Ok, my problem is this:

I want to have $count = the # of file written by the loop. Adding 3 every time the loop is run. At the end of the script I want to be able to echo the total # of files written.

In what i have, the value for $count increases as it should until the end of the looop, where the value of $count returns to 0

count=0

#there is more code in here in my script, I just pasted the relevant part.

cat 10tapes | while read tapename
do
dd bs=64k if=/dev/nst0 of=$tapename.header.ebcdic
echo "Header Complete"
dd bs=64k if=/dev/nst0 of=$tapename.data.ebcdic
echo "Data Complete"
dd bs=64k if=/dev/nst0 of=$tapename.trailer.ebcdic
echo "Trailer Complete"
chmod -w $tapename*
ls -l $tapename*
echo Rewinding Tape
mt -f /dev/nst0 rewind
echo Ejecting Tape
mt -f /dev/nst0 eject
echo Finished with tape $tapename
(( count=$count+3 ))
echo "******* DEBUG COUNT $count *********"
done

echo "******* DEBUG COUNT $count after done *********"
# The first DEBUG COUNT line gives the correct value.
# The second DEBUG COUNT gives the value of $count as 0
# I think The While loop is eating my variable, and I don't know how to get it out. Perhaps this question belongs in the newbie forum?

Use this while construct instead:

while read tapename
do
...
done <10tapes

Use something like expr etc. for addition... there are too many ways to add

HTH.

Ok, this worked.... odd... I don't suppose you could explain Why it worked? Or, more importantly what was happening to my variable the way i was doing it?

I remember i started out trying to use a while loop like this one, but I had a different problem which lead to me using cat. Now i feel silly


Thanks alot for your help!


And Dustu76, I must admit i had no idea what was happening in the code you posted. I am still new to this whole thing. Trying to get as much practice in as I can though. Need to really get it all in my head

In regard to using expr for addition. I'm not sure why, I just think the double parentheses look nicer. Does it somehow work better to use expr? or is it just a personal preference thing.

You could use let too like :
count=1
let "count+=3"
echo $count

No.

LasseW is right. That's because when you use pipes, each side of the pipe is ran as a subshell. And there's (almost) no way a subshell can export a value to the parent shell.
If you want to run , and still have A in the current shell, the general solution is to do instead. Of course, if B is cat "b", this can be replaced by and if B is echo "b", this can be replaced by Yves.

If theYinYeti is right, then in my earlier post, how come the ksh is aware of the increments & reports then correctly? Seems like the answer also depends on the shell you are using.

As far as using expr, let, (()) etc., you can choose anything that suits you. I find let & (()) faster than expr 'cause they are builtins. However (()) & let don't work with my version of sh:

HTH.

true.

eg:
another reason I prefer ksh

I second that billy