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GHC 9.14.1 · lts/ghc-9.14.x · 7a6c33e · 2026-10-12

Modulegraphviz-2999.20.2.1Haskell2010

Data.GraphViz.Commands.IO

Various utility functions to help with custom I/O of Dot code.

Contents

Encoding
Operations on files
Operations on handles
Special cases for standard input and output
Running external commands

Synopsis

value toUTF8
value writeDotFile
value readDotFile
value hPutDot
value hPutCompactDot
value hGetDot
value hGetStrict
value putDot
value readDot
value runCommand

Packagegraphviz-2999.20.2.1
Exports10
LanguageHaskell2010
LicenceBSD-3-Clause
SourceIO.hs

Encoding

By default, Dot code should be in UTF-8. However, by usage of the charset attribute, users are able to specify that the ISO-8859-1 (aka Latin1) encoding should be used instead: http://www.graphviz.org/doc/info/attrs.html#d:charset

To simplify matters, graphviz does not work with ISO-8859-1. If you wish to deal with existing Dot code that uses this encoding, you will need to manually read that file in to a Text value.

If a non-UTF-8 encoding is used, then a GraphvizException will be thrown.

valuetoUTF8 :: ByteString -> Text

Explicitly convert a (lazy) ByteString to a Text value using UTF-8 encoding, throwing a GraphvizException if there is a decoding error.

Operations on files

valuewriteDotFile :: PrintDotRepr dg n => FilePath -> dg n -> IO ()

Write the specified DotRepr to file.

valuereadDotFile :: ParseDotRepr dg n => FilePath -> IO (dg n)

Read in and parse a DotRepr value from a file.

Operations on handles

valuehPutDot :: PrintDotRepr dg n => Handle -> dg n -> IO ()

Output the DotRepr to the specified Handle.

valuehPutCompactDot :: PrintDotRepr dg n => Handle -> dg n -> IO ()

Output the DotRepr to the spcified Handle in a more compact, machine-oriented form.

valuehGetDot :: ParseDotRepr dg n => Handle -> IO (dg n)

Read in and parse a DotRepr value from the specified Handle.

valuehGetStrict :: Handle -> IO Text

Strictly read in a Text value using an appropriate encoding.

Special cases for standard input and output

valueputDot :: PrintDotRepr dg n => dg n -> IO ()

Print the specified DotRepr to stdout.

valuereadDot :: ParseDotRepr dg n => IO (dg n)

Read in and parse a DotRepr value from stdin.

Running external commands

valuerunCommand

:: PrintDotRepr dg n
=> String
Command to run
-> [String]
Command-line arguments
-> (Handle -> IO a)
Obtaining the output; should be strict.
-> dg n
-> IO a

Run an external command on the specified DotRepr. Remember to use hSetBinaryMode on the Handle for the output function if necessary.

If the command was unsuccessful, then a GraphvizException is thrown.

For performance reasons, a temporary file is used to store the generated Dot code. As such, this is only suitable for local commands.