Shell Functions Basic Shell Features Shell Expansions
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 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
is not given, the variable is assigned the null string. All
values undergo tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote
removal (detailed below). If the variable has its
attribute set (see the description of the
declare builtin in
Bash Builtins), then value
is subject to arithmetic expansion even if the
expansion is not used (see Arithmetic Expansion).
Word splitting is not performed, with the exception
"$@" as explained below.
Filename expansion is not performed.