What is the sigaction function?
The sigaction() function examines, changes, or both examines and changes the action associated with a specific signal. The sig argument must be one of the macros defined in the header file. If sigaction() fails, the action for the signal sig is not changed.
Which sigaction flag is used to prevent a system call from being interrupted?
You can set sa_mask in your sigaction call to block certain signals while a particular signal handler runs. This way, the signal handler can run without being interrupted itself by signals.
What is a signal action?
The sigaction() system call is used to change the action taken by a process on receipt of a specific signal. (See signal(7) for an overview of signals.) signum specifies the signal and can be any valid signal except SIGKILL and SIGSTOP. If act is non-NULL, the new action for signal signum is installed from act.
Where is sigaction defined?
The structure sigaction, used to describe an action to be taken, is defined in the header to include at least the following members: Member Type. Member Name. Description. void(*) (int)
What is struct sigaction?
The sigaction structure specifies how to handle a signal. You’ll use this structure when you call sigaction() or SignalAction() The members include the following: void (*sa_sigaction) (int signo, siginfo_t *info, void *other); The address of a signal handler or action for queued signals.
What does signal () do in C?
This function returns the previous value of the signal handler, or SIG_ERR on error.
What does sigaction do in C?
sigaction(sig, act, oact) means “set the disposition for sig to act , and store the old disposition in oact ”. Its return value is 0 or -1, indicating whether the system call errored.
What causes interrupted system call?
Interruption of a system call by a signal handler occurs only in the case of various blocking system calls, and happens when the system call is interrupted by a signal handler that was explicitly established by the programmer.
How does sigaction work in C?
sigaction(sig, act, oact) means “set the disposition for sig to act , and store the old disposition in oact ”. Its return value is 0 or -1, indicating whether the system call errored. Those struct sigaction s are “dispositions”, meaning they express what to do when the given signal is received.
What does sigaction return in C?
The return value from sigaction is zero if it succeeds, and -1 on failure. The following errno error conditions are defined for this function: EINVAL. The signum argument is not valid, or you are trying to trap or ignore SIGKILL or SIGSTOP .
What are the advantages of sigaction over signal?
The signal() function does not (necessarily) block other signals from arriving while the current handler is executing; sigaction() can block other signals until the current handler returns. The signal() function (usually) resets the signal action back to SIG_DFL (default) for almost all signals.
How is code related to SIG in sigaction?
where sig is the signal number, code is additional information on certain signals, scp is a pointer to the sigcontext structure, and addr is additional address information. Much the same information is available in the objects pointed to by the second argument of the signal handler specified when SA_SIGINFO is set.
How is the sa handler field used in sigaction?
If the sa_handler field specifies a signal-catching function, the sa_mask field identifies a set of signals that shall be added to the process’ signal mask before the signal-catching function is invoked. The sa_flags field can be used to modify the behavior of the specified signal.
What happens if sigaction fails in Linux man?
If sigaction () fails, no new signal handler is installed. It is unspecified whether an attempt to set the action for a signal that cannot be caught or ignored to SIG_DFL is ignored or causes an error to be returned with errno set to [EINVAL].
Where is the sigaction bit flag set in Linux?
The SA_SIGINFO bit flag is set in the sa_flags field of the sigaction structure, and the implementation does not support either the Realtime Signals Extension option, or the XSI Extension option. An attempt was made to set the action to SIG_DFL for a signal that cannot be caught or ignored (or both).