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

using awk:

awk '{a[NR]=$0;if($0 && !s)s=NR;}
    END{e=NR;
        for(i=NR;i>1;i--) 
            if(a[i]){ e=i; break; } 
        for(i=s;i<=e;i++)
            print a[i];}' yourFile