System.Process.ListLike

Generalized versions of the functions readProcess, and readProcessWithExitCode.

Documentation

class ListLikeIO a c => ListLikePlus a c where

Class of types which can be used as the input and outputs of these process functions.

Methods

setModes :: a -> (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle) -> IO ()

Perform initialization on the handles returned by createProcess based on this ListLikePlus instance - typically setting binary mode on all the file descriptors if the element type is Word8. If this is not done, reading something other than text (such as a .jpg or .pdf file) will usually fail with a decoding error.

readChunks :: Handle -> IO [a]

Read the list of chunks from this handle. For lazy types this is just a call to hGetContents followed by toChunks. For strict types it might return a singleton list. Strings are trickier.

Instances

ListLikePlus String Char

This String instance is implemented using the Lazy Text instance. Otherwise (without some serious coding) String would be a strict instance . Note that the readProcess in the process library is strict, while our equivalent is not - see test4 in Tests/Dots.hs.

ListLikePlus ByteString Word8

ListLikePlus ByteString Word8

ListLikePlus Text Char

ListLikePlus Text Char

readProcessInterleaved :: (ListLikePlus a c, Monoid b) => (ProcessHandle -> b) -> (ExitCode -> b) -> (a -> b) -> (a -> b) -> CreateProcess -> a -> IO b

Read the output of a process and use the argument functions to convert it into a Monoid, preserving the order of appearance of the different chunks of output from standard output and standard error.

readInterleaved :: forall a b c. (ListLikePlus a c, Monoid b) => b -> [(a -> b, Handle)] -> IO b -> IO b

Simultaneously read the output from several file handles, using the associated functions to add them to a Monoid b in the order they appear. This closes each handle on EOF, because AFAIK it is the only useful thing to do with a file handle that has reached EOF.

readCreateProcessWithExitCode

Arguments

:: forall a c . ListLikePlus a c

=> CreateProcess

process to run

-> a

standard input

-> IO (ExitCode, a, a)

exitcode, stdout, stderr, exception

An implementation of readProcessWithExitCode with a two generalizations: (1) The input and outputs can be any instance of ListLikePlus, and (2) The CreateProcess is passes an argument, so you can use either proc or rawSystem and you can modify its fields such as cwd before the process starts

readCreateProcess

Arguments

:: ListLikePlus a c

=> CreateProcess

process to run

-> a

standard input

-> IO a

stdout

An implementation of readProcess with a two generalizations: (1) The input and outputs can be any instance of ListLikePlus, and (2) The CreateProcess is passes an argument, so you can use either proc or rawSystem and you can modify its fields such as cwd before the process starts

This can't be implemented by calling readProcessInterleaved because the std_err field needs to be set to Inherit, which means that createProcess returns no stderr handle. Instead, we have a nearly identical copy of the readProcessInterleaved code which only passes one pair readInterleaved. REMEMBER to keep these two in sync if there are future changes!

readProcessWithExitCode

Arguments

:: ListLikePlus a c

=> FilePath

command to run

-> [String]

any arguments

-> a

standard input

-> IO (ExitCode, a, a)

exitcode, stdout, stderr

A version of readProcessWithExitCode that uses any instance of ListLikePlus instead of String, implemented using readCreateProcessWithExitCode.

readProcess

Arguments

:: ListLikePlus a c

=> FilePath

command to run

-> [String]

any arguments

-> a

standard input

-> IO a

stdout

Implementation of readProcess that uses any instance of ListLikePlus instead of String, implemented using readCreateProcess.

showCmdSpecForUser :: CmdSpec -> String