Shell Programming and Scripting

Nice trick for the reverse order!

Edit:
My solution above does not return the expected result on large dictionaries. The w array gets out of sequence. Updated version inspired by Scrutinizer's backwards loop:

Code:

awk '{le=length;w[le] = w[le] ? w[le]"\n"$0 : $0} END {for(i=length(w);i>=1;i--)  print w[i]}'

For your specific AWK implementation, the number of member's in the array may affect the order in which the members are retrieved, but, more generally, the problem is that you were depending on undefined behavior. A solution that gives the desired result with gawk could fail on nawk. A solution that works with version N of some awk implementation could fail on version N+1 of that same implementation. And in none of those cases is an implementation not complying with the standard.

From Opengroup :: AWK:
The OP never stated their operating system. If it's not GNU/Linux, tac may not be available.

In my opinion, in post #2, bipinajith linked to the nicest solution. The only thing it needs is a cut to dedecorate:

Code:

awk '{print length "\t" $0}' | sort -n | cut -f2-

These days, 40,000 lines isn't very many. Any machine that can run the perl interpreter can make short work of such a file. Unless the sort pipeline will be executed many times in a tight loop, there's no point in sacrificing simplicity, readability, and maintainability for efficiency.

Sounds like your C program is buggy. Perhaps you should post your C program to the programming forum for help.

Perl and AWK (gawk, mawk, nawk, busybox awk) are C programs themselves. And since they're general purpose interpreters, your specialized C program should not be outperformed.

Regards,
Alister