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signal handling documention

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git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@291 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
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stasinos 2002-01-11 16:53:57 +00:00
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docs/yap.tex
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@ -2798,7 +2798,7 @@ Integers are sorted in increasing order;
atoms are sorted in lexicographic order;
@item
compound terms are ordered first by name, then by arity of the main
functor and finally by their arguments i left-to-right order.
functor, and finally by their arguments in left-to-right order.
@end itemize
@table @code
@ -5432,6 +5432,48 @@ if the alarm is sent. It uses @code{catch/3} to handle the case the
@code{alarm} is sent. Then it starts the alarm, calls the goal
@var{Goal}, and disables the alarm on success or failure.
@item on_signal(+@var{Signal},?@var{OldAction},+@var{Callable})
@findex on_signal/3
@snindex on_signal/3
@cnindex on_signal/3
Set the interrupt handler for soft interrupt @var{Signal} to be
@var{Callable}. @var{OldAction} is unified with the previous handler.
Only a subset of the software interrupts (signals) can have their
handlers maniputated through @code{on_signal/3}.
Their POSIX names, YAP names and default behaviour is given below.
The "YAP name" of the signal is the atom that is associated with
each signal, and should be used as the first argument to
@code{on_signal/3}. It is chosen so that it matches the signal's POSIX
name.
@code{on_signal/3} succeeds, unless when called with an invalid
signal name or one that is not supported on this platform. No checks
are made on the handler provided by the user.
@table @code
@item SIGHUP (Hangup)
sig_hup in YAP; Reconsult the initialisation files
~/.yaprc, ~/.prologrc and ~/prolog.ini.
@item SIGUSR1 and SIGUSR2 (User signals)
sig_usr1 and sig_usr2 in YAP; Print a message and halt.
@end table
A special case is made, where if @var{Callable} is bound to
@code{default}, then the default handler is restored for that signal.
A call in the form @code{on_signal(@var{S},@var{H},@var{H})} can be used
to retrieve a signal's current handler without changing it.
It must be noted that although a signal can be received at all times,
the handler is not executed while Yap is waiting for a query at the
prompt. The signal will be, however, registered and dealt with as soon
as the user makes a query.
Please also note, that neither POSIX Operating Systems nor Yap guarantee
that the order of delivery and handling is going to correspond with the
order of dispatch.
@end table
@node Term Modification, Profiling, OS, Top