¿Cómo se comunica con el proceso de padres e hijos?

How do you communicate with the parent and child process?

In this post, the communication between child and parent processes is done using kill() and signal(), fork() system call.

1. fork() creates the child process from the parent.
2. The parent can then send messages to child using the pid and kill().
3. The child picks up these signals with signal() and calls appropriate functions.

A child process inherits most of its attributes, such as file descriptors, from its parent. Each process may create many child processes but will have at most one parent process; if a process does not have a parent this usually indicates that it was created directly by the kernel.

If there are at least one child processes running when the call to wait() is made, the caller will be blocked until one of its child processes exits. At that moment, the caller resumes its execution. If there is no child process running when the call to wait() is made, then this wait() has no effect at all.

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.)

* The child does not inherit process-associated record locks from its parent (fcntl(2)). (On the other hand, it does inherit fcntl(2) open file description locks and flock(2) locks from its parent.) * The prctl(2) PR_SET_PDEATHSIG setting is reset so that the child does not receive a signal when its parent terminates.

The above call returns the process ID of the terminated child on success and -1 on failure. The waitpid () system call suspends the execution of the current process and waits indefinitely until the specified children (as per pid value) terminates. The termination status from the child is available in the status.

The parent can use the system call wait () or waitpid () along with the macros WIFEXITED and WEXITSTATUS with it to learn about the status of its stopped child. (*)wait () system call : It suspends execution of the calling process until one of its children terminates. Syntax of wait () system call: pid_t wait (int *status);

How is this generally done? You can get the exit status of the child via the first argument of wait (), or the second argument of waitpid (), and then using the macros WIFEXITED and WEXITSTATUS with it. waitpid () will block until the process with the supplied process ID exits.

The parent of the child process is init process, which is the very first process initiating all the tasks. To monitor the child process execution state, to check whether the child process is running or stopped or to check the execution status, etc. the wait () system calls and its variants is used.