String

Class

A String object has an arbitrary sequence of bytes, typically representing text or binary data. A String object may be created using String::new or as literals.

String objects differ from Symbol objects in that Symbol objects are designed to be used as identifiers, instead of text or data.

You can create a String object explicitly with:

You can convert certain objects to Strings with:

Some String methods modify self. Typically, a method whose name ends with ! modifies self and returns self; often a similarly named method (without the !) returns a new string.

In general, if there exist both bang and non-bang version of method, the bang! mutates and the non-bang! does not. However, a method without a bang can also mutate, such as String#replace.

Substitution Methods

These methods perform substitutions:

  • String#sub: One substitution (or none); returns a new string.

  • String#sub!: One substitution (or none); returns self.

  • String#gsub: Zero or more substitutions; returns a new string.

  • String#gsub!: Zero or more substitutions; returns self.

Each of these methods takes:

  • A first argument, pattern (string or regexp), that specifies the substring(s) to be replaced.

  • Either of these:

    • A second argument, replacement (string or hash), that determines the replacing string.

    • A block that will determine the replacing string.

The examples in this section mostly use methods String#sub and String#gsub; the principles illustrated apply to all four substitution methods.

Argument pattern

Argument pattern is commonly a regular expression:

s = 'hello'
s.sub(/[aeiou]/, '*')  # => "h*llo"
s.gsub(/[aeiou]/, '*') # => "h*ll*"
s.gsub(/[aeiou]/, '')  # => "hll"
s.sub(/ell/, 'al')     # => "halo"
s.gsub(/xyzzy/, '*')   # => "hello"
'THX1138'.gsub(/\d+/, '00') # => "THX00"

When pattern is a string, all its characters are treated as ordinary characters (not as regexp special characters):

'THX1138'.gsub('\d+', '00') # => "THX1138"

String replacement

If replacement is a string, that string will determine the replacing string that is to be substituted for the matched text.

Each of the examples above uses a simple string as the replacing string.

String replacement may contain back-references to the pattern’s captures:

  • \n (n a non-negative integer) refers to $n.

  • \k<name> refers to the named capture name.

See regexp.rdoc for details.

Note that within the string replacement, a character combination such as $& is treated as ordinary text, and not as a special match variable. However, you may refer to some special match variables using these combinations:

  • \& and \0 correspond to $&, which contains the complete matched text.

  • \' corresponds to $', which contains string after match.

  • \` corresponds to $`, which contains string before match.

  • + corresponds to $+, which contains last capture group.

See regexp.rdoc for details.

Note that \\ is interpreted as an escape, i.e., a single backslash.

Note also that a string literal consumes backslashes. See String Literals for details about string literals.

A back-reference is typically preceded by an additional backslash. For example, if you want to write a back-reference \& in replacement with a double-quoted string literal, you need to write "..\\&..".

If you want to write a non-back-reference string \& in replacement, you need first to escape the backslash to prevent this method from interpreting it as a back-reference, and then you need to escape the backslashes again to prevent a string literal from consuming them: "..\\\\&..".

You may want to use the block form to avoid a lot of backslashes.

Hash replacement

If argument replacement is a hash, and pattern matches one of its keys, the replacing string is the value for that key:

h = {'foo' => 'bar', 'baz' => 'bat'}
'food'.sub('foo', h) # => "bard"

Note that a symbol key does not match:

h = {foo: 'bar', baz: 'bat'}
'food'.sub('foo', h) # => "d"

Block

In the block form, the current match string is passed to the block; the block’s return value becomes the replacing string:

 s = '@'
'1234'.gsub(/\d/) {|match| s.succ! } # => "ABCD"

Special match variables such as $1, $2, $`, $&, and $' are set appropriately.

What’s Here

First, what’s elsewhere. Class String:

Here, class String provides methods that are useful for:

Methods for Creating a String

  • ::new

    Returns a new string.

  • ::try_convert

    Returns a new string created from a given object.

Methods for a Frozen/Unfrozen String

  • #+string

    Returns a string that is not frozen: self, if not frozen; self.dup otherwise.

  • #-string

    Returns a string that is frozen: self, if already frozen; self.freeze otherwise.

  • freeze

    Freezes self, if not already frozen; returns self.

Methods for Querying

Counts

  • length, size

    Returns the count of characters (not bytes).

  • empty?

    Returns true if self.length is zero; false otherwise.

  • bytesize

    Returns the count of bytes.

  • count

    Returns the count of substrings matching given strings.

Substrings

  • #=~

    Returns the index of the first substring that matches a given Regexp or other object; returns nil if no match is found.

  • index

    Returns the index of the first occurrence of a given substring; returns nil if none found.

  • rindex

    Returns the index of the last occurrence of a given substring; returns nil if none found.

  • include?

    Returns true if the string contains a given substring; false otherwise.

  • match

    Returns a MatchData object if the string matches a given Regexp; nil otherwise.

  • match?

    Returns true if the string matches a given Regexp; false otherwise.

  • start_with?

    Returns true if the string begins with any of the given substrings.

  • end_with?

    Returns true if the string ends with any of the given substrings.

Encodings

  • encoding

    Returns the Encoding object that represents the encoding of the string.

  • unicode_normalized?

    Returns true if the string is in Unicode normalized form; false otherwise.

  • valid_encoding?

    Returns true if the string contains only characters that are valid for its encoding.

  • ascii_only?

    Returns true if the string has only ASCII characters; false otherwise.

Other

  • sum

    Returns a basic checksum for the string: the sum of each byte.

  • hash

    Returns the integer hash code.

Methods for Comparing

  • #==, #===

    Returns true if a given other string has the same content as self.

  • eql?

    Returns true if the content is the same as the given other string.

  • #<=>

    Returns -1, 0, or 1 as a given other string is smaller than, equal to, or larger than self.

  • casecmp

    Ignoring case, returns -1, 0, or 1 as a given other string is smaller than, equal to, or larger than self.

  • casecmp?

    Returns true if the string is equal to a given string after Unicode case folding; false otherwise.

Methods for Modifying a String

Each of these methods modifies self.

Insertion

  • insert

    Returns self with a given string inserted at a given offset.

  • <<

    Returns self concatenated with a given string or integer.

Substitution

  • sub!

    Replaces the first substring that matches a given pattern with a given replacement string; returns self if any changes, nil otherwise.

  • gsub!

    Replaces each substring that matches a given pattern with a given replacement string; returns self if any changes, nil otherwise.

  • succ!, next!

    Returns self modified to become its own successor.

  • replace

    Returns self with its entire content replaced by a given string.

  • reverse!

    Returns self with its characters in reverse order.

  • setbyte

    Sets the byte at a given integer offset to a given value; returns the argument.

  • tr!

    Replaces specified characters in self with specified replacement characters; returns self if any changes, nil otherwise.

  • tr_s!

    Replaces specified characters in self with specified replacement characters, removing duplicates from the substrings that were modified; returns self if any changes, nil otherwise.

Casing

  • capitalize!

    Upcases the initial character and downcases all others; returns self if any changes, nil otherwise.

  • downcase!

    Downcases all characters; returns self if any changes, nil otherwise.

  • upcase!

    Upcases all characters; returns self if any changes, nil otherwise.

  • swapcase!

    Upcases each downcase character and downcases each upcase character; returns self if any changes, nil otherwise.

Encoding

  • encode!

    Returns self with all characters transcoded from one given encoding into another.

  • unicode_normalize!

    Unicode-normalizes self; returns self.

  • scrub!

    Replaces each invalid byte with a given character; returns self.

  • force_encoding

    Changes the encoding to a given encoding; returns self.

Deletion

  • clear

    Removes all content, so that self is empty; returns self.

  • slice!, []=

    Removes a substring determined by a given index, start/length, range, regexp, or substring.

  • squeeze!

    Removes contiguous duplicate characters; returns self.

  • delete!

    Removes characters as determined by the intersection of substring arguments.

  • lstrip!

    Removes leading whitespace; returns self if any changes, nil otherwise.

  • rstrip!

    Removes trailing whitespace; returns self if any changes, nil otherwise.

  • strip!

    Removes leading and trailing whitespace; returns self if any changes, nil otherwise.

  • chomp!

    Removes trailing record separator, if found; returns self if any changes, nil otherwise.

  • chop!

    Removes trailing whitespace if found, otherwise removes the last character; returns self if any changes, nil otherwise.

Methods for Converting to New String

Each of these methods returns a new String based on self, often just a modified copy of self.

Extension

  • *

    Returns the concatenation of multiple copies of self,

  • +

    Returns the concatenation of self and a given other string.

  • center

    Returns a copy of self centered between pad substring.

  • concat

    Returns the concatenation of self with given other strings.

  • prepend

    Returns the concatenation of a given other string with self.

  • ljust

    Returns a copy of self of a given length, right-padded with a given other string.

  • rjust

    Returns a copy of self of a given length, left-padded with a given other string.

Encoding

  • b

    Returns a copy of self with ASCII-8BIT encoding.

  • scrub

    Returns a copy of self with each invalid byte replaced with a given character.

  • unicode_normalize

    Returns a copy of self with each character Unicode-normalized.

  • encode

    Returns a copy of self with all characters transcoded from one given encoding into another.

Substitution

  • dump

    Returns a copy of +self with all non-printing characters replaced by xHH notation and all special characters escaped.

  • undump

    Returns a copy of +self with all \xNN notation replace by \uNNNN notation and all escaped characters unescaped.

  • sub

    Returns a copy of self with the first substring matching a given pattern replaced with a given replacement string;.

  • gsub

    Returns a copy of self with each substring that matches a given pattern replaced with a given replacement string.

  • succ, next

    Returns the string that is the successor to self.

  • reverse

    Returns a copy of self with its characters in reverse order.

  • tr

    Returns a copy of self with specified characters replaced with specified replacement characters.

  • tr_s

    Returns a copy of self with specified characters replaced with specified replacement characters, removing duplicates from the substrings that were modified.

  • %

    Returns the string resulting from formatting a given object into self

Casing

  • capitalize

    Returns a copy of self with the first character upcased and all other characters downcased.

  • downcase

    Returns a copy of self with all characters downcased.

  • upcase

    Returns a copy of self with all characters upcased.

  • swapcase

    Returns a copy of self with all upcase characters downcased and all downcase characters upcased.

Deletion

  • delete

    Returns a copy of self with characters removed

  • delete_prefix

    Returns a copy of self with a given prefix removed.

  • delete_suffix

    Returns a copy of self with a given suffix removed.

  • lstrip

    Returns a copy of self with leading whitespace removed.

  • rstrip

    Returns a copy of self with trailing whitespace removed.

  • strip

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

  • chomp

    Returns a copy of self with a trailing record separator removed, if found.

  • chop

    Returns a copy of self with trailing whitespace or the last character removed.

  • squeeze

    Returns a copy of self with contiguous duplicate characters removed.

  • [], slice

    Returns a substring determined by a given index, start/length, or range, or string.

  • byteslice

    Returns a substring determined by a given index, start/length, or range.

  • chr

    Returns the first character.

Duplication

  • to_s, $to_str

    If self is a subclass of String, returns self copied into a String; otherwise, returns self.

Methods for Converting to Non-String

Each of these methods converts the contents of self to a non-String.

Characters, Bytes, and Clusters

  • bytes

    Returns an array of the bytes in self.

  • chars

    Returns an array of the characters in self.

  • codepoints

    Returns an array of the integer ordinals in self.

  • getbyte

    Returns an integer byte as determined by a given index.

  • grapheme_clusters

    Returns an array of the grapheme clusters in self.

Splitting

  • lines

    Returns an array of the lines in self, as determined by a given record separator.

  • partition

    Returns a 3-element array determined by the first substring that matches a given substring or regexp,

  • rpartition

    Returns a 3-element array determined by the last substring that matches a given substring or regexp,

  • split

    Returns an array of substrings determined by a given delimiter – regexp or string – or, if a block given, passes those substrings to the block.

Matching

  • scan

    Returns an array of substrings matching a given regexp or string, or, if a block given, passes each matching substring to the block.

  • unpack

    Returns an array of substrings extracted from self according to a given format.

  • unpack1

    Returns the first substring extracted from self according to a given format.

Numerics

  • hex

    Returns the integer value of the leading characters, interpreted as hexadecimal digits.

  • oct

    Returns the integer value of the leading characters, interpreted as octal digits.

  • ord

    Returns the integer ordinal of the first character in self.

  • to_i

    Returns the integer value of leading characters, interpreted as an integer.

  • to_f

    Returns the floating-point value of leading characters, interpreted as a floating-point number.

Strings and Symbols

  • inspect

    Returns copy of self, enclosed in double-quotes, with special characters escaped.

  • to_sym, intern

    Returns the symbol corresponding to self.

Methods for Iterating

  • each_byte

    Calls the given block with each successive byte in self.

  • each_char

    Calls the given block with each successive character in self.

  • each_codepoint

    Calls the given block with each successive integer codepoint in self.

  • each_grapheme_cluster

    Calls the given block with each successive grapheme cluster in self.

  • each_line

    Calls the given block with each successive line in self, as determined by a given record separator.

  • upto

    Calls the given block with each string value returned by successive calls to succ.

Class Methods

String.new(string = '') → new_string

String.new(string = '', encoding: encoding) → new_string

String.new(string = '', capacity: size) → new_string
::

Returns a new String that is a copy of string.

With no arguments, returns the empty string with the Encoding ASCII-8BIT:

s = String.new
s # => ""
s.encoding # => #<Encoding:ASCII-8BIT>

With the single String argument string, returns a copy of string with the same encoding as string:

s = String.new("Que veut dire \u{e7}a?")
s # => "Que veut dire \u{e7}a?"
s.encoding # => #<Encoding:UTF-8>

Literal strings like "" or here-documents always use script encoding, unlike String.new.

With keyword encoding, returns a copy of str with the specified encoding:

s = String.new(encoding: 'ASCII')
s.encoding # => #<Encoding:US-ASCII>
s = String.new('foo', encoding: 'ASCII')
s.encoding # => #<Encoding:US-ASCII>

Note that these are equivalent:

s0 = String.new('foo', encoding: 'ASCII')
s1 = 'foo'.force_encoding('ASCII')
s0.encoding == s1.encoding # => true

With keyword capacity, returns a copy of str; the given capacity may set the size of the internal buffer, which may affect performance:

String.new(capacity: 1) # => ""
String.new(capacity: 4096) # => ""

The string, encoding, and capacity arguments may all be used together:

String.new('hello', encoding: 'UTF-8', capacity: 25)

String.try_convert(object) → object, new_string, or nil
::

If object is a String object, returns object.

Otherwise if object responds to :to_str, calls object.to_str and returns the result.

Returns nil if object does not respond to :to_str.

Raises an exception unless object.to_str returns a String object.

Instance Methods

string % object → new_string
#

Returns the result of formatting object into the format specification self (see Kernel#sprintf for formatting details):

"%05d" % 123 # => "00123"

If self contains multiple substitutions, object must be an Array or Hash containing the values to be substituted:

"%-5s: %016x" % [ "ID", self.object_id ] # => "ID   : 00002b054ec93168"
"foo = %{foo}" % {foo: 'bar'} # => "foo = bar"
"foo = %{foo}, baz = %{baz}" % {foo: 'bar', baz: 'bat'} # => "foo = bar, baz = bat"

string * integer → new_string
#

Returns a new String containing integer copies of self:

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

string + other_string → new_string
#

Returns a new String containing other_string concatenated to self:

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

+string → new_string or self
#

Returns self if self is not frozen.

Otherwise. returns self.dup, which is not frozen.

-string → frozen_string
#

Returns a frozen, possibly pre-existing copy of the string.

The returned String will be deduplicated as long as it does not have any instance variables set on it.

string << object → string
#

Concatenates object to self and returns self:

s = 'foo'
s << 'bar' # => "foobar"
s          # => "foobar"

If object is an Integer, the value is considered a codepoint and converted to a character before concatenation:

s = 'foo'
s << 33 # => "foo!"

Related: String#concat, which takes multiple arguments.

string <=> other_string → -1, 0, 1, or nil
#

Compares self and other_string, returning:

  • -1 if other_string is larger.

  • 0 if the two are equal.

  • 1 if other_string is smaller.

  • nil if the two are incomparable.

Examples:

'foo' <=> 'foo' # => 0
'foo' <=> 'food' # => -1
'food' <=> 'foo' # => 1
'FOO' <=> 'foo' # => -1
'foo' <=> 'FOO' # => 1
'foo' <=> 1 # => nil

string == object → true or false
#

Returns true if object has the same length and content; as self; false otherwise:

s = 'foo'
s == 'foo' # => true
s == 'food' # => false
s == 'FOO' # => false

Returns false if the two strings’ encodings are not compatible:

"\u{e4 f6 fc}".encode("ISO-8859-1") == ("\u{c4 d6 dc}") # => false

If object is not an instance of String but responds to to_str, then the two strings are compared using object.==.

string === object → true or false
#
An alias for ==

string =~ regexp → integer or nil

string =~ object → integer or nil
#

Returns the Integer index of the first substring that matches the given regexp, or nil if no match found:

'foo' =~ /f/ # => 0
'foo' =~ /o/ # => 1
'foo' =~ /x/ # => nil

Note: also updates Regexp-related global variables.

If the given object is not a Regexp, returns the value returned by object =~ self.

Note that string =~ regexp is different from regexp =~ string (see Regexp#=~):

number= nil
"no. 9" =~ /(?<number>\d+)/
number # => nil (not assigned)
/(?<number>\d+)/ =~ "no. 9"
number #=> "9"

string[index] → new_string or nil

string[start, length] → new_string or nil

string[range] → new_string or nil

string[regexp, capture = 0] → new_string or nil

string[substring] → new_string or nil
#

Returns the substring of self specified by the arguments.

When the single Integer argument index is given, returns the 1-character substring found in self at offset index:

'bar'[2] # => "r"

Counts backward from the end of self if index is negative:

'foo'[-3] # => "f"

Returns nil if index is out of range:

'foo'[3] # => nil
'foo'[-4] # => nil

When the two Integer arguments start and length are given, returns the substring of the given length found in self at offset start:

'foo'[0, 2] # => "fo"
'foo'[0, 0] # => ""

Counts backward from the end of self if start is negative:

'foo'[-2, 2] # => "oo"

Special case: returns a new empty String if start is equal to the length of self:

'foo'[3, 2] # => ""

Returns nil if start is out of range:

'foo'[4, 2] # => nil
'foo'[-4, 2] # => nil

Returns the trailing substring of self if length is large:

'foo'[1, 50] # => "oo"

Returns nil if length is negative:

'foo'[0, -1] # => nil

When the single Range argument range is given, derives start and length values from the given range, and returns values as above:

  • 'foo'[0..1] is equivalent to 'foo'[0, 2].

  • 'foo'[0...1] is equivalent to 'foo'[0, 1].

When the Regexp argument regexp is given, and the capture argument is 0, returns the first matching substring found in self, or nil if none found:

'foo'[/o/] # => "o"
'foo'[/x/] # => nil
s = 'hello there'
s[/[aeiou](.)\1/] # => "ell"
s[/[aeiou](.)\1/, 0] # => "ell"

If argument capture is given and not 0, it should be either an Integer capture group index or a String or Symbol capture group name; the method call returns only the specified capture (see Regexp Capturing):

s = 'hello there'
s[/[aeiou](.)\1/, 1] # => "l"
s[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, "non_vowel"] # => "l"
s[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, :vowel] # => "e"

If an invalid capture group index is given, nil is returned. If an invalid capture group name is given, IndexError is raised.

When the single String argument substring is given, returns the substring from self if found, otherwise nil:

'foo'['oo'] # => "oo"
'foo'['xx'] # => nil

String#slice is an alias for String#[].

str[integer] = new_str

str[integer, integer] = new_str

str[range] = aString

str[regexp] = new_str

str[regexp, integer] = new_str

str[regexp, name] = new_str

str[other_str] = new_str
#

Element Assignment—Replaces some or all of the content of str. The portion of the string affected is determined using the same criteria as String#[]. 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 Integer allows you to specify which portion of the match to replace (effectively using the MatchData indexing rules. The forms that take an Integer 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.

str.ascii_only? → true or false
#

Returns true for a string which has only ASCII characters.

"abc".force_encoding("UTF-8").ascii_only?          #=> true
"abc\u{6666}".force_encoding("UTF-8").ascii_only?  #=> false

str.b → str
#

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

str.bytes → an_array
#

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.

bytesize → integer
#

Returns the count of bytes in self:

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

Related: String#length.

byteslice(index, length = 1) → string or nil

byteslice(range) → string or nil
#

Returns a substring of self, or nil if the substring cannot be constructed.

With integer arguments index and length given, returns the substring beginning at the given index of the given length (if possible), or nil if length is negative or index falls outside of self:

s = '0123456789' # => "0123456789"
s.byteslice(2)   # => "2"
s.byteslice(200) # => nil
s.byteslice(4, 3)  # => "456"
s.byteslice(4, 30) # => "456789"
s.byteslice(4, -1) # => nil
s.byteslice(40, 2) # => nil

In either case above, counts backwards from the end of self if index is negative:

s = '0123456789'   # => "0123456789"
s.byteslice(-4)    # => "6"
s.byteslice(-4, 3) # => "678"

With Range argument range given, returns byteslice(range.begin, range.size):

s = '0123456789'    # => "0123456789"
s.byteslice(4..6)   # => "456"
s.byteslice(-6..-4) # => "456"
s.byteslice(5..2)   # => "" # range.size is zero.
s.byteslice(40..42) # => nil

In all cases, a returned string has the same encoding as self:

s.encoding              # => #<Encoding:UTF-8>
s.byteslice(4).encoding # => #<Encoding:UTF-8>

capitalize(*options) → string
#

Returns a string containing the characters in self; the first character is upcased; the remaining characters are downcased:

s = 'hello World!' # => "hello World!"
s.capitalize       # => "Hello world!"

The casing may be affected by the given options; see Case Mapping.

Related: String#capitalize!.

capitalize!(*options) → self or nil
#

Upcases the first character in self; downcases the remaining characters; returns self if any changes were made, nil otherwise:

s = 'hello World!' # => "hello World!"
s.capitalize!      # => "Hello world!"
s                  # => "Hello world!"
s.capitalize!      # => nil

The casing may be affected by the given options; see Case Mapping.

Related: String#capitalize.

casecmp(other_string) → -1, 0, 1, or nil
#

Compares self.downcase and other_string.downcase; returns:

  • -1 if other_string.downcase is larger.

  • 0 if the two are equal.

  • 1 if other_string.downcase is smaller.

  • nil if the two are incomparable.

Examples:

'foo'.casecmp('foo') # => 0
'foo'.casecmp('food') # => -1
'food'.casecmp('foo') # => 1
'FOO'.casecmp('foo') # => 0
'foo'.casecmp('FOO') # => 0
'foo'.casecmp(1) # => nil

See Case Mapping.

Related: String#casecmp?.

casecmp?(other_string) → true, false, or nil
#

Returns true if self and other_string are equal after Unicode case folding, otherwise false:

'foo'.casecmp?('foo') # => true
'foo'.casecmp?('food') # => false
'food'.casecmp?('foo') # => false
'FOO'.casecmp?('foo') # => true
'foo'.casecmp?('FOO') # => true

Returns nil if the two values are incomparable:

'foo'.casecmp?(1) # => nil

See Case Mapping.

Related: String#casecmp.

str.center(width, padstr=' ') → new_str
#

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"

str.chars → an_array
#

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.

str.chomp(separator=$/) → new_str
#

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"

str.chomp!(separator=$/) → str or nil
#

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

str.chop → new_str
#

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. 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       #=> ""

str.chop! → str or nil
#

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

chr → string
#

Returns a string containing the first character of self:

s = 'foo' # => "foo"
s.chr     # => "f"

clear → self
#

Removes the contents of self:

s = 'foo' # => "foo"
s.clear   # => ""

str.codepoints → an_array
#

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.

concat(*objects) → string
#

Concatenates each object in objects to self and returns self:

s = 'foo'
s.concat('bar', 'baz') # => "foobarbaz"
s                      # => "foobarbaz"

For each given object object that is an Integer, the value is considered a codepoint and converted to a character before concatenation:

s = 'foo'
s.concat(32, 'bar', 32, 'baz') # => "foo bar baz"

Related: String#<<, which takes a single argument.

str.count([other_str]+) → integer
#

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

str.crypt(salt_str) → new_str
#

Returns the string generated by calling crypt(3) standard library function with str and salt_str, in this order, as its arguments. Please do not use this method any longer. It is legacy; provided only for backward compatibility with ruby scripts in earlier days. It is bad to use in contemporary programs for several reasons:

  • Behaviour of C’s crypt(3) depends on the OS it is run. The generated string lacks data portability.

  • On some OSes such as Mac OS, crypt(3) never fails (i.e. silently ends up in unexpected results).

  • On some OSes such as Mac OS, crypt(3) is not thread safe.

  • So-called “traditional” usage of crypt(3) is very very very weak. According to its manpage, Linux’s traditional crypt(3) output has only 2**56 variations; too easy to brute force today. And this is the default behaviour.

  • In order to make things robust some OSes implement so-called “modular” usage. To go through, you have to do a complex build-up of the salt_str parameter, by hand. Failure in generation of a proper salt string tends not to yield any errors; typos in parameters are normally not detectable.

    • For instance, in the following example, the second invocation of String#crypt is wrong; it has a typo in “round=” (lacks “s”). However the call does not fail and something unexpected is generated.

      "foo".crypt("$5$rounds=1000$salt$") # OK, proper usage
"foo".crypt("$5$round=1000$salt$")  # Typo not detected

  • Even in the “modular” mode, some hash functions are considered archaic and no longer recommended at all; for instance module $1$ is officially abandoned by its author: see phk.freebsd.dk/sagas/md5crypt_eol/ . For another instance module $3$ is considered completely broken: see the manpage of FreeBSD.

  • On some OS such as Mac OS, there is no modular mode. Yet, as written above, crypt(3) on Mac OS never fails. This means even if you build up a proper salt string it generates a traditional DES hash anyways, and there is no way for you to be aware of.

    "foo".crypt("$5$rounds=1000$salt$") # => "$5fNPQMxC5j6."

If for some reason you cannot migrate to other secure contemporary password hashing algorithms, install the string-crypt gem and require 'string/crypt' to continue using it.

str.delete([other_str]+) → new_str
#

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 String#count.

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

str.delete!([other_str]+) → str or nil
#

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

str.delete_prefix(prefix) → new_str
#

Returns a copy of str with leading prefix deleted.

"hello".delete_prefix("hel") #=> "lo"
"hello".delete_prefix("llo") #=> "hello"

str.delete_prefix!(prefix) → self or nil
#

Deletes leading prefix from str, returning nil if no change was made.

"hello".delete_prefix!("hel") #=> "lo"
"hello".delete_prefix!("llo") #=> nil

str.delete_suffix(suffix) → new_str
#

Returns a copy of str with trailing suffix deleted.

"hello".delete_suffix("llo") #=> "he"
"hello".delete_suffix("hel") #=> "hello"

str.delete_suffix!(suffix) → self or nil
#

Deletes trailing suffix from str, returning nil if no change was made.

"hello".delete_suffix!("llo") #=> "he"
"hello".delete_suffix!("hel") #=> nil

downcase(*options) → string
#

Returns a string containing the downcased characters in self:

s = 'Hello World!' # => "Hello World!"
s.downcase         # => "hello world!"

The casing may be affected by the given options; see Case Mapping.

Related: String#downcase!, String#upcase, String#upcase!.

downcase!(*options) → self or nil
#

Downcases the characters in self; returns self if any changes were made, nil otherwise:

s = 'Hello World!' # => "Hello World!"
s.downcase!        # => "hello world!"
s                  # => "hello world!"
s.downcase!        # => nil

The casing may be affected by the given options; see Case Mapping.

Related: String#downcase, String#upcase, String#upcase!.

dump → string
#

Returns a printable version of self, enclosed in double-quotes, with special characters escaped, and with non-printing characters replaced by hexadecimal notation:

"hello \n ''".dump    # => "\"hello \\n ''\""
"\f\x00\xff\\\"".dump # => "\"\\f\\x00\\xFF\\\\\\\"\""

Related: String#undump (inverse of String#dump).

str.each_byte {|integer| block } → str

str.each_byte → an_enumerator
#

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

str.each_char {|cstr| block } → str

str.each_char → an_enumerator
#

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

str.each_codepoint {|integer| block } → str

str.each_codepoint → an_enumerator
#

Passes the Integer ordinal of each character in str, also known as a codepoint when applied to Unicode strings to the given block. For encodings other than UTF-8/UTF-16(BE|LE)/UTF-32(BE|LE), values are directly derived from the binary representation of each character.

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

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

produces:

104 101 108 108 111 1593

str.each_grapheme_cluster {|cstr| block } → str

str.each_grapheme_cluster → an_enumerator
#

Passes each grapheme cluster in str to the given block, or returns an enumerator if no block is given. Unlike String#each_char, this enumerates by grapheme clusters defined by Unicode Standard Annex #29 unicode.org/reports/tr29/

"a\u0300".each_char.to_a.size #=> 2
"a\u0300".each_grapheme_cluster.to_a.size #=> 1

str.each_line(separator=$/, chomp: false) {|substr| block } → str

str.each_line(separator=$/, chomp: false) → an_enumerator
#

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 chomp is true, separator will be removed from the end of each line.

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

"hello\nworld".each_line {|s| p s}
# prints:
#   "hello\n"
#   "world"

"hello\nworld".each_line('l') {|s| p s}
# prints:
#   "hel"
#   "l"
#   "o\nworl"
#   "d"

"hello\n\n\nworld".each_line('') {|s| p s}
# prints
#   "hello\n\n"
#   "world"

"hello\nworld".each_line(chomp: true) {|s| p s}
# prints:
#   "hello"
#   "world"

"hello\nworld".each_line('l', chomp: true) {|s| p s}
# prints:
#   "he"
#   ""
#   "o\nwor"
#   "d"

empty? → true or false
#

Returns true if the length of self is zero, false otherwise:

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

str.encode(encoding, **options) → str

str.encode(dst_encoding, src_encoding, **options) → str

str.encode(**options) → str
#

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 keyword arguments give details for conversion. The arguments are:

: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.

str.encode!(encoding, **options) → str

str.encode!(dst_encoding, src_encoding, **options) → str
#

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 keyword arguments give details for conversion. See String#encode for details. Returns the string even if no changes were made.

obj.encoding → encoding
#

Returns the Encoding object that represents the encoding of obj.

str.end_with?([suffixes]+) → true or false
#

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

eql?(object) → true or false
#

Returns true if object has the same length and content; as self; false otherwise:

s = 'foo'
s.eql?('foo') # => true
s.eql?('food') # => false
s.eql?('FOO') # => false

Returns false if the two strings’ encodings are not compatible:

"\u{e4 f6 fc}".encode("ISO-8859-1").eql?("\u{c4 d6 dc}") # => false

str.force_encoding(encoding) → str
#

Changes the encoding to encoding and returns self.

freeze
#
No documentation available

getbyte(index) → integer
#

Returns the byte at zero-based index as an integer:

s = 'abcde'  # => "abcde"
s.getbyte(0) # => 97
s.getbyte(1) # => 98

Related: String#setbyte.

str.grapheme_clusters → an_array
#

Returns an array of grapheme clusters in str. This is a shorthand for str.each_grapheme_cluster.to_a.

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

gsub(pattern, replacement) → new_string

gsub(pattern) {|match| ... } → new_string

gsub(pattern) → enumerator
#

Returns a copy of self with all occurrences of the given pattern replaced.

See Substitution Methods.

Returns an Enumerator if no replacement and no block given.

Related: String#sub, String#sub!, String#gsub!.

gsub!(pattern, replacement) → self or nil

gsub!(pattern) {|match| ... } → self or nil

gsub!(pattern) → an_enumerator
#

Performs the specified substring replacement(s) on self; returns self if any replacement occurred, nil otherwise.

See Substitution Methods.

Returns an Enumerator if no replacement and no block given.

Related: String#sub, String#gsub, String#sub!.

hash → integer
#

Returns the integer hash value for self. The value is based on the length, content and encoding of self.

Related: Object#hash.

str.hex → integer
#

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

include? other_string → true or false
#

Returns true if self contains other_string, false otherwise:

s = 'foo'
s.include?('f')    # => true
s.include?('fo')   # => true
s.include?('food') # => false

index(substring, offset = 0) → integer or nil

index(regexp, offset = 0) → integer or nil
#

Returns the Integer index of the first occurrence of the given substring, or nil if none found:

'foo'.index('f') # => 0
'foo'.index('o') # => 1
'foo'.index('oo') # => 1
'foo'.index('ooo') # => nil

Returns the Integer index of the first match for the given Regexp regexp, or nil if none found:

'foo'.index(/f/) # => 0
'foo'.index(/o/) # => 1
'foo'.index(/oo/) # => 1
'foo'.index(/ooo/) # => nil

Integer argument offset, if given, specifies the position in the string to begin the search:

'foo'.index('o', 1) # => 1
'foo'.index('o', 2) # => 2
'foo'.index('o', 3) # => nil

If offset is negative, counts backward from the end of self:

'foo'.index('o', -1) # => 2
'foo'.index('o', -2) # => 1
'foo'.index('o', -3) # => 1
'foo'.index('o', -4) # => nil

Related: String#rindex.

replace(other_string) -> self
#

Replaces the contents of self with the contents of other_string:

s = 'foo'        # => "foo"
s.replace('bar') # => "bar"

insert(index, other_string) → self
#

Inserts the given other_string into self; returns self.

If the Integer index is positive, inserts other_string at offset index:

'foo'.insert(1, 'bar') # => "fbaroo"

If the Integer index is negative, counts backward from the end of self and inserts other_string at offset index+1 (that is, after self[index]):

'foo'.insert(-2, 'bar') # => "fobaro"

inspect → string
#

Returns a printable version of self, enclosed in double-quotes, and with special characters escaped:

s = "foo\tbar\tbaz\n"
# => "foo\tbar\tbaz\n"
s.inspect
# => "\"foo\\tbar\\tbaz\\n\""

str.intern → symbol
#

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"

String#iseuc => true or false
#

Returns whether self‘s encoding is EUC-JP or not.

String#isjis => true or false
#

Returns whether self‘s encoding is ISO-2022-JP or not.

String#issjis => true or false
#

Returns whether self‘s encoding is Shift_JIS or not.

String#isutf8 => true or false
#

Returns whether self‘s encoding is UTF-8 or not.

String#kconv(to_enc, from_enc)
#

Convert self to to_enc. to_enc and from_enc are given as constants of Kconv or Encoding objects.

length → integer
#

Returns the count of characters (not bytes) in self:

"\x80\u3042".length # => 2
"hello".length # => 5

String#size is an alias for String#length.

Related: String#bytesize.

str.lines(separator=$/, chomp: false) → an_array
#

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

If chomp is true, separator will be removed from the end of each line.

"hello\nworld\n".lines              #=> ["hello\n", "world\n"]
"hello  world".lines(' ')           #=> ["hello ", " ", "world"]
"hello\nworld\n".lines(chomp: true) #=> ["hello", "world"]

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

str.ljust(integer, padstr=' ') → new_str
#

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"

str.lstrip → new_str
#

Returns a copy of the receiver with leading whitespace removed. See also String#rstrip and String#strip.

Refer to String#strip for the definition of whitespace.

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

str.lstrip! → self or nil
#

Removes leading whitespace from the receiver. Returns the altered receiver, or nil if no change was made. See also String#rstrip! and String#strip!.

Refer to String#strip for the definition of whitespace.

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

match(pattern, offset = 0) → matchdata or nil

match(pattern, offset = 0) {|matchdata| ... } → object
#

Returns a Matchdata object (or nil) based on self and the given pattern.

Note: also updates Regexp-related global variables.

  • Computes regexp by converting pattern (if not already a Regexp).

    regexp = Regexp.new(pattern)

  • Computes matchdata, which will be either a MatchData object or nil (see Regexp#match):

    matchdata = <tt>regexp.match(self)

With no block given, returns the computed matchdata:

'foo'.match('f') # => #<MatchData "f">
'foo'.match('o') # => #<MatchData "o">
'foo'.match('x') # => nil

If Integer argument offset is given, the search begins at index offset:

'foo'.match('f', 1) # => nil
'foo'.match('o', 1) # => #<MatchData "o">

With a block given, calls the block with the computed matchdata and returns the block’s return value:

'foo'.match(/o/) {|matchdata| matchdata } # => #<MatchData "o">
'foo'.match(/x/) {|matchdata| matchdata } # => nil
'foo'.match(/f/, 1) {|matchdata| matchdata } # => nil

match?(pattern, offset = 0) → true or false
#

Returns true or false based on whether a match is found for self and pattern.

Note: does not update Regexp-related global variables.

Computes regexp by converting pattern (if not already a Regexp).

regexp = Regexp.new(pattern)

Returns true if self+.match(regexp) returns a Matchdata object, false otherwise:

'foo'.match?(/o/) # => true
'foo'.match?('o') # => true
'foo'.match?(/x/) # => false

If Integer argument offset is given, the search begins at index offset:

'foo'.match?('f', 1) # => false
'foo'.match?('o', 1) # => true

next
#
An alias for succ

next!
#
An alias for succ!

str.oct → integer
#

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 honored. See Kernel#Integer.

str.ord → integer
#

Returns the Integer ordinal of a one-character string.

"a".ord         #=> 97

str.partition(sep) → [head, sep, tail]

str.partition(regexp) → [head, match, tail]
#

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(*other_strings) → string
#

Prepends each string in other_strings to self and returns self:

s = 'foo'
s.prepend('bar', 'baz') # => "barbazfoo"
s                       # => "barbazfoo"

Related: String#concat.

replace(other_string) → self
#
An alias for initialize_copy

reverse → string
#

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

'stressed'.reverse # => "desserts"

reverse! → self
#

Returns self with its characters reversed:

s = 'stressed'
s.reverse! # => "desserts"
s          # => "desserts"

rindex(substring, offset = self.length) → integer or nil

rindex(regexp, offset = self.length) → integer or nil
#

Returns the Integer index of the last occurrence of the given substring, or nil if none found:

'foo'.rindex('f') # => 0
'foo'.rindex('o') # => 2
'foo'.rindex('oo') # => 1
'foo'.rindex('ooo') # => nil

Returns the Integer index of the last match for the given Regexp regexp, or nil if none found:

'foo'.rindex(/f/) # => 0
'foo'.rindex(/o/) # => 2
'foo'.rindex(/oo/) # => 1
'foo'.rindex(/ooo/) # => nil

The last match means starting at the possible last position, not the last of longest matches.

'foo'.rindex(/o+/) # => 2
$~ #=> #<MatchData "o">

To get the last longest match, needs to combine with negative lookbehind.

'foo'.rindex(/(?<!o)o+/) # => 1
$~ #=> #<MatchData "oo">

Or String#index with negative lookforward.

'foo'.index(/o+(?!.*o)/) # => 1
$~ #=> #<MatchData "oo">

Integer argument offset, if given and non-negative, specifies the maximum starting position in the

string to _end_ the search:

 'foo'.rindex('o', 0) # => nil
 'foo'.rindex('o', 1) # => 1
 'foo'.rindex('o', 2) # => 2
 'foo'.rindex('o', 3) # => 2

If offset is a negative Integer, the maximum starting position in the string to end the search is the sum of the string’s length and offset:

'foo'.rindex('o', -1) # => 2
'foo'.rindex('o', -2) # => 1
'foo'.rindex('o', -3) # => nil
'foo'.rindex('o', -4) # => nil

Related: String#index.

str.rjust(integer, padstr=' ') → new_str
#

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"

str.rpartition(sep) → [head, sep, tail]

str.rpartition(regexp) → [head, match, tail]
#

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"]

The match from the end means starting at the possible last position, not the last of longest matches.

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

To partition at the last longest match, needs to combine with negative lookbehind.

"hello".rpartition(/(?<!l)l+/)  #=> ["he", "ll", "o"]

Or String#partition with negative lookforward.

"hello".partition(/l+(?!.*l)/)  #=> ["he", "ll", "o"]

str.rstrip → new_str
#

Returns a copy of the receiver with trailing whitespace removed. See also String#lstrip and String#strip.

Refer to String#strip for the definition of whitespace.

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

str.rstrip! → self or nil
#

Removes trailing whitespace from the receiver. Returns the altered receiver, or nil if no change was made. See also String#lstrip! and String#strip!.

Refer to String#strip for the definition of whitespace.

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

str.scan(pattern) → array

str.scan(pattern) {|match, ...| block } → str
#

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

str.scrub → new_str

str.scrub(repl) → new_str

str.scrub{|bytes|} → new_str
#

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.unpack1('H*')+'>' } #=> "abc\u3042<e380>"

str.scrub! → str

str.scrub!(repl) → str

str.scrub!{|bytes|} → str
#

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.unpack1('H*')+'>' } #=> "abc\u3042<e380>"

setbyte(index, integer) → integer
#

Sets the byte at zero-based index to integer; returns integer:

s = 'abcde'      # => "abcde"
s.setbyte(0, 98) # => 98
s                # => "bbcde"

Related: String#getbyte.

str.shellescape => string
#

Escapes str so that it can be safely used in a Bourne shell command line.

See Shellwords.shellescape for details.

str.shellsplit => array
#

Splits str into an array of tokens in the same way the UNIX Bourne shell does.

See Shellwords.shellsplit for details.

size
#
An alias for length

slice(*args)
#
An alias for []

slice!(index) → new_string or nil

slice!(start, length) → new_string or nil

slice!(range) → new_string or nil

slice!(regexp, capture = 0) → new_string or nil

slice!(substring) → new_string or nil
#

Removes the substring of self specified by the arguments; returns the removed substring.

See String#[] for details about the arguments that specify the substring.

A few examples:

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"

str.split(pattern=nil, [limit]) → an_array

str.split(pattern=nil, [limit]) {|sub| block } → str
#

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 and trailing 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)               #=> []

If a block is given, invoke the block with each split substring.

str.squeeze([other_str]*) → new_str
#

Builds a set of characters from the other_str parameter(s) using the procedure described for String#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"

str.squeeze!([other_str]*) → str or nil
#

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

str.start_with?([prefixes]+) → true or false
#

Returns true if str starts with one of the prefixes given. Each of the prefixes should be a String or a Regexp.

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

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

str.strip → new_str
#

Returns a copy of the receiver 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 #=> ""
"hello".strip           #=> "hello"

str.strip! → self or nil
#

Removes leading and trailing whitespace from the receiver. Returns the altered receiver, or nil if there was no change.

Refer to String#strip for the definition of whitespace.

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

sub(pattern, replacement) → new_string

sub(pattern) {|match| ... } → new_string
#

Returns a copy of self with only the first occurrence (not all occurrences) of the given pattern replaced.

See Substitution Methods.

Related: String#sub!, String#gsub, String#gsub!.

sub!(pattern, replacement) → self or nil

sub!(pattern) {|match| ... } → self or nil
#

Returns self with only the first occurrence (not all occurrences) of the given pattern replaced.

See Substitution Methods.

Related: String#sub, String#gsub, String#gsub!.

succ → new_str
#

Returns the successor to self. The successor is calculated by incrementing characters.

The first character to be incremented is the rightmost alphanumeric: or, if no alphanumerics, the rightmost character:

'THX1138'.succ # => "THX1139"
'<<koala>>'.succ # => "<<koalb>>"
'***'.succ # => '**+'

The successor to a digit is another digit, “carrying” to the next-left character for a “rollover” from 9 to 0, and prepending another digit if necessary:

'00'.succ # => "01"
'09'.succ # => "10"
'99'.succ # => "100"

The successor to a letter is another letter of the same case, carrying to the next-left character for a rollover, and prepending another same-case letter if necessary:

'aa'.succ # => "ab"
'az'.succ # => "ba"
'zz'.succ # => "aaa"
'AA'.succ # => "AB"
'AZ'.succ # => "BA"
'ZZ'.succ # => "AAA"

The successor to a non-alphanumeric character is the next character in the underlying character set’s collating sequence, carrying to the next-left character for a rollover, and prepending another character if necessary:

s = 0.chr * 3
s # => "\x00\x00\x00"
s.succ # => "\x00\x00\x01"
s = 255.chr * 3
s # => "\xFF\xFF\xFF"
s.succ # => "\x01\x00\x00\x00"

Carrying can occur between and among mixtures of alphanumeric characters:

s = 'zz99zz99'
s.succ # => "aaa00aa00"
s = '99zz99zz'
s.succ # => "100aa00aa"

The successor to an empty String is a new empty String:

''.succ # => ""

String#next is an alias for String#succ.

succ! → self
#

Equivalent to String#succ, but modifies self in place; returns self.

String#next! is an alias for String#succ!.

str.sum(n=16) → integer
#

Returns a basic n-bit checksum of the characters in str, where n is the optional Integer 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.

swapcase(*options) → string
#

Returns a string containing the characters in self, with cases reversed; each uppercase character is downcased; each lowercase character is upcased:

s = 'Hello World!' # => "Hello World!"
s.swapcase         # => "hELLO wORLD!"

The casing may be affected by the given options; see Case Mapping.

Related: String#swapcase!.

swapcase!(*options) → self or nil
#

Upcases each lowercase character in self; downcases uppercase character; returns self if any changes were made, nil otherwise:

s = 'Hello World!' # => "Hello World!"
s.swapcase!        # => "hELLO wORLD!"
s                  # => "Hello World!"
''.swapcase!       # => nil

The casing may be affected by the given options; see Case Mapping.

Related: String#swapcase.

str.to_c → complex
#

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.

str.to_d → bigdecimal
#

Returns the result of interpreting leading characters in str as a BigDecimal.

require 'bigdecimal'
require 'bigdecimal/util'

"0.5".to_d             # => 0.5e0
"123.45e1".to_d        # => 0.12345e4
"45.67 degrees".to_d   # => 0.4567e2

See also BigDecimal::new.

to_f → float
#

Returns the result of interpreting leading characters in self as a Float:

'3.14159'.to_f  # => 3.14159
'1.234e-2'.to_f # => 0.01234

Characters past a leading valid number (in the given base) are ignored:

'3.14 (pi to two places)'.to_f # => 3.14

Returns zero if there is no leading valid number:

'abcdef'.to_f # => 0.0

to_i(base = 10) → integer
#

Returns the result of interpreting leading characters in self as an integer in the given base (which must be in (2..36)):

'123456'.to_i     # => 123456
'123def'.to_i(16) # => 1195503

Characters past a leading valid number (in the given base) are ignored:

'12.345'.to_i   # => 12
'12345'.to_i(2) # => 1

Returns zero if there is no leading valid number:

'abcdef'.to_i # => 0
'2'.to_i(2)   # => 0

str.to_r → rational
#

Returns the result of interpreting leading characters in str as a rational. Leading whitespace and extraneous characters past the end of a valid number are ignored. Digit sequences can be separated by an underscore. If there is not a valid number at the start of str, zero is returned. This method never raises an exception.

'  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)

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.

"0.3".to_r == 3/10r  #=> true
0.3.to_r   == 3/10r  #=> false

See also Kernel#Rational.

to_s → self or string
#

Returns self if self is a String, or self converted to a String if self is a subclass of String.

String#to_str is an alias for String#to_s.

to_str
#
An alias for to_s

str.to_sym → symbol
#
An alias for intern

String#toeuc => string
#

Convert self to EUC-JP

String#tojis => string
#

Convert self to ISO-2022-JP

String#tolocale => string
#

Convert self to locale encoding

String#tosjis => string
#

Convert self to Shift_JIS

String#toutf16 => string
#

Convert self to UTF-16

String#toutf32 => string
#

Convert self to UTF-32

String#toutf8 => string
#

Convert self to UTF-8

str.tr(from_str, to_str) => new_str
#

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'"

str.tr!(from_str, to_str) → str or nil
#

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

str.tr_s(from_str, to_str) → new_str
#

Processes a copy of str as described under String#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"

str.tr_s!(from_str, to_str) → str or nil
#

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

undump → string
#

Returns an unescaped version of self:

s_orig = "\f\x00\xff\\\""    # => "\f\u0000\xFF\\\""
s_dumped = s_orig.dump       # => "\"\\f\\x00\\xFF\\\\\\\"\""
s_undumped = s_dumped.undump # => "\f\u0000\xFF\\\""
s_undumped == s_orig         # => true

Related: String#dump (inverse of String#undump).

str.unicode_normalize(form=:nfc)
#

Unicode Normalization—Returns a normalized form of str, using Unicode normalizations NFC, NFD, NFKC, or NFKD. The normalization form used is determined by form, which can be any of the four values :nfc, :nfd, :nfkc, or :nfkd. The default is :nfc.

If the string is not in a Unicode Encoding, then an Exception is raised. In this context, ‘Unicode Encoding’ means any of UTF-8, UTF-16BE/LE, and UTF-32BE/LE, as well as GB18030, UCS_2BE, and UCS_4BE. Anything other than UTF-8 is implemented by converting to UTF-8, which makes it slower than UTF-8.

"a\u0300".unicode_normalize        #=> "\u00E0"
"a\u0300".unicode_normalize(:nfc)  #=> "\u00E0"
"\u00E0".unicode_normalize(:nfd)   #=> "a\u0300"
"\xE0".force_encoding('ISO-8859-1').unicode_normalize(:nfd)
                                   #=> Encoding::CompatibilityError raised

str.unicode_normalize!(form=:nfc)
#

Destructive version of String#unicode_normalize, doing Unicode normalization in place.

str.unicode_normalized?(form=:nfc)
#

Checks whether str is in Unicode normalization form form, which can be any of the four values :nfc, :nfd, :nfkc, or :nfkd. The default is :nfc.

If the string is not in a Unicode Encoding, then an Exception is raised. For details, see String#unicode_normalize.

"a\u0300".unicode_normalized?        #=> false
"a\u0300".unicode_normalized?(:nfd)  #=> true
"\u00E0".unicode_normalized?         #=> true
"\u00E0".unicode_normalized?(:nfd)   #=> false
"\xE0".force_encoding('ISO-8859-1').unicode_normalized?
                                     #=> Encoding::CompatibilityError raised

str.unpack(format) → anArray

str.unpack(format, offset: anInteger) → anArray
#

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 String#unpack1, 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)
J             | Integer | pointer width unsigned, native endian (uintptr_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)
j             | Integer | pointer width signed, native endian (intptr_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.)
J!            | Integer | uintptr_t, native endian (same with J)
              |         |
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.)
j!            | Integer | intptr_t, native endian (same with j)
              |         |
S> s> S!> s!> | Integer | same as the directives without ">" except
L> l> L!> l!> |         | big endian
I!> i!>       |         |
Q> q> Q!> q!> |         | "S>" is the same as "n"
J> j> J!> j!> |         | "L>" is the same as "N"
              |         |
S< s< S!< s!< | Integer | same as the directives without "<" except
L< l< L!< l!< |         | little endian
I!< i!<       |         |
Q< q< Q!< q!< |         | "S<" is the same as "v"
J< j< J!< j!< |         | "L<" is the same as "V"
              |         |
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

The keyword offset can be given to start the decoding after skipping the specified amount of bytes:

"abc".unpack("C*") # => [97, 98, 99]
"abc".unpack("C*", offset: 2) # => [99]
"abc".unpack("C*", offset: 4) # => offset outside of string (ArgumentError)

HISTORY

  • J, J! j, and j! are available since Ruby 2.3.

  • Q_, Q!, q_, and q! are available since Ruby 2.1.

  • I!<, i!<, I!>, and i!> are available since Ruby 1.9.3.

str.unpack1(format) → obj

str.unpack1(format, offset: anInteger) → obj
#

Decodes str (which may contain binary data) according to the format string, returning the first value extracted.

See also String#unpack, Array#pack.

Contrast with String#unpack:

"abc \0\0abc \0\0".unpack('A6Z6')   #=> ["abc", "abc "]
"abc \0\0abc \0\0".unpack1('A6Z6')  #=> "abc"

In that case data would be lost but often it’s the case that the array only holds one value, especially when unpacking binary data. For instance:

"\xff\x00\x00\x00".unpack("l")         #=>  [255]
"\xff\x00\x00\x00".unpack1("l")        #=>  255

Thus unpack1 is convenient, makes clear the intention and signals the expected return value to those reading the code.

The keyword offset can be given to start the decoding after skipping the specified amount of bytes:

"abc".unpack1("C*") # => 97
"abc".unpack1("C*", offset: 2) # => 99
"abc".unpack1("C*", offset: 4) # => offset outside of string (ArgumentError)

upcase(*options) → string
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Returns a string containing the upcased characters in self:

s = 'Hello World!' # => "Hello World!"
s.upcase           # => "HELLO WORLD!"

The casing may be affected by the given options; see Case Mapping.

Related: String#upcase!, String#downcase, String#downcase!.

upcase!(*options) → self or nil
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Upcases the characters in self; returns self if any changes were made, nil otherwise:

s = 'Hello World!' # => "Hello World!"
s.upcase!          # => "HELLO WORLD!"
s                  # => "HELLO WORLD!"
s.upcase!          # => nil

The casing may be affected by the given options; see Case Mapping.

Related: String#upcase, String#downcase, String#downcase!.

upto(other_string, exclusive = false) {|string| ... } → self

upto(other_string, exclusive = false) → new_enumerator
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With a block given, calls the block with each String value returned by successive calls to String#succ; the first value is self, the next is self.succ, and so on; the sequence terminates when value other_string is reached; returns self:

'a8'.upto('b6') {|s| print s, ' ' } # => "a8"

Output:

a8 a9 b0 b1 b2 b3 b4 b5 b6

If argument exclusive is given as a truthy object, the last value is omitted:

'a8'.upto('b6', true) {|s| print s, ' ' } # => "a8"

Output:

a8 a9 b0 b1 b2 b3 b4 b5

If other_string would not be reached, does not call the block:

'25'.upto('5') {|s| fail s }
'aa'.upto('a') {|s| fail s }

With no block given, returns a new Enumerator:

'a8'.upto('b6') # => #<Enumerator: "a8":upto("b6")>

str.valid_encoding? → true or false
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Returns true for a string which is 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