regex

cargo add regex

.             any character except new line (includes new line with s flag)
\d            digit (\p{Nd})
\D            not digit
\pX           Unicode character class identified by a one-letter name
\p{Greek}     Unicode character class (general category or script)
\PX           Negated Unicode character class identified by a one-letter name
\P{Greek}     negated Unicode character class (general category or script)

[xyz]         A character class matching either x, y or z (union).
[^xyz]        A character class matching any character except x, y and z.
[a-z]         A character class matching any character in range a-z.
[[:alpha:]]   ASCII character class ([A-Za-z])
[[:^alpha:]]  Negated ASCII character class ([^A-Za-z])
[x[^xyz]]     Nested/grouping character class (matching any character except y and z)
[a-y&&xyz]    Intersection (matching x or y)
[0-9&&[^4]]   Subtraction using intersection and negation (matching 0-9 except 4)
[0-9--4]      Direct subtraction (matching 0-9 except 4)
[a-g~~b-h]    Symmetric difference (matching `a` and `h` only)
[\[\]]        Escaping in character classes (matching [ or ])

xy    concatenation (x followed by y)
x|y   alternation (x or y, prefer x)

x*        zero or more of x (greedy)
x+        one or more of x (greedy)
x?        zero or one of x (greedy)
x*?       zero or more of x (ungreedy/lazy)
x+?       one or more of x (ungreedy/lazy)
x??       zero or one of x (ungreedy/lazy)
x{n,m}    at least n x and at most m x (greedy)
x{n,}     at least n x (greedy)
x{n}      exactly n x
x{n,m}?   at least n x and at most m x (ungreedy/lazy)
x{n,}?    at least n x (ungreedy/lazy)
x{n}?     exactly n x

^     the beginning of text (or start-of-line with multi-line mode)
$     the end of text (or end-of-line with multi-line mode)
\A    only the beginning of text (even with multi-line mode enabled)
\z    only the end of text (even with multi-line mode enabled)
\b    a Unicode word boundary (\w on one side and \W, \A, or \z on other)
\B    not a Unicode word boundary

(exp)          numbered capture group (indexed by opening parenthesis)
(?P<name>exp)  named (also numbered) capture group (names must be alpha-numeric)
(?<name>exp)   named (also numbered) capture group (names must be alpha-numeric)
(?:exp)        non-capturing group
(?flags)       set flags within current group
(?flags:exp)   set flags for exp (non-capturing)

\*          literal *, works for any punctuation character: \.+*?()|[]{}^$
\a          bell (\x07)
\f          form feed (\x0C)
\t          horizontal tab
\n          new line
\r          carriage return
\v          vertical tab (\x0B)
\123        octal character code (up to three digits) (when enabled)
\x7F        hex character code (exactly two digits)
\x{10FFFF}  any hex character code corresponding to a Unicode code point
\u007F      hex character code (exactly four digits)
\u{7F}      any hex character code corresponding to a Unicode code point
\U0000007F  hex character code (exactly eight digits)
\U{7F}      any hex character code corresponding to a Unicode code point

[[:alnum:]]    alphanumeric ([0-9A-Za-z])
[[:alpha:]]    alphabetic ([A-Za-z])
[[:ascii:]]    ASCII ([\x00-\x7F])
[[:blank:]]    blank ([\t ])
[[:cntrl:]]    control ([\x00-\x1F\x7F])
[[:digit:]]    digits ([0-9])
[[:graph:]]    graphical ([!-~])
[[:lower:]]    lower case ([a-z])
[[:print:]]    printable ([ -~])
[[:punct:]]    punctuation ([!-/:-@\[-`{-~])
[[:space:]]    whitespace ([\t\n\v\f\r ])
[[:upper:]]    upper case ([A-Z])
[[:word:]]     word characters ([0-9A-Za-z_])
[[:xdigit:]]   hex digit ([0-9A-Fa-f])

use regex::Regex;
fn main() -> Result<(), Box<dyn std::error::Error>> {
    let input = "hello, world!";
    let pattern = Regex::new(r"hello, (world|universe)!")?;
    
    let is_match = pattern.is_match(input);
    println!("Is match: {}", is_match); // true
    Ok(())
}

    let pattern = regex::Regex::new(r"hello, (world|universe)!")?;
    let input = "hello, world!";
    let first_match = pattern.find(input);

    println!("First match: {}", first_match.unwrap().as_str());

    let pattern = regex::Regex::new(r"hello, (world|universe)!")?;
    let input = "hello, world! hello, universe!";
    let matches: Vec<_> = pattern.find_iter(input).collect(); // find_iter()
    matches.iter().for_each(|i| println!("{}", i.as_str()));
    // matches = Vec<match> и содержит все совпадения