Shell Programming and Scripting

I'm sorry if something like this has already been posted, but I didn't find anything like it.

I'm using ksh The code that I've come up with will initially print what I want, but will then keep repeating the second number. I'm just trying to teach myself and can't seem to find the code to work. Basically, when you enter a number at the command line, it should print that number and each number after it, but not 0. See the attachment for what I have.

Code:

#num=$1
#echo $num
while [ "$1" -gt 0 ]; do
 echo $num
 ((num=$1-1))
done

So I assume $1 is a positive number... but the value of $1 doesn't change, so the loop is going to loop forever! Plus that syntax for substracting one from $num won't work. Try this:

Code:

num=$1
while [ $num -gt 0 ]; do
 echo $num
 num=`expr $num - 1`
done

Yes, $1 is supposed to be a positive number. I inserted your code that you gave me but it gives me an error about not having a command argument. I tested it with Countdown 8, it would print out the 8 then tell me I need a command argument. I appreciate your help. Back to the books and trying new things. Thank you again!

When I use the code exactly as below, I get the numbers 1 to 8, each printing on their own line, in decreasing order. Does it tell you anything else in that error? Post it exactly as you see it.

Code:

if [ "$1" ]
then
num=$1
while [ $num -gt 0 ]; do
 echo $num
 num=`expr $num - 1`
done
else
 echo You did it wrong
fi

That syntax will work fine in most shells. It was introduced in ksh. It is now in most modern shells including bash.

((num=num-1))
is actually much better than:
num=`expr $num - 1`
unless your shell happens to have expr as a builtin.

My command line: /Practice>Countdown 8
Output: 8
Countdown[6]: $num: unknown test operator

this is what it says when executed

Thanks Perderabo.. didn't realize there was such an easy way! Try this, scott:

Code:

if [ "$1" ]; then
  num=$1
  while [ $num -gt 0 ]; do
    echo $num
    ((num=num-1))
  done
else
  echo You did it wrong
fi

It looks like your only mistake was ((num=$1-1)) because it causes an endless loop.