NAME

CGI::Tiny - Common Gateway Interface, with no frills

SYNOPSIS

#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use CGI::Tiny;

cgi {
  my $cgi = $_;
  $cgi->set_error_handler(sub {
    my ($cgi, $error, $rendered) = @_;
    warn $error;
    unless ($rendered) {
      if ($cgi->response_status_code == 413) {
        $cgi->render(json => {error => 'Request body limit exceeded'});
      } elsif ($cgi->response_status_code == 400) {
        $cgi->render(json => {error => 'Bad request'});
      } else {
        $cgi->render(json => {error => 'Internal server error'});
      }
    }
  });

  my $method = $cgi->method;
  my $fribble;
  if ($method eq 'GET' or $method eq 'HEAD') {
    $fribble = $cgi->query_param('fribble');
  } elsif ($method eq 'POST') {
    $fribble = $cgi->body_param('fribble');
  } else {
    $cgi->set_response_status(405)->render;
    exit;
  }
  die "Invalid fribble parameter" unless length $fribble;

  if ($cgi->param('download')) {
    $cgi->set_response_disposition(attachment => 'fribble.json');
  }
  $cgi->render(json => {fribble => $fribble});
};

DESCRIPTION

CGI::Tiny provides a modern interface to write CGI scripts to dynamically respond to HTTP requests as defined in RFC 3875. It is intended to be:

Minimal

CGI::Tiny contains a small amount of code and (on modern Perls) no non-core requirements. No framework needed.
Simple

CGI::Tiny is straightforward to use, avoids anything magical or surprising, and provides easy access to the most commonly needed features.
Robust

CGI::Tiny's interface is designed to help the developer follow best practices and avoid common pitfalls and vulnerabilities by default.
Lazy

CGI::Tiny only loads code or processes information once it is needed, so simple requests can be handled without unnecessary overhead.
Restrained

CGI::Tiny is designed for the CGI protocol which executes the program again for every request. It is not suitable for persistent protocols like FastCGI or PSGI.
Flexible

CGI::Tiny can be used with other modules to handle tasks like routing and templating, and doesn't impose unnecessary constraints to reading input or rendering output.

Most applications are better written in a PSGI-compatible framework (e.g. Dancer2 or Mojolicious) and deployed in a persistent application server so that the application does not have to start up again every time it receives a request. CGI::Tiny, and the CGI protocol in general, is only suited for restricted deployment environments that can only run CGI scripts, or applications that don't need to scale.

See "COMPARISON TO CGI.PM".

This module's interface is currently EXPERIMENTAL and may be changed incompatibly if needed.

USAGE

CGI::Tiny's interface is a regular function called cgi exported by default.

use CGI::Tiny;
cgi {
  my $cgi = $_;
  # set up error handling on $cgi
  # inspect request data via $cgi
  # set response headers if needed via $cgi
  # render response with $cgi->render or $cgi->render_chunk
};

The code block is immediately run with $_ set to a CGI::Tiny object, which "METHODS" can be called on to read request information and render a response.

If an exception is thrown within the code block, or the code block does not render a response, it will run the handler set by "set_error_handler" if any, or by default emit the error as a warning and (if nothing has been rendered yet) render a 500 Internal Server Error. The default server error will also be rendered if the process ends abnormally between importing from CGI::Tiny and the start of the cgi block.

Note that the cgi block's current implementation as a regular exported subroutine is an implementation detail, and future implementations reserve the right to provide it as an XSUB or keyword for performance reasons. You should not rely on @_ to be set, and you should not use return to exit the block; use exit to end a CGI script early after rendering a response.

DATA SAFETY

CGI::Tiny does not provide any special affordances for taint mode as it is overeager, imprecise, and can significantly impact performance. Web developers should instead proactively take care not to use any request data (including request headers, form fields, or other request content) directly in an unsafe manner, as it can make the program vulnerable to injections that cause undesired or dangerous behavior. The most common risks to watch out for include:

System commands

Do not interpolate arbitrary data into a shell command, such as with system or backticks. Data can be safely passed as command arguments using methods that bypass the shell, such as the list form of system, or modules like IPC::System::Simple, IPC::ReadpipeX, and IPC::Run3. If shell features are needed, data can be escaped for bourne-style shells with String::ShellQuote.
Database queries

Do not interpolate arbitrary data into database queries. Data can be safely passed to database queries using placeholders.
Regex

Do not interpolate arbitrary data into regular expressions, such as the m// or s/// operators, or the first argument to split. Data can be safely included in a regex to match it as an exact string by escaping it with the quotemeta function or equivalent \Q escape sequence.
HTML

Do not interpolate arbitrary data into HTML. Data can be safely included in HTML by escaping it with "escape_html", or passing it to an HTML template engine with an auto-escape feature; see "Templating".

EXTENDING

CGI::Tiny is a minimal interface to the CGI protocol, but can be extended with the use of other CPAN modules.

Fatpacking

App::FatPacker can be used to pack CGI::Tiny, as well as any other pure-perl dependencies, into a CGI script so that it can be deployed to other systems without having to install the dependencies there. As a bonus, this means the script doesn't have to load those modules separately from disk on every execution.

Just keep in mind that the script will have to be repacked to update those dependencies, and CGI scripts greatly benefit from efficient XS tools which cannot be packed this way.

$ fatpack pack script.source.cgi > script.cgi

To pack in optional modules, such as JSON support for Perls older than 5.14:

$ fatpack trace --use=JSON::PP script.source.cgi
$ fatpack packlists-for $(cat fatpacker.trace) > packlists
$ fatpack tree $(cat packlists)
$ fatpack file script.source.cgi > script.cgi

JSON

CGI::Tiny has built in support for parsing and rendering JSON content with JSON::PP. CGI scripts that deal with JSON content will greatly benefit from installing Cpanel::JSON::XS version 4.09 or newer for efficient encoding and decoding, which will be used automatically if available.

Templating

HTML and XML responses are most easily managed with templating. A number of CPAN modules provide this capability.

Text::Xslate is an efficient template engine designed for HTML/XML.

#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use CGI::Tiny;
use Text::Xslate;
use Data::Section::Simple 'get_data_section';

cgi {
  my $cgi = $_;
  my $foo = $cgi->query_param('foo');
  my $tx = Text::Xslate->new(path => ['templates'], cache => 0);

  # from templates/
  $cgi->render(html => $tx->render('index.tx', {foo => $foo}));

  # or from __DATA__
  my $template = get_data_section 'index.tx';
  $cgi->render(html => $tx->render_string($template, {foo => $foo}));
};

__DATA__
@@ index.tx
<html><body><h1><: $foo :></h1></body></html>

Mojo::Template is a lightweight HTML/XML template engine in the Mojo toolkit.

#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use CGI::Tiny;
use Mojo::Template;
use Mojo::File 'curfile';
use Mojo::Loader 'data_section';

cgi {
  my $cgi = $_;
  my $foo = $cgi->query_param('foo');
  my $mt = Mojo::Template->new(auto_escape => 1, vars => 1);

  # from templates/
  my $template_path = curfile->sibling('templates', 'index.html.ep');
  $cgi->render(html => $mt->render_file($template_path, {foo => $foo}));

  # or from __DATA__
  my $template = data_section __PACKAGE__, 'index.html.ep';
  $cgi->render(html => $mt->render($template, {foo => $foo}));
};

__DATA__
@@ index.html.ep
<html><body><h1><%= $foo %></h1></body></html>

Files

Modules like Path::Tiny and MIME::Types can help with file responses. Be aware that Perl and some operating systems work with filenames in encoded bytes (usually UTF-8), but this module works with parameters in Unicode characters, so non-ASCII filenames make things trickier.

#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use CGI::Tiny;
use Path::Tiny;
use MIME::Types;
use Unicode::UTF8 qw(encode_utf8 decode_utf8);

cgi {
  my $cgi = $_;

  my $filename = $cgi->query_param('filename');
  unless (length $filename) {
    $cgi->set_response_status(404)->render(text => 'Not Found');
    exit;
  }

  # get files from public/ next to cgi-bin/
  my $public_dir = path(__FILE__)->realpath->parent->sibling('public');
  my $encoded_filename = encode_utf8 $filename;
  my $filepath = $public_dir->child($encoded_filename);

  # ensure file exists, is readable, and is not a directory
  unless (-r $filepath and !-d _) {
    $cgi->set_response_status(404)->render(text => 'Not Found');
    exit;
  }

  # ensure file path doesn't escape the public/ directory
  unless ($public_dir->subsumes($filepath->realpath)) {
    $cgi->set_response_status(404)->render(text => 'Not Found');
    exit;
  }

  my $basename = decode_utf8 $filepath->basename;
  my $mime = MIME::Types->new->mimeTypeOf($basename);
  $cgi->set_response_type($mime->type) if defined $mime;
  $cgi->set_response_disposition(attachment => $basename)->render(file => $filepath);
};

Sessions

Basic authentication has historically been used to provide a simplistic login session mechanism which relies on the client to send the credentials with every subsequent request in that browser session. However, it does not have a reliable logout or session expiration mechanism.

#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use CGI::Tiny;
use MIME::Base64 qw(encode_base64 decode_base64);
use Unicode::UTF8 'decode_utf8';

cgi {
  my $cgi = $_;

  my $authed_user;
  if (defined(my $auth = $cgi->header('Authorization'))) {
    if (my ($hash) = $auth =~ m/^Basic (\S+)/i) {
      my ($user, $pass) = split /:/, decode_utf8(decode_base64($hash)), 2;
      $authed_user = $user if verify_password($user, $pass);
    }
  }

  unless (defined $authed_user) {
    $cgi->add_response_header('WWW-Authenticate' => 'Basic realm="My Website", charset="UTF-8"');
    $cgi->set_response_status(401)->render;
    exit;
  }

  # do authed stuff
};

A more sophisticated login session mechanism is to store a session cookie in the client, associated with a server-side session stored in a file or database. Login credentials only need to be validated once per session, and subsequently the session ID stored in the cookie will be sent by the client with each request. This type of session can be ended by expiring the session cookie and invalidating the session data on the server.

#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use CGI::Tiny;

cgi {
  my $cgi = $_;

  my ($authed_user, $session_id);
  if ($cgi->path eq '/login') {
    if ($cgi->method eq 'GET' or $cgi->method eq 'HEAD') {
      $cgi->render(html => login_form_template(login_failed => 0));
      exit;
    } elsif ($cgi->method eq 'POST') {
      my $user = $cgi->body_param('login_user');
      my $pass = $cgi->body_param('login_pass');
      if (verify_password($user, $pass)) {
        $session_id = store_new_session($user);
        $authed_user = $user;
      } else {
        $cgi->render(html => login_form_template(login_failed => 1));
        exit;
      }
    }
  } elsif (defined($session_id = $cgi->cookie('myapp_session'))) {
    if ($cgi->path eq '/logout') {
      invalidate_session($session_id);
      # expire session cookie
      $cgi->add_response_cookie(myapp_session => $session_id, 'Max-Age' => 0, Path => '/', HttpOnly => 1);
      $cgi->render(redirect => $cgi->script_name . '/login');
      exit;
    } else {
      $authed_user = get_session_user($session_id);
    }
  }

  unless (defined $authed_user) {
    $cgi->render(redirect => $cgi->script_name . '/login');
    exit;
  }

  # set/refresh session cookie
  $cgi->add_response_cookie(myapp_session => $session_id, 'Max-Age' => 3600, Path => '/', HttpOnly => 1);

  # do authed stuff
};

Regardless of the session mechanism, login credentials should only be sent over HTTPS, and passwords should be stored on the server using a secure one-way hash, such as with Crypt::Passphrase.

Logging

CGI scripts can usually log errors directly to STDERR with the warn function, and rely on the CGI server to log them to a file, but you will likely need to encode errors to UTF-8 if you expect them to contain non-ASCII text.

Minimal loggers like Log::Any can also be used to redirect errors and warnings to a file or other logging mechanism specific to the CGI script, encode them to bytes automatically, and also log debugging information when the log level is set to debug. Just make sure the CGI server has permission to create and write to the logging target.

#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use CGI::Tiny;
use Log::Any;
use Log::Any::Adapter
  {category => 'cgi-script'}, # only log our category here
  File => '/path/to/log/file.log',
  binmode => ':encoding(UTF-8)',
  log_level => $ENV{MY_CGI_LOG_LEVEL} || 'info';

my $log = Log::Any->get_logger(category => 'cgi-script');

local $SIG{__WARN__} = sub {
  my ($warning) = @_;
  chomp $warning;
  $log->warn($warning);
};

cgi {
  my $cgi = $_;

  $cgi->set_error_handler(sub {
    my ($cgi, $error, $rendered) = @_;
    chomp $error;
    $log->error($error);
  });

  # only logged if MY_CGI_LOG_LEVEL=debug set in CGI server environment
  $log->debugf('Method: %s, Path: %s, Query: %s', $cgi->method, $cgi->path, $cgi->query);

  # handle the actual request
};

Routing

Web applications use routing to serve multiple types of requests from one application. Routes::Tiny can be used to organize this with CGI::Tiny, using REQUEST_METHOD and PATH_INFO (which is the URL path after the CGI script name).

#!/usr/bin/perl
use strict;
use warnings;
use utf8;
use CGI::Tiny;
use Routes::Tiny;

my %dispatch = (
  foos => sub {
    my ($cgi) = @_;
    my $method = $cgi->method;
    ...
  },
  get_foo => sub {
    my ($cgi, $captures) = @_;
    my $id = $captures->{id};
    ...
  },
  put_foo => sub {
    my ($cgi, $captures) = @_;
    my $id = $captures->{id};
    ...
  },
);

cgi {
  my $cgi = $_;

  my $routes = Routes::Tiny->new;
  # /script.cgi/foo
  $routes->add_route('/foo', name => 'foos');
  # /script.cgi/foo/42
  $routes->add_route('/foo/:id', method => 'GET', name => 'get_foo');
  $routes->add_route('/foo/:id', method => 'PUT', name => 'put_foo');

  if (defined(my $match = $routes->match($cgi->path, method => $cgi->method))) {
    $dispatch{$match->name}->($cgi, $match->captures);
  } else {
    $cgi->set_response_status(404)->render(text => 'Not Found');
  }
};

METHODS

The following methods can be called on the CGI::Tiny object provided to the cgi code block.

Setup

set_error_handler

$cgi = $cgi->set_error_handler(sub {
  my ($cgi, $error, $rendered) = @_;
  ...
});

Sets an error handler to run in the event of an exception or if the script ends without rendering a response. The handler will be called with the CGI::Tiny object, the error value, and a boolean indicating whether response headers have been rendered yet.

The error value can be any exception thrown by Perl or user code. It should generally not be included in any response rendered to the client, but instead warned or logged.

Exceptions may occur before or after response headers have been rendered. If response headers have not been rendered, error handlers may inspect "response_status_code" and/or render some error response. The response status code will be set to 500 when this handler is called if it has not been set to a specific 400- or 500-level error status.

If the error handler itself throws an exception, that error and the original error will be emitted as a warning. If no response has been rendered after the error handler completes or dies, a default error response will be rendered.

Note that the error handler is only meant for logging and customization of the final error response in a failed request dispatch; to handle exceptions within standard application flow without causing an error response, use an exception handling mechanism such as Syntax::Keyword::Try or Feature::Compat::Try (which will use the new try feature if available).

set_request_body_buffer

$cgi = $cgi->set_request_body_buffer(256*1024);

Sets the buffer size (number of bytes to read at once) for reading the request body. Defaults to the value of the CGI_TINY_REQUEST_BODY_BUFFER environment variable or 262144 (256 KiB). A value of 0 will use the default value.

set_request_body_limit

$cgi = $cgi->set_request_body_limit(16*1024*1024);

Sets the limit in bytes for the request body. Defaults to the value of the CGI_TINY_REQUEST_BODY_LIMIT environment variable or 16777216 (16 MiB). A value of 0 will remove the limit (not recommended unless you have other safeguards on memory usage).

Since the request body is not parsed until needed, methods that parse the request body like "body" or "upload" will set the response status to 413 Payload Too Large and throw an exception if the content length is over the limit. Files uploaded through a multipart/form-data request body also count toward this limit, though they are streamed to temporary files when parsed.

set_multipart_form_options

$cgi = $cgi->set_multipart_form_options({discard_files => 1, tempfile_args => [SUFFIX => '.dat']});

Set a hash reference of options to pass when parsing a multipart/form-data request body with "parse_multipart_form_data" in CGI::Tiny::Multipart. No effect after the form data has been parsed such as by calling "body_params" or "uploads" for the first time.

Note that options like parse_as_files and on_file_buffer can alter the content and file keys of the form field structure returned by "body_parts". Thus "uploads" may not contain file and may instead contain content, and "body_params" text field values may be read from file, which will be expected to be a seekable filehandle if present.

set_multipart_form_charset

$cgi = $cgi->set_multipart_form_charset('UTF-8');

Sets the default charset for decoding multipart/form-data forms, defaults to UTF-8. Parameter and upload field names, upload filenames, and text parameter values that don't specify a charset will be decoded from this charset. Set to an empty string to disable this decoding, effectively interpreting such values in ISO-8859-1.

set_input_handle

$cgi = $cgi->set_input_handle($fh);

Sets the input handle to read the request body from. If not set, reads from STDIN. The handle will have binmode applied before reading to remove any translation layers.

set_output_handle

$cgi = $cgi->set_output_handle($fh);

Sets the output handle to print the response to. If not set, prints to STDOUT. The handle will have binmode applied before printing to remove any translation layers.

Request Environment

CGI::Tiny provides direct access to CGI request meta-variables via methods that map to the equivalent uppercase names (and a few short aliases). Since CGI does not distinguish between missing and empty values, missing values will be normalized to an empty string.

auth_type

# AUTH_TYPE="Basic"
my $auth_type = $cgi->auth_type;

The authentication scheme used in the Authorization HTTP request header if any.

content_length

# CONTENT_LENGTH="42"
my $content_length = $cgi->content_length;

The size in bytes of the request body content if any.

content_type

# CONTENT_TYPE="text/plain;charset=UTF-8"
my $content_type = $cgi->content_type;

The MIME type of the request body content if any.

gateway_interface

# GATEWAY_INTERFACE="CGI/1.1"
my $gateway_inteface = $cgi->gateway_interface;

The CGI version used for communication with the CGI server.

path_info

path

# PATH_INFO="/foo/42"
my $path = $cgi->path_info;
my $path = $cgi->path;

The URL path following the SCRIPT_NAME in the request URL if any.

path_translated

# PATH_TRANSLATED="/var/www/html/foo/42"
my $path_translated = $cgi->path_translated;

A local file path derived from PATH_INFO by the CGI server, as if it were a request to the document root, if it chooses to provide it.

query_string

query

# QUERY_STRING="foo=bar"
my $query = $cgi->query_string;
my $query = $cgi->query;

The query string component of the request URL.

remote_addr

# REMOTE_ADDR="8.8.8.8"
my $remote_addr = $cgi->remote_addr;

The IPv4 or IPv6 address of the requesting client.

remote_host

# REMOTE_HOST="example.com"
my $remote_host = $cgi->remote_host;

The domain name of the requesting client if available, or REMOTE_ADDR.

remote_ident

# REMOTE_IDENT="someuser"
my $remote_ident = $cgi->remote_ident;

The identity of the client reported by an RFC 1413 ident request if available.

remote_user

# REMOTE_USER="someuser"
my $remote_user = $cgi->remote_user;

The user identity provided as part of an AUTH_TYPE authenticated request.

request_method

method

# REQUEST_METHOD="GET"
my $method = $cgi->request_method;
my $method = $cgi->method;

The HTTP request method verb.

script_name

# SCRIPT_NAME="/cgi-bin/script.cgi"
my $script_name = $cgi->script_name;

The host-relative URL path to the CGI script.

server_name

# SERVER_NAME="example.com"
my $server_name = $cgi->server_name;

The hostname of the server as the target of the request, such as from the Host HTTP request header.

server_port

# SERVER_PORT="443"
my $server_port = $cgi->server_port;

The TCP port on which the server received the request.

server_protocol

# SERVER_PROTOCOL="HTTP/1.1"
my $server_protocol = $cgi->server_protocol;

The HTTP protocol version of the request.

server_software

# SERVER_SOFTWARE="Apache\/2.4.37 (centos)"
my $server_software = $cgi->server_software;

The name and version of the CGI server.

Request Parsing

headers

my $hashref = $cgi->headers;

Hash reference of available request header names and values. Header names are represented in lowercase.

my $value = $cgi->header('Accept-Language');

Retrieve the value of a request header by name (case insensitive). CGI request headers can only contain a single value, which may be combined from multiple values.

cookies

my $pairs = $cgi->cookies;

Retrieve request cookies as an ordered array reference of name/value pairs, represented as two-element array references.

cookie_names

my $arrayref = $cgi->cookie_names;

Retrieve request cookie names as an ordered array reference.

my $value = $cgi->cookie('foo');

Retrieve the value of a request cookie by name. If multiple cookies were passed with the same name, returns the last value. Use "cookie_array" to get multiple values of a cookie name.

cookie_array

my $arrayref = $cgi->cookie_array('foo');

Retrieve values of a request cookie name as an ordered array reference.

params

my $pairs = $cgi->params;

Retrieve URL query string parameters and application/x-www-form-urlencoded or multipart/form-data body parameters as an ordered array reference of name/value pairs, represented as two-element array references. Names and values are decoded to Unicode characters.

Query parameters are returned first, followed by body parameters. Use "query_params" or "body_params" to retrieve query or body parameters separately.

Note that this will read the text form fields into memory as in "body_params".

param_names

my $arrayref = $cgi->param_names;

Retrieve URL query string parameter names and application/x-www-form-urlencoded or multipart/form-data body parameter names, decoded to Unicode characters, as an ordered array reference.

Query parameter names are returned first, followed by body parameter names (without duplication). Use "query_param_names" or "body_param_names" to retrieve query or body parameter names separately.

Note that this will read the text form fields into memory as in "body_params".

param

my $value = $cgi->param('foo');

Retrieve value of a named URL query string parameter or application/x-www-form-urlencoded or multipart/form-data body parameter, decoded to Unicode characters.

If the parameter name was passed multiple times, returns the last body parameter value if any, otherwise the last query parameter value. Use "param_array" to get multiple values of a parameter, or "query_param" or "body_param" to retrieve the last query or body parameter value specifically.

Note that this will read the text form fields into memory as in "body_params".

param_array

my $arrayref = $cgi->param_array('foo');

Retrieve values of a named URL query string parameter or application/x-www-form-urlencoded or multipart/form-data body parameter, decoded to Unicode characters, as an ordered array reference.

Query parameter values will be returned first, followed by body parameter values. Use "query_param_array" or "body_param_array" to retrieve query or body parameter values separately.

Note that this will read the text form fields into memory as in "body_params".

query_params

my $pairs = $cgi->query_params;

Retrieve URL query string parameters as an ordered array reference of name/value pairs, represented as two-element array references. Names and values are decoded to Unicode characters.

query_param_names

my $arrayref = $cgi->query_param_names;

Retrieve URL query string parameter names, decoded to Unicode characters, as an ordered array reference.

query_param

my $value = $cgi->query_param('foo');

Retrieve value of a named URL query string parameter, decoded to Unicode characters.

If the parameter name was passed multiple times, returns the last value. Use "query_param_array" to get multiple values of a parameter.

query_param_array

my $arrayref = $cgi->query_param_array('foo');

Retrieve values of a named URL query string parameter, decoded to Unicode characters, as an ordered array reference.

body

my $bytes = $cgi->body;

Retrieve the request body as bytes.

Note that this will read the whole request body into memory, so make sure the "set_request_body_limit" can fit well within the available memory.

Not available after calling "body_parts", "body_params", or "uploads" (or related accessors) on a multipart/form-data request, since this type of request body is not retained in memory after parsing.

body_json

my $data = $cgi->body_json;

Decode an application/json request body from UTF-8-encoded JSON.

Note that this will read the whole request body into memory, so make sure the "set_request_body_limit" can fit well within the available memory.

body_params

my $pairs = $cgi->body_params;

Retrieve application/x-www-form-urlencoded or multipart/form-data body parameters as an ordered array reference of name/value pairs, represented as two-element array references. Names and values are decoded to Unicode characters.

Note that this will read the text form fields into memory, so make sure the "set_request_body_limit" can fit well within the available memory. multipart/form-data file uploads will be streamed to temporary files accessible via "uploads" and related methods.

body_param_names

my $arrayref = $cgi->body_param_names;

Retrieve application/x-www-form-urlencoded or multipart/form-data body parameter names, decoded to Unicode characters, as an ordered array reference.

Note that this will read the text form fields into memory as in "body_params".

body_param

my $value = $cgi->body_param('foo');

Retrieve value of a named application/x-www-form-urlencoded or multipart/form-data body parameter, decoded to Unicode characters.

If the parameter name was passed multiple times, returns the last value. Use "body_param_array" to get multiple values of a parameter.

Note that this will read the text form fields into memory as in "body_params".

body_param_array

my $arrayref = $cgi->body_param_array('foo');

Retrieve values of a named application/x-www-form-urlencoded or multipart/form-data body parameter, decoded to Unicode characters, as an ordered array reference.

Note that this will read the text form fields into memory as in "body_params".

body_parts

my $parts = $cgi->body_parts;

Retrieve multipart/form-data request body parts as an ordered array reference using "parse_multipart_form_data" in CGI::Tiny::Multipart. Most applications should retrieve multipart form data through "body_params" and "uploads" (or related accessors) instead.

Note that this will read the text form fields into memory, so make sure the "set_request_body_limit" can fit well within the available memory. File uploads will be streamed to temporary files.

uploads

my $pairs = $cgi->uploads;

Retrieve multipart/form-data file uploads as an ordered array reference of name/upload pairs, represented as two-element array references. Names are decoded to Unicode characters.

Note that this will read the text form fields into memory, so make sure the "set_request_body_limit" can fit well within the available memory.

File uploads are represented as a hash reference containing the following keys:

filename: Original filename supplied to file input. An empty filename may indicate that no file was submitted.
content_type: Content-Type of uploaded file, undef if unspecified.
size: File size in bytes.
file: File::Temp object storing the file contents in a temporary file, which will be cleaned up when the CGI script ends by default. The filehandle will be open with the seek pointer at the start of the file for reading.

upload_names

my $arrayref = $cgi->upload_names;

Retrieve multipart/form-data file upload names, decoded to Unicode characters, as an ordered array reference.

Note that this will read the text form fields into memory as in "uploads".

upload

my $upload = $cgi->upload('foo');

Retrieve a named multipart/form-data file upload. If the upload name was passed multiple times, returns the last value. Use "upload_array" to get multiple uploads with the same name.

See "uploads" for details on the representation of the upload.

Note that this will read the text form fields into memory as in "uploads".

upload_array

my $arrayref = $cgi->upload_array('foo');

Retrieve all multipart/form-data file uploads of the specified name as an ordered array reference.

See "uploads" for details on the representation of the uploads.

Note that this will read the text form fields into memory as in "uploads".

Response

set_nph

$cgi = $cgi->set_nph;
$cgi = $cgi->set_nph(1);

If set to a true value or called without a value before rendering response headers, CGI::Tiny will act as a NPH (Non-Parsed Header) script and render full HTTP response headers. This may be required for some CGI servers, or enable unbuffered responses or HTTP extensions not supported by the CGI server.

No effect after response headers have been rendered.

set_response_body_buffer

$cgi = $cgi->set_response_body_buffer(128*1024);

Sets the buffer size (number of bytes to read at once) for streaming a file or handle response body with "render" or "render_chunk". Defaults to the value of the CGI_TINY_RESPONSE_BODY_BUFFER environment variable or 131072 (128 KiB). A value of 0 will use the default value.

set_response_status

$cgi = $cgi->set_response_status(404);
$cgi = $cgi->set_response_status('500 Internal Server Error');

Sets the response HTTP status code. A full status string including a human-readable message will be used as-is. A bare status code must be a known HTTP status code and will have the standard human-readable message appended.

No effect after response headers have been rendered.

The CGI protocol assumes a status of 200 OK if no response status is set.

set_response_disposition

$cgi = $cgi->set_response_disposition('attachment');
$cgi = $cgi->set_response_disposition(attachment => $filename);
$cgi = $cgi->set_response_disposition('inline'); # default behavior
$cgi = $cgi->set_response_disposition(inline => $filename);

Sets the response Content-Disposition header to indicate how the client should present the response, with an optional filename specified in Unicode characters. attachment suggests to download the content as a file, and inline suggests to display the content inline (the default behavior). No effect after response headers have been rendered.

set_response_type

$cgi = $cgi->set_response_type('application/xml');

Sets the response Content-Type header, to override autodetection in "render" or "render_chunk". undef will remove the override. No effect after response headers have been rendered.

set_response_charset

$cgi = $cgi->set_response_charset('UTF-8');

Set charset to use when rendering text, html, or xml response content, defaults to UTF-8.

add_response_header

$cgi = $cgi->add_response_header('Content-Language' => 'en');

Adds a custom response header. No effect after response headers have been rendered.

Note that header names are case insensitive and CGI::Tiny does not attempt to deduplicate or munge headers that have been added manually. Headers are printed in the response in the same order added, and adding the same header multiple times will result in multiple instances of that response header.

add_response_cookie

$cgi = $cgi->add_response_cookie($name => $value,
  Expires   => 'Sun, 06 Nov 1994 08:49:37 GMT',
  HttpOnly  => 1,
  'Max-Age' => 3600,
  Path      => '/foo',
  SameSite  => 'Strict',
  Secure    => 1,
);

Adds a Set-Cookie response header. No effect after response headers have been rendered.

Note that cookie values should only consist of ASCII characters and may not contain any control characters, space characters, or the characters ",;\. More complex values can be encoded to UTF-8 and base64 for transport.

use Unicode::UTF8 'encode_utf8';
use MIME::Base64 'encode_base64';
my $encoded_value = encode_base64 encode_utf8($value), '';
$cgi->add_response_cookie(foo => $encoded_value, %attrs);

use Unicode::UTF8 'decode_utf8';
use MIME::Base64 'decode_base64';
my $value = decode_utf8 decode_base64 $cgi->cookie('foo');

Data structures can be encoded to JSON and base64 for transport.

use Cpanel::JSON::XS 'encode_json';
use MIME::Base64 'encode_base64';
my $encoded_value = encode_base64 encode_json(\%hash), '';
$cgi->add_response_cookie(foo => $encoded_value, %attrs);

use Cpanel::JSON::XS 'decode_json';
use MIME::Base64 'decode_base64';
my $hashref = decode_json decode_base64 $cgi->cookie('foo');

Optional cookie attributes are specified in key-value pairs after the cookie name and value. Cookie attribute names are case-insensitive.

Domain: Domain for which cookie is valid.
Expires: Expiration date string for cookie. "epoch_to_date" can be used to generate the appropriate date string format.
HttpOnly: If set to a true value, the cookie will be restricted from client-side scripts.
Max-Age: Max age of cookie before it expires, in seconds, as an alternative to specifying Expires.
Path: URL path for which cookie is valid.
SameSite: Strict to restrict the cookie to requests from the same site, Lax to allow it additionally in certain cross-site requests. This attribute is currently part of a draft specification so its handling may change, but it is supported by most browsers.
Secure: If set to a true value, the cookie will be restricted to HTTPS requests.

reset_response_headers

$cgi = $cgi->reset_response_headers;

Remove any pending response headers set by "add_response_header" or "add_response_cookie". No effect after response headers have been rendered.

response_status_code

my $code = $cgi->response_status_code;

Numerical response HTTP status code that will be sent when headers are rendered, as set by "set_response_status" or an error occurring. Defaults to 200.

render

$cgi = $cgi->render;                        # default Content-Type:
$cgi = $cgi->render(text     => $text);     # text/plain;charset=$charset
$cgi = $cgi->render(html     => $html);     # text/html;charset=$charset
$cgi = $cgi->render(xml      => $xml);      # application/xml;charset=$charset
$cgi = $cgi->render(json     => $ref);      # application/json;charset=UTF-8
$cgi = $cgi->render(data     => $bytes);    # application/octet-stream
$cgi = $cgi->render(file     => $filepath); # application/octet-stream
$cgi = $cgi->render(redirect => $url);

Renders response headers and then fixed-length response content of a type indicated by the first parameter, if any. A Content-Length header will be set to the length of the encoded response content, and further calls to render or "render_chunk" will throw an exception. Use "render_chunk" instead to render without a Content-Length header.

The Content-Type response header will be set according to "set_response_type", or autodetected depending on the data type of any non-empty response content passed.

The Date response header will be set to the current time as an HTTP date string if not set manually.

If the "request_method" is HEAD, any provided response content will be ignored (other than redirect URLs) and Content-Length will be set to 0.

text, html, or xml data is expected to be decoded Unicode characters, and will be encoded according to "set_response_charset" (UTF-8 by default). Unicode::UTF8 will be used for efficient UTF-8 encoding if available.

json data structures will be encoded to JSON and UTF-8.

data or file will render bytes from a string or local file path respectively. A handle, or a file whose size cannot be determined accurately from the filesystem, must be rendered using "render_chunk" since its Content-Length cannot be determined beforehand.

redirect will set a Location header to redirect the client to another URL. The response status will be set to 302 Found unless a different 300-level status has been set with "set_response_status". It will set a Content-Length of 0, and it will not set a Content-Type response header.

render_chunk

$cgi = $cgi->render_chunk;                        # default Content-Type:
$cgi = $cgi->render_chunk(text   => $text);       # text/plain;charset=$charset
$cgi = $cgi->render_chunk(html   => $html);       # text/html;charset=$charset
$cgi = $cgi->render_chunk(xml    => $xml);        # application/xml;charset=$charset
$cgi = $cgi->render_chunk(json   => $ref);        # application/json;charset=UTF-8
$cgi = $cgi->render_chunk(data   => $bytes);      # application/octet-stream
$cgi = $cgi->render_chunk(file   => $filepath);   # application/octet-stream
$cgi = $cgi->render_chunk(handle => $filehandle); # application/octet-stream

Renders response headers the first time it is called, and then chunked response content of a type indicated by the first parameter, if any. No Content-Length header will be set, and render_chunk may be called additional times with more response content.

render_chunk does not impose a chunked response, it simply does not generate a Content-Length header. For content where the total encoded content length is known in advance but the content can't be passed to a single "render" call, a Content-Length header can be set manually with "add_response_header", and then render_chunk may be used to render each part.

The Content-Type response header will be set according to "set_response_type", or autodetected depending on the data type passed in the first call to render_chunk, or to application/octet-stream if there is no more appropriate value. It will be set even if no content is passed to the first render_chunk call, in case content is rendered in subsequent calls.

The Date response header will be set to the current time as an HTTP date string if not set manually.

If the "request_method" is HEAD, any provided response content will be ignored.

json data structures will be encoded to JSON and UTF-8.

data, file, or handle will render bytes from a string, local file path, or open filehandle respectively. A handle will have binmode applied to remove any translation layers, and its contents will be streamed until EOF.

redirect responses must be rendered with "render".

FUNCTIONS

The following convenience functions are provided but not exported.

epoch_to_date

my $date = CGI::Tiny::epoch_to_date $epoch;

Convert a Unix epoch timestamp, such as returned by time, to a RFC 1123 HTTP date string suitable for use in HTTP headers such as Date and Expires.

date_to_epoch

my $epoch = CGI::Tiny::date_to_epoch $date;

Parse a RFC 1123 HTTP date string to a Unix epoch timestamp. For compatibility as required by RFC 7231, legacy RFC 850 and ANSI C asctime date formats are also recognized. Returns undef if the string does not parse as any of these formats.

# RFC 1123
my $epoch = CGI::Tiny::date_to_epoch 'Sun, 06 Nov 1994 08:49:37 GMT';

# RFC 850
my $epoch = CGI::Tiny::date_to_epoch 'Sunday, 06-Nov-94 08:49:37 GMT';

# asctime
my $epoch = CGI::Tiny::date_to_epoch 'Sun Nov  6 08:49:37 1994';

escape_html

my $escaped = CGI::Tiny::escape_html $text;

Escapes characters that are unsafe for embedding in HTML text. The characters &<>"' will each be replaced with the corresponding HTML character reference (HTML entity).

This functionality is built into most HTML template engines; see "Templating". For more general HTML entity escaping and unescaping use HTML::Entities.

ENVIRONMENT

CGI::Tiny recognizes the following environment variables, in addition to the standard CGI environment variables.

CGI_TINY_REQUEST_BODY_BUFFER: Default value for "set_request_body_buffer".
CGI_TINY_REQUEST_BODY_LIMIT: Default value for "set_request_body_limit".
CGI_TINY_RESPONSE_BODY_BUFFER: Default value for "set_response_body_buffer".

DEBUGGING COMMANDS

CGI::Tiny scripts can be executed from the commandline for debugging purposes. A command can be passed as the first argument to help set up the CGI environment.

These commands are considered a development interface and come with no stability guarantee.

$ ./script.cgi get '/?foo=bar'
$ ./script.cgi head
$ ./script.cgi post '/form' -C 'one=value' -C 'two=value' --content='foo=bar+baz'
    -H 'Content-Type: application/x-www-form-urlencoded'
$ ./script.cgi put -H "Content-Length: $(stat --printf='%s' foo.dat)"
    -H "Content-Type: $(file -bi foo.dat)" <foo.dat
$ ./script.cgi delete -v '/item/42'

The get, head, post, put, and delete commands will emulate a request of the specified "request_method". A following URL parameter will be passed as the "path_info" and "query_string" if present.

Request content may be provided through STDIN but the Content-Length request header must be set to the size of the input as required by the CGI spec.

The response will be printed to STDOUT as normal. You may wish to redirect the output of the command to a file or hexdump program if the response is expected not to be printable text in the character encoding of your terminal.

Options may follow the command:

--content=<string>, -c <string>: Passes the string value as request body content and sets the Content-Length request header to its size.
--cookie=<string>, -C <string>: String values of the form name=value will be passed as request cookies. Can appear multiple times.
--header=<string>, -H <string>: String values of the form Name: value will be passed as request headers. Can appear multiple times. If the same header name is provided multiple times, the values will be joined with commas, which is only valid for certain headers.
--verbose, -v: Includes response CGI headers (or HTTP headers in NPH mode) in the output before response content. Enabled automatically for head.

COMPARISON TO CGI.PM

Traditionally, the CGI module (referred to as CGI.pm to differentiate it from the CGI protocol) has been used to write Perl CGI scripts. This module fills a similar need but has a number of interface differences to be aware of.

There is no CGI::Tiny object constructor; the object is accessible within the cgi block, only reads request data from the environment once it is accessed, and ensures that a valid response is rendered to avoid gateway errors even in the event of an exception or premature exit.
Instead of global variables like $CGI::POST_MAX, global behavior settings are applied to the CGI::Tiny object inside the cgi block.
Exceptions within the cgi block are handled by default by rendering a server error response and emitting the error as a warning. This can be customized with "set_error_handler".
Request parameter accessors in CGI::Tiny are not context sensitive, as context sensitivity can lead to surprising behavior and vulnerabilities. "param", "query_param", "body_param", and "upload" always return a single value; "param_array", "query_param_array", "body_param_array", and "upload_array" must be used to retrieve multi-value parameters.
CGI::Tiny's "param" accessor is also not method-sensitive; it accesses either query or body request parameters with the same behavior regardless of request method, and query and body request parameters can be accessed separately with "query_param" and "body_param" respectively.
CGI::Tiny's "param" accessor only retrieves text parameters; uploaded files and their metadata are accessed with "upload" and related methods.
CGI::Tiny decodes request parameters to Unicode characters automatically, and "render"/"render_chunk" provide methods to encode response content from Unicode characters to UTF-8 by default.
In CGI.pm, response headers must be printed manually before any response content is printed to avoid malformed responses. In CGI::Tiny, the "render" or "render_chunk" methods are used to print response content, and automatically print response headers when first called. redirect responses are also handled by "render".
In CGI::Tiny, a custom response status is set by calling "set_response_status" before the first "render" or "render_chunk", which only requires the status code and will add the appropriate human-readable status message itself.
Response setters are distinct methods from request accessors in CGI::Tiny. "content_type", "header", and "cookie" are used to access request data, and "set_response_type", "add_response_header", and "add_response_cookie" are used to set response headers for the pending response before the first call to "render" or "render_chunk".
CGI::Tiny does not provide any HTML generation helpers, as this functionality is much better implemented by other robust implementations on CPAN; see "Templating".
CGI::Tiny does not do any implicit encoding of cookie values or the Expires header or cookie attribute. The "epoch_to_date" convenience function is provided to render appropriate Expires date values.

There are a number of alternatives to CGI.pm but they do not sufficiently address the design issues; primarily, none of them gracefully handle exceptions or failure to render a response, and several of them have no features for rendering responses.

CGI::Simple shares all of the interface design problems of CGI.pm, though it does not reimplement the HTML generation helpers.
CGI::Thin is ancient and only implements parsing of request query or body parameters, without decoding them to Unicode characters.
CGI::Minimal has context-sensitive parameter accessors, and only implements parsing of request query/body parameters (without decoding them to Unicode characters) and uploads.
CGI::Lite has context-sensitive parameter accessors, and only implements parsing of request query/body parameters (without decoding them to Unicode characters), uploads, and cookies.
CGI::Easy has a robust interface, but pre-parses all request information.

CAVEATS

CGI is an extremely simplistic protocol and relies particularly on the global state of environment variables and the STDIN and STDOUT standard filehandles. CGI::Tiny does not prevent you from messing with these interfaces directly, but it may result in confusion.

CGI::Tiny eschews certain sanity checking for performance reasons. For example, Content-Type and other header values set for the response should only contain ASCII text with no control characters, but CGI::Tiny does not verify this (though it does verify they do not contain newline characters to protect against HTTP response splitting).

Field names and filenames in multipart/form-data requests do not have a well-defined escape mechanism for special characters, so CGI::Tiny will not attempt to decode these names from however the client passes them aside from "set_multipart_form_charset". For best compatibility, form field names should be ASCII without double quotes or semicolons.

BUGS

Report any issues on the public bugtracker.

AUTHOR

Dan Book <dbook@cpan.org>

COPYRIGHT AND LICENSE

This is free software, licensed under:

The Artistic License 2.0 (GPL Compatible)

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