Simple way to insert line to particular position in file

Question

I need to insert string to text file, for example, before first line from the end.

STRINGS=`wc -l $OLDFILE \
    | awk '{print $1-1}' \
    | sed "s/$DOLLAR/+/g" \
    | tr -d \\\n \
    | sed "s/+$DOLLAR//" \
    | bc`
ADDFILE=$3
head -n $STRINGS $OLDFILE > $NEWFILE
cat $ADDFILE >> $NEWFILE
tail -n 1 $OLDFILE >> $NEWFILE

Can you suggest simple way to perform that? Thanks

Answer 1

awk 'f==1{print last}{last=$0;f=1}END{print "NEW WORD\n"$0}' file

Answer 2

Maybe a bit simpler:

(tail -1 "$OLDFILE"; echo "hello there"; tac "$OLDFILE" | tail -n +2) | tac > "$NEWFILE"

Answer 3

Another (pure-bash) solution:

prev=
print=
while read line; do
    if [ "$print" ]; then
        echo $prev
    fi
    print=1
    prev="$line"
done < "$OLDFILE"
echo "hello there"
echo "$prev"

Answer 4

The most simple one:

head -n -1 "$OLDFILE"
echo "hello there"
tail -1 "$OLDFILE"