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Signal handlers can be set with signal() or sigaction(). The behavior of signal() has been changed multiple times across history and its use is discouraged. [3] It is only portable when used to set a signal's disposition to SIG_DFL or SIG_IGN. Signal handlers can be specified for all but two signals (SIGKILL and SIGSTOP cannot be caught ...
If a signal handler is not installed for a particular signal, the default handler is used. Otherwise the signal is intercepted and the signal handler is invoked. The process can also specify two default behaviors, without creating a handler: ignore the signal (SIG_IGN) and use the default signal handler (SIG_DFL).
This sends the "terminal stop" signal (SIGTSTP) to the process group. By default, SIGTSTP causes processes receiving it to stop, and control is returned to the shell. However, a process can register a signal handler for or ignore SIGTSTP. A process can also be paused with the "stop" signal (SIGSTOP), which cannot be caught or ignored.
The signal number is passed as an integer argument to this function. The sa_mask member specifies additional signals to be blocked during the execution of signal handler. sa_mask must be initialized with sigemptyset(3). The sa_flags member specifies some additional flags. sa_sigaction is an alternate signal handler with different set of parameters.
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In asynchronous serial communication, a signal at the end of a character that prepares the receiving device for the reception of a subsequent character. A stop signal is usually limited to one signal element having any duration equal to or greater than a specified minimum value. A signal to a receiving mechanism to wait for the next signal.
On POSIX-compliant platforms, SIGHUP ("signal hang up") is a signal sent to a process when its controlling terminal is closed. It was originally designed to notify the process of a serial line drop. SIGHUP is a symbolic constant defined in the header file signal.h .
Traditionally, a device has an interrupt line (pin) which it asserts when it wants to signal an interrupt to the host processing environment. This traditional form of interrupt signalling is an out-of-band form of control signalling since it uses a dedicated path to send such control information, separately from the main data path.