Struct Regex

pub struct Regex(/* private fields */);

A compiled regular expression.

Implementations

impl Regex

pub fn new(re: &str) -> Result<Regex>

Parse and compile a regex with default options, see RegexBuilder.

Returns an Error if the pattern could not be parsed.

pub fn as_str(&self) -> &str

Returns the original string of this regex.

pub fn is_match(&self, text: &str) -> Result<bool>

Check if the regex matches the input text.

Example

Test if some text contains the same word twice:

let re = Regex::new(r"(\w+) \1").unwrap();
assert!(re.is_match("mirror mirror on the wall").unwrap());

pub fn find<'t>(&self, text: &'t str) -> Result<Option<Match<'t>>>

Find the first match in the input text.

If you have capturing groups in your regex that you want to extract, use the [captures()] method.

Example

Find a word that is followed by an exclamation point:

let re = Regex::new(r"\w+(?=!)").unwrap();
assert_eq!(re.find("so fancy!").unwrap().unwrap().as_str(), "fancy");

pub fn captures<'t>(&self, text: &'t str) -> Result<Option<Captures<'t>>>

Returns the capture groups for the first match in text.

If no match is found, then Ok(None) is returned.

Examples

Finding matches and capturing parts of the match:

let re = Regex::new(r"(\d{4})-(\d{2})-(\d{2})").unwrap();
let text = "The date was 2018-04-07";
let captures = re.captures(text).unwrap().unwrap();

assert_eq!(captures.get(1).unwrap().as_str(), "2018");
assert_eq!(captures.get(2).unwrap().as_str(), "04");
assert_eq!(captures.get(3).unwrap().as_str(), "07");
assert_eq!(captures.get(0).unwrap().as_str(), "2018-04-07");

pub fn captures_from_pos<'t>( &self, text: &'t str, pos: usize, ) -> Result<Option<Captures<'t>>>

Returns the capture groups for the first match in text, starting from the specified byte position pos.

Examples

Finding captures starting at a position:

let re = Regex::new(r"(?m:^)(\d+)").unwrap();
let text = "1 test 123\n2 foo";
let captures = re.captures_from_pos(text, 7).unwrap().unwrap();

let group = captures.get(1).unwrap();
assert_eq!(group.as_str(), "2");
assert_eq!(group.start(), 11);
assert_eq!(group.end(), 12);

Note that in some cases this is not the same as using the captures methods and passing a slice of the string, see the capture that we get when we do this:

let re = Regex::new(r"(?m:^)(\d+)").unwrap();
let text = "1 test 123\n2 foo";
let captures = re.captures(&text[7..]).unwrap().unwrap();
assert_eq!(captures.get(1).unwrap().as_str(), "123");

This matched the number “123” because it’s at the beginning of the text of the string slice.

Trait Implementations

impl Debug for Regex

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Shows the original regular expression.