SIGPOLL

SIGPOLL is a signal used in the POSIX-compliant operating systems, such as UNIX and Linux, to notify processes of certain I/O events, specifically the availability of new data on a file descriptor. It is part of the signals related to asynchronous I/O (input/output) operations, enabling processes to react promptly to event-driven data transfers without continuous polling.

The SIGPOLL signal is primarily used within the context of device drivers and network socket operations. When a device or network socket has data ready to be read, the operating system can send a SIGPOLL signal to a process that has registered interest in that event, typically through the use of signal-driven I/O mechanisms. This allows applications to handle data more efficiently, especially in scenarios involving high-speed data transfer or multiple simultaneous I/O sources.

In practice, a process can register for SIGPOLL notifications using system calls like sigaction() or the interface mechanisms provided for asynchronous I/O. When the specified event occurs, the process receives the SIGPOLL signal, enabling it to perform appropriate data processing or resource management.

SIGPOLL is crucial for event-driven programming paradigms, particularly in network servers and real-time applications, where timely responses to I/O events improve performance and scalability. It is part of a broader set of signals that facilitate asynchronous processing and efficient resource utilization in modern operating systems.

There may be variations in the exact implementation or behavior of SIGPOLL across different UNIX-like systems, but its core purpose remains consistent—to signal the availability of data and facilitate responsive I/O operations.