The while statement has the general form: while command-list1 do command-list2 done . The commands in command-list1 are executed; and if the exit status of the last command in that list is 0 (zero), the commands in command-list2 are executed. ... This is identical in function to the while command except that the loop is executed as long as the exit status of command-list1 is non-zero. The exit status of a while/until command is the exit status of the last command executed in command-list2 . ...