Question

I am using bash with linux to accomplish adding content to the top of a file.
Thus far i know that i am able to get this done by using a temporary file. so
i am doing it this way:

tac lines.bar > lines.foo
echo "a" >> lines.foo 
tac lines.foo > lines.bar 

But is there a better way of doing this without having to write a second file?

Answer 1

echo a | cat - file1 > file2

same as shellter’s

and sed in one line.

sed -i -e '1 i<whatever>' file1

this will insert to file1 inplace.
the sed example i referred to