Chapter 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 primarily concerned with the Shell and Utilities portion of the posix 1003.1 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 token 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. The value is restricted to eight bits, so the maximum value is 255. 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. Names 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 [Redirec- tions], page 31, for a list of redirection operators. Operators contain at least one unquoted metacharacter. process group

A collection of related processes each having the same process group id. process group ID

A unique identifier 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.