unix-2.3.0.1: POSIX functionalitySource codeContentsIndex
System.Posix.Process
Portabilitynon-portable (requires POSIX)
Stabilityprovisional
Maintainerlibraries@haskell.org
Contents
Processes
Forking and executing
Exiting
Process environment
Process groups
Sessions
Process times
Scheduling priority
Process status
Description
POSIX process support. See also the System.Cmd and System.Process modules in the process package.
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 ProcessIDSource

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. Another example is the I/O manager thread: since the I/O manager isn't running in the child, attempting to do any Handle-based I/O will deadlock.

Using forkProcess in order to do executeFile is likely to work. Anything else: you're on your own.

executeFileSource
:: FilePathCommand
-> BoolSearch PATH?
-> [String]Arguments
-> Maybe [(String, String)]Environment
-> IO ()
executeFile cmd args env calls one of the execv* 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 execv* as arg[0]; the argument list passed to executeFile therefore begins with arg[1].
Exiting
exitImmediately :: ExitCode -> IO ()Source
exitImmediately status calls _exit to terminate the process with the indicated exit status. The operation never returns.
Process environment
getProcessID :: IO ProcessIDSource
getProcessID calls getpid to obtain the ProcessID for the current process.
getParentProcessID :: IO ProcessIDSource
getProcessID calls getppid to obtain the ProcessID for the parent of the current process.
getProcessGroupID :: IO ProcessGroupIDSource
getProcessGroupID calls getpgrp to obtain the ProcessGroupID for the current process.
Process groups
createProcessGroup :: ProcessID -> IO ProcessGroupIDSource
createProcessGroup pid calls setpgid to make process pid a new process group leader.
joinProcessGroup :: ProcessGroupID -> IO ()Source
joinProcessGroup pgid calls setpgid to set the ProcessGroupID of the current process to pgid.
setProcessGroupID :: ProcessID -> ProcessGroupID -> IO ()Source
setProcessGroupID pid pgid calls setpgid to set the ProcessGroupID for process pid to pgid.
Sessions
createSession :: IO ProcessGroupIDSource
createSession calls setsid to create a new session with the current process as session leader.
Process times
data ProcessTimes Source
Constructors
ProcessTimes
elapsedTime :: ClockTick
userTime :: ClockTick
systemTime :: ClockTick
childUserTime :: ClockTick
childSystemTime :: ClockTick
getProcessTimes :: IO ProcessTimesSource
getProcessTimes calls times to obtain time-accounting information for the current process and its children.
Scheduling priority
nice :: Int -> IO ()Source
getProcessPriority :: ProcessID -> IO IntSource
getProcessGroupPriority :: ProcessGroupID -> IO IntSource
getUserPriority :: UserID -> IO IntSource
setProcessPriority :: ProcessID -> Int -> IO ()Source
setProcessGroupPriority :: ProcessGroupID -> Int -> IO ()Source
setUserPriority :: UserID -> Int -> IO ()Source
Process status
data ProcessStatus Source
Constructors
Exited ExitCode
Terminated Signal
Stopped Signal
show/hide Instances
getProcessStatus :: Bool -> Bool -> ProcessID -> IO (Maybe ProcessStatus)Source
getProcessStatus blk stopped pid calls waitpid, returning Just tc, the ProcessStatus for process pid if it 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.
getAnyProcessStatus :: Bool -> Bool -> IO (Maybe (ProcessID, ProcessStatus))Source
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))Source
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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