regex - sed insert line command OSX

Question

I'm trying to insert text to the third line in a file using sed, and the syntax I've found on other forums is:

sed -i '' "3i text to insert" file

When I use this however, I get an error:

sed: 1: "3i text to insert": extra characters after  at the end of i command

I can't seem to figure out what is causing the problem. I'm using OSX, which is why I have an empty ' ' as my extension.

Thanks!

Answer 1

You should put a newline directly after the :

sed '3i
text to insert' file

This is actually the behaviour defined by the POSIX specification. The fact that GNU sed allows you to specify the text to be inserted on the same line is an extension.

---

If for some reason you need to use double quotes around the sed command, then you must escape the backslash at the end of the first line:

sed "3i\
text to insert" file

This is because a double-quoted string is processed first by the shell, and followed by a newline is removed:

$ echo "abc
def"
abcdef