Chapter 2: Definitions

These definitions are used throughout the remainder of this manual.


`POSIX`	A family of open system standards based on Unix. Bash is concerned with POSIX 1003.2, the Shell and Tools Standard.
`blank`	A space or tab character.
`builtin`	A command that is implemented internally by the shell itself, rather than by an executable program somewhere in the file system.
`control operator`	A `word` that performs a control function. It is a `newline` or one of the following: ``\|\|`', ``&&`', ``&`', ``;`', ``;;`', ``\|`', ``(`', or ``)`'.
`exit status`	The value returned by a command to its caller.
`field`	A unit of text that is the result of one of the shell expansions. After expansion, when executing a command, the resulting fields are used as the command name and arguments.
`filename`	A string of characters used to identify a file.
`job`	A set of processes comprising a pipeline, and any processes descended from it, that are all in the same process group.
`job control`	A mechanism by which users can selectively stop (suspend) and restart (resume) execution of processes.
`metacharacter`	A character that, when unquoted, separates words. A metacharacter is a `blank` or one of the following characters: ``\|`', ``&`', ``;`', ``(`', ``)`', ``<`', or ``>`'.
`name`	A `word` consisting solely of letters, numbers, and underscores, and beginning with a letter or underscore. `Name`s are used as shell variable and function names. Also referred to as an `identifier`.
`operator`	A `control operator` or a `redirection operator`. See Redirections, for a list of redirection operators.
`process group`	A collection of related processes each having the same process group ID.
`process group ID`	A unique identifer that represents a `process group` during its lifetime.
`reserved word`	A `word` that has a special meaning to the shell. Most reserved words introduce shell flow control constructs, such as `for` and `while`.
`return status`	A synonym for `exit status`.
`signal`	A mechanism by which a process may be notified by the kernal of an event occurring in the system.
`special builtin`	A shell builtin command that has been classified as special by the POSIX.2 standard.
`token`	A sequence of characters considered a single unit by the shell. It is either a `word` or an `operator`.
`word`	A `token` that is not an `operator`.

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Basic Shell Features