signal, sigset, sighold, sigrelse, sigignore, sigpause -
simplified signal management for application processes
void (*signal (int sig, void (*disp)(int)))(int);
void (*sigset(int sig, void (*disp)(int)))(int);
int sighold(int sig);
int sigrelse(int sig);
int sigignore(int sig);
int sigpause(int sig);
These functions provide simplified signal management for
application processes. See signal(3HEAD) for an explanation
of general signal concepts.
The signal() and sigset() functions modify signal disposi-
tions. The sig argument specifies the signal, which may be
any signal except SIGKILL and SIGSTOP. The disp argument
specifies the signal's disposition, which may be SIG_DFL,
SIG_IGN, or the address of a signal handler. If signal() is
used, disp is the address of a signal handler, and sig is
not SIGILL, SIGTRAP, or SIGPWR, the system first sets the
signal's disposition to SIG_DFL before executing the signal
handler. If sigset() is used and disp is the address of a
signal handler, the system adds sig to the calling process's
signal mask before executing the signal handler; when the
signal handler returns, the system restores the calling
process's signal mask to its state prior to the delivery of
the signal. In addition, if sigset() is used and disp is
equal to SIG_HOLD, sig is added to the calling process's
signal mask and the signal's disposition remains unchanged.
The sighold() function adds sig to the calling process's
The sigrelse() function removes sig from the calling
process's signal mask.
The sigignore() function sets the disposition of sig to
The sigpause() function removes sig from the calling
process's signal mask and suspends the calling process
until a signal is received.
Upon successful completion, signal() returns the signal's
previous disposition. Otherwise, it returns SIG_ERR and
sets errno to indicate the error.
Upon successful completion, sigset() returns SIG_HOLD if the
signal had been blocked or the signal's previous disposition
if it had not been blocked. Otherwise, it returns SIG_ERR
and sets errno to indicate the error.
Upon successful completion, sighold(), sigrelse(), sigig-
nore(), and sigpause(), return 0. Otherwise, they return
-1 and set errno to indicate the error.
These functions fail if:
EINTR A signal was caught during the execution sigpause().
The value of the sig argument is not a valid signal or
is equal to SIGKILL or SIGSTOP.
The sighold() function used in conjunction with sigrelse()
or sigpause() may be used to establish critical regions of
code that require the delivery of a signal to be temporarily
If signal() or sigset() is used to set SIGCHLD's disposi-
tion to a signal handler, SIGCHLD will not be sent when the
calling process's children are stopped or continued.
If any of the above functions are used to set SIGCHLD's
disposition to SIG_IGN, the calling process's child
processes will not create zombie processes when they ter-
minate (see exit(2)). If the calling process subsequently
waits for its children, it blocks until all of its children
terminate; it then returns -1 with errno set to ECHILD (see
wait(2) and waitid(2)).
The system guarantees that if more than one instance of the
same signal is generated to a process, at least one signal
will be received. It does not guarantee the reception of
every generated signal.
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | MT-Safe |
exit(2), kill(2), pause(2), sigaction(2), sigsend(2),
wait(2), waitid(2), signal(3HEAD), attributes(5)
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