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3.4.1 Positional Parameters The shell's command-line arguments. 3.4.2 Special Parameters Parameters with special meanings.
A parameter is an entity that stores values.
It can be a
name, a number, or one of the special characters
For the shell's purposes, a variable is a parameter denoted by a
A variable has a value and zero or more attributes.
Attributes are assigned using the
declare builtin command
(see the description of the
declare builtin in 4.2 Bash Builtin Commands).
A parameter is set if it has been assigned a value. The null string is
a valid value. Once a variable is set, it may be unset only by using
unset builtin command.
A variable may be assigned to by a statement of the form
integerattribute set, then value is subject to arithmetic expansion even if the
$((...))expansion is not used (see section 3.5.5 Arithmetic Expansion). Word splitting is not performed, with the exception of
"$@"as explained below. Filename expansion is not performed. Assignment statements may also appear as arguments to the