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

System.Posix.Process

Contents

Processes

Description

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

Synopsis

Processes

Forking and executing

forkProcess :: IO () -> IO ProcessID Source

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.

GHC note: forkProcess is not currently supported when using multiple processors (+RTS -N), although it is supported with -threaded as long as only one processor is being used.

executeFile Source

Arguments

:: FilePath	Command
-> Bool	Search PATH?
-> [String]	Arguments
-> Maybe [(String, String)]	Environment
-> IO a

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 ProcessID Source

getProcessID calls getpid to obtain the ProcessID for the current process.

getParentProcessID :: IO ProcessID Source

getProcessID calls getppid to obtain the ProcessID for the parent of the current process.

getProcessGroupID :: IO ProcessGroupID Source

getProcessGroupID calls getpgrp to obtain the ProcessGroupID for the current process.

Process groups

createProcessGroup :: ProcessID -> IO ProcessGroupID Source

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 ProcessGroupID Source

createSession calls setsid to create a new session with the current process as session leader.

Process times

data ProcessTimes Source

Constructors

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

getProcessTimes :: IO ProcessTimes Source

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

Scheduling priority

nice :: Int -> IO ()Source

getProcessPriority :: ProcessID -> IO Int Source

getProcessGroupPriority :: ProcessGroupID -> IO Int Source

getUserPriority :: UserID -> IO Int Source

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

Instances

Eq ProcessStatus
Ord ProcessStatus
Show ProcessStatus

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.