Process +System -package

Packages
package
base
process
unix

POSIX process support. See also the System.Cmd and System.Process modules in the process package.

Operations for creating and interacting with sub-processes.

CreateProcess :: CmdSpec -> Maybe FilePath -> Maybe [(String, String)] -> StdStream -> StdStream -> StdStream -> Bool -> Bool -> CreateProcess

process System.Process

data CreateProcess

process System.Process

createProcess :: CreateProcess -> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)

process System.Process

This is the most general way to spawn an external process. The process can be a command line to be executed by a shell or a raw command with a list of arguments. The stdin, stdout, and stderr streams of the new process may individually be attached to new pipes, to existing Handles, or just inherited from the parent (the default.) The details of how to create the process are passed in the CreateProcess record. To make it easier to construct a CreateProcess, the functions proc and shell are supplied that fill in the fields with default values which can be overriden as needed. createProcess returns (mb_stdin_hdl, mb_stdout_hdl, mb_stderr_hdl, p), * if std_in == CreatePipe, then mb_stdin_hdl will be Just h, connected to the child process's stdin. * otherwise, mb_stdin_hdl == Nothing Similarly for mb_stdout_hdl and mb_stderr_hdl. For example, to execute a simple ls command: > r <- createProcess (proc "ls" []) To create a pipe from which to read the output of ls: > (_, Just hout, _, _) <- > createProcess (proc "ls" []){ std_out = CreatePipe } To also set the directory in which to run ls: > (_, Just hout, _, _) <- > createProcess (proc "ls" []){ cwd = Just "\home\bob", > std_out = CreatePipe }

createProcessGroup :: ProcessID -> IO ProcessGroupID

unix System.Posix.Process.ByteString, unix System.Posix.Process

createProcessGroup pid calls setpgid to make process pid a new process group leader. This function is currently deprecated, and might be changed to making the current process a new process group leader in future versions.

createProcessGroupFor :: ProcessID -> IO ProcessGroupID

unix System.Posix.Process.ByteString, unix System.Posix.Process

createProcessGroupFor pid calls setpgid to make process pid a new process group leader.

forkProcess :: IO () -> IO ProcessID

unix System.Posix.Process.ByteString, unix System.Posix.Process

forkProcess corresponds to the POSIX fork system call. The IO action passed as an argument is executed in the child process; no other threads will be copied to the child process. On success, forkProcess returns the child's ProcessID to the parent process; in case of an error, an exception is thrown. forkProcess comes with a giant warning: since any other running threads are not copied into the child process, it's easy to go wrong: e.g. by accessing some shared resource that was held by another thread in the parent.

getAnyProcessStatus :: Bool -> Bool -> IO (Maybe (ProcessID, ProcessStatus))

unix System.Posix.Process.ByteString, unix System.Posix.Process

getAnyProcessStatus blk stopped calls waitpid, returning Just (pid, tc), the ProcessID and ProcessStatus for any child process if one is available, Nothing otherwise. If blk is False, then WNOHANG is set in the options for waitpid, otherwise not. If stopped is True, then WUNTRACED is set in the options for waitpid, otherwise not.

getGroupProcessStatus :: Bool -> Bool -> ProcessGroupID -> IO (Maybe (ProcessID, ProcessStatus))

unix System.Posix.Process.ByteString, unix System.Posix.Process

getGroupProcessStatus blk stopped pgid calls waitpid, returning Just (pid, tc), the ProcessID and ProcessStatus for any process in group pgid if one is available, Nothing otherwise. If blk is False, then WNOHANG is set in the options for waitpid, otherwise not. If stopped is True, then WUNTRACED is set in the options for waitpid, otherwise not.

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