1signal(3UCB) SunOS/BSD Compatibility Library Functions signal(3UCB)
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6 signal - simplified software signal facilities
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9 /usr/ucb/cc [ flag ... ] file ...
10 #include <signal.h>
11 void (*signal(sig, func))()
13 int sig;
14 void (*func)();
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18 signal() is a simplified interface to the more general sigvec(3UCB)
19 facility. Programs that use signal() in preference to sigvec() are
20 more likely to be portable to all systems.
21 A signal is generated by some abnormal event, initiated by a user at a
24 terminal (quit, interrupt, stop), by a program error (bus error, etc.),
25 by request of another program (kill), or when a process is stopped
26 because it wishes to access its control terminal while in the back‐
27 ground (see termio(7I)). Signals are optionally generated when a
28 process resumes after being stopped, when the status of child processes
29 changes, or when input is ready at the control terminal. Most signals
30 cause termination of the receiving process if no action is taken; some
31 signals instead cause the process receiving them to be stopped, or are
32 simply discarded if the process has not requested otherwise. Except for
33 the SIGKILL and SIGSTOP signals, the signal() call allows signals
34 either to be ignored or to interrupt to a specified location. See
35 sigvec(3UCB) for a complete list of the signals.
36 If func is SIG_DFL, the default action for signal sig is reinstated;
39 this default is termination (with a core image for starred signals)
40 except for signals marked with · or a dagger. Signals marked with · are
41 discarded if the action is SIG_DFL; signals marked with a dagger cause
42 the process to stop. If func is SIG_IGN the signal is subsequently
43 ignored and pending instances of the signal are discarded. Otherwise,
44 when the signal occurs further occurrences of the signal are automati‐
45 cally blocked and func is called.
46 A return from the function unblocks the handled signal and continues
49 the process at the point it was interrupted.
50 If a caught signal occurs during certain functions, terminating the
53 call prematurely, the call is automatically restarted. In particular
54 this can occur during a read(2) or write(2) on a slow device (such as a
55 terminal; but not a file) and during a wait(3C).
56 The value of signal() is the previous (or initial) value of func for
59 the particular signal.
60 After a fork(2) or vfork(2) the child inherits all signals. An exec(2)
63 resets all caught signals to the default action; ignored signals remain
64 ignored.
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67 The previous action is returned on a successful call. Otherwise,−1 is
68 returned and errno is set to indicate the error.
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71 signal() will fail and no action will take place if the following
72 occurs:
73 EINVAL sig is not a valid signal number, or is SIGKILL or SIGSTOP.
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78 kill(1), exec(2), fcntl(2), fork(2), getitimer(2), getrlimit(2),
79 kill(2), read(2), sigaction(2), write(2), abort(3C), ptrace(3C),
80 setjmp(3C), setjmp(3UCB), sigblock(3UCB), signal(3C), signal.h(3HEAD),
81 sigstack(3UCB), sigvec(3UCB), wait(3C), wait(3UCB), termio(7I)
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84 Use of these interfaces should be restricted to only applications writ‐
85 ten on BSD platforms. Use of these interfaces with any of the system
86 libraries or in multi-threaded applications is unsupported.
87 The handler routine func can be declared:
90 void handler(signum) int signum;
92 Here signum is the signal number. See sigvec(3UCB) for more informa‐
96 tion.
97SunOS 5.11 30 Oct 2007 signal(3UCB)