4.4BSD/usr/share/man/cat2/sigvec.0
SIGVEC(2) BSD Programmer's Manual SIGVEC(2)
NNAAMMEE
ssiiggvveecc - software signal facilities
SSYYNNOOPPSSIISS
##iinncclluuddee <<ssiiggnnaall..hh>>
struct sigvec {
void (*sv_handler)();
sigset_t sv_mask;
int sv_flags;
};
ssiiggvveecc(_i_n_t _s_i_g, _s_t_r_u_c_t _s_i_g_v_e_c _*_v_e_c, _s_t_r_u_c_t _s_i_g_v_e_c _*_o_v_e_c);
DDEESSCCRRIIPPTTIIOONN
TThhiiss iinntteerrffaaccee iiss mmaaddee oobbssoolleettee bbyy ssiiggaaccttiioonn((22))..
The system defines a set of signals that may be delivered to a process.
Signal delivery resembles the occurence of a hardware interrupt: the sig-
nal is blocked from further occurrence, the current process context is
saved, and a new one is built. A process may specify a _h_a_n_d_l_e_r to which
a signal is delivered, or specify that a signal is to be _b_l_o_c_k_e_d or
_i_g_n_o_r_e_d. 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 _s_i_g_n_a_l _s_t_a_c_k.
All signals have the same _p_r_i_o_r_i_t_y. Signal routines execute with the sig-
nal that caused their invocation _b_l_o_c_k_e_d, but other signals may yet oc-
cur. A global _s_i_g_n_a_l _m_a_s_k 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 sig-
block(2) or sigsetmask(2) call, or when a signal is delivered to the pro-
cess.
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
_b_l_o_c_k_e_d by the process then it is delivered to the process. When a sig-
nal is delivered, the current state of the process is saved, a new signal
mask is calculated (as described below), and the signal handler is in-
voked. The call to the handler is arranged so that if the signal han-
dling routine returns normally the process will resume execution in the
context from before the signal's delivery. If the process wishes to re-
sume 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 sigblock or
sigsetmask call is made). This mask is formed by taking the current sig-
nal mask, adding the signal to be delivered, and _o_r'ing in the signal
mask associated with the handler to be invoked.
SSiiggvveecc() assigns a handler for a specific signal. If _v_e_c is non-zero, it
specifies a handler routine and mask to be used when delivering the spec-
ified signal. Further, if the SV_ONSTACK bit is set in _s_v___f_l_a_g_s, the
system will deliver the signal to the process on a _s_i_g_n_a_l _s_t_a_c_k, speci-
fied with sigaltstack(2). If _o_v_e_c is non-zero, the previous handling in-
formation for the signal is returned to the user.
The following is a list of all signals with names as in the include file
<_s_i_g_n_a_l_._h>:
NNAAMMEE DDeeffaauulltt AAccttiioonn DDeessccrriippttiioonn
SIGHUP terminate process terminal line hangup
SIGINT terminate process interrupt program
SIGQUIT create core image quit program
SIGILL create core image illegal instruction
SIGTRAP create core image trace trap
SIGABRT create core image abort(2) call (formerly SIGIOT)
SIGEMT create core image emulate instruction executed
SIGFPE create core image floating-point exception
SIGKILL terminate process kill program
SIGBUS create core image bus error
SIGSEGV create core image segmentation violation
SIGSYS create core image system call given invalid
argument
SIGPIPE terminate process write on a pipe with no reader
SIGALRM terminate process real-time timer expired
SIGTERM terminate process software termination signal
SIGURG discard signal urgent condition present on
socket
SIGSTOP stop process stop (cannot be caught or
ignored)
SIGTSTP stop process stop signal generated from
keyboard
SIGCONT discard signal continue after stop
SIGCHLD discard signal child status has changed
SIGTTIN stop process background read attempted from
control terminal
SIGTTOU stop process background write attempted to
control terminal
SIGIO discard signal I/O is possible on a descriptor
(see fcntl(2))
SIGXCPU terminate process cpu time limit exceeded (see
setrlimit(2))
SIGXFSZ terminate process file size limit exceeded (see
setrlimit(2))
SIGVTALRM terminate process virtual time alarm (see
setitimer(2))
SIGPROF terminate process profiling timer alarm (see
setitimer(2))
SIGWINCH discard signal Window size change
SIGINFO discard signal status request from keyboard
SIGUSR1 terminate process User defined signal 1
SIGUSR2 terminate process User defined signal 2
Once a signal handler is installed, it remains installed until another
ssiiggvveecc() call is made, or an execve(2) is performed. A signal-specific
default action may be reset by setting _s_v___h_a_n_d_l_e_r to SIG_DFL. The de-
faults are process termination, possibly with core dump; no action; stop-
ping the process; or continuing the process. See the above signal list
for each signal's default action. If _s_v___h_a_n_d_l_e_r is SIG_IGN 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 EINTR error return by setting the SV_INTERRUPT bit in _s_v___f_l_a_g_s. The
affected system calls include read(2), write(2), sendto(2),
recvfrom(2), sendmsg(2) and recvmsg(2) on a communications channel or a
slow device (such as a terminal, but not a regular file) and during a
wait(2) or ioctl(2). However, calls that have already committed are not
restarted, but instead return a partial success (for example, a short
read count).
After a fork(2) or vfork(2) all signals, the signal mask, the signal
stack, and the restart/interrupt flags are inherited by the child.
Execve(2) 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.
NNOOTTEESS
The mask specified in _v_e_c is not allowed to block SIGKILL or SIGSTOP.
This is done silently by the system.
The SV_INTERRUPT flag is not available in 4.2BSD, hence it should not be
used if backward compatibility is needed.
RREETTUURRNN VVAALLUUEESS
A 0 value indicated that the call succeeded. A -1 return value indicates
an error occurred and _e_r_r_n_o is set to indicated the reason.
EERRRROORRSS
SSiiggvveecc() will fail and no new signal handler will be installed if one of
the following occurs:
[EFAULT] Either _v_e_c or _o_v_e_c points to memory that is not a valid part of
the process address space.
[EINVAL] _S_i_g is not a valid signal number.
[EINVAL] An attempt is made to ignore or supply a handler for SIGKILL or
SIGSTOP.
SSEEEE AALLSSOO
kill(1), kill(2), ptrace(2), sigaction(2), sigaltstack(2),
sigblock(2), sigpause(2), sigprocmask(2), sigsetmask(2),
sigsuspend(2), setjmp(3), siginterrupt(3), signal(3,) sigsetops(3),
tty(4)
EEXXAAMMPPLLEE
On the VAX-11 The handler routine can be declared:
void handler(sig, code, scp)
int sig, code;
struct sigcontext *scp;
Here _s_i_g is the signal number, into which the hardware faults and traps
are mapped as defined below. _C_o_d_e is a parameter that is either a con-
stant as given below or, for compatibility mode faults, the code provided
by the hardware (Compatibility mode faults are distinguished from the
other SIGILL traps by having PSL_CM set in the psl). _S_c_p is a pointer to
the _s_i_g_c_o_n_t_e_x_t structure (defined in <_s_i_g_n_a_l_._h>), used to restore the
context from before the signal.
BBUUGGSS
This manual page is still confusing.
4th Berkeley Distribution June 2, 1993 3