z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

that if you just enter $d to refer to the dth positional parameter, d can only
be a single digit; with brace brackets, number can be greater than 9.) Since
braces mark the beginning and end of the name, you can have a letter or
digit immediately following the expression.
${variable[arithmetic expression]}
Expands to the value of an element in an array named variable. The
arithmetic expression gives the subscript of the array. (See “Arithmetic
Substitution” on page 562.)
${variable [*]}
Expands to all the elements in the array variable, separated by the first
character of the value of $IFS.
${variable [@]$}
When unquoted, is the same as ${ variable[*]} When quoted as “${variable
[@]$} ,” it expands to all the elements in the array variable, with each
element quoted individually.
${#parameter}
Expands to the number of characters in the value of the given parameter.
${#} Expands to the number of positional parameters.
${# *} Expands to the number of positional parameters.
${#@} Expands to the number of positional parameters.
${#variable [*]}
Expands to the number of elements in the array named variable. Elements
that do not have assigned values do not count. For example, if you only
assign values to elements 0 and 4, the number of elements is 2. Elements 1
through 3 do not count.
${parameter:–word}
Expands to the value of parameter if it is defined and has a nonempty
value; otherwise, it expands word. This means that you can use word as a
default value if the parameter isn’t defined.
${parameter–word}
Is similar to the preceding construct, except that the parameter is expanded
if defined, even if the value is empty.
${variable:=word}
Expands word with parameter expansion and assigns the result to variable,
provided that variable is not defined or has an empty value. The result is
the expansion of variable, whether or not word was expanded.
${variable=word}
Is similar to the preceding construct, except that the variable must be
undefined (it cannot just be null) for word to be expanded.
${parameter:?word}
Expands to the value of parameter provided that it is defined and
non-empty. If parameter isn’t defined or is null, sh expands and displays
word as a message. If word is empty, sh displays a default message. After
a non-interactive shell has displayed a message, it ends.
${parameter?word}
Is similar to the preceding construct, except that sh displays word only if
parameter is undefined.
sh
Chapter 2. Shell command descriptions 561