Table of Contents
struct sigvec {
void (*sv_handler)();
sigset_t sv_mask;
int sv_flags;
};
This interface is made obsolete by sigaction(2)
. The
system defines a set of signals that may be delivered to a process. Signal
delivery resembles the occurrence of a hardware interrupt: the signal is
blocked from further occurrence, the current process context is saved,
and a new one is built. A process may specify a to which a signal is delivered,
or specify that a signal is to be or A process may also specify that
a default action is to be taken by the system when a signal occurs. Normally,
signal handlers execute on the current stack of the process. This may be
changed, on a per-handler basis, so that signals are taken on a special
All signals have the same Signal routines execute with the signal that
caused their invocation but other signals may yet occur. A global defines
the set of signals currently blocked from delivery to a process. The signal
mask for a process is initialized from that of its parent (normally 0).
It may be changed with a or call, or when a signal is delivered to the
process. When a signal condition arises for a process, the signal is added
to a set of signals pending for the process. If the signal is not currently
by the process then it is delivered to the process. When a signal is delivered,
the current state of the process is saved, a new signal mask is calculated
(as described below), and the signal handler is invoked. The call to the
handler is arranged so that if the signal handling routine returns normally
the process will resume execution in the context from before the signal’s
delivery. If the process wishes to resume in a different context, then it
must arrange to restore the previous context itself. When a signal is delivered
to a process a new signal mask is installed for the duration of the process’
signal handler (or until a or call is made). This mask is formed by taking
the current signal mask, adding the signal to be delivered, and in the
signal mask associated with the handler to be invoked. assigns a handler
for a specific signal. If is non-zero, it specifies a handler routine and
mask to be used when delivering the specified signal. Further, if the bit
is set in the system will deliver the signal to the process on a specified
with If is non-zero, the previous handling information for the signal
is returned to the user. The following is a list of all signals with names
as in the include file call (formerly is possible
on a descriptor (see Once a signal handler is installed,
it remains installed until another call is made, or an is performed. A
signal-specific default action may be reset by setting to The defaults
are process termination, possibly with core dump; no action; stopping the
process; or continuing the process. See the above signal list for each signal’s
default action. If is current and pending instances of the signal are
ignored and discarded. If a signal is caught during the system calls listed
below, the call is normally restarted. The call can be forced to terminate
prematurely with an error return by setting the bit in The affected
system calls include and on a communications channel or a slow device
(such as a terminal, but not a regular file) and during a or However,
calls that have already committed are not restarted, but instead return
a partial success (for example, a short read count). After a or all signals,
the signal mask, the signal stack, and the restart/interrupt flags are
inherited by the child. reinstates the default action for all signals
which were caught and resets all signals to be caught on the user stack.
Ignored signals remain ignored; the signal mask remains the same; signals
that interrupt system calls continue to do so.
The mask specified in
is not allowed to block or This is done silently by the system. The
flag is not available in hence it should not be used if backward compatibility
is needed.
A 0 value indicated that the call succeeded. A -1
return value indicates an error occurred and is set to indicated the reason.
will fail and no new signal handler will be installed if one of
the following occurs: Either or points to memory that is not a valid
part of the process address space. is not a valid signal number. An attempt
is made to ignore or supply a handler for or
On the The handler routine can be declared: void handler(sig,
code, scp) int sig, code; struct sigcontext *scp; Here is the signal
number, into which the hardware faults and traps are mapped as defined
below. is a parameter that is either a constant as given below or, for
compatibility mode faults, the code provided by the hardware (Compatibility
mode faults are distinguished from the other traps by having set in the
psl). is a pointer to the structure (defined in used to restore the context
from before the signal.
This manual page is still confusing.
Table of Contents