Signal
An OS-delivered notification to a process (like SIGTERM or SIGKILL) used for interrupts, termination, and other asynchronous events.
Definition
A signal is an asynchronous notification delivered by the OS to a process.
Signals are used for interrupts, termination requests, and other events. Some signals can be handled by the process. Some cannot.
Common signals you’ll encounter
SIGTERM: request to terminate (often used for graceful shutdown)SIGINT: interrupt (commonly from Ctrl+C)SIGKILL: force termination (cannot be handled. The OS stops the process immediately)
Why signals matter
Signals are a major control path in production: shutdown, restarts, deploy rollouts, and operator interventions often boil down to “a signal was sent”.
See also: Unix signals list