Definitions

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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 Redirections, for a list of redirection operators. Operators contain at least one unquotedmetacharacter. 
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.

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