Portability	non-portable (uses Control.Monad.State)
Stability	experimental
Maintainer	Anders Kaseorg <andersk@mit.edu>
Safe Haskell	None

Network.CGI

Contents

CGI monad
Error handling
Logging
Output
Error pages
Input
Environment
Request information
Program and request URI
Content negotiation
Content type
Cookies
URL encoding
Compatibility with the old API

Description

Simple Library for writing CGI programs. See http://hoohoo.ncsa.uiuc.edu/cgi/interface.html for the CGI specification.

This version of the library is for systems with version 2.0 or greater of the network package. This includes GHC 6.6 and later. For older systems, see http://www.cs.chalmers.se/~bringert/darcs/cgi-compat/doc/

Based on the original Haskell binding for CGI:

Original Version by Erik Meijer mailto:erik@cs.ruu.nl. Further hacked on by Sven Panne mailto:sven.panne@aedion.de. Further hacking by Andy Gill mailto:andy@galconn.com. A new, hopefully more flexible, interface and support for file uploads by Bjorn Bringert mailto:bjorn@bringert.net.

Here is a simple example, including error handling (not that there is much that can go wrong with Hello World):

 import Network.CGI

 cgiMain :: CGI CGIResult
 cgiMain = output "Hello World!"

 main :: IO ()
 main = runCGI (handleErrors cgiMain)

Synopsis

CGI monad

class Monad m => MonadCGI m Source

The class of CGI monads. Most CGI actions can be run in any monad which is an instance of this class, which means that you can use your own monad transformers to add extra functionality.

Instances

(Monad (CGIT m), Monad m) => MonadCGI (CGIT m)

data CGIT m a Source

The CGIT monad transformer.

Instances

MonadTrans CGIT
(Monad (CGIT m), MonadCatchIO m) => MonadError SomeException (CGIT m)
Monad m => Monad (CGIT m)
(Functor m, Monad m) => Functor (CGIT m)
(MonadIO (CGIT m), MonadCatchIO m) => MonadCatchIO (CGIT m)
(Monad (CGIT m), MonadIO m) => MonadIO (CGIT m)
(Monad (CGIT m), Monad m) => MonadCGI (CGIT m)
(Typeable1 m, Typeable a) => Typeable (CGIT m a)

data CGIResult Source

The result of a CGI program.

Instances

Eq CGIResult
Ord CGIResult
Read CGIResult
Show CGIResult
Typeable CGIResult

type CGI a = CGIT IO aSource

A simple CGI monad with just IO.

class Monad m => MonadIO m where

Monads in which IO computations may be embedded. Any monad built by applying a sequence of monad transformers to the IO monad will be an instance of this class.

Instances should satisfy the following laws, which state that liftIO is a transformer of monads:

```
liftIO . return = return
```

liftIO (m >>= f) = liftIO m >>= (liftIO . f)

Methods

liftIO :: IO a -> m a

Lift a computation from the IO monad.

Instances

MonadIO IO
(Monad (ListT m), MonadIO m) => MonadIO (ListT m)
(Monad (MaybeT m), MonadIO m) => MonadIO (MaybeT m)
(Monad (IdentityT m), MonadIO m) => MonadIO (IdentityT m)
(Monad (CGIT m), MonadIO m) => MonadIO (CGIT m)
(Monad (ContT r m), MonadIO m) => MonadIO (ContT r m)
(Monad (ErrorT e m), Error e, MonadIO m) => MonadIO (ErrorT e m)
(Monad (ReaderT r m), MonadIO m) => MonadIO (ReaderT r m)
(Monad (StateT s m), MonadIO m) => MonadIO (StateT s m)
(Monad (StateT s m), MonadIO m) => MonadIO (StateT s m)
(Monad (WriterT w m), Monoid w, MonadIO m) => MonadIO (WriterT w m)
(Monad (WriterT w m), Monoid w, MonadIO m) => MonadIO (WriterT w m)
(Monad (ParsecT s u m), MonadIO m) => MonadIO (ParsecT s u m)
(Monad (RWST r w s m), Monoid w, MonadIO m) => MonadIO (RWST r w s m)
(Monad (RWST r w s m), Monoid w, MonadIO m) => MonadIO (RWST r w s m)

liftIO :: MonadIO m => forall a. IO a -> m a

Lift a computation from the IO monad.

runCGI :: MonadIO m => CGIT m CGIResult -> m ()Source

Run a CGI action. Typically called by the main function. Reads input from stdin and writes to stdout. Gets CGI environment variables from the program environment.

Error handling

throwCGI :: (MonadCGI m, MonadIO m) => SomeException -> m aSource

Throw an exception in a CGI monad. The monad is required to be a MonadIO, so that we can use throwIO to guarantee ordering.

catchCGI :: (MonadCGI m, MonadCatchIO m) => m a -> (SomeException -> m a) -> m aSource

Catches any expection thrown by a CGI action, and uses the given exception handler if an exception is thrown.

tryCGI :: (MonadCGI m, MonadCatchIO m) => m a -> m (Either SomeException a)Source

Catches any exception thrown by an CGI action, and returns either the exception, or if no exception was raised, the result of the action.

handleExceptionCGI :: (MonadCGI m, MonadCatchIO m) => m a -> (SomeException -> m a) -> m aSource

Deprecated version of catchCGI. Use catchCGI instead.

handleErrors :: (MonadCGI m, MonadCatchIO m) => m CGIResult -> m CGIResult Source

Catches any exception thrown by the given CGI action, returns an error page with a 500 Internal Server Error, showing the exception information, and logs the error.

Typical usage:

 cgiMain :: CGI CGIResult
 cgiMain = ...

 main :: IO ()
 main = runCGI (handleErrors cgiMain)

Logging

logCGI :: MonadIO m => String -> m ()Source

Logs some message using the server's logging facility. FIXME: does this have to be more general to support FastCGI etc? Maybe we should store log messages in the CGIState?

Output

output Source

Arguments

:: MonadCGI m
=> String	The string to output.
-> m CGIResult

Output a String. The output is assumed to be text/html, encoded using ISO-8859-1. To change this, set the Content-type header using setHeader.

outputFPS Source

Arguments

:: MonadCGI m
=> ByteString	The string to output.
-> m CGIResult

Output a ByteString. The output is assumed to be text/html, encoded using ISO-8859-1. To change this, set the Content-type header using setHeader.

outputNothing :: MonadCGI m => m CGIResult Source

Do not output anything (except headers).

redirect Source

Arguments

:: MonadCGI m
=> String	A URL to redirect to.
-> m CGIResult

Redirect to some location.

setHeader Source

Arguments

:: MonadCGI m
=> String	Header name.
-> String	Header value.
-> m ()

Add a response header. Example:

 setHeader "Content-type" "text/plain"

setStatus Source

Arguments

:: MonadCGI m
=> Int	HTTP status code, e.g. `404`
-> String	HTTP status message, e.g. `Not Found`
-> m ()

Set the HTTP response status.

Error pages

outputError Source

Arguments

:: (MonadCGI m, MonadIO m)
=> Int	HTTP Status code
-> String	Status message
-> [String]	Error information
-> m CGIResult

Output an error page to the user, with the given HTTP status code in the response. Also logs the error information using logCGI.

outputException :: (MonadCGI m, MonadIO m) => SomeException -> m CGIResult Source

Output a 500 Internal Server Error with information from an Exception.

outputNotFound Source

Arguments

:: (MonadIO m, MonadCGI m)
=> String	The name of the requested resource.
-> m CGIResult

Use outputError to output and log a 404 Not Found error.

outputMethodNotAllowed Source

Arguments

:: (MonadIO m, MonadCGI m)
=> [String]	The allowed methods.
-> m CGIResult

Use outputError to output and log a 405 Method Not Allowed error.

outputInternalServerError Source

Arguments

:: (MonadIO m, MonadCGI m)
=> [String]	Error information.
-> m CGIResult

Use outputError to output and log a 500 Internal Server Error.

Input

getInput Source

Arguments

:: MonadCGI m
=> String	The name of the variable.
-> m (Maybe String)	The value of the variable, or Nothing, if it was not set.

Get the value of an input variable, for example from a form. If the variable has multiple values, the first one is returned. Example:

 query <- getInput "query"

getInputFPS Source

Arguments

:: MonadCGI m
=> String	The name of the variable.
-> m (Maybe ByteString)	The value of the variable, or Nothing, if it was not set.

Like getInput, but returns a ByteString.

readInput Source

Arguments

:: (Read a, MonadCGI m)
=> String	The name of the variable.
-> m (Maybe a)	`Nothing` if the variable does not exist or if the value could not be interpreted at the desired type.

Same as getInput, but tries to read the value to the desired type.

getBody :: MonadCGI m => m String Source

Get the uninterpreted request body as a String

getBodyFPS :: MonadCGI m => m ByteString Source

Get the uninterpreted request body as lazy ByteString

getInputs :: MonadCGI m => m [(String, String)]Source

Get the names and values of all inputs. Note: the same name may occur more than once in the output, if there are several values for the name.

getInputsFPS :: MonadCGI m => m [(String, ByteString)]Source

Get the names and values of all inputs. Note: the same name may occur more than once in the output, if there are several values for the name.

getInputNames :: MonadCGI m => m [String]Source

Get the names of all input variables.

getMultiInput Source

Arguments

:: MonadCGI m
=> String	The name of the variable.
-> m [String]	The values of the variable, or the empty list if the variable was not set.

Get all the values of an input variable, for example from a form. This can be used to get all the values from form controls which allow multiple values to be selected. Example:

 vals <- getMultiInput "my_checkboxes"

getMultiInputFPS Source

Arguments

:: MonadCGI m
=> String	The name of the variable.
-> m [ByteString]	The values of the variable, or the empty list if the variable was not set.

Same as getMultiInput but using ByteStrings.

getInputFilename Source

Arguments

:: MonadCGI m
=> String	The name of the variable.
-> m (Maybe String)	The file name corresponding to the input, if there is one.

Get the file name of an input.

getInputContentType Source

Arguments

:: MonadCGI m
=> String	The name of the variable.
-> m (Maybe String)	The content type, formatted as a string.

Get the content-type of an input, if the input exists, e.g. image/jpeg. For non-file inputs, this function returns text/plain. You can use parseContentType to get a structured representation of the the content-type value.

Environment

getVar Source

Arguments

:: MonadCGI m
=> String	The name of the variable.
-> m (Maybe String)

Get the value of a CGI environment variable. Example:

 remoteAddr <- getVar "REMOTE_ADDR"

getVarWithDefault Source

Arguments

:: MonadCGI m
=> String	The name of the variable.
-> String	Default value
-> m String

getVars :: MonadCGI m => m [(String, String)]Source

Get all CGI environment variables and their values.

Request information

serverName :: MonadCGI m => m String Source

The server's hostname, DNS alias, or IP address as it would appear in self-referencing URLs.

serverPort :: MonadCGI m => m Int Source

The port number to which the request was sent.

requestMethod :: MonadCGI m => m String Source

The method with which the request was made. For HTTP, this is "GET", "HEAD", "POST", etc.

pathInfo :: MonadCGI m => m String Source

The extra path information, as given by the client. This is any part of the request path that follows the CGI program path. If the string returned by this function is not empty, it is guaranteed to start with a '/'.

Note that this function returns an unencoded string. Make sure to percent-encode any characters that are not allowed in URI paths before using the result of this function to construct a URI. See progURI, queryURI and requestURI for a higher-level interface.

pathTranslated :: MonadCGI m => m String Source

The path returned by pathInfo, but with virtual-to-physical mapping applied to it.

scriptName :: MonadCGI m => m String Source

A virtual path to the script being executed, used for self-referencing URIs.

Note that this function returns an unencoded string. Make sure to percent-encode any characters that are not allowed in URI paths before using the result of this function to construct a URI. See progURI, queryURI and requestURI for a higher-level interface.

queryString :: MonadCGI m => m String Source

The information which follows the ? in the URL which referenced this program. This is the percent-encoded query information. For most normal uses, getInput and friends are probably more convenient.

remoteHost :: MonadCGI m => m (Maybe String)Source

The hostname making the request. If the server does not have this information, Nothing is returned. See also remoteAddr.

remoteAddr :: MonadCGI m => m String Source

The IP address of the remote host making the request.

authType :: MonadCGI m => m (Maybe String)Source

If the server supports user authentication, and the script is protected, this is the protocol-specific authentication method used to validate the user.

remoteUser :: MonadCGI m => m (Maybe String)Source

If the server supports user authentication, and the script is protected, this is the username they have authenticated as.

requestContentType :: MonadCGI m => m (Maybe String)Source

For queries which have attached information, such as HTTP POST and PUT, this is the content type of the data. You can use parseContentType to get a structured representation of the the content-type value.

requestContentLength :: MonadCGI m => m (Maybe Int)Source

For queries which have attached information, such as HTTP POST and PUT, this is the length of the content given by the client.

requestHeader :: MonadCGI m => String -> m (Maybe String)Source

Gets the value of the request header with the given name. The header name is case-insensitive. Example:

 requestHeader "User-Agent"

Program and request URI

progURI :: MonadCGI m => m URI Source

Attempts to reconstruct the absolute URI of this program. This does not include any extra path information or query parameters. See queryURI for that. If the server is rewriting request URIs, this URI can be different from the one requested by the client. See also requestURI.

Characters in the components of the returned URI are escaped when needed, as required by Network.URI.

queryURI :: MonadCGI m => m URI Source

Like progURI, but the returned URI also includes any extra path information, and any query parameters. If the server is rewriting request URIs, this URI can be different from the one requested by the client. See also requestURI.

Characters in the components of the returned URI are escaped when needed, as required by Network.URI.

requestURI :: MonadCGI m => m URI Source

Attempts to reconstruct the absolute URI requested by the client, including extra path information and query parameters. If no request URI rewriting is done, or if the web server does not provide the information needed to reconstruct the request URI, this function returns the same value as queryURI.

Characters in the components of the returned URI are escaped when needed, as required by Network.URI.

Content negotiation

class Eq a => Acceptable a Source

Instances

Acceptable ContentType
Acceptable Language
Acceptable ContentEncoding
Acceptable Charset

data Accept a Source

Instances

Show a => Show (Accept a)
HeaderValue a => HeaderValue (Accept a)

newtype Charset Source

Constructors

Charset String

Instances

Eq Charset
Ord Charset
Show Charset
HeaderValue Charset
Acceptable Charset

newtype ContentEncoding Source

Constructors

ContentEncoding String

Instances

Eq ContentEncoding
Ord ContentEncoding
Show ContentEncoding
HeaderValue ContentEncoding
Acceptable ContentEncoding

newtype Language Source

Constructors

Language String

Instances

Eq Language
Ord Language
Show Language
HeaderValue Language
Acceptable Language

requestAccept :: MonadCGI m => m (Maybe (Accept ContentType))Source

requestAcceptCharset :: MonadCGI m => m (Maybe (Accept Charset))Source

requestAcceptEncoding :: MonadCGI m => m (Maybe (Accept ContentEncoding))Source

requestAcceptLanguage :: MonadCGI m => m (Maybe (Accept Language))Source

negotiate :: Acceptable a => [a] -> Maybe (Accept a) -> [a]Source

Content type

data ContentType Source

A MIME media type value. The Show instance is derived automatically. Use showContentType to obtain the standard string representation. See http://www.ietf.org/rfc/rfc2046.txt for more information about MIME media types.

Constructors

ContentType

Fields

ctType :: String: The top-level media type, the general type of the data. Common examples are "text", "image", "audio", "video", "multipart", and "application".
ctSubtype :: String: The media subtype, the specific data format. Examples include "plain", "html", "jpeg", "form-data", etc.
ctParameters :: [(String, String)]: Media type parameters. On common example is the charset parameter for the "text" top-level type, e.g. ("charset","ISO-8859-1").

Instances

Eq ContentType
Ord ContentType
Read ContentType
Show ContentType
HeaderValue ContentType
Acceptable ContentType

showContentType :: ContentType -> String Source

parseContentType :: Monad m => String -> m ContentType Source

Parse the standard representation of a content-type. If the input cannot be parsed, this function calls fail with a (hopefully) informative error message.

Cookies

data Cookie Source

Contains all information about a cookie set by the server.

Constructors

Cookie

Fields

cookieName :: String: Name of the cookie.
cookieValue :: String: Value of the cookie.
cookieExpires :: Maybe CalendarTime: Expiry date of the cookie. If Nothing, the cookie expires when the browser sessions ends. If the date is in the past, the client should delete the cookie immediately.
cookieDomain :: Maybe String: The domain suffix to which this cookie will be sent.
cookiePath :: Maybe String: The path to which this cookie will be sent.
cookieSecure :: Bool: True if this cookie should only be sent using secure means.

newCookie Source

Arguments

:: String	Name
-> String	Value
-> Cookie	Cookie

Construct a cookie with only name and value set. This client will expire when the browser sessions ends, will only be sent to the server and path which set it and may be sent using any means.

getCookie Source

Arguments

:: MonadCGI m
=> String	The name of the cookie.
-> m (Maybe String)	`Nothing` if the cookie does not exist.

Get the value of a cookie.

readCookie Source

Arguments

:: (Read a, MonadCGI m)
=> String	The name of the cookie.
-> m (Maybe a)	`Nothing` if the cookie does not exist or if the value could not be interpreted at the desired type.

Same as getCookie, but tries to read the value to the desired type.

setCookie :: MonadCGI m => Cookie -> m ()Source

Set a cookie.

deleteCookie :: MonadCGI m => Cookie -> m ()Source

Delete a cookie from the client

URL encoding

formEncode :: [(String, String)] -> String Source

Formats name-value pairs as application/x-www-form-urlencoded.

urlEncode :: String -> String Source

Converts a single value to the application/x-www-form-urlencoded encoding.

formDecode :: String -> [(String, String)]Source

Gets the name-value pairs from application/x-www-form-urlencoded data.

urlDecode :: String -> String Source

Converts a single value from the application/x-www-form-urlencoded encoding.

Compatibility with the old API

module Network.CGI.Compat

Eq Cookie
Ord Cookie
Read Cookie
Show Cookie