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.