Get specific line from text file using just shell script

I am trying to get a specific line from a text file.

So far, online I have only seen stuff like sed, (I can only use the sh -not bash or sed or anything like that). I need to do this only using a basic shell script.

cat file | while read line
    do
       #do something
    done

I know how to iterate through lines, as shown above, but what if I just need to get the contents of a particular line

sed:

sed '5!d' file

awk:

awk 'NR==5' file

Assuming line is a variable which holds your required line number, if you can use head and tail, then it is quite simple:

head -n $line file | tail -1

If not, this should work:

x=0
want=5
cat lines | while read line; do
  x=$(( x+1 ))
  if [ $x -eq "$want" ]; then
    echo $line
    break
  fi
done

You could use sed -n 5p file.

You can also get a range, e.g., sed -n 5,10p file.