Development.Shake.Command

Execute a system command. Before running command make sure you need any files that are used by the command.

This function takes a list of options (often just [], see CmdOption for the available options), the name of the executable (either a full name, or a program on the $PATH) and a list of arguments. The result is often (), but can be a tuple containg any of Stdout, Stderr and Exit. Some examples:

command_ [] "gcc" ["-c","myfile.c"]                          -- compile a file, throwing an exception on failure
Exit c <- command [] "gcc" ["-c",myfile]                     -- run a command, recording the exit code
(Exit c, Stderr err) <- command [] "gcc" ["-c","myfile.c"]   -- run a command, recording the exit code and error output
Stdout out <- command [] "gcc" ["-MM","myfile.c"]            -- run a command, recording the output
command_ [Cwd "generated"] "gcc" ["-c",myfile]               -- run a command in a directory

Unless you retrieve the ExitCode using Exit, any ExitFailure will throw an error, including the Stderr in the exception message. If you capture the Stdout or Stderr, that stream will not be echoed to the console, unless you use the option EchoStdout or EchoStderr.

If you use command inside a do block and do not use the result, you may get a compile-time error about being unable to deduce CmdResult. To avoid this error, use command_.

By default the stderr stream will be captured for use in error messages, and also echoed. To only echo pass WithStderr False, which causes no streams to be captured by Shake, and certain programs (e.g. gcc) to detect they are running in a terminal.

A version of command where you do not require any results, used to avoid errors about being unable to deduce CmdResult.

Build or execute a system command. Before using cmd to run a command, make sure you need any files that are used by the command.

• String arguments are treated as a list of whitespace separated arguments.

• [String] arguments are treated as a list of literal arguments.

• CmdOption arguments are used as options.

• CmdArgument arguments, which can be built by cmd itself, are spliced into the containing command.

Typically only string literals should be passed as String arguments. When using variables prefer [myvar] so that if myvar contains spaces they are properly escaped.

As some examples, here are some calls, and the resulting command string:

cmd_ "git log --pretty=" "oneline"           -- git log --pretty= oneline
cmd_ "git log --pretty=" ["oneline"]         -- git log --pretty= oneline
cmd_ "git log" ("--pretty=" ++ "oneline")    -- git log --pretty=oneline
cmd_ "git log" ("--pretty=" ++ "one line")   -- git log --pretty=one line
cmd_ "git log" ["--pretty=" ++ "one line"]   -- git log "--pretty=one line"

More examples, including return values, see this translation of the examples given for the command function:

cmd_ "gcc -c myfile.c"                                       -- compile a file, throwing an exception on failure
Exit c <- cmd "gcc -c" [myfile]                              -- run a command, recording the exit code
(Exit c, Stderr err) <- cmd "gcc -c myfile.c"                -- run a command, recording the exit code and error output
Stdout out <- cmd "gcc -MM myfile.c"                         -- run a command, recording the output
cmd (Cwd "generated") "gcc -c" [myfile] :: Action ()         -- run a command in a directory

let gccCommand = cmd "gcc -c" :: CmdArgument                 -- build a sub-command. cmd can return CmdArgument values as well as execute commands
cmd (Cwd "generated") gccCommand [myfile]                 -- splice that command into a greater command

If you use cmd inside a do block and do not use the result, you may get a compile-time error about being unable to deduce CmdResult. To avoid this error, use cmd_. If you enable OverloadedStrings or OverloadedLists you may have to give type signatures to the arguments, or use the more constrained command instead.

The cmd function can also be run in the IO monad, but then Traced is ignored and command lines are not echoed. As an example:

cmd (Cwd "generated") Shell "gcc -c myfile.c" :: IO ()

See cmd. Same as cmd except with a unit result. cmd is to cmd_ as command is to command_.

The identity function which requires the inner argument to be (). Useful for functions with overloaded return types.

\(x :: Maybe ()) -> unit x == x

The arguments to cmd - see cmd for examples and semantics.

The arguments to cmd - see cmd for examples and semantics.

Class to convert an a to a CmdArgument

A type annotation, equivalent to the first argument, but in variable argument contexts, gives a clue as to what return type is expected (not actually enforced).

Collect the stdout of the process. If used, the stdout will not be echoed to the terminal, unless you include EchoStdout. The value type may be either String, or either lazy or strict ByteString.

Note that most programs end their output with a trailing newline, so calling ghc --numeric-version will result in Stdout of "6.8.3\n". If you want to automatically trim the resulting string, see StdoutTrim.

Like Stdout but remove all leading and trailing whitespaces.

Collect the stderr of the process. If used, the stderr will not be echoed to the terminal, unless you include EchoStderr. The value type may be either String, or either lazy or strict ByteString.

Collect the stdout and stderr of the process. If used, the stderr and stdout will not be echoed to the terminal, unless you include EchoStdout and EchoStderr. The value type may be either String, or either lazy or strict ByteString.

Collect the ExitCode of the process. If you do not collect the exit code, any ExitFailure will cause an exception.

Collect the ProcessHandle of the process. If you do collect the process handle, the command will run asyncronously and the call to cmd / command will return as soon as the process is spawned. Any Stdout / Stderr captures will return empty strings.

Collect the time taken to execute the process. Can be used in conjunction with CmdLine to write helper functions that print out the time of a result.

timer :: (CmdResult r, MonadIO m) => (forall r . CmdResult r => m r) -> m r
timer act = do
    (CmdTime t, CmdLine x, r) <- act
    liftIO $ putStrLn $ "Command " ++ x ++ " took " ++ show t ++ " seconds"
    pure r

run :: IO ()
run = timer $ cmd "ghc --version"

Collect the command line used for the process. This command line will be approximate - suitable for user diagnostics, but not for direct execution.

The results produced by fsatrace. All files will be absolute paths. You can get the results for a cmd by requesting a value of type [FSATrace].

A class for specifying what results you want to collect from a process. Values are formed of Stdout, Stderr, Exit and tuples of those.

The allowable String-like values that can be captured.

Options passed to command or cmd to control how processes are executed.

Deprecated: Use AddPath. This function will be removed in a future version.

Add a prefix and suffix to the $PATH environment variable. For example:

opt <- addPath ["/usr/special"] []
cmd opt "userbinary --version"

Would prepend /usr/special to the current $PATH, and the command would pick /usr/special/userbinary, if it exists. To add other variables see addEnv.

Deprecated: Use AddEnv. This function will be removed in a future version.

Add a single variable to the environment. For example:

opt <- addEnv [("CFLAGS","-O2")]
cmd opt "gcc -c main.c"

Would add the environment variable $CFLAGS with value -O2. If the variable $CFLAGS was already defined it would be overwritten. If you wish to modify $PATH see addPath.