Bash Reference Manual - 2. Definitions

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# 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 section 3.6 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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