NAME
signal - change the action for a signal
SYNOPSIS
integer*4 function signal(signum, proc, flag)
integer*4 signum, flag
external proc
For 64-bit environments:
integer*8 function signal(signum, proc, flag)
integer*8 flag
integer*4 signum
external proc
When compiling for 64-bit environments, with compiler option
-xarch=v9, proc, and flag must be declared integer*8 as well
as any variables receiving the result from signal.
DESCRIPTION
If a process incurs a signal (see signal(3)), the default
action is usually to clean up and abort. You can choose to
write an alternative signal handling routine. A call to
signal is the way this alternate action is specified to the
system.
Input:
signum is the signal number (see signal(3)).
proc is the name of a user signal handling routine.
If flag is negative, then proc must be the name of the user
signal handling routine.
If flag is zero or positive, then proc is ignored and the
value of flag is passed to the system as the signal action
definition. In particular, this is how previously saved
signal actions can be restored.
Two possible values for flag have specific meanings:
0 means "use the default action." See NOTES below.
1 means "ignore this signal."
Output:
A positive returned value is the previous action defini-
tion.
A value greater than 1 is the address of a routine that was
to have been called on occurrence of the given signal.
A negative returned value is the negation of a system error
code. See perror(3F).
The returned value can be used in subsequent calls to sig-
nal to restore a previous action definition.
FILES
libfui.a, libfui.so.
SEE ALSO
kill(1), signal(3c), kill(3F)
NOTES
When a negative flag value is desired in a V9 environment,
use the INTEGER*8 literal value -1_8 in the call to signal.
If the user signal handler is called, it is passed the sig-
nal number as an integer argument.
This function may fail if the code for a function passed to
it as flag is loaded at addresses with the high bit set.
This will be interpreted as a negative value for flag when
the behavior for positive values is desired. This is less
likely to happen in 64-bit environments, or with
statically-linked code.