Haskell Hierarchical Libraries (unix package) Contents Index

System.Posix.Process Portability non-portable (requires POSIX) Stability provisional Maintainer libraries@haskell.org

Contents Processes Forking and executing Exiting Process environment Process groups Sessions Process times Scheduling priority Process status

Description

POSIX process support

Synopsis

forkProcess :: IO () -> IO ProcessID executeFile :: FilePath -> Bool -> [String] -> Maybe [(String, String)] -> IO () exitImmediately :: ExitCode -> IO () getProcessID :: IO ProcessID getParentProcessID :: IO ProcessID getProcessGroupID :: IO ProcessGroupID createProcessGroup :: ProcessID -> IO ProcessGroupID joinProcessGroup :: ProcessGroupID -> IO () setProcessGroupID :: ProcessID -> ProcessGroupID -> IO () createSession :: IO ProcessGroupID data ProcessTimes = ProcessTimes { elapsedTime :: ClockTick userTime :: ClockTick systemTime :: ClockTick childUserTime :: ClockTick childSystemTime :: ClockTick } getProcessTimes :: IO ProcessTimes nice :: Int -> IO () getProcessPriority :: ProcessID -> IO Int getProcessGroupPriority :: ProcessGroupID -> IO Int getUserPriority :: UserID -> IO Int setProcessPriority :: ProcessID -> Int -> IO () setProcessGroupPriority :: ProcessGroupID -> Int -> IO () setUserPriority :: UserID -> Int -> IO () data ProcessStatus = Exited ExitCode | Terminated Signal | Stopped Signal getProcessStatus :: Bool -> Bool -> ProcessID -> IO (Maybe ProcessStatus) getAnyProcessStatus :: Bool -> Bool -> IO (Maybe (ProcessID, ProcessStatus)) getGroupProcessStatus :: Bool -> Bool -> ProcessGroupID -> IO (Maybe (ProcessID, ProcessStatus))

Processes

Forking and executing

forkProcess :: IO () -> IO ProcessID

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.

executeFile :: FilePath -> Bool -> [String] -> Maybe [(String, String)] -> IO ()

literal>executeFile cmd args env</literal calls one of the function>execv*</function family, depending on whether or not the current PATH is to be searched for the command, and whether or not an environment is provided to supersede the process's current environment. The basename (leading directory names suppressed) of the command is passed to function>execv*</function> as <varname>arg[0]</varname; the argument list passed to function>executeFile</function therefore begins with varname>arg[1]</varname.

Exiting

exitImmediately :: ExitCode -> IO ()

literal>exitImmediately status</literal> calls <function>&lowbar;exit</function to terminate the process with the indicated exit literal>status</literal. The operation never returns.

Process environment

getProcessID :: IO ProcessID

function>getProcessID</function> calls <function>getpid</function to obtain the literal>ProcessID</literal for the current process.

getParentProcessID :: IO ProcessID

function>getProcessID</function> calls <function>getppid</function> to obtain the <literal>ProcessID</literal for the parent of the current process.

getProcessGroupID :: IO ProcessGroupID

function>getProcessGroupID</function> calls <function>getpgrp</function to obtain the literal>ProcessGroupID</literal for the current process.

Process groups

createProcessGroup :: ProcessID -> IO ProcessGroupID

literal>createProcessGroup pid</literal> calls <function>setpgid</function to make process literal>pid</literal a new process group leader.

joinProcessGroup :: ProcessGroupID -> IO ()

literal>joinProcessGroup pgid</literal> calls <function>setpgid</function to set the literal>ProcessGroupID</literal> of the current process to <literal>pgid</literal.

setProcessGroupID :: ProcessID -> ProcessGroupID -> IO ()

literal>setProcessGroupID pid pgid</literal> calls <function>setpgid</function to set the literal>ProcessGroupID</literal> for process <literal>pid</literal> to <literal>pgid</literal.

Sessions

createSession :: IO ProcessGroupID

function>createSession</function> calls <function>setsid</function to create a new session with the current process as session leader.

Process times

data ProcessTimes

Constructors ProcessTimes elapsedTime :: ClockTick userTime :: ClockTick systemTime :: ClockTick childUserTime :: ClockTick childSystemTime :: ClockTick

getProcessTimes :: IO ProcessTimes

function>getProcessTimes</function> calls <function>times</function to obtain time-accounting information for the current process and its children.

Scheduling priority

nice :: Int -> IO ()

getProcessPriority :: ProcessID -> IO Int

getProcessGroupPriority :: ProcessGroupID -> IO Int

getUserPriority :: UserID -> IO Int

setProcessPriority :: ProcessID -> Int -> IO ()

setProcessGroupPriority :: ProcessGroupID -> Int -> IO ()

setUserPriority :: UserID -> Int -> IO ()

Process status

data ProcessStatus

Constructors Exited ExitCode Terminated Signal Stopped Signal Instances Eq ProcessStatus Ord ProcessStatus Show ProcessStatus

getProcessStatus :: Bool -> Bool -> ProcessID -> IO (Maybe ProcessStatus)

literal>getProcessStatus blk stopped pid</literal> calls <function>waitpid</function, returning literal>Just tc</literal>, the <literal>ProcessStatus</literal> for process <literal>pid</literal if it is available, literal>Nothing</literal> otherwise. If <literal>blk</literal> is <literal>False</literal, then literal>WNOHANG</literal> is set in the options for <function>waitpid</function, otherwise not. If literal>stopped</literal> is <literal>True</literal>, then <literal>WUNTRACED</literal is set in the options for function>waitpid</function, otherwise not.

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

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

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

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

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