posix
Class Signal

java.lang.Object
  posix.Signal

public class Signal
extends Object

A posix signal. A posix signal represents an external event of some sort. For instance, SIGINTR means that a user interrupt signal was raised by the tty driver - usually because the user pressed the INTR key (typically ^C).

Some posix signals represent internal software errors. For example SIGBUS means that a load or store was attempted with incorrect alignment. We do not handle these internal events for Java - only the JVM could do something sensible with them. Furthermore, some posix signals are probably used by the JVM itself. For example, SIGCHLD means that a process started via Runtime.exec() has terminated. For this reason, only selected signals are exported via static constants.

Each Signal is in one of three states. SIG_DFL means that the default action is taken when the signal is received. This usually means stopping the JVM process. Whether any cleanup takes place depends on the JVM. SIG_IGN means that the signal is ignored. SIG_EVT means that the signal is converted to a JDK1.1 style Java event.

WARNING

The Signal class will not crash. However, whether or not a given signal can actually be trapped is highly dependent on both OS and JVM implementation. When multiple threads listen to the same signal, posix does not specify which thread gets the signal. So do not rely on a signal being trapped on all platforms. This may be rectified in the future if JNI provides some kind of signal interface, or posix provides some way of reliably distributing signals to multiple threads.

Field Summary

static int	SIG_DFL
static int	SIG_EVT
static int	SIG_IGN
static Signal	SIGDANGER Paging space is low, or power failure.
static Signal	SIGHUP The terminal or X session has disconnected.
static Signal	SIGINT The user has sent an interrupt.
static Signal	SIGQUIT The user has sent a diagnostic abort.
static Signal	SIGTERM The process is being terminated.
static Signal	SIGUSR1 Application dependent signal.
static Signal	SIGUSR2 Application dependent signal.
static Signal	SIGWINCH The terminal window has changed size.

Method Summary

void	addSignalListener(SignalListener l)
int	getAction()
void	kill(int pid) Send this Signal to another process.
static int	kill(int pid, int sig) Send signal to process using posix call.
void	processSignal() Send a SignalEvent to all listeners.
void	removeSignalListener(SignalListener l)
void	setAction(int action) Set the signal handling action type.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SIGHUP

public static final Signal SIGHUP

The terminal or X session has disconnected.

SIGINT

public static final Signal SIGINT

The user has sent an interrupt.

SIGQUIT

public static final Signal SIGQUIT

The user has sent a diagnostic abort.

SIGUSR1

public static final Signal SIGUSR1

Application dependent signal.

SIGUSR2

public static final Signal SIGUSR2

Application dependent signal.

SIGDANGER

public static final Signal SIGDANGER

Paging space is low, or power failure.

SIGTERM

public static final Signal SIGTERM

The process is being terminated.

SIGWINCH

public static final Signal SIGWINCH

The terminal window has changed size.

SIG_DFL

public static final int SIG_DFL

See Also:

Constant Field Values

SIG_IGN

public static final int SIG_IGN

See Also:

Constant Field Values

SIG_EVT

public static final int SIG_EVT

See Also:

Constant Field Values

Method Detail

setAction

public void setAction(int action)

Set the signal handling action type.

Parameters:

action - one of SIG_DFL,SIG_IGN,SIG_EVT

Throws:

IllegalStateException - if the JVM already traps this signal

getAction

public final int getAction()

addSignalListener

public void addSignalListener(SignalListener l)

removeSignalListener

public void removeSignalListener(SignalListener l)

processSignal

public void processSignal()

Send a SignalEvent to all listeners.

kill

public static int kill(int pid,
                       int sig)

Send signal to process using posix call.

Parameters:

pid - process id to signal

sig - native signal index

Returns:

0 on success or errno

kill

public void kill(int pid)
          throws IPCException

Send this Signal to another process.

Parameters:

pid - the Posix process id

Throws:

IPCException