Class: String

Returns true if str has a length of zero.

"hello".empty?   #=> false
" ".empty?       #=> false
"".empty?        #=> true

Returns true for a string which encoded correctly.

"\xc2\xa1".force_encoding("UTF-8").valid_encoding?  #=> true
"\xc2".force_encoding("UTF-8").valid_encoding?      #=> false
"\x80".force_encoding("UTF-8").valid_encoding?      #=> false

Copy — Returns a new String containing integer copies of the receiver. integer must be greater than or equal to 0.

"Ho! " * 3   #=> "Ho! Ho! Ho! "
"Ho! " * 0   #=> ""

Concatenation—Returns a new String containing other_str concatenated to str.

"Hello from " + self.to_s   #=> "Hello from main"

If the string is frozen, then return duplicated mutable string.

If the string is not frozen, then return the string itself.

If the string is frozen, then return the string itself.

If the string is not frozen, then duplicate the string freeze it and return it.

Append—Concatenates the given object to str. If the object is a ::Integer, it is considered as a codepoint, and is converted to a character before concatenation.

a = "hello "
a << "world"   #=> "hello world"
a.concat(33)   #=> "hello world!"

Comparison—Returns -1, 0, +1 or nil depending on whether string is less than, equal to, or greater than other_string.

nil is returned if the two values are incomparable.

If the strings are of different lengths, and the strings are equal when compared up to the shortest length, then the longer string is considered greater than the shorter one.

<=> is the basis for the methods <, <=, >, >=, and between?, included from module ::Comparable. The method #== does not use Comparable#==.

"abcdef" <=> "abcde"     #=> 1
"abcdef" <=> "abcdef"    #=> 0
"abcdef" <=> "abcdefg"   #=> -1
"abcdef" <=> "ABCDEF"    #=> 1
"abcdef" <=> 1           #=> nil

Equality

Returns whether str == obj, similar to Object#==.

If obj is not an instance of String but responds to #to_str, then the two strings are compared using case equality Object#===.

Otherwise, returns similarly to #eql?, comparing length and content.

Alias for #==.

Match—If obj is a ::Regexp, use it as a pattern to match against str,and returns the position the match starts, or nil if there is no match. Otherwise, invokes obj.=~, passing str as an argument. The default =~ in ::Object returns nil.

Note: str =~ regexp is not the same as regexp =~ str. Strings captured from named capture groups are assigned to local variables only in the second case.

"cat o' 9 tails" =~ /\d/   #=> 7
"cat o' 9 tails" =~ 9      #=> nil

Element Reference — If passed a single #index, returns a substring of one character at that index. If passed a start index and a #length, returns a substring containing #length characters starting at the start index. If passed a range, its beginning and end are interpreted as offsets delimiting the substring to be returned.

In these three cases, if an index is negative, it is counted from the end of the string. For the start and range cases the starting index is just before a character and an index matching the string's size. Additionally, an empty string is returned when the starting index for a character range is at the end of the string.

Returns nil if the initial index falls outside the string or the length is negative.

If a ::Regexp is supplied, the matching portion of the string is returned. If a capture follows the regular expression, which may be a capture group index or name, follows the regular expression that component of the ::MatchData is returned instead.

If a match_str is given, that string is returned if it occurs in the string.

Returns nil if the regular expression does not match or the match string cannot be found.

a = "hello there"

a[1]                   #=> "e"
a[2, 3]                #=> "llo"
a[2..3]                #=> "ll"

a[-3, 2]               #=> "er"
a[7..-2]               #=> "her"
a[-4..-2]              #=> "her"
a[-2..-4]              #=> ""

a[11, 0]               #=> ""
a[11]                  #=> nil
a[12, 0]               #=> nil
a[12..-1]              #=> nil

a[/[aeiou](.)\1/]      #=> "ell"
a[/[aeiou](.)\1/, 0]   #=> "ell"
a[/[aeiou](.)\1/, 1]   #=> "l"
a[/[aeiou](.)\1/, 2]   #=> nil

a[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, "non_vowel"] #=> "l"
a[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, "vowel"]     #=> "e"

a["lo"]                #=> "lo"
a["bye"]               #=> nil

Element Assignment—Replaces some or all of the content of str. The portion of the string affected is determined using the same criteria as #[]. If the replacement string is not the same length as the text it is replacing, the string will be adjusted accordingly. If the regular expression or string is used as the index doesn't match a position in the string, ::IndexError is raised. If the regular expression form is used, the optional second ::Fixnum allows you to specify which portion of the match to replace (effectively using the ::MatchData indexing rules. The forms that take a ::Fixnum will raise an ::IndexError if the value is out of range; the ::Range form will raise a ::RangeError, and the ::Regexp and String will raise an ::IndexError on negative match.

Returns a copied string whose encoding is ASCII-8BIT.

Returns an array of bytes in str. This is a shorthand for str.each_byte.to_a.

If a block is given, which is a deprecated form, works the same as #each_byte.

Returns the length of str in bytes.

"\x80\u3042".bytesize  #=> 4
"hello".bytesize       #=> 5

Byte Reference—If passed a single ::Fixnum, returns a substring of one byte at that position. If passed two ::Fixnum objects, returns a substring starting at the offset given by the first, and a length given by the second. If given a ::Range, a substring containing bytes at offsets given by the range is returned. In all three cases, if an offset is negative, it is counted from the end of str. Returns nil if the initial offset falls outside the string, the length is negative, or the beginning of the range is greater than the end. The encoding of the resulted string keeps original encoding.

"hello".byteslice(1)     #=> "e"
"hello".byteslice(-1)    #=> "o"
"hello".byteslice(1, 2)  #=> "el"
"\x80\u3042".byteslice(1, 3) #=> "\u3042"
"\x03\u3042\xff".byteslice(1..3) #=> "\u3042"

Returns a copy of str with the first character converted to uppercase and the remainder to lowercase. Note: case conversion is effective only in ASCII region.

"hello".capitalize    #=> "Hello"
"HELLO".capitalize    #=> "Hello"
"123ABC".capitalize   #=> "123abc"

Modifies str by converting the first character to uppercase and the remainder to lowercase. Returns nil if no changes are made. Note: case conversion is effective only in ASCII region.

a = "hello"
a.capitalize!   #=> "Hello"
a               #=> "Hello"
a.capitalize!   #=> nil

Case-insensitive version of #<=>.

"abcdef".casecmp("abcde")     #=> 1
"aBcDeF".casecmp("abcdef")    #=> 0
"abcdef".casecmp("abcdefg")   #=> -1
"abcdef".casecmp("ABCDEF")    #=> 0

Centers str in width. If width is greater than the length of str, returns a new String of length width with str centered and padded with padstr; otherwise, returns str.

"hello".center(4)         #=> "hello"
"hello".center(20)        #=> "       hello        "
"hello".center(20, '123') #=> "1231231hello12312312"

Returns an array of characters in str. This is a shorthand for str.each_char.to_a.

If a block is given, which is a deprecated form, works the same as #each_char.

Returns a new String with the given record separator removed from the end of str (if present). If $/ has not been changed from the default Ruby record separator, then chomp also removes carriage return characters (that is it will remove \n, \r, and \r\n). If $/ is an empty string, it will remove all trailing newlines from the string.

"hello".chomp                #=> "hello"
"hello\n".chomp              #=> "hello"
"hello\r\n".chomp            #=> "hello"
"hello\n\r".chomp            #=> "hello\n"
"hello\r".chomp              #=> "hello"
"hello \n there".chomp       #=> "hello \n there"
"hello".chomp("llo")         #=> "he"
"hello\r\n\r\n".chomp('')    #=> "hello"
"hello\r\n\r\r\n".chomp('')  #=> "hello\r\n\r"

Modifies str in place as described for #chomp, returning str, or nil if no modifications were made.

Returns a new String with the last character removed. If the string ends with \r\n, both characters are removed. Applying chop to an empty string returns an empty string. #chomp is often a safer alternative, as it leaves the string unchanged if it doesn't end in a record separator.

"string\r\n".chop   #=> "string"
"string\n\r".chop   #=> "string\n"
"string\n".chop     #=> "string"
"string".chop       #=> "strin"
"x".chop.chop       #=> ""

Processes str as for #chop, returning str, or nil if str is the empty string. See also #chomp!.

Returns a one-character string at the beginning of the string.

a = "abcde"
a.chr    #=> "a"

Makes string empty.

a = "abcde"
a.clear    #=> ""

Returns an array of the ::Integer ordinals of the characters in str. This is a shorthand for str.each_codepoint.to_a.

If a block is given, which is a deprecated form, works the same as #each_codepoint.

Alias for #<<.

Each other_str parameter defines a set of characters to count. The intersection of these sets defines the characters to count in str. Any other_str that starts with a caret ^ is negated. The sequence c1-c2 means all characters between c1 and c2. The backslash character \ can be used to escape ^ or - and is otherwise ignored unless it appears at the end of a sequence or the end of a other_str.

a = "hello world"
a.count "lo"                   #=> 5
a.count "lo", "o"              #=> 2
a.count "hello", "^l"          #=> 4
a.count "ej-m"                 #=> 4

"hello^world".count "\\^aeiou" #=> 4
"hello-world".count "a\\-eo"   #=> 4

c = "hello world\\r\\n"
c.count "\\"                   #=> 2
c.count "\\A"                  #=> 0
c.count "X-\\w"                #=> 3

Applies a one-way cryptographic hash to str by invoking the standard library function crypt(3) with the given salt string. While the format and the result are system and implementation dependent, using a salt matching the regular expression \A[a-zA-Z0-9./]{2} should be valid and safe on any platform, in which only the first two characters are significant.

This method is for use in system specific scripts, so if you want a cross-platform hash function consider using Digest or OpenSSL instead.

Returns a copy of str with all characters in the intersection of its arguments deleted. Uses the same rules for building the set of characters as #count.

"hello".delete "l","lo"        #=> "heo"
"hello".delete "lo"            #=> "he"
"hello".delete "aeiou", "^e"   #=> "hell"
"hello".delete "ej-m"          #=> "ho"

Performs a #delete operation in place, returning str, or nil if str was not modified.

Returns a copy of str with all uppercase letters replaced with their lowercase counterparts. The operation is locale insensitive—only characters “A'' to “Z'' are affected. Note: case replacement is effective only in ASCII region.

"hEllO".downcase   #=> "hello"

Downcases the contents of str, returning nil if no changes were made. Note: case replacement is effective only in ASCII region.

Produces a version of str with all non-printing characters replaced by \nnn notation and all special characters escaped.

"hello \n ''".dump  #=> "\"hello \\n ''\"

Passes each byte in str to the given block, or returns an enumerator if no block is given.

"hello".each_byte {|c| print c, ' ' }

produces:

104 101 108 108 111

Passes each character in str to the given block, or returns an enumerator if no block is given.

"hello".each_char {|c| print c, ' ' }

produces:

h e l l o

Passes the ::Integer ordinal of each character in str, also known as a codepoint when applied to Unicode strings to the given block.

If no block is given, an enumerator is returned instead.

"hello\u0639".each_codepoint {|c| print c, ' ' }

produces:

104 101 108 108 111 1593

Splits str using the supplied parameter as the record separator ($/ by default), passing each substring in turn to the supplied block. If a zero-length record separator is supplied, the string is split into paragraphs delimited by multiple successive newlines.

If no block is given, an enumerator is returned instead.

print "Example one\n"
"hello\nworld".each_line {|s| p s}
print "Example two\n"
"hello\nworld".each_line('l') {|s| p s}
print "Example three\n"
"hello\n\n\nworld".each_line('') {|s| p s}

produces:

Example one
"hello\n"
"world"
Example two
"hel"
"l"
"o\nworl"
"d"
Example three
"hello\n\n\n"
"world"

The first form returns a copy of str transcoded to encoding #encoding. The second form returns a copy of str transcoded from src_encoding to dst_encoding. The last form returns a copy of str transcoded to Encoding.default_internal.

By default, the first and second form raise ::Encoding::UndefinedConversionError for characters that are undefined in the destination encoding, and ::Encoding::InvalidByteSequenceError for invalid byte sequences in the source encoding. The last form by default does not raise exceptions but uses replacement strings.

The options ::Hash gives details for conversion and can have the following keys:

:invalid

If the value is :replace, #encode replaces invalid byte sequences in str with the replacement character. The default is to raise the Encoding::InvalidByteSequenceError exception

:undef

If the value is :replace, #encode replaces characters which are undefined in the destination encoding with the replacement character. The default is to raise the Encoding::UndefinedConversionError.

:replace

Sets the replacement string to the given value. The default replacement string is “uFFFD” for Unicode encoding forms, and “?” otherwise.

:fallback

Sets the replacement string by the given object for undefined character. The object should be a Hash, a Proc, a Method, or an object which has [] method. Its key is an undefined character encoded in the source encoding of current transcoder. Its value can be any encoding until it can be converted into the destination encoding of the transcoder.

:xml

The value must be :text or :attr. If the value is :text #encode replaces undefined characters with their (upper-case hexadecimal) numeric character references. '&', '<', and '>' are converted to “&amp;”, “&lt;”, and “&gt;”, respectively. If the value is :attr, #encode also quotes the replacement result (using '“'), and replaces '”' with “&quot;”.

:cr_newline

Replaces LF (“n”) with CR (“r”) if value is true.

:crlf_newline

Replaces LF (“n”) with CRLF (“rn”) if value is true.

:universal_newline

Replaces CRLF (“rn”) and CR (“r”) with LF (“n”) if value is true.

The first form transcodes the contents of str from str.encoding to #encoding. The second form transcodes the contents of str from src_encoding to dst_encoding. The options ::Hash gives details for conversion. See #encode for details. Returns the string even if no changes were made.

Alias for Regexp#encoding.

Returns true if str ends with one of the suffixes given.

"hello".end_with?("ello")               #=> true

# returns true if one of the suffixes matches.
"hello".end_with?("heaven", "ello")     #=> true
"hello".end_with?("heaven", "paradise") #=> false

Two strings are equal if they have the same length and content.

Changes the encoding to #encoding and returns self.

returns the indexth byte as an integer.

Returns a copy of str with the all occurrences of pattern substituted for the second argument. The pattern is typically a ::Regexp; if given as a String, any regular expression metacharacters it contains will be interpreted literally, e.g. '\\d' will match a backlash followed by 'd', instead of a digit.

If replacement is a String it will be substituted for the matched text. It may contain back-references to the pattern's capture groups of the form \\d, where d is a group number, or \\k<n>, where n is a group name. If it is a double-quoted string, both back-references must be preceded by an additional backslash. However, within replacement the special match variables, such as $&, will not refer to the current match.

If the second argument is a ::Hash, and the matched text is one of its keys, the corresponding value is the replacement string.

In the block form, the current match string is passed in as a parameter, and variables such as $1, $2, $`, $&, and $' will be set appropriately. The value returned by the block will be substituted for the match on each call.

The result inherits any tainting in the original string or any supplied replacement string.

When neither a block nor a second argument is supplied, an ::Enumerator is returned.

"hello".gsub(/[aeiou]/, '*')                  #=> "h*ll*"
"hello".gsub(/([aeiou])/, '<\1>')             #=> "h<e>ll<o>"
"hello".gsub(/./) {|s| s.ord.to_s + ' '}      #=> "104 101 108 108 111 "
"hello".gsub(/(?<foo>[aeiou])/, '{\k<foo>}')  #=> "h{e}ll{o}"
'hello'.gsub(/[eo]/, 'e' => 3, 'o' => '*')    #=> "h3ll*"

Performs the substitutions of #gsub in place, returning str, or nil if no substitutions were performed. If no block and no replacement is given, an enumerator is returned instead.

Return a hash based on the string's length, content and encoding.

See also Object#hash.

Treats leading characters from str as a string of hexadecimal digits (with an optional sign and an optional 0x) and returns the corresponding number. Zero is returned on error.

"0x0a".hex     #=> 10
"-1234".hex    #=> -4660
"0".hex        #=> 0
"wombat".hex   #=> 0

Returns true if str contains the given string or character.

"hello".include? "lo"   #=> true
"hello".include? "ol"   #=> false
"hello".include? ?h     #=> true

Returns the index of the first occurrence of the given substring or pattern (regexp) in str. Returns nil if not found. If the second parameter is present, it specifies the position in the string to begin the search.

"hello".index('e')             #=> 1
"hello".index('lo')            #=> 3
"hello".index('a')             #=> nil
"hello".index(?e)              #=> 1
"hello".index(/[aeiou]/, -3)   #=> 4

Alias for #replace.

Inserts other_str before the character at the given index, modifying str. Negative indices count from the end of the string, and insert after the given character. The intent is insert aString so that it starts at the given index.

"abcd".insert(0, 'X')    #=> "Xabcd"
"abcd".insert(3, 'X')    #=> "abcXd"
"abcd".insert(4, 'X')    #=> "abcdX"
"abcd".insert(-3, 'X')   #=> "abXcd"
"abcd".insert(-1, 'X')   #=> "abcdX"

Returns a printable version of str, surrounded by quote marks, with special characters escaped.

str = "hello"
str[3] = "\b"
str.inspect       #=> "\"hel\\bo\""

Returns the ::Symbol corresponding to str, creating the symbol if it did not previously exist. See Symbol#id2name.

"Koala".intern         #=> :Koala
s = 'cat'.to_sym       #=> :cat
s == :cat              #=> true
s = '@cat'.to_sym      #=> :@cat
s == :@cat             #=> true

This can also be used to create symbols that cannot be represented using the :xxx notation.

'cat and dog'.to_sym   #=> :"cat and dog"

Returns the character length of str.

Returns an array of lines in str split using the supplied record separator ($/ by default). This is a shorthand for str.each_line(separator).to_a.

If a block is given, which is a deprecated form, works the same as #each_line.

If integer is greater than the length of str, returns a new String of length integer with str left justified and padded with padstr; otherwise, returns str.

"hello".ljust(4)            #=> "hello"
"hello".ljust(20)           #=> "hello               "
"hello".ljust(20, '1234')   #=> "hello123412341234123"

Returns a copy of str with leading whitespace removed. See also #rstrip and #strip.

Refer to #strip for the definition of whitespace.

"  hello  ".lstrip   #=> "hello  "
"hello".lstrip       #=> "hello"

Removes leading whitespace from str, returning nil if no change was made. See also #rstrip! and #strip!.

Refer to #strip for the definition of whitespace.

"  hello  ".lstrip   #=> "hello  "
"hello".lstrip!      #=> nil

Converts pattern to a ::Regexp (if it isn't already one), then invokes its match method on str. If the second parameter is present, it specifies the position in the string to begin the search.

'hello'.match('(.)\1')      #=> #<MatchData "ll" 1:"l">
'hello'.match('(.)\1')[0]   #=> "ll"
'hello'.match(/(.)\1/)[0]   #=> "ll"
'hello'.match('xx')         #=> nil

If a block is given, invoke the block with ::MatchData if match succeed, so that you can write

str.match(pat) {|m| ...}

instead of

if m = str.match(pat)
  #...
end

The return value is a value from block execution in this case.

Returns the successor to str. The successor is calculated by incrementing characters starting from the rightmost alphanumeric (or the rightmost character if there are no alphanumerics) in the string. Incrementing a digit always results in another digit, and incrementing a letter results in another letter of the same case. Incrementing nonalphanumerics uses the underlying character set's collating sequence.

If the increment generates a “carry,'' the character to the left of it is incremented. This process repeats until there is no carry, adding an additional character if necessary.

"abcd".succ        #=> "abce"
"THX1138".succ     #=> "THX1139"
"<<koala>>".succ   #=> "<<koalb>>"
"1999zzz".succ     #=> "2000aaa"
"ZZZ9999".succ     #=> "AAAA0000"
"***".succ         #=> "**+"

Equivalent to #succ, but modifies the receiver in place.

Treats leading characters of str as a string of octal digits (with an optional sign) and returns the corresponding number. Returns 0 if the conversion fails.

"123".oct       #=> 83
"-377".oct      #=> -255
"bad".oct       #=> 0
"0377bad".oct   #=> 255

If str starts with 0, radix indicators are hornored. See Kernel.Integer.

Return the ::Integer ordinal of a one-character string.

"a".ord         #=> 97

Searches sep or pattern (regexp) in the string and returns the part before it, the match, and the part after it. If it is not found, returns two empty strings and str.

"hello".partition("l")         #=> ["he", "l", "lo"]
"hello".partition("x")         #=> ["hello", "", ""]
"hello".partition(/.l/)        #=> ["h", "el", "lo"]

Prepend—Prepend the given string to str.

a = "world"
a.prepend("hello ") #=> "hello world"
a                   #=> "hello world"

Replaces the contents and taintedness of str with the corresponding values in other_str.

s = "hello"         #=> "hello"
s.replace "world"   #=> "world"

Returns a new string with the characters from str in reverse order.

"stressed".reverse   #=> "desserts"

Reverses str in place.

Returns the index of the last occurrence of the given substring or pattern (regexp) in str. Returns nil if not found. If the second parameter is present, it specifies the position in the string to end the search—characters beyond this point will not be considered.

"hello".rindex('e')             #=> 1
"hello".rindex('l')             #=> 3
"hello".rindex('a')             #=> nil
"hello".rindex(?e)              #=> 1
"hello".rindex(/[aeiou]/, -2)   #=> 1

If integer is greater than the length of str, returns a new String of length integer with str right justified and padded with padstr; otherwise, returns str.

"hello".rjust(4)            #=> "hello"
"hello".rjust(20)           #=> "               hello"
"hello".rjust(20, '1234')   #=> "123412341234123hello"

Searches sep or pattern (regexp) in the string from the end of the string, and returns the part before it, the match, and the part after it. If it is not found, returns two empty strings and str.

"hello".rpartition("l")         #=> ["hel", "l", "o"]
"hello".rpartition("x")         #=> ["", "", "hello"]
"hello".rpartition(/.l/)        #=> ["he", "ll", "o"]

Returns a copy of str with trailing whitespace removed. See also #lstrip and #strip.

Refer to #strip for the definition of whitespace.

"  hello  ".rstrip   #=> "  hello"
"hello".rstrip       #=> "hello"

Removes trailing whitespace from str, returning nil if no change was made. See also #lstrip! and #strip!.

Refer to #strip for the definition of whitespace.

"  hello  ".rstrip   #=> "  hello"
"hello".rstrip!      #=> nil

Both forms iterate through str, matching the pattern (which may be a ::Regexp or a String). For each match, a result is generated and either added to the result array or passed to the block. If the pattern contains no groups, each individual result consists of the matched string, $&. If the pattern contains groups, each individual result is itself an array containing one entry per group.

a = "cruel world"
a.scan(/\w+/)        #=> ["cruel", "world"]
a.scan(/.../)        #=> ["cru", "el ", "wor"]
a.scan(/(...)/)      #=> [["cru"], ["el "], ["wor"]]
a.scan(/(..)(..)/)   #=> [["cr", "ue"], ["l ", "wo"]]

And the block form:

a.scan(/\w+/) {|w| print "<<#{w}>> " }
print "\n"
a.scan(/(.)(.)/) {|x,y| print y, x }
print "\n"

produces:

<<cruel>> <<world>>
rceu lowlr

If the string is invalid byte sequence then replace invalid bytes with given replacement character, else returns self. If block is given, replace invalid bytes with returned value of the block.

"abc\u3042\x81".scrub #=> "abc\u3042\uFFFD"
"abc\u3042\x81".scrub("*") #=> "abc\u3042*"
"abc\u3042\xE3\x80".scrub{|bytes| '<'bytes.unpack('H*')[0]'>' } #=> "abc\u3042<e380>"

If the string is invalid byte sequence then replace invalid bytes with given replacement character, else returns self. If block is given, replace invalid bytes with returned value of the block.

"abc\u3042\x81".scrub! #=> "abc\u3042\uFFFD"
"abc\u3042\x81".scrub!("*") #=> "abc\u3042*"
"abc\u3042\xE3\x80".scrub!{|bytes| '<'bytes.unpack('H*')[0]'>' } #=> "abc\u3042<e380>"

modifies the indexth byte as integer.

Alias for #length.

Alias for #[].

Deletes the specified portion from str, and returns the portion deleted.

string = "this is a string"
string.slice!(2)        #=> "i"
string.slice!(3..6)     #=> " is "
string.slice!(/s.*t/)   #=> "sa st"
string.slice!("r")      #=> "r"
string                  #=> "thing"

Divides str into substrings based on a delimiter, returning an array of these substrings.

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.

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. If pattern contains groups, the respective matches will be returned in the array as well.

If pattern is nil, the value of $; is used. If $; is nil (which is the default), str is split on whitespace as if ` ' were specified.

If the limit parameter is omitted, trailing null fields are suppressed. If limit is a positive number, at most that number of split substrings will be returned (captured groups will be returned as well, but are not counted towards the limit). 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.

When the input str is empty an empty ::Array is returned as the string is considered to have no fields to split.

" 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", "", ""]

"1:2:3".split(/(:)()()/, 2)     #=> ["1", ":", "", "", "2:3"]

"".split(',', -1)               #=> []

Builds a set of characters from the other_str parameter(s) using the procedure described for #count. Returns a new string where runs of the same character that occur in this set are replaced by a single character. If no arguments are given, all runs of identical characters are replaced by a single character.

"yellow moon".squeeze                  #=> "yelow mon"
"  now   is  the".squeeze(" ")         #=> " now is the"
"putters shoot balls".squeeze("m-z")   #=> "puters shot balls"

Squeezes str in place, returning either str, or nil if no changes were made.

Returns true if str starts with one of the prefixes given.

"hello".start_with?("hell")               #=> true

# returns true if one of the prefixes matches.
"hello".start_with?("heaven", "hell")     #=> true
"hello".start_with?("heaven", "paradise") #=> false

Returns a copy of str with leading and trailing whitespace removed.

Whitespace is defined as any of the following characters: null, horizontal tab, line feed, vertical tab, form feed, carriage return, space.

"    hello    ".strip   #=> "hello"
"\tgoodbye\r\n".strip   #=> "goodbye"
"\x00\t\n\v\f\r ".strip #=> ""

Removes leading and trailing whitespace from str. Returns nil if str was not altered.

Refer to #strip for the definition of whitespace.

Returns a copy of str with the first occurrence of pattern replaced by the second argument. The pattern is typically a Regexp; if given as a String, any regular expression metacharacters it contains will be interpreted literally, e.g. '\\d' will match a backlash followed by 'd', instead of a digit.

If replacement is a String it will be substituted for the matched text. It may contain back-references to the pattern's capture groups of the form "\d", where d is a group number, or "\k<n>", where n is a group name. If it is a double-quoted string, both back-references must be preceded by an additional backslash. However, within replacement the special match variables, such as &$, will not refer to the current match. If replacement is a String that looks like a pattern's capture group but is actually not a pattern capture group e.g. "\'", then it will have to be preceded by two backslashes like so "\\'".

If the second argument is a ::Hash, and the matched text is one of its keys, the corresponding value is the replacement string.

In the block form, the current match string is passed in as a parameter, and variables such as $1, $2, $`, $&, and $' will be set appropriately. The value returned by the block will be substituted for the match on each call.

The result inherits any tainting in the original string or any supplied replacement string.

"hello".sub(/[aeiou]/, '*')                  #=> "h*llo"
"hello".sub(/([aeiou])/, '<\1>')             #=> "h<e>llo"
"hello".sub(/./) {|s| s.ord.to_s + ' ' }     #=> "104 ello"
"hello".sub(/(?<foo>[aeiou])/, '*\k<foo>*')  #=> "h*e*llo"
'Is SHELL your preferred shell?'.sub(/[[:upper:]]{2,}/, ENV)
 #=> "Is /bin/bash your preferred shell?"

Performs the same substitution as #sub in-place.

Returns str if a substitution was performed or nil if no substitution was performed.

Alias for #next.

Alias for #next!.

Returns a basic n-bit checksum of the characters in str, where n is the optional ::Fixnum parameter, defaulting to 16. The result is simply the sum of the binary value of each byte in str modulo 2**n - 1. This is not a particularly good checksum.

Returns a copy of str with uppercase alphabetic characters converted to lowercase and lowercase characters converted to uppercase. Note: case conversion is effective only in ASCII region.

"Hello".swapcase          #=> "hELLO"
"cYbEr_PuNk11".swapcase   #=> "CyBeR_pUnK11"

Equivalent to #swapcase, but modifies the receiver in place, returning str, or nil if no changes were made. Note: case conversion is effective only in ASCII region.

Returns a complex which denotes the string form. The parser ignores leading whitespaces and trailing garbage. Any digit sequences can be separated by an underscore. Returns zero for null or garbage string.

'9'.to_c           #=> (9+0i)
'2.5'.to_c         #=> (2.5+0i)
'2.5/1'.to_c       #=> ((5/2)+0i)
'-3/2'.to_c        #=> ((-3/2)+0i)
'-i'.to_c          #=> (0-1i)
'45i'.to_c         #=> (0+45i)
'3-4i'.to_c        #=> (3-4i)
'-4e2-4e-2i'.to_c  #=> (-400.0-0.04i)
'-0.0-0.0i'.to_c   #=> (-0.0-0.0i)
'1/2+3/4i'.to_c    #=> ((1/2)+(3/4)*i)
'ruby'.to_c        #=> (0+0i)

See Kernel.Complex.

Returns the result of interpreting leading characters in str as a floating point number. Extraneous characters past the end of a valid number are ignored. If there is not a valid number at the start of str, 0.0 is returned. This method never raises an exception.

"123.45e1".to_f        #=> 1234.5
"45.67 degrees".to_f   #=> 45.67
"thx1138".to_f         #=> 0.0

Returns the result of interpreting leading characters in str as an integer base base (between 2 and 36). Extraneous characters past the end of a valid number are ignored. If there is not a valid number at the start of str, 0 is returned. This method never raises an exception when base is valid.

"12345".to_i             #=> 12345
"99 red balloons".to_i   #=> 99
"0a".to_i                #=> 0
"0a".to_i(16)            #=> 10
"hello".to_i             #=> 0
"1100101".to_i(2)        #=> 101
"1100101".to_i(8)        #=> 294977
"1100101".to_i(10)       #=> 1100101
"1100101".to_i(16)       #=> 17826049

Returns a rational which denotes the string form. The parser ignores leading whitespaces and trailing garbage. Any digit sequences can be separated by an underscore. Returns zero for null or garbage string.

NOTE: '0.3'.to_r isn't the same as 0.3.to_r. The former is equivalent to '3/10'.to_r, but the latter isn't so.

'  2  '.to_r       #=> (2/1)
'300/2'.to_r       #=> (150/1)
'-9.2'.to_r        #=> (-46/5)
'-9.2e2'.to_r      #=> (-920/1)
'1_234_567'.to_r   #=> (1234567/1)
'21 june 09'.to_r  #=> (21/1)
'21/06/09'.to_r    #=> (7/2)
'bwv 1079'.to_r    #=> (0/1)

See Kernel.Rational.

Returns self.

If called on a subclass of String, converts the receiver to a String object.

Alias for #to_s.

Alias for #intern.

Returns a copy of str with the characters in from_str replaced by the corresponding characters in #to_str. If #to_str is shorter than from_str, it is padded with its last character in order to maintain the correspondence.

"hello".tr('el', 'ip')      #=> "hippo"
"hello".tr('aeiou', '*')    #=> "h*ll*"
"hello".tr('aeiou', 'AA*')  #=> "hAll*"

Both strings may use the c1-c2 notation to denote ranges of characters, and from_str may start with a ^, which denotes all characters except those listed.

"hello".tr('a-y', 'b-z')    #=> "ifmmp"
"hello".tr('^aeiou', '*')   #=> "*e**o"

The backslash character \ can be used to escape ^ or - and is otherwise ignored unless it appears at the end of a range or the end of the from_str or #to_str:

"hello^world".tr("\\^aeiou", "*") #=> "h*ll**w*rld"
"hello-world".tr("a\\-eo", "*")   #=> "h*ll**w*rld"

"hello\r\nworld".tr("\r", "")   #=> "hello\nworld"
"hello\r\nworld".tr("\\r", "")  #=> "hello\r\nwold"
"hello\r\nworld".tr("\\\r", "") #=> "hello\nworld"

"X['\\b']".tr("X\\", "")   #=> "['b']"
"X['\\b']".tr("X-\\]", "") #=> "'b'"

Translates str in place, using the same rules as #tr. Returns str, or nil if no changes were made.

Processes a copy of str as described under #tr, then removes duplicate characters in regions that were affected by the translation.

"hello".tr_s('l', 'r')     #=> "hero"
"hello".tr_s('el', '*')    #=> "h*o"
"hello".tr_s('el', 'hx')   #=> "hhxo"

Performs #tr_s processing on str in place, returning str, or nil if no changes were made.

Decodes str (which may contain binary data) according to the format string, returning an array of each value extracted. The format string consists of a sequence of single-character directives, summarized in the table at the end of this entry. Each directive may be followed by a number, indicating the number of times to repeat with this directive. An asterisk (“*'') will use up all remaining elements. The directives sSiIlL may each be followed by an underscore (“_'') or exclamation mark (“!'') to use the underlying platform's native size for the specified type; otherwise, it uses a platform-independent consistent size. Spaces are ignored in the format string. See also Array#pack.

"abc \0\0abc \0\0".unpack('A6Z6')   #=> ["abc", "abc "]
"abc \0\0".unpack('a3a3')           #=> ["abc", " \000\000"]
"abc \0abc \0".unpack('Z*Z*')       #=> ["abc ", "abc "]
"aa".unpack('b8B8')                 #=> ["10000110", "01100001"]
"aaa".unpack('h2H2c')               #=> ["16", "61", 97]
"\xfe\xff\xfe\xff".unpack('sS')     #=> [-2, 65534]
"now=20is".unpack('M*')             #=> ["now is"]
"whole".unpack('xax2aX2aX1aX2a')    #=> ["h", "e", "l", "l", "o"]

This table summarizes the various formats and the Ruby classes returned by each.

Integer      |         |
Directive    | Returns | Meaning
-----------------------------------------------------------------
   C         | Integer | 8-bit unsigned (unsigned char)
   S         | Integer | 16-bit unsigned, native endian (uint16_t)
   L         | Integer | 32-bit unsigned, native endian (uint32_t)
   Q         | Integer | 64-bit unsigned, native endian (uint64_t)
             |         |
   c         | Integer | 8-bit signed (signed char)
   s         | Integer | 16-bit signed, native endian (int16_t)
   l         | Integer | 32-bit signed, native endian (int32_t)
   q         | Integer | 64-bit signed, native endian (int64_t)
             |         |
   S_, S!    | Integer | unsigned short, native endian
   I, I_, I! | Integer | unsigned int, native endian
   L_, L!    | Integer | unsigned long, native endian
   Q_, Q!    | Integer | unsigned long long, native endian (ArgumentError
             |         | if the platform has no long long type.)
             |         | (Q_ and Q! is available since Ruby 2.1.)
             |         |
   s_, s!    | Integer | signed short, native endian
   i, i_, i! | Integer | signed int, native endian
   l_, l!    | Integer | signed long, native endian
   q_, q!    | Integer | signed long long, native endian (ArgumentError
             |         | if the platform has no long long type.)
             |         | (q_ and q! is available since Ruby 2.1.)
             |         |
   S> L> Q>  | Integer | same as the directives without ">" except
   s> l> q>  |         | big endian
   S!> I!>   |         | (available since Ruby 1.9.3)
   L!> Q!>   |         | "S>" is same as "n"
   s!> i!>   |         | "L>" is same as "N"
   l!> q!>   |         |
             |         |
   S< L< Q<  | Integer | same as the directives without "<" except
   s< l< q<  |         | little endian
   S!< I!<   |         | (available since Ruby 1.9.3)
   L!< Q!<   |         | "S<" is same as "v"
   s!< i!<   |         | "L<" is same as "V"
   l!< q!<   |         |
             |         |
   n         | Integer | 16-bit unsigned, network (big-endian) byte order
   N         | Integer | 32-bit unsigned, network (big-endian) byte order
   v         | Integer | 16-bit unsigned, VAX (little-endian) byte order
   V         | Integer | 32-bit unsigned, VAX (little-endian) byte order
             |         |
   U         | Integer | UTF-8 character
   w         | Integer | BER-compressed integer (see Array.pack)

Float        |         |
Directive    | Returns | Meaning
-----------------------------------------------------------------
   D, d      | Float   | double-precision, native format
   F, f      | Float   | single-precision, native format
   E         | Float   | double-precision, little-endian byte order
   e         | Float   | single-precision, little-endian byte order
   G         | Float   | double-precision, network (big-endian) byte order
   g         | Float   | single-precision, network (big-endian) byte order

String       |         |
Directive    | Returns | Meaning
-----------------------------------------------------------------
   A         | String  | arbitrary binary string (remove trailing nulls and ASCII spaces)
   a         | String  | arbitrary binary string
   Z         | String  | null-terminated string
   B         | String  | bit string (MSB first)
   b         | String  | bit string (LSB first)
   H         | String  | hex string (high nibble first)
   h         | String  | hex string (low nibble first)
   u         | String  | UU-encoded string
   M         | String  | quoted-printable, MIME encoding (see RFC2045)
   m         | String  | base64 encoded string (RFC 2045) (default)
             |         | base64 encoded string (RFC 4648) if followed by 0
   P         | String  | pointer to a structure (fixed-length string)
   p         | String  | pointer to a null-terminated string

Misc.        |         |
Directive    | Returns | Meaning
-----------------------------------------------------------------
   @         | ---     | skip to the offset given by the length argument
   X         | ---     | skip backward one byte
   x         | ---     | skip forward one byte

Returns a copy of str with all lowercase letters replaced with their uppercase counterparts. The operation is locale insensitive—only characters “a'' to “z'' are affected. Note: case replacement is effective only in ASCII region.

"hEllO".upcase   #=> "HELLO"

Upcases the contents of str, returning nil if no changes were made. Note: case replacement is effective only in ASCII region.

Iterates through successive values, starting at str and ending at other_str inclusive, passing each value in turn to the block. The #succ method is used to generate each value. If optional second argument exclusive is omitted or is false, the last value will be included; otherwise it will be excluded.

If no block is given, an enumerator is returned instead.

"a8".upto("b6") {|s| print s, ' ' }
for s in "a8".."b6"
  print s, ' '
end

produces:

a8 a9 b0 b1 b2 b3 b4 b5 b6
a8 a9 b0 b1 b2 b3 b4 b5 b6

If str and other_str contains only ascii numeric characters, both are recognized as decimal numbers. In addition, the width of string (e.g. leading zeros) is handled appropriately.

"9".upto("11").to_a   #=> ["9", "10", "11"]
"25".upto("5").to_a   #=> []
"07".upto("11").to_a  #=> ["07", "08", "09", "10", "11"]