Nth of a file - bis

Shell Programming and Scripting
1

I've seen that it has been suggested to use awk to show e.g. the 50th line in a file

awk 'NR==50{print;exit}' file

What about if instead of a number I try to use a variable? e.g. COUNT

awk 'NR==$COUNT{print;exit}' file
awk 'NR==${COUNT}{print;exit}' file

I can't make it work,

Thanks,

2 
awk 'NR == C {print;exit}' C=$COUNT file

Or

awk -v C=$COUNT 'NR == C {print;exit}' file

Or

awk 'NR == '$COUNT' {print; exit}' file

Or with sed:

sed -n "${COUNT}p" file

Or

head -$COUNT | tail -1

(etc...)