These definitions are used throughout the remainder of this manual.
A family of open system standards based on Unix. Bash
is concerned with POSIX 1003.2, the Shell and Tools Standard.
A space or tab character.
A command that is implemented internally by the shell itself, rather
than by an executable program somewhere in the file system.
word that performs a control function. It is a
or one of the following:
'||', '&&', '&', ';', ';;',
'|', '(', or ')'.
The value returned by a command to its caller. The value is restricted
to eight bits, so the maximum value is 255.
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.
A string of characters used to identify a file.
A set of processes comprising a pipeline, and any processes descended
from it, that are all in the same process group.
A mechanism by which users can selectively stop (suspend) and restart
(resume) execution of processes.
A character that, when unquoted, separates words. A metacharacter is
blank or one of the following characters:
'|', '&', ';', '(', ')', '<', or
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
control operator or a
See section 3.6 Redirections, for a list of redirection operators.
A collection of related processes each having the same process
process group ID
A unique identifier that represents a
during its lifetime.
word that has a special meaning to the shell. Most reserved
words introduce shell flow control constructs, such as
A synonym for
A mechanism by which a process may be notified by the kernel
of an event occurring in the system.
A shell builtin command that has been classified as special by the
POSIX 1003.2 standard.
A sequence of characters considered a single unit by the shell. It is
word or an
token that is not an