2 .TH sel 3 "23 July 1999" "Straylight/Edgeware" "mLib utilities library"
4 sig \- more controlled signal handling
10 .B "#include <mLib/sig.h>"
12 .ds mT \fBvoid sig_add(
13 .BI "\*(mTsig *" s ", int " n ,
14 .BI "\h'\w'\*(mT'u'void (*" proc ")(int " n ", void *" p "), void *" p );
15 .BI "void sig_remove(sig *" s );
16 .BI "void sig_init(sel_state *" s );
21 subsystem uses the I/O multiplexing capabilities of
25 for details) to provide a more convenient interface for handling signals
26 which don't need to be dealt with `right away'. Like the I/O system,
28 doesn't allocate any memory for itself: you have to give it space to
31 The system needs to be initialized before use. To do this, you must
34 passing it the address of an initialized multiplexor object. Signals
35 handled through this interface will only be delivered when
37 is called on that multiplexor.
39 To register interest in a signal, call
41 passing it the following arguments:
44 A pointer to an (uninitialized) object of type
46 This will be used by the system to retain information about this signal
47 claim. You use the address of this object to remove the handler again
51 The number of the signal you want to handle.
54 .BI "void (*" proc ")(int " n ", void *" p )
55 A function to call when the signal is detected. The function is passed
56 the signal number and the pointer
62 A pointer argument to be passed to
64 when the signal is detected.
66 Removing a handler is easy. Call
68 with the address of the
70 structure you passed to
72 .SS "Multiple signal handlers"
73 You may have multiple signal handlers for a signal. All of them are
74 called in some unspecified order when the signal occurs.
76 A signal's disposition is remembered when a handler for it is added and
77 there are no handlers already registered. When the last handler for a
78 signal is removed, its disposition is restored to its initial remembered
80 .SH "BUGS AND CAVEATS"
83 system attempts to set the
85 flag on signal handlers it creates that signal occurrences don't
86 interrupt system calls. This won't be done on systems which don't
87 define this flag, for obvious reasons.
91 flag is also set, so that stopped child processes aren't reported by a
92 signal. This is normally right, but ought to be configurable.
94 Mark Wooding, <mdw@distorted.org.uk>