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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 26 |
1 files changed, 26 insertions, 0 deletions
@@ -11142,6 +11142,32 @@ Note that the certain signals like sig-quit and sig-kill cannot be handled. Please observe the signal documentation in the IEEE POSIX standard, and your platform. +A signal handling function must take two arguments. It is of the form: + + (lambda (signal async-p) ...) + +The signal argument is an integer indicating the signal number for which the +handler is being invoked. The asyncp-p argument is a boolean value, nil or t. +If it is t, it indicates that the handler is being invoked +asynchronously---directly in a signal handling context. If it is nil, then it +is a deferred call. Handlers may do more things in a deferred call, such +as terminate by throwing exceptions, and perform I/O. + +The return value of a handler is normally ignored. However if it invoked +asynchronously (the async-p argument is true), then if the handler returns +a true value (any value other than nil), the handler is understood as +requesting that it be deferred. This means that the signal will be marked +as deferred, and handler will be called one more time again at some later +time in a deferred context (async-p nil). This is not guaranteed, however; +it's possible that another signal will arrive before that happens, +possibly resulting in an async call. + +If a handler is invoked synchronously, then its return value is ignored. + +In the current implementation, signals do not queue. If a signal is delivered +to the process again, while it is marked as deferred, it simply stays deferred; +there is no counter associated with a signal, only a boolean flag. + .SS The sig-check function .TP |