Shell supports a set of loops such as for, while and until to execute a set of statements repeatedly. The body of the loop is contained between do and done statement. The for loop doesn't test a condition, but uses a list instead.
for variable in list
do
statements
done
The while loop executes the statements as long as the condition remains true.
while [ condition ]
do
statements
done
The until loop complements the while construct in the sense that the statements are executed as long as the condition remains false.
until [ condition ]
do
statements
done
