Chapter 2: Definitions
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. 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 [Redirections], page 22
, 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.
3
4 Bash Reference Manual 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 1003.2
standard.
token word
A sequence of characters considered a single unit by the shell. It is either a word or an operator.
A token that is not an operator.
