Network.CGI

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:[e-mail]. Further hacked on by Sven Panne mailto:[e-mail]. Further hacking by Andy Gill mailto:[e-mail]. A new, hopefully more flexible, interface and support for file uploads by Bjorn Bringert mailto:[e-mail].

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)

CGI monad

class Monad m => MonadCGI m

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.

Minimal complete definition

cgiAddHeader, cgiGet

Instances

Monad m => MonadCGI (CGIT m)

data CGIT m a

The CGIT monad transformer.

Instances

MonadTrans CGIT

MonadCatch m => MonadError SomeException (CGIT m)

Monad m => Monad (CGIT m)

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

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

MonadThrow m => MonadThrow (CGIT m)

MonadCatch m => MonadCatch (CGIT m)

MonadMask m => MonadMask (CGIT m)

MonadIO m => MonadIO (CGIT m)

Monad m => MonadCGI (CGIT m)

Typeable ((* -> *) -> * -> *) CGIT

data CGIResult

The result of a CGI program.

Instances

Eq CGIResult

Ord CGIResult

Read CGIResult

Show CGIResult

Typeable * CGIResult

type CGI a = CGIT IO a

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

MonadIO m => MonadIO (ListT m)

MonadIO m => MonadIO (MaybeT m)

MonadIO m => MonadIO (IdentityT m)

MonadIO m => MonadIO (CGIT m)

MonadIO m => MonadIO (ContT r m)

MonadIO m => MonadIO (ReaderT r m)

MonadIO m => MonadIO (StateT s m)

MonadIO m => MonadIO (StateT s m)

MonadIO m => MonadIO (ExceptT e m)

(Error e, MonadIO m) => MonadIO (ErrorT e m)

(Monoid w, MonadIO m) => MonadIO (WriterT w m)

(Monoid w, MonadIO m) => MonadIO (WriterT w m)

MonadIO m => MonadIO (ParsecT s u m)

(Monoid w, MonadIO m) => MonadIO (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 ()

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, MonadThrow m) => SomeException -> m a

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

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

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

tryCGI :: (Functor m, MonadCGI m, MonadCatch m) => m a -> m (Either SomeException a)

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, MonadCatch m) => m a -> (SomeException -> m a) -> m a

Deprecated: Use catchCGI instead.

Deprecated version of catchCGI. Use catchCGI instead.

handleErrors :: (MonadCGI m, MonadCatch m, MonadIO m) => m CGIResult -> m CGIResult

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 ()

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

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

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

Do not output anything (except headers).

redirect

Arguments

:: MonadCGI m

=> String

A URL to redirect to.

-> m CGIResult

Redirect to some location.

setHeader

Arguments

:: MonadCGI m

=> String

Header name.

-> String

Header value.

-> m ()

Add a response header. Example:

setHeader "Content-type" "text/plain"

setStatus

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

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

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

outputNotFound

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

Arguments

:: (MonadIO m, MonadCGI m)

=> [String]

The allowed methods.

-> m CGIResult

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

outputInternalServerError

Arguments

:: (MonadIO m, MonadCGI m)

=> [String]

Error information.

-> m CGIResult

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

Input

getInput

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

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

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

Get the uninterpreted request body as a String

getBodyFPS :: MonadCGI m => m ByteString

Get the uninterpreted request body as lazy ByteString

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

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)]

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]

Get the names of all input variables.

getMultiInput

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

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

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

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

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

Arguments

:: MonadCGI m

=> String

The name of the variable.

-> String

Default value

-> m String

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

Get all CGI environment variables and their values.

Request information

serverName :: MonadCGI m => m String

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

serverPort :: MonadCGI m => m Int

The port number to which the request was sent.

requestMethod :: MonadCGI m => m String

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

pathInfo :: MonadCGI m => m String

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

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

scriptName :: MonadCGI m => m String

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

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)

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

remoteAddr :: MonadCGI m => m String

The IP address of the remote host making the request.

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

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)

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)

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)

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)

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

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

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

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

Minimal complete definition

includes, top

Instances

Acceptable ContentType

Acceptable Language

Acceptable ContentEncoding

Acceptable Charset

data Accept a

Instances

Show a => Show (Accept a)

HeaderValue a => HeaderValue (Accept a)

newtype Charset

Constructors

Charset String

Instances

Eq Charset

Ord Charset

Show Charset

HeaderValue Charset

Acceptable Charset

newtype ContentEncoding

Constructors

ContentEncoding String

Instances

Eq ContentEncoding

Ord ContentEncoding

Show ContentEncoding

HeaderValue ContentEncoding

Acceptable ContentEncoding

newtype Language

Constructors

Language String

Instances

Eq Language

Ord Language

Show Language

HeaderValue Language

Acceptable Language

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

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

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

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

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

Content type

data ContentType :: *

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

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

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

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.

Instances

Eq Cookie

Ord Cookie

Read Cookie

Show Cookie

newCookie

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

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

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 ()

Set a cookie.

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

Delete a cookie from the client

URL encoding

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

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

urlEncode :: String -> String

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

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

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

urlDecode :: String -> String

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

Compatibility with the old API

module Network.CGI.Compat