signal.2 (2010 09)

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signal(2) signal(2)

NAME

signal(), sigset(), sighold(), sigrelse(), sigignore(), sigpause() - signal management

SYNOPSIS

#include <signal.h>

void (*signal(int sig, void (*func)(int)))(int);

int sighold(int sig);

int sigignore(int sig);

int sigpause(int sig);

int sigrelse(int sig);

void (*sigset(int sig, void (*disp)(int)))(int);

DESCRIPTION

The functions described in this reference page provide simpliﬁed signal management:

• The

signal() function chooses one of three ways in which receipt of the signal number sig is to be

subsequently handled.

• The

sigset() function is used to modify signal dispositions.

• The

sighold() function adds sig to the calling process’ signal mask.

• The

sigrelse() function removes sig from the calling process’ signal mask.

• The

sigignore() function sets the disposition of sig to SIG_IGN.

• The

sigpause() function removes sig from the calling process’ signal mask and suspends the calling

process until a signal is received.

The system deﬁnes a set of signals that can be delivered to a process. The set of signals is deﬁned in sig-

nal(5), along with the meaning and side effects of each signal. An alternate mechanism for handling

these signals is deﬁned here. The facilities described here should not be used in conjunction with the

other facilities described under signal(2), sigvector (2), sigblock (2), sigsetmask (2), sigpause (3C), and sig-

space (2).

The

signal() function chooses one of three ways in which receipt of the signal number sig is to be sub-

sequently handled. If the value of func is

SIG_DFL, default handling for that signal will occur. If the

value of func is SIG_IGN, the signal will be ignored. Otherwise, func must point to a function to be

called when that signal occurs. Such a function is called a signal handler.

When a signal occurs, if func points to a function, ﬁrst the equivalent of:

signal(sig, SIG_DFL);

is executed or an implementation-dependent blocking of the signal is performed. (If the value of sig is

SIGILL, whether the reset to SIG_DFL occurs is implementation-dependent.) Next the equivalent of:

(*func)(sig);

is executed. The func function may terminate by executing a return statement or by calling abort(),

exit(),orlongjmp().Iffunc() executes a return statement and the value of sig was SIGFPE or

any other implementation-dependent value corresponding to a computational exception, the behavior is

undeﬁned. Otherwise, the program will resume execution at the point it was interrupted.

If the signal occurs other than as the result of calling

abort(), kill(), raise(),

pthread_kill(),orsigqueue(), the behavior is undeﬁned if the signal handler calls any function

in the standard library other than one of the functions listed on the thread_safety(5) manpage or refers to

any object with static storage duration other than by assigning a value to a static storage duration vari-

able of type volatile sig_atomic_t . Furthermore, if such a call fails, the value of errno is indeterminate.

At program startup, the equivalent of:

signal(sig, SIG_IGN);

is executed for some signals, and the equivalent of:

signal(sig, SIG_DFL);

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (4 pages)

PAGE 1
signal(2) signal(2) NAME signal(), sigset(), sighold(), sigrelse(), sigignore(), sigpause() - signal management SYNOPSIS #include
PAGE 2
signal(2) signal(2) is executed for all other signals (see exec). Acceptable values for sig are described in signal (5). Acceptable values for func are: SIG_DFL Execute the default action, which varies depending on the signal. The default action for most signals is to terminate the process (see signal (5)). A pending signal is discarded (whether or not it is blocked) if action is set to SIG_DFL but the default action of the pending signal is to ignore the signal (as in the case of SIGCLD).
PAGE 3
signal(2) signal(2) If disp is not SIG_DFL, SIG_IGN, or SIG_HOLD, it must be a pointer to a function, the signal-catching handler, that is called when signal sig occurs. Before calling the signal-catching handler, the system signal action of sig is set to SIG_HOLD. Any pending signal of this type is released. This handler address is retained across calls to the other signal management functions listed here.
PAGE 4
signal(2) signal(2) then test the variables. If they have not changed, call sigpause() to wait for the signal. Threads Considerations The signal disposition (such as catch/ignore/default) established by signal() is shared by all threads in the process. Blocked signal masks are maintained by each thread. The use of this function is unspecified in a multithreaded process. For more information regarding signals and threads, refer to signal (5).