How do I prepend a text to a file (the opposite of >>)?
You cannot do it with bash redirections alone; the opposite of >> does not exist....
To insert content at the beginning of a file, you can use an editor:
ed -s file << EOF 1i header line 1 header line 2 . w EOF
Please note that this will not work if the file is empty. ed will also add a newline character to the end of the file if it's missing.
Or you can rewrite the file, using things like:
{ echo line; cat file ;} >tmpfile && mv tmpfile file
echo line | cat - file > tmpfile && mv tmpfile fileor lots of other solutions.