How do I split a string in Rust?

199
votes

From the documentation, it's not clear. In Java you could use the split method like so:

"some string 123 ffd".split("123");
5
rust
doc.rust-lang.org/std/string/struct.String.html – Dulguun Otgon
@bow Is there a way to make it a String array instead of a vector? – Greg
I'm not aware of any way to do that, directly at least. You'd probably have to manually iterate over the Split and set it into the array. Of course this means the number of items in each split must be the same since arrays are fixed size and you have to have the array defined before. I imagine this may be more trouble than simply creating a Vec. – bow

5 Answers

234
votes

Use split()

let mut split = "some string 123 ffd".split("123");

This gives an iterator, which you can loop over, or collect() into a vector.

for s in split {
    println!("{}", s)
}
let vec = split.collect::<Vec<&str>>();
// OR
let vec: Vec<&str> = split.collect();
80
votes

There are three simple ways:

  1. By separator:

     s.split("separator")  |  s.split('/')  |  s.split(char::is_numeric)

  2. By whitespace:

     s.split_whitespace()

  3. By newlines:

     s.lines()

  4. By regex: (using regex crate)

     Regex::new(r"\s").unwrap().split("one two three")

The result of each kind is an iterator:

let text = "foo\r\nbar\n\nbaz\n";
let mut lines = text.lines();

assert_eq!(Some("foo"), lines.next());
assert_eq!(Some("bar"), lines.next());
assert_eq!(Some(""), lines.next());
assert_eq!(Some("baz"), lines.next());

assert_eq!(None, lines.next());
42
votes

There is a special method split for struct String:

fn split<'a, P>(&'a self, pat: P) -> Split<'a, P> where P: Pattern<'a>

Split by char:

let v: Vec<&str> = "Mary had a little lamb".split(' ').collect();
assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);

Split by string:

let v: Vec<&str> = "lion::tiger::leopard".split("::").collect();
assert_eq!(v, ["lion", "tiger", "leopard"]);

Split by closure:

let v: Vec<&str> = "abc1def2ghi".split(|c: char| c.is_numeric()).collect();
assert_eq!(v, ["abc", "def", "ghi"]);
22
votes

split returns an Iterator, which you can convert into a Vec using collect: split_line.collect::<Vec<_>>(). Going through an iterator instead of returning a Vec directly has several advantages:

  • split is lazy. This means that it won't really split the line until you need it. That way it won't waste time splitting the whole string if you only need the first few values: split_line.take(2).collect::<Vec<_>>(), or even if you need only the first value that can be converted to an integer: split_line.filter_map(|x| x.parse::<i32>().ok()).next(). This last example won't waste time attempting to process the "23.0" but will stop processing immediately once it finds the "1".
  • split makes no assumption on the way you want to store the result. You can use a Vec, but you can also use anything that implements FromIterator<&str>, for example a LinkedList or a VecDeque, or any custom type that implements FromIterator<&str>.
9
votes

There's also split_whitespace()

fn main() {
    let words: Vec<&str> = "   foo   bar\t\nbaz   ".split_whitespace().collect();
    println!("{:?}", words);
    // ["foo", "bar", "baz"] 
}