Trim

fn main() {
    let s = "   Hello Rust!   ";
    // trim移除字符串开始末尾的空格 
    // "Hello Rust!"
    println!("{}", s.trim());

    // trim_start移除字符串开始的空格
    // "Hello Rust!   "
    println!("{}", s.trim_start());

    // trim_end移除字符串末尾的空格
    // "   Hello Rust!"
    println!("{}", s.trim_end());

    let s = "abcabcabcHello Rust!abcabcabc";

    // trim_start_matches移除字符串开始匹配的字符串
    // "Hello Rust!abcabcabc"
    println!("{}", s.trim_start_matches("abc"));

    // trim_start_matches移除字符串开始匹配的字符串
    // "abcabcabcHello Rust!"
    println!("{}", s.trim_end_matches("abc"));
}