Definitions (Bash Reference Manual)
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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 anewline
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
space
,tab
,newline
, or one of the following characters: ‘|
’, ‘&
’, ‘;
’, ‘(
’, ‘)
’, ‘<
’, or ‘>
’.name
A
word
consisting solely of letters, numbers, and underscores, and beginning with a letter or underscore.Name
s are used as shell variable and function names. Also referred to as anidentifier
.operator
A
control operator
or aredirection 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 asfor
andwhile
.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 anoperator
.word
A sequence of characters treated as a unit by the shell. Words may not include unquoted
metacharacters
.
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