Terms

Background

Background describes processes usually running at a lower priority and with their input disconnected from the interactive session. Input and output are usually directed to a file or other process.

Background Processes

Background processes are autonomous processes that run under UNIX without requiring user interaction.

bash

bash stands for the GNU Bourne Again Shell and is based on the Bourne shell, sh, the original command interpreter.

Bourne Shell

This shell is the original standard user interface to UNIX that supported limited programming capability.

BSD

BSD is an acronym for Berkeley Software Distribution.

BSD UNIX

This version of UNIX was developed by Berkeley Software Distribution and written at University of California, Berkeley.

C Shell

This user interface for UNIX, written by Bill Joy at Berkeley, features C programming-like syntax.

Child Processes

See subprocesses.

Child Shells

See subshells.

Daemons

Daemons are system-related background processes that often run with the permissions of root and services requests from other processes.

Korn Shell

This shell is a user interface for UNIX with extensive scripting (programming) support. It was written by David G. Korn. The shell features command-line editing and also accepts scripts written for the Bourne shell.

Parent Process Identifier

The parent process identifier is shown in the heading of the ps command as PPID. This is the process identifier of the parent process. See also parent processes.

Parent Processes

These processes control other processes that are often referred to as child processes or subprocesses. See processes.

Parent Shell

This shell controls other shells, which are often referred to as child shells or subshells. The login shell is typically the parent shell. See shells.

Process Identifier

The process identifier is shown in the heading of the ps command as pid. It is the unique number assigned to every process running in the system.

Processes

Processes are discrete, running programs under UNIX. The user’s interactive session is a process. A process can invoke (run) and control another program that is then referred to as a subprocess. Ultimately, everything a user does is a subprocess of the operating system.

Shell

The shell is the part of UNIX that handles user input and invokes other programs to run commands. It includes a programming language. See also Bourne shell, C shell, Korn shell, tcsh, and bash.

Shell or Command Prompt

The prompt is a single character or set of characters that the UNIX shell displays at which a user can enter a command or set of commands.

Shell Scripts

Shell scripts are programs written using a shell programming language like those supported by Bourne, Korn, or C shells.

Subprocesses

Subprocesses run under the control of other processes, which are often referred to as parent processes. See processes.

Subshells

Subshells run under the control of another shell, which is often referred to as the parent shell. Typically, the login shell is the parent shell. See shells.

tcsh

This is a C shell-like user interface featuring command-line editing.