signaaliputket

Signaaliputket, or signal pipes, are a mechanism in Unix-like operating systems for inter-process communication (IPC). They allow a parent process to send data to a child process, or vice versa, in a unidirectional flow. A signal pipe is essentially a file that can be read from and written to. When data is written to the pipe, it is buffered by the operating system until a process reads it.

The primary use of signal pipes is for managing the lifecycle of child processes. For example, a parent process might use a signal pipe to notify its child that it is about to terminate. The child process can then read this signal from the pipe and perform any necessary cleanup operations before exiting. This is crucial for preventing zombie processes, which are processes that have terminated but whose entries remain in the process table because their parent has not yet acknowledged their termination.

Signal pipes are created using the pipe() system call, which returns two file descriptors: one for reading and one for writing. Data can then be written to the writing file descriptor and read from the reading file descriptor. When a process exits, any open file descriptors, including those for signal pipes, are automatically closed. This closing action can also serve as a signal to other processes reading from or writing to the pipe. For instance, if a process is writing to a pipe and the reading end is closed, the write operation will typically fail with an error, which can be interpreted as a signal that the other end is no longer active.