Returns the integer index of the first match for the given argument, or nil if none found; the search of self is forward, and begins at position offset (in characters).
With string argument substring, returns the index of the first matching substring in self:
'foo'.index('f') # => 0 'foo'.index('o') # => 1 'foo'.index('oo') # => 1 'foo'.index('ooo') # => nil 'тест'.index('с') # => 2 'こんにちは'.index('ち') # => 3
With Regexp argument regexp, returns the index of the first match in self:
'foo'.index(/o./) # => 1 'foo'.index(/.o/) # => 0
With positive integer offset, begins the search at position offset:
'foo'.index('o', 1) # => 1 'foo'.index('o', 2) # => 2 'foo'.index('o', 3) # => nil 'тест'.index('с', 1) # => 2 'こんにちは'.index('ち', 2) # => 3
With negative integer offset, selects the search position by counting 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 'foo'.index(/o./, -2) # => 1 'foo'.index(/.o/, -2) # => 1
Related: String#rindex.
Returns the Integer byte-based index of the first occurrence of the given substring, or nil if none found:
'foo'.byteindex('f') # => 0 'foo'.byteindex('o') # => 1 'foo'.byteindex('oo') # => 1 'foo'.byteindex('ooo') # => nil
Returns the Integer byte-based index of the first match for the given Regexp regexp, or nil if none found:
'foo'.byteindex(/f/) # => 0 'foo'.byteindex(/o/) # => 1 'foo'.byteindex(/oo/) # => 1 'foo'.byteindex(/ooo/) # => nil
Integer argument offset, if given, specifies the byte-based position in the string to begin the search:
'foo'.byteindex('o', 1) # => 1 'foo'.byteindex('o', 2) # => 2 'foo'.byteindex('o', 3) # => nil
If offset is negative, counts backward from the end of self:
'foo'.byteindex('o', -1) # => 2 'foo'.byteindex('o', -2) # => 1 'foo'.byteindex('o', -3) # => 1 'foo'.byteindex('o', -4) # => nil
If offset does not land on character (codepoint) boundary, IndexError is raised.
Related: String#index, String#byterindex.
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.
Returns the Integer byte-based index of the last occurrence of the given substring, or nil if none found:
'foo'.byterindex('f') # => 0 'foo'.byterindex('o') # => 2 'foo'.byterindex('oo') # => 1 'foo'.byterindex('ooo') # => nil
Returns the Integer byte-based index of the last match for the given Regexp regexp, or nil if none found:
'foo'.byterindex(/f/) # => 0 'foo'.byterindex(/o/) # => 2 'foo'.byterindex(/oo/) # => 1 'foo'.byterindex(/ooo/) # => nil
The last match means starting at the possible last position, not the last of longest matches.
'foo'.byterindex(/o+/) # => 2 $~ #=> #<MatchData "o">
To get the last longest match, needs to combine with negative lookbehind.
'foo'.byterindex(/(?<!o)o+/) # => 1 $~ #=> #<MatchData "oo">
Or String#byteindex with negative lookforward.
'foo'.byteindex(/o+(?!.*o)/) # => 1 $~ #=> #<MatchData "oo">
Integer argument offset, if given and non-negative, specifies the maximum starting byte-based position in the string to end the search:
'foo'.byterindex('o', 0) # => nil 'foo'.byterindex('o', 1) # => 1 'foo'.byterindex('o', 2) # => 2 'foo'.byterindex('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'.byterindex('o', -1) # => 2 'foo'.byterindex('o', -2) # => 1 'foo'.byterindex('o', -3) # => nil 'foo'.byterindex('o', -4) # => nil
If offset does not land on character (codepoint) boundary, IndexError is raised.
Related: String#byteindex.
Returns a printable version of self, enclosed in double-quotes, and with special characters escaped:
s = "foo\tbar\tbaz\n" s.inspect # => "\"foo\\tbar\\tbaz\\n\""
Forms substrings (“lines”) of self according to the given arguments (see String#each_line for details); returns the lines in an array.
Returns an array of the codepoints in self; each codepoint is the integer value for a character:
'hello'.codepoints # => [104, 101, 108, 108, 111] 'тест'.codepoints # => [1090, 1077, 1089, 1090] 'こんにちは'.codepoints # => [12371, 12435, 12395, 12385, 12399]
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 true if self contains other_string, false otherwise:
s = 'foo' s.include?('f') # => true s.include?('fo') # => true s.include?('food') # => false
Returns the Encoding object that represents the encoding of obj.
Returns true if self is not Infinity, -Infinity, or NaN, false otherwise:
f = 2.0 # => 2.0 f.finite? # => true f = 1.0/0.0 # => Infinity f.finite? # => false f = -1.0/0.0 # => -Infinity f.finite? # => false f = 0.0/0.0 # => NaN f.finite? # => false
Returns a string containing a representation of self; depending of the value of self, the string representation may contain:
A fixed-point number.
3.14.to_s # => "3.14"
A number in “scientific notation” (containing an exponent).
(10.1**50).to_s # => "1.644631821843879e+50"
‘Infinity’.
(10.1**500).to_s # => "Infinity"
‘-Infinity’.
(-10.1**500).to_s # => "-Infinity"
‘NaN’ (indicating not-a-number).
(0.0/0.0).to_s # => "NaN"
Forces the fiber to be blocking for the duration of the block. Returns the result of the block.
See the “Non-blocking fibers” section in class docs for details.
Returns true if fiber is blocking and false otherwise. Fiber is non-blocking if it was created via passing blocking: false to Fiber.new, or via Fiber.schedule.
Note that, even if the method returns false, the fiber behaves differently only if Fiber.scheduler is set in the current thread.
See the “Non-blocking fibers” section in class docs for details.
Returns false if the current fiber is non-blocking. Fiber is non-blocking if it was created via passing blocking: false to Fiber.new, or via Fiber.schedule.
If the current Fiber is blocking, the method returns 1. Future developments may allow for situations where larger integers could be returned.
Note that, even if the method returns false, Fiber behaves differently only if Fiber.scheduler is set in the current thread.
See the “Non-blocking fibers” section in class docs for details.
Sets the position in self to zero; see Dir As Stream-Like:
dir = Dir.new('example') dir.read # => "." dir.read # => ".." dir.pos # => 2 dir.rewind # => #<Dir:example> dir.pos # => 0
Removes the directory at dirpath from the underlying file system:
Dir.rmdir('foo') # => 0
Raises an exception if the directory is not empty.
Creates a new name for an existing file using a hard link. Will not overwrite new_name if it already exists (raising a subclass of SystemCallError). Not available on all platforms.
File.link("testfile", ".testfile") #=> 0 IO.readlines(".testfile")[0] #=> "This is line one\n"
Creates a symbolic link called new_name for the existing file old_name. Raises a NotImplemented exception on platforms that do not support symbolic links.
File.symlink("testfile", "link2test") #=> 0
Returns the name of the file referenced by the given link. Not available on all platforms.
File.symlink("testfile", "link2test") #=> 0 File.readlink("link2test") #=> "testfile"
Deletes the named files, returning the number of names passed as arguments. Raises an exception on any error. Since the underlying implementation relies on the unlink(2) system call, the type of exception raised depends on its error type (see linux.die.net/man/2/unlink) and has the form of e.g. Errno::ENOENT.
See also Dir::rmdir.
Returns the current umask value for this process. If the optional argument is given, set the umask to that value and return the previous value. Umask values are subtracted from the default permissions, so a umask of 0222 would make a file read-only for everyone.
File.umask(0006) #=> 18 File.umask #=> 6