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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 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. 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 section 3.6 Redirections, 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.

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
A sequence of characters considered a single unit by the shell. It is either a word or an operator.

word
A token that is not an operator.


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