bash shell script iterate through array values

Tagged: Bourne shell scripting

Having an array of variables is of no use unless you can use those values somehow. This recipe shows a few methods for looping through the values of an array in the bash shell.

Given the array definition:

names=( Jennifer Tonya Anna Sadie )

The following expression evaluates into all values of the array:

${names[@]}

and can be used anywhere a variable or string can be used.

A simple for loop can iterate through this array one value at a time:

for name in ${names[@]}
do
echo $name
# other stuff on $name
done

This scrip will loop through the array values and print them out, one per line. Additional statements can be placed within the loop body to take further action, such as modifying each file in an array of filenames.

Sometimes it is useful to loop through an array and know the numeric index of the array you are using (for example, so that you can reference another array with the same index). The same loop in the example above can be achieved this way, too:

for (( i = 0 ; i < ${#names[@]} ; i++ ))
do
echo ${names[$i]}
# yadda yadda
done

In this example, the value ${#names[@]} evaluates into the number of elements in the array (4 in this case). The individual elements of the array are accessed, one at a time, using the index integer $i as ${names[$i]}