_list('list_name', ['eenie','meenie','minie','moe'], ['eenie','moe'],5,'true',{'moe'=>{'class'=>'red'}}); -or- print $query->scrolling_list('list_name', ['eenie','meenie','minie','moe'], ['eenie','moe'],5,'true', \%labels,%attributes); -or- print $query->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(1,8) the popup menu(3x,n,n tk_menuSetFocus), 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(5,8) parameter version(1,3,5), 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(7,n,1 builtins) 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 an associative array 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(3x,n,n tk_menuSetFocus) item. It's a pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to another associative array 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 val- ues of the selected items can be retrieved with: @selected = $query->param('list_name'); JAVASCRIPTING: scrolling_list() recognizes the following event han- dlers: -onChange, -onFocus, -onMouseOver, -onMouseOut and -onBlur. See textfield() for the description of when these handlers are called. CREATING A GROUP OF RELATED CHECKBOXES print $query->checkbox_group(-name=>'group_name', -values=>['eenie','meenie','minie','moe'], -default=>['eenie','moe'], -linebreak=>'true', -labels=>\%labels, -attributes=>\%attributes); print $query->checkbox_group('group_name', ['eenie','meenie','minie','moe'], ['eenie','moe'],'true',\%labels, {'moe'=>{'class'=>'red'}}); HTML3-COMPATIBLE BROWSERS ONLY: print $query->checkbox_group(-name=>'group_name', -values=>['eenie','meenie','minie','moe'], -rows=2,-columns=>2); checkbox_group() creates a list of checkboxes that are related by the same name. Parameters: 1. The first and second arguments are the checkbox name and values, respectively (-name and -values). As in(1,8) the popup menu(3x,n,n tk_menuSetFocus), 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(1,8) 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(7,n,1 builtins) 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 hori- zontal line. 4. The optional fifth argument is a pointer to an associative array relating the checkbox values to the user-visible labels that will be printed next to them (-labels). If not provided, the values will be used as the default. 5. HTML3-compatible browsers (such as Netscape) can take advantage of the optional parameters -rows, and -columns. These parameters cause checkbox_group() to return an HTML3 compatible table contain- ing the checkbox group formatted with the specified number of rows and columns. You can provide just the -columns parameter if(3,n) you wish; checkbox_group will calculate the correct number of rows for you. 6. The optional sixth parameter (-attributes) is provided to assign any of the common HTML attributes to an individual menu(3x,n,n tk_menuSetFocus) item. It's a pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to another associative array with the attribute's name as the key and the attribute's value as the value. To include row and column headings in(1,8) the returned table, you can use the -rowheaders and -colheaders parameters. Both of these accept(2,8) a pointer to an array of headings to use. The headings are just decorative. They don't reorganize the interpretation of the checkboxes -- they're still a single named(5,8) unit. 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 = $query->param('group_name'); The value returned by checkbox_group() is actually an array of button elements. You can capture them and use them within tables, lists, or in(1,8) other creative ways: @h = $query->checkbox_group(-name=>'group_name',-values=>\@values); &use_in_creative_way(@h); JAVASCRIPTING: checkbox_group() recognizes the -onClick parameter. This specifies a JavaScript code fragment or function call to be exe- cuted every time(1,2,n) the user clicks on any of the buttons in(1,8) the group. You can retrieve the identity of the particular button clicked on using the "this" variable. CREATING A STANDALONE CHECKBOX print $query->checkbox(-name=>'checkbox_name', -checked=>1, -value=>'ON', -label=>'CLICK ME'); -or- print $query->checkbox('checkbox_name','checked','ON','CLICK ME'); checkbox() is used to create an isolated checkbox that isn't logically related to any others. 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 check- box 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 = $query->param('checkbox_name'); JAVASCRIPTING: checkbox() recognizes the -onClick parameter. See checkbox_group() for further details. CREATING A RADIO BUTTON GROUP print $query->radio_group(-name=>'group_name', -values=>['eenie','meenie','minie'], -default=>'meenie', -linebreak=>'true', -labels=>\%labels, -attributes=>\%attributes); -or- print $query->radio_group('group_name',['eenie','meenie','minie'], 'meenie','true',\%labels,\%attributes); HTML3-COMPATIBLE BROWSERS ONLY: print $query->radio_group(-name=>'group_name', -values=>['eenie','meenie','minie','moe'], -rows=2,-columns=>2); radio_group() creates a set(7,n,1 builtins) 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(1,8) the second argument, either using an anonymous array, as shown, or by referencing a named(5,8) array as in(1,8) "\@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(7,n,1 builtins) to 'true' to put line breaks between the buttons, creating a vertical list. 5. The optional fifth parameter (-labels) is a pointer to an associa- tive array relating the radio button values to user-visible labels to be used in(1,8) the display. If not provided, the values themselves are displayed. 6. HTML3-compatible browsers (such as Netscape) can take advantage of the optional parameters -rows, and -columns. These parameters cause radio_group() to return an HTML3 compatible table containing the radio group formatted with the specified number of rows and columns. You can provide just the -columns parameter if(3,n) you wish; radio_group will calculate the correct number of rows for you. 6. The optional sixth parameter (-attributes) is provided to assign any of the common HTML attributes to an individual menu(3x,n,n tk_menuSetFocus) item. It's a pointer to an associative array relating menu(3x,n,n tk_menuSetFocus) values to another associative array with the attribute's name as the key and the attribute's value as the value. To include row and column headings in(1,8) the returned table, you can use the -rowheader and -colheader parameters. Both of these accept(2,8) 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(5,8) unit. When the form is processed, the selected radio button can be retrieved using: $which_radio_button = $query->param('group_name'); The value returned by radio_group() is actually an array of button ele- ments. You can capture them and use them within tables, lists, or in(1,8) other creative ways: @h = $query->radio_group(-name=>'group_name',-values=>\@values); &use_in_creative_way(@h); CREATING A SUBMIT BUTTON print $query->submit(-name=>'button_name', -value=>'value'); -or- print $query->submit('button_name','value'); submit() will create the query submission button. Every form should have one of these. Parameters: 1. The first argument (-name) is optional. You can give the button a name if(3,n) you have several submission buttons in(1,8) your form and you want to distinguish between them. 2. The second argument (-value) is also optional. This gives the but- ton a value that will be passed to your script in(1,8) 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 = $query->param('button_name'); JAVASCRIPTING: radio_group() recognizes the -onClick parameter. See checkbox_group() for further details. CREATING A RESET BUTTON print $query->reset(1,7,1 tput) reset(1,7,1 tput)() creates the "reset(1,7,1 tput)" button. Note that it restores the form to its value from the last time(1,2,n) the script was called, NOT necessarily to the defaults. Note that this conflicts with the Perl reset(1,7,1 tput)() built-in. Use CORE::reset() to get the original reset(1,7,1 tput) function. CREATING A DEFAULT BUTTON print $query->defaults('button_label') defaults() creates a button that, when invoked, will cause the form to be completely reset(1,7,1 tput) to its defaults, wiping out all the changes the user ever made. CREATING A HIDDEN FIELD print $query->hidden(-name=>'hidden_name', -default=>['value1','value2'...]); -or- print $query->hidden('hidden_name','value1','value2'...); hidden() produces a text field that can't be seen by the user. It is useful for passing state variable information from one invocation of the script to the next. 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(5,8) parameter style of calling, you can pro- vide a single value here or a reference to a whole list Fetch the value of a hidden field this way: $hidden_value = $query->param('hidden_name'); Note, that just like all the other form elements, the value of a hidden field is "sticky". If you want to replace a hidden field with some other values after the script has been called once you'll have to do it manually: $query->param('hidden_name','new','values','here'); CREATING A CLICKABLE IMAGE BUTTON print $query->image_button(-name=>'button_name', -src=>'/source/URL', -align=>'MIDDLE'); -or- print $query->image_button('button_name','/source/URL','MIDDLE'); image_button() produces a clickable image. When it's clicked on the position of the click is returned to your script as "button_name.x" and "button_name.y", where "button_name" is the name you've assigned to it. JAVASCRIPTING: image_button() recognizes the -onClick parameter. See checkbox_group() for further details. 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 = $query->param('button_name.x'); $y = $query->param('button_name.y'); CREATING A JAVASCRIPT ACTION BUTTON print $query->button(-name=>'button_name', -value=>'user visible label', -onClick=>"do_something()"); -or- print $query->button('button_name',"do_something()"); button() produces a button that is compatible with Netscape 2.0's JavaScript. When it's pressed the fragment of JavaScript code pointed to by the -onClick parameter will be executed. On non-Netscape browsers this form element will probably not even display. HTTP COOKIES Netscape browsers versions 1.1 and higher, and all versions of Internet Explorer, support a so-called "cookie" designed to