1.返回字符串的長度

chomp和chop的區別:

chomp:去掉字符串末尾的/n或/r
chop:去掉字符串末尾的最后一個字符,不管是/n/r還是普通字符

split是String類的一個類方法，我根據ri String.split提供的內容簡單翻譯一下。
----------------------------------------------------------- String#split
str.split(pattern=$;, [limit]) => anArray
------------------------------------------------------------------------
Divides _str_ into substrings based on a delimiter, returning an
array of these substrings.
將一個字符串用分隔符分割成一些子字符串，并返回一個包含這些子字符串的數組。

If _pattern_ is a +String+, then its contents are used as the
delimiter when splitting _str_. If _pattern_ is a single space,
_str_ is split on whitespace, with leading whitespace and runs of
contiguous whitespace characters ignored.
如果pattern部分是一個字符串，那么用它作分割符來分隔，如果pattern是一個空格，那么在空格處分割，并且臨近的空格被忽略。

If _pattern_ is a +Regexp+, _str_ is divided where the pattern
matches. Whenever the pattern matches a zero-length string, _str_
is split into individual characters.
如果pattern是個正則表達式，那么在匹配pattern的地方分割，當pattern是長度為0的字符串，那么split將把字符串分割為單個字符

If _pattern_ is omitted, the value of +$;+ is used. If +$;+ is
+nil+ (which is the default), _str_ is split on whitespace as if `
' were specified.
如果pattern被忽略，將用$;來分隔，如果$;沒有設置（就是在默認狀態），split將制定空格' '
If the _limit_ parameter is omitted, trailing null fields are
suppressed. If _limit_ is a positive number, at most that number of
fields will be returned (if _limit_ is +1+, the entire string is
returned as the only entry in an array). If negative, there is no
limit to the number of fields returned, and trailing null fields
are not suppressed.
如果limit參數被忽略，跟蹤空段被抑制，如果limit是個正數，那么至多返回limit個字段（如果是1，那么將整個字符串作為一個字段返回），如果是個負數，那么跟蹤空段不被抑制。

" now's the time".split #=> ["now's", "the", "time"]
" now's the time".split(' ') #=> ["now's", "the", "time"]
" now's the time".split(/ /) #=> ["", "now's", "", "the", "time"]
"1, 2.34,56, 7".split(%r{,/s*}) #=> ["1", "2.34", "56", "7"]
"hello".split(//) #=> ["h", "e", "l", "l", "o"]
"hello".split(//, 3) #=> ["h", "e", "llo"]
"hi mom".split(%r{/s*}) #=> ["h", "i", "m", "o", "m"]

"mellow yellow".split("ello") #=> ["m", "w y", "w"]
"1,2,,3,4,,".split(' ,') #=> ["1", "2", "", "3", "4"]
"1,2,,3,4,,".split(',', 4) #=> ["1", "2", "", "3,4,,"]
"1,2,,3,4,,".split(',', -4) #=> ["1", "2", "", "3", "4", "", ""]

如果包含特殊字符，注意轉義
"wo | shi | yi | ge | bing".split(//s*/|/s*) #豎杠別忘了轉義

還有它和String.scan的區別，split中的pattern是分隔符，而scan中的pattern指的是要匹配的東西。

"123=342=4234=523421=6424".scan(//d+/) #=> ["123","342","4234","523421","6424"]


如果匹配項被括起來，那么則會保留分割符，例如：

"Three little words".split(//s+/) #===>["three","little",words"]
"Three little words".split(/(/s+)/) #===>["three"," ","little"," ","words"] 保留了空格