After reading last week's tip, you should have a basic understanding of how to assign values (elements) to an indexed array, and then access them individually based on their position in the array.

One example from last week demonstrated how to access and print each array element using a while loop:

$ i=0
$ while [ $i -lt 3 ]
> do
> print ${colors[$i]}
> (( i=i+1 ))
> done
RED
GREEN
BLUE
$

Hard-coding the number of elements in the array is fine for demonstrating a new concept, but obviously not very practical when it comes to using it within a shell script.  Most of the time you will not know how may elements will be stored in the array, or the number may be dynamic - changing each time the script is invoked.

Fortunately, there is an operator for determining the number of array elements:

${#arrayname[*]}

Comparing this to the syntax used for accessing individual array elements,

${arrayname[subscript]}

$ i=0
$ NUM_OF_ELEMENTS=${#colors[*]}
$ while [ $i -lt $NUM_OF_ELEMENTS ]
> do
> print ${colors[$i]}
> (( i=i+1 ))
> done
RED
GREEN
BLUE
$

$ i=0
$ while [ $i -lt ${#colors[*]} ]
> do
> print ${colors[$i]}
> (( i=i+1 ))
> done
RED
GREEN
BLUE
$

$ print ${colors[*]}
RED GREEN BLUE
$