Search results
Results from the WOW.Com Content Network
In Unix-like operating systems, new processes are created by the fork() system call. The PID is returned to the parent process , enabling it to refer to the child in further function calls. The parent may, for example, wait for the child to terminate with the waitpid() function, or terminate the process with kill() .
The systemd daemon serves as the root of the user space's process tree; the first process (PID 1) has a special role on Unix systems, as it replaces the parent of a process when the original parent terminates. Therefore, the first process is particularly well suited for the purpose of monitoring daemons.
However, if the parent process lingers in collecting the child's data (or fails to do it at all), the system has no option but keep the child's pid and termination data in the process table indefinitely. Such a terminated process whose data has not been collected is called a zombie process, or simply a zombie, in the UNIX parlance. The name is ...
The traditional Unix system does not have the functionality to create a new process running a new executable program in one step, which explains the importance of exec for Unix programming. Other systems may use spawn as the main tool for running executables. Its result is equivalent to the fork–exec sequence of Unix-like
It is an interface which is required for compliance with the POSIX and Single UNIX Specification standards. It is usually implemented as a C standard library wrapper to the fork, clone, or other system calls of the kernel. Fork is the primary method of process creation on Unix-like operating systems.
PID controllers often provide acceptable control using default tunings, but performance can generally be improved by careful tuning, and performance may be unacceptable with poor tuning. Usually, initial designs need to be adjusted repeatedly through computer simulations until the closed-loop system performs or compromises as desired.
PID controller (proportional-integral-derivative controller), a control concept used in automation; Piping and instrumentation diagram (P&ID), a diagram in the process industry which shows the piping of the process flow etc. Principal ideal domain, an algebraic structure; Process identifier, a number used by many operating systems to identify a ...
In a POSIX-conformant operating system, a process group denotes a collection of one or more processes. [1] Among other things, a process group is used to control the distribution of a signal; when a signal is directed to a process group, the signal is delivered to each process that is a member of the group.