can add a text line to text files?
As an example, I have learned the under-mentioned code.
echo '/opt/lampp/lampp start' > /etc/rc.d/rc.local
But this caused only one line as the above-mentioned ceode at the file.
So, I should edit ever text files.
Is it possible to add a text line to a text file?
And one more, also is it possible to add a text line to some line of a text file?