1SIGNAL(3F) SIGNAL(3F)
2
6 signal - change the action for a signal
7
9 integer function signal(signum, proc, flag)
10 integer signum, flag
11 external proc
12
14 When a process incurs a signal (see signal(3C)) the default action is
15 usually to clean up and abort. The user may choose to write an alter‐
16 native signal handling routine. A call to signal is the way this
17 alternate action is specified to the system.
18 Signum is the signal number (see signal(3C)). If flag is negative,
20 then proc must be the name of the user signal handling routine. If
21 flag is zero or positive, then proc is ignored and the value of flag is
22 passed to the system as the signal action definition. In particular,
23 this is how previously saved signal actions can be restored. Two pos‐
24 sible values for flag have specific meanings: 0 means "use the default
25 action" (See NOTES below), 1 means "ignore this signal".
26 A positive returned value is the previous action definition. A value
28 greater than 1 is the address of a routine that was to have been called
29 on occurrence of the given signal. The returned value can be used in
30 subsequent calls to signal in order to restore a previous action defi‐
31 nition. A negative returned value is the negation of a system error
32 code. (See perror(3F))
33
35 /usr/lib/libU77.a
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38 signal(3C), kill(3F), kill(1)
39
41 f77 arranges to trap certain signals when a process is started. The
42 only way to restore the default f77 action is to save the returned
43 value from the first call to signal.
44 If the user signal handler is called, it will be passed the signal num‐
46 ber as an integer argument.
474.2 Berkeley Distribution May 15, 1985 SIGNAL(3F)