If the following example, which sets the `IFS` environment variable to a line feed character...

```
IFS=$'\n'

```

* What does the **dollar sign** mean
**exactly**?
* What does it do in this specific
case?
* Where can I read more on this specific usage (Google doesn't allow special characters in searches and I don't know what to look for otherwise)?

I know what the `IFS` environment variable is, and what the `\n` character is (line feed), but why not just use the following form: 
`IFS="\n"` (which does not work)?

For example, if I want to loop through every line of a file and want to use a for loop, I could do this:

```
for line in (< /path/to/file); do
    echo "Line: $line"
done

```

However, this won't work right unless `IFS` is set to a line feed character. To get it to work, I'd have to do this:

```
OLDIFS=$IFS
IFS=$'\n'
for line in (< /path/to/file); do
    echo "Line: $line"
done
IFS=$OLDIFS

```

**Note:** I don't need another way for doing the same thing, I know many other already... I'm only curious about that `$'\n'` and wondered if anyone could give me an explanation on it.