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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
: 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.

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 [[#Redirections|Redirections]], 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. 

return status
: A synonym for exit status.

signal
: A mechanism by which a process may be notified by the kernel of an event occurring in the system. 

special builtin
: A shell builtin command that has been classified as special by the POSIX standard. 

token
: A sequence of characters considered a single unit by the shell. It is either a word or an operator. 

word
: A sequence of characters treated as a unit by the shell. Words may not include unquoted metacharacters.