Removing trailing / starting newlines with sed, awk, tr, and friends

Question

I would like to remove all of the empty lines from a file, but only when they are at the end/start of a file (that is, if there are no non-empty lines before them, at the start;

Answer 1

In bash, using cat, wc, grep, sed, tail and head:

# number of first line that contains non-empty character
i=`grep -n "^[^\B*]"  | sed -e 's/:.*//' | head -1`
# number of hte last one
j=`grep -n "^[^\B*]"  | sed -e 's/:.*//' | tail -1`
# overall number of lines:
k=`cat  | wc -l`
# how much empty lines at the end of file we have?
m=$(($k-$j))
# let strip last m lines!
cat  | head -n-$m
# now we have to strip first i lines and we are done 8-)
cat  | tail -n+$i

Man, it's definitely worth to learn "real" programming language to avoid that ugliness!