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 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.