*signals*

The value of this variable is an alist of signal numbers and handlers.

The handling of operating system dependent signals generated during program execution is not part of Common Lisp. A signal is a small integer. The list of valid signals is given in a system dependent file, usually on UNIX something like /usr/include/signals.h. Signals are either synchronous or asynchronous, but there is no distinction made in this interface--the handling of both types of signals is the same. A handler for a signal is a function of two arguments, signal number and t. If there is no handler for a particular signal, then some default action is invoked, which is usually to signal an error. Signal handlers should return a true value if they handle the signal, so that other, nested handlers are are not invoked to handle the signal. A signal that is posted during a gc is processed immediately after the gc finishes.

See also set-signal-handler, add-signal-handler, remove-signal-handler, and with-signal-handler.

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Created 2019.8.20.