UNIX for Dummies Questions & Answers

1.
on prompt,i wrote
eval echo \$p[12]

ive defined p1 n p12 as variables n i wanted their values to be printed on the screen but this did not happen.
how else can i acheive the same result with eval ??


2.
when i write : grep "asb*[Mn]" a1.txt , the search pattern's metacharacters, by virtue of being enclosed within(" "), are not intrpreted by the shell.
who then interprets it before the kernel executes the command?

For your first question, you can do this a couple of ways, two of which are below....

Code:

for i in 1 2 3 4 5 6 7 8 9 10 11 12
do
  eval echo \$p$i
done

or

Code:

i=1
while [ "$i" -le "12" ]; do
  eval echo \$p$i
  (( i = i + 1 ))
done

There are many other ways of doing this too....

Cheers
ZB

thanks for the alternatives..but a few doubts follow
(n i must sincerely thank u guys for the help)

1.isnt the way i gave the command ie :
eval echo \$p[12]

alright? i believe this will be expanded, by the shell to p1 and p2 so in effect, after the shell has worked on the command it will look like :
eval echo \$p1 \$p2

but obviously this is not what the shell is doing,in fact it complains that :
parameter p not set

so how is the shell interpreting the command?why arent the metacharacters "[" and "]" being used to derive the meaning i take it to be.

2.
can u plz also look into the 2nd question from my first post

Please read the rules - I deleted your new thread (eval) due to the fact you are asking the same question as in this post. Keep your questions in the same thread as you did here and do not try to 'bump' to get a response.