Module (chicken process signal)
This module offers procedures for dealing with POSIX process signals.
Please note that signals are very POSIX-specific. Windows only supports rudimentary in-process signals for dealing with user interrupts, segmentation violations, floating-point exceptions and the like. Inter-process signals are not supported. Therefore, most of the procedures here are not available on native Windows builds. If that's the case, the description contains a note.
set-alarm!
[procedure] (set-alarm! SECONDS)Sets an internal timer to raise the signal/alrm after SECONDS are elapsed. You can use the make-signal-handler procedure to write a handler for this signal.
NOTE: On native Windows builds (all except cygwin), this procedure is unimplemented and will raise an error.
make-signal-handler
[procedure] (make-signal-handler SIGNUM ...)Establishes a handler for the POSIX signals with the numbers SIGNUM ... and returns a procedure of zero or one argument. Should one of the given signals be raised, then it will be stored in a queue. Invoking the procedure returned by make-signal-handler with zero arguments or with the argument #f will remove the oldest entry in the queue and return it to the caller. Invoking the procedure with argument #t when no signal was raised since the creation of the signal handler or the most recent call to the handler will result in suspending the execution until one of the signals given in SIGNUM ... occurs.
Notes:
- when signals arrive in quick succession (specifically, before the handler for a signal has been started), then signals will be queued (up to a certain limit); the order in which the queued signals will be handled is not specified
- Any signal handlers for the signals signal/segv, signal/bus, signal/fpe and signal/ill will be ignored and these signals will always trigger an exception, unless the executable was started with the -:S runtime option. This feature is only available on platforms that support the sigprocmask(3) POSIX API function.
signal-ignore
[procedure] (signal-ignore SIGNUM)Ignores any future occurrences if the signal SIGNUM by setting its disposition to SIG_IGN.
signal-default
[procedure] (signal-default SIGNUM)Sets the default disposition for the signal SIGNUM by setting its disposition to SIG_DFL.
set-signal-mask!
[procedure] (set-signal-mask! SIGLIST)Sets the signal mask of the current process to block all signals given in the list SIGLIST. Signals masked in that way will not be delivered to the current process.
NOTE: On native Windows builds (all except cygwin), this procedure is unimplemented and will raise an error.
signal-mask
[procedure] (signal-mask)Returns the signal mask of the current process.
NOTE: On native Windows builds (all except cygwin), this procedure is unimplemented and will raise an error.
signal-masked?
[procedure] (signal-masked? SIGNUM)Returns whether the signal for the code SIGNUM is currently masked.
NOTE: On native Windows builds (all except cygwin), this procedure is unimplemented and will raise an error.
signal-mask!
[procedure] (signal-mask! SIGNUM)Masks (blocks) the signal for the code SIGNUM.
NOTE: On native Windows builds (all except cygwin), this procedure is unimplemented and will raise an error.
signal-unmask!
[procedure] (signal-unmask! SIGNUM)Unmasks (unblocks) the signal for the code SIGNUM.
NOTE: On native Windows builds (all except cygwin), this procedure is unimplemented and will raise an error.
Signal codes
[constant] signal/term[constant] signal/kill
[constant] signal/int
[constant] signal/hup
[constant] signal/fpe
[constant] signal/ill
[constant] signal/segv
[constant] signal/abrt
[constant] signal/trap
[constant] signal/quit
[constant] signal/alrm
[constant] signal/vtalrm
[constant] signal/prof
[constant] signal/io
[constant] signal/urg
[constant] signal/chld
[constant] signal/cont
[constant] signal/stop
[constant] signal/tstp
[constant] signal/pipe
[constant] signal/xcpu
[constant] signal/xfsz
[constant] signal/usr1
[constant] signal/usr2
[constant] signal/bus
[constant] signal/winch
[constant] signal/break
[constant] signals-list
These variables contain signal codes for use with process-signal, set-signal-handler!, signal-handler, signal-masked?, signal-mask!, or signal-unmask!.
NOTE: On native Windows builds (all except cygwin), only signal/term, signal/int, signal/fpe, signal/ill, signal/segv, signal/abrt, signal/break have an actual value. The others are all defined as zero, because those signals don't exist on Windows.
NOTE: On UNIX builds and cygwin, signal/break is defined as zero because it only exists on Windows.
To get a list of signals that are known to exist on the current platform, you can check signals-list which is a list of integers (signal numbers).
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