System.Posix.Signals

POSIX signal support

The Signal type

type Signal = CInt

Specific signals

nullSignal :: Signal

internalAbort :: Signal

sigABRT :: CInt

realTimeAlarm :: Signal

sigALRM :: CInt

busError :: Signal

sigBUS :: CInt

processStatusChanged :: Signal

sigCHLD :: CInt

continueProcess :: Signal

sigCONT :: CInt

floatingPointException :: Signal

sigFPE :: CInt

lostConnection :: Signal

sigHUP :: CInt

illegalInstruction :: Signal

sigILL :: CInt

keyboardSignal :: Signal

sigINT :: CInt

killProcess :: Signal

sigKILL :: CInt

openEndedPipe :: Signal

sigPIPE :: CInt

keyboardTermination :: Signal

sigQUIT :: CInt

segmentationViolation :: Signal

sigSEGV :: CInt

softwareStop :: Signal

sigSTOP :: CInt

softwareTermination :: Signal

sigTERM :: CInt

keyboardStop :: Signal

sigTSTP :: CInt

backgroundRead :: Signal

sigTTIN :: CInt

backgroundWrite :: Signal

sigTTOU :: CInt

userDefinedSignal1 :: Signal

sigUSR1 :: CInt

userDefinedSignal2 :: Signal

sigUSR2 :: CInt

pollableEvent :: Signal

sigPOLL :: CInt

profilingTimerExpired :: Signal

sigPROF :: CInt

badSystemCall :: Signal

sigSYS :: CInt

breakpointTrap :: Signal

sigTRAP :: CInt

urgentDataAvailable :: Signal

sigURG :: CInt

virtualTimerExpired :: Signal

sigVTALRM :: CInt

cpuTimeLimitExceeded :: Signal

sigXCPU :: CInt

fileSizeLimitExceeded :: Signal

sigXFSZ :: CInt

Sending signals

raiseSignal :: Signal -> IO ()

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

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

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

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

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

Handling signals

data Handler

The actions to perform when a signal is received.

Constructors

Default

Ignore

Catch (IO ())

CatchOnce (IO ())

CatchInfo (SignalInfo -> IO ())

Since: 2.7.0.0

CatchInfoOnce (SignalInfo -> IO ())

Since: 2.7.0.0

data SignalInfo

Information about a received signal (derived from siginfo_t).

Since: 2.7.0.0

Constructors

SignalInfo

Fields

• siginfoSignal :: Signal
• siginfoError :: Errno
• siginfoSpecific :: SignalSpecificInfo

data SignalSpecificInfo

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

Since: 2.7.0.0

Constructors

NoSignalSpecificInfo

SigChldInfo

Fields

• siginfoPid :: ProcessID
• siginfoUid :: UserID
• siginfoStatus :: ProcessStatus

installHandler

Arguments

:: 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

emptySignalSet :: SignalSet

fullSignalSet :: SignalSet

reservedSignals :: SignalSet

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

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

inSignalSet :: Signal -> SignalSet -> Bool

The process signal mask

getSignalMask :: IO SignalSet

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

setSignalMask :: SignalSet -> IO ()

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

blockSignals :: SignalSet -> IO ()

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

unblockSignals :: SignalSet -> IO ()

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

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

Waiting for signals

getPendingSignals :: IO SignalSet

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

awaitSignal :: Maybe SignalSet -> IO ()

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.

The NOCLDSTOP flag

setStoppedChildFlag :: Bool -> IO Bool

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

queryStoppedChildFlag :: IO Bool

Queries the current state of the stopped child flag.