"The purpose of this project is to code a small data exchage program using UNIX signals".
Terms:
- Understanding of the signal and sigaction.
- Different types of signals.
- signal() vs. sigaction().
- Syntex of the sigaction().
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Signals are software interruptions that are utilized to interrupt a running process to execute another action.
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Different types of signals such SIGINT, SIGABRT, SIGQUIT, SIGUSR1, SIGUSR2 and many others... When a signal is activated, the process sends a signal to the kernel, which the utilizes the sig_handler() to perforn one of three possible actions: ignore, catch, default. Certain signals cannot be ignored, such as SIGKILL, SIGSTOP. The signal is caught when the process registers a function with the kernel to handle the interruption. If a signal executes its defailt behavior, it indicaties that the process is using the SIG_DFL signal.
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The signal() has several undesirable characteristics that sigaction() avoids - unless you use the flags explicitly added to sigaction() to allow it to faithfully simulate the old signal() behavior. The function signal() does not block other signals from arriving withe the current hndler is execution; The signal() fuction resets the signal cation back to SIG_DFL for almost all signals.
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sigemptyset(&sa.sa_mask);: Clears the signal set in sa.sa_mask, indicating that no signals will be blocked while the signal handler is executing. The sa_mask field indicates any signals that should be blocked while the signal handler is being executed. The sa_flags field determines a number of different things, but the inpertant ones are whether we get the exetended information.
SA_RESTART: This flag, when set, causes interrupted system calls to be automatically restarted by the operating system after the signal handler returns. It's useful to avoid manual restarts of interrupted system calls.
SA_SIGINFO: When this flag is set, it indicates that the signal handler takes three arguments: the signal number, a pointer to a siginfo_t structure (providing additional information about the signal), and a pointer to a ucontext_t (providing a snapshot of the current execution context). This is useful for more detailed information about the signal.