Function

sigaction invokes the sigaction callable service to examine, change, or both examine and change the action associated with a specific signal for all the threads in the process.

Parameters

signal

The signal, as specified by a numeric value or a predefined variable beginning with SIG.

Variable	Description
SIGABND	Abend
SIGABRT	Abnormal termination
SIGALRM	Timeout
SIGBUS	Bus error
SIGCHLD	Child process terminated or stopped
SIGCONT	Continue if stopped
SIGFPE	Erroneous arithmetic operation, such as division by zero or an operation resulting in an overflow
SIGHUP	Hangup detected on the controlling terminal
SIGILL	Termination that cannot be caught or ignored
SIGINT	Interactive attention
SIGIO	Completion of input or output
SIGIOERR	Error on input/output; used by the C runtime library
SIGKILL	Termination that cannot be caught or ignored
SIGPIPE	Write on a pipe with no readers
SIGPOLL	Pollable event
SIGPROF	Profiling timer expired
SIGQUIT	Interactive termination
SIGSEGV	Detection of an incorrect memory reference
SIGSTOP	Stop that cannot be caught or ignored
SIGSYS	Bad system call
SIGTERM	Termination
SIGTRAP	Trap used by the ptrace callable service
SIGTSTP	Interactive stop
SIGTTIN	Read from a controlling terminal attempted by a member of a background process group
SIGTTOU	Write from a controlling terminal attempted by a member of a background process group
SIGURG	High bandwidth data is available at a socket
SIGUSR1	Reserved as application-defined signal 1
SIGUSR2	Reserved as application-defined signal 2
SIGVTALRM	Virtual timer expired
SIGXCPU	CPU time limit exceeded
SIGXFSZ	File size limit exceeded

new_handler

Specifies the new setting for handling the signal. The following predefined variables can be used for new_handler:

Variable	Description
SIG_CAT	Set signal handling to catch the signal.
SIG_DFL	Set signal handling to the default action.
SIG_IGN	Set signal handling to ignore the signal.
SIG_QRY	Query the handling for that signal.

new_flag

Used to modify the behavior of the specified signal. Specify one of these:

Variable	Description
0	Use the default behavior.
SA_NOCLDWAIT	Do not create zombie processes when child processes exit.
SA_RESETHAND	Reset the signal action to the default, SIG_DFL, when delivered.
SA_NOCLDSTOP	Do not generate SIGCHLD when the child processes stop.

old_handler

A variable name for the buffer where the system returns the old (current) signal handling action.

old_flag

The name of the variable that will store the old (current) signal action flags.

Usage notes

1. If new_handler is set to the action SIG_DFL for a signal that cannot be caught or ignored, the sigaction request is ignored and the return value is set to 0.
2. Setting a signal action to ignore for a signal that is pending causes the pending signal to be discarded.
3. Setting signal action SIG_IGN or catch for signals SIGSTOP or SIGKILL is not allowed.
4. Setting signal action SIG_IGN for SIGCHLD or SIGIO is not allowed.
5. The sigaction caller's thread must be registered for signals. You can register the thread by calling syscalls('SIGON'). If the thread is not registered for signals, the sigaction service fails with an ERRNO of EINVAL and ERRNOJR of JRNotSigSetup.