for and while loops

The for statement

Like other programming languages, UNIX has a for statement (count controlled loop). For example:

for i in {1..5}

do

   echo $i

done

The loop can also be reversed e.g. for i in {5..1}

We can also have an infinite loop – but with a break:

for ((;;))

do

   echo "Enter value "

   read value

   if (($value == 99))

      then

          break

   fi

done

Nested loops are also possible e.g.

            for i in { }

               for j in {}   etc.

Exercise 3: Using a nested for loop, write a script which displays the 12 times tables e.g. 1 x 1, etc followed by 2 x 1 until 12 x 1 to 12 x 12. After each table, set a pause (sleep) and clear the screen and continue.

Assessment 2

Time: approx 1 hour

Topics

• Awk – lab 3
• sed – lab 4
• use of test command
• at & cron
• run-levels + use of inittab
• use of /etc/sudoers
• for statement – lab 10

As before, you may not use class or lab notes (including electronic version) but you may use any system resource including man pages, google, etc.