I have a file with this content:

```
dog 
cat

```

and I want to add a sentence (I have a) before every sentence, so the new content should be:

```
I have a dog
I have a cat

```

I tried with

```
sed -i 'I have a ' file

```

But I get something like this

```
I have a 
dog
I have a
cat

```

Which would be the correct use of sed? Is there another way of doing?