Shell Programming and Scripting

 
tail -r temp | nawk 'NR>30'|tail -r

awk 'NR==FNR{n=NR;next}FNR<=n-c-1' c=30 file file

awk 'NR>c{print A[NR%c]} {A[NR%c]=$0}' c=30 file

lines=$(cat x.txt | wc -l)  # numberOfLines

echo "--------------------------"
# delete lines between 1-$line = rest is output
sed  "1,${line}d" x.txt

echo "--------------------------"
((line=line-1))  
# print (p) starting from line $line to end
sed -n "$line,\$p" x.txt

tail -r temp | nawk 'NR>30'|tail -r