/Haskell 7


Copyright (c) The University of Glasgow 2002
License BSD-style (see the file libraries/base/LICENSE)
Maintainer libraries@haskell.org
Stability provisional
Portability non-portable (requires POSIX)
Safe Haskell Trustworthy
Language Haskell2010


POSIX signal support

The Signal type

type Signal = CInt Source

Specific signals

nullSignal :: Signal Source

internalAbort :: Signal Source

sigABRT :: CInt Source

realTimeAlarm :: Signal Source

sigALRM :: CInt Source

busError :: Signal Source

sigBUS :: CInt Source

processStatusChanged :: Signal Source

sigCHLD :: CInt Source

continueProcess :: Signal Source

sigCONT :: CInt Source

floatingPointException :: Signal Source

sigFPE :: CInt Source

lostConnection :: Signal Source

sigHUP :: CInt Source

illegalInstruction :: Signal Source

sigILL :: CInt Source

keyboardSignal :: Signal Source

sigINT :: CInt Source

killProcess :: Signal Source

sigKILL :: CInt Source

openEndedPipe :: Signal Source

sigPIPE :: CInt Source

keyboardTermination :: Signal Source

sigQUIT :: CInt Source

segmentationViolation :: Signal Source

sigSEGV :: CInt Source

softwareStop :: Signal Source

sigSTOP :: CInt Source

softwareTermination :: Signal Source

sigTERM :: CInt Source

keyboardStop :: Signal Source

sigTSTP :: CInt Source

backgroundRead :: Signal Source

sigTTIN :: CInt Source

backgroundWrite :: Signal Source

sigTTOU :: CInt Source

userDefinedSignal1 :: Signal Source

sigUSR1 :: CInt Source

userDefinedSignal2 :: Signal Source

sigUSR2 :: CInt Source

pollableEvent :: Signal Source

sigPOLL :: CInt Source

profilingTimerExpired :: Signal Source

sigPROF :: CInt Source

badSystemCall :: Signal Source

sigSYS :: CInt Source

breakpointTrap :: Signal Source

sigTRAP :: CInt Source

urgentDataAvailable :: Signal Source

sigURG :: CInt Source

virtualTimerExpired :: Signal Source

sigVTALRM :: CInt Source

cpuTimeLimitExceeded :: Signal Source

sigXCPU :: CInt Source

fileSizeLimitExceeded :: Signal Source

sigXFSZ :: CInt Source

Sending signals

raiseSignal :: Signal -> IO () Source

raiseSignal int calls kill to signal the current process with interrupt signal int.

signalProcess :: Signal -> ProcessID -> IO () Source

signalProcess int pid calls kill to signal process pid with interrupt signal int.

signalProcessGroup :: Signal -> ProcessGroupID -> IO () Source

signalProcessGroup int pgid calls kill to signal all processes in group pgid with interrupt signal int.

Handling signals

data Handler Source

The actions to perform when a signal is received.


Catch (IO ())
CatchOnce (IO ())
CatchInfo (SignalInfo -> IO ())


CatchInfoOnce (SignalInfo -> IO ())


data SignalInfo Source

Information about a received signal (derived from siginfo_t).


data SignalSpecificInfo Source

Information specific to a particular type of signal (derived from siginfo_t).


installHandler Source


:: Signal
-> Handler
-> Maybe SignalSet

other signals to block

-> IO Handler

old handler

installHandler int handler iset calls sigaction to install an interrupt handler for signal int. If handler is Default, SIG_DFL is installed; if handler is Ignore, SIG_IGN is installed; if handler is Catch action, a handler is installed which will invoke action in a new thread when (or shortly after) the signal is received. If iset is Just s, then the sa_mask of the sigaction structure is set to s; otherwise it is cleared. The previously installed signal handler for int is returned

Signal sets

data SignalSet Source

emptySignalSet :: SignalSet Source

fullSignalSet :: SignalSet Source

reservedSignals :: SignalSet Source

A set of signals reserved for use by the implementation. In GHC, this will normally include either sigVTALRM or sigALRM.

addSignal :: Signal -> SignalSet -> SignalSet infixr 9 Source

deleteSignal :: Signal -> SignalSet -> SignalSet infixr 9 Source

inSignalSet :: Signal -> SignalSet -> Bool Source

The process signal mask

getSignalMask :: IO SignalSet Source

getSignalMask calls sigprocmask to determine the set of interrupts which are currently being blocked.

setSignalMask :: SignalSet -> IO () Source

setSignalMask mask calls sigprocmask with SIG_SETMASK to block all interrupts in mask.

blockSignals :: SignalSet -> IO () Source

blockSignals mask calls sigprocmask with SIG_BLOCK to add all interrupts in mask to the set of blocked interrupts.

unblockSignals :: SignalSet -> IO () Source

unblockSignals mask calls sigprocmask with SIG_UNBLOCK to remove all interrupts in mask from the set of blocked interrupts.

The alarm timer

scheduleAlarm :: Int -> IO Int Source

scheduleAlarm i calls alarm to schedule a real time alarm at least i seconds in the future.

Waiting for signals

getPendingSignals :: IO SignalSet Source

getPendingSignals calls sigpending to obtain the set of interrupts which have been received but are currently blocked.

awaitSignal :: Maybe SignalSet -> IO () Source

awaitSignal iset suspends execution until an interrupt is received. If iset is Just s, awaitSignal calls sigsuspend, installing s as the new signal mask before suspending execution; otherwise, it calls sigsuspend with current signal mask. Note that RTS scheduler signal (either virtualTimerExpired or realTimeAlarm) could cause premature termination of this call. It might be necessary to block that signal before invocation of awaitSignal with blockSignals reservedSignals.

awaitSignal returns when signal was received and processed by a signal handler, or if the signal could not be caught. If you have installed any signal handlers with installHandler, it may be wise to call yield directly after awaitSignal to ensure that the signal handler runs as promptly as possible.


setStoppedChildFlag :: Bool -> IO Bool Source

Tells the system whether or not to set the SA_NOCLDSTOP flag when installing new signal handlers.

queryStoppedChildFlag :: IO Bool Source

Queries the current state of the stopped child flag.

© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).