Reassociates the stream with another stream, which may be of a different class. This method may be used to redirect an existing stream to a new destination.
With argument other_io given, reassociates with that stream:
# Redirect $stdin from a file. f = File.open('t.txt') $stdin.reopen(f) f.close # Redirect $stdout to a file. f = File.open('t.tmp', 'w') $stdout.reopen(f) f.close
With argument path given, reassociates with a new stream to that file path:
$stdin.reopen('t.txt') $stdout.reopen('t.tmp', 'w')
Optional keyword arguments opts specify:
Encoding options.
Behaves like IO#readpartial, except that it uses low-level system functions.
This method should not be used with other stream-reader methods.
Behaves like IO#readpartial, except that it:
Reads at the given offset (in bytes).
Disregards, and does not modify, the stream’s position (see Position).
Bypasses any user space buffering in the stream.
Because this method does not disturb the stream’s state (its position, in particular), pread allows multiple threads and processes to use the same IO object for reading at various offsets.
f = File.open('t.txt') f.read # => "First line\nSecond line\n\nFourth line\nFifth line\n" f.pos # => 52 # Read 12 bytes at offset 0. f.pread(12, 0) # => "First line\n" # Read 9 bytes at offset 8. f.pread(9, 8) # => "ne\nSecon" f.close
Not available on some platforms.
Reads and returns all remaining line from the stream; does not modify $_. See Line IO.
With no arguments given, returns lines as determined by line separator $/, or nil if none:
f = File.new('t.txt') f.readlines # => ["First line\n", "Second line\n", "\n", "Fourth line\n", "Fifth line\n"] f.readlines # => [] f.close
With only string argument sep given, returns lines as determined by line separator sep, or nil if none; see Line Separator:
f = File.new('t.txt') f.readlines('li') # => ["First li", "ne\nSecond li", "ne\n\nFourth li", "ne\nFifth li", "ne\n"] f.close
The two special values for sep are honored:
f = File.new('t.txt') # Get all into one string. f.readlines(nil) # => ["First line\nSecond line\n\nFourth line\nFifth line\n"] # Get paragraphs (up to two line separators). f.rewind f.readlines('') # => ["First line\nSecond line\n\n", "Fourth line\nFifth line\n"] f.close
With only integer argument limit given, limits the number of bytes in each line; see Line Limit:
f = File.new('t.txt') f.readlines(8) # => ["First li", "ne\n", "Second l", "ine\n", "\n", "Fourth l", "ine\n", "Fifth li", "ne\n"] f.close
With arguments sep and limit given, combines the two behaviors (see Line Separator and Line Limit).
Optional keyword argument chomp specifies whether line separators are to be omitted:
f = File.new('t.txt') f.readlines(chomp: true) # => ["First line", "Second line", "", "Fourth line", "Fifth line"] f.close
Reads up to maxlen bytes from the stream; returns a string (either a new string or the given out_string). Its encoding is:
The unchanged encoding of out_string, if out_string is given.
ASCII-8BIT, otherwise.
Contains maxlen bytes from the stream, if available.
Otherwise contains all available bytes, if any available.
Otherwise is an empty string.
With the single non-negative integer argument maxlen given, returns a new string:
f = File.new('t.txt') f.readpartial(20) # => "First line\nSecond l" f.readpartial(20) # => "ine\n\nFourth line\n" f.readpartial(20) # => "Fifth line\n" f.readpartial(20) # Raises EOFError. f.close
With both argument maxlen and string argument out_string given, returns modified out_string:
f = File.new('t.txt') s = 'foo' f.readpartial(20, s) # => "First line\nSecond l" s = 'bar' f.readpartial(0, s) # => "" f.close
This method is useful for a stream such as a pipe, a socket, or a tty. It blocks only when no data is immediately available. This means that it blocks only when all of the following are true:
The byte buffer in the stream is empty.
The content of the stream is empty.
The stream is not at EOF.
When blocked, the method waits for either more data or EOF on the stream:
If more data is read, the method returns the data.
If EOF is reached, the method raises EOFError.
When not blocked, the method responds immediately:
Returns data from the buffer if there is any.
Otherwise returns data from the stream if there is any.
Otherwise raises EOFError if the stream has reached EOF.
Note that this method is similar to sysread. The differences are:
If the byte buffer is not empty, read from the byte buffer instead of “sysread for buffered IO (IOError)”.
It doesn’t cause Errno::EWOULDBLOCK and Errno::EINTR. When readpartial meets EWOULDBLOCK and EINTR by read system call, readpartial retries the system call.
The latter means that readpartial is non-blocking-flag insensitive. It blocks on the situation IO#sysread causes Errno::EWOULDBLOCK as if the fd is blocking mode.
Examples:
# # Returned Buffer Content Pipe Content r, w = IO.pipe # w << 'abc' # "" "abc". r.readpartial(4096) # => "abc" "" "" r.readpartial(4096) # (Blocks because buffer and pipe are empty.) # # Returned Buffer Content Pipe Content r, w = IO.pipe # w << 'abc' # "" "abc" w.close # "" "abc" EOF r.readpartial(4096) # => "abc" "" EOF r.readpartial(4096) # raises EOFError # # Returned Buffer Content Pipe Content r, w = IO.pipe # w << "abc\ndef\n" # "" "abc\ndef\n" r.gets # => "abc\n" "def\n" "" w << "ghi\n" # "def\n" "ghi\n" r.readpartial(4096) # => "def\n" "" "ghi\n" r.readpartial(4096) # => "ghi\n" "" ""
Reads bytes from the stream; the stream must be opened for reading (see Access Modes):
If maxlen is nil, reads all bytes using the stream’s data mode.
Otherwise reads up to maxlen bytes in binary mode.
Returns a string (either a new string or the given out_string) containing the bytes read. The encoding of the string depends on both maxLen and out_string:
maxlen is nil: uses internal encoding of self (regardless of whether out_string was given).
maxlen not nil:
out_string given: encoding of out_string not modified.
out_string not given: ASCII-8BIT is used.
Without Argument out_string
When argument out_string is omitted, the returned value is a new string:
f = File.new('t.txt') f.read # => "First line\nSecond line\n\nFourth line\nFifth line\n" f.rewind f.read(30) # => "First line\r\nSecond line\r\n\r\nFou" f.read(30) # => "rth line\r\nFifth line\r\n" f.read(30) # => nil f.close
If maxlen is zero, returns an empty string.
With Argument out_string
When argument out_string is given, the returned value is out_string, whose content is replaced:
f = File.new('t.txt') s = 'foo' # => "foo" f.read(nil, s) # => "First line\nSecond line\n\nFourth line\nFifth line\n" s # => "First line\nSecond line\n\nFourth line\nFifth line\n" f.rewind s = 'bar' f.read(30, s) # => "First line\r\nSecond line\r\n\r\nFou" s # => "First line\r\nSecond line\r\n\r\nFou" s = 'baz' f.read(30, s) # => "rth line\r\nFifth line\r\n" s # => "rth line\r\nFifth line\r\n" s = 'bat' f.read(30, s) # => nil s # => "" f.close
Note that this method behaves like the fread() function in C. This means it retries to invoke read(2) system calls to read data with the specified maxlen (or until EOF).
This behavior is preserved even if the stream is in non-blocking mode. (This method is non-blocking-flag insensitive as other methods.)
If you need the behavior like a single read(2) system call, consider readpartial, read_nonblock, and sysread.
Related: IO#write.
Reads and returns the next 1-character string from the stream; raises EOFError if already at end-of-stream. See Character IO.
f = File.open('t.txt') f.readchar # => "F" f.close f = File.open('t.rus') f.readchar.ord # => 1090 f.close
Reads and returns the next byte (in range 0..255) from the stream; raises EOFError if already at end-of-stream. See Byte IO.
f = File.open('t.txt') f.readbyte # => 70 f.close f = File.open('t.rus') f.readbyte # => 209 f.close
Related: IO#getbyte (will not raise EOFError).
Repositions the stream to its beginning, setting both the position and the line number to zero; see Position and Line Number:
f = File.open('t.txt') f.tell # => 0 f.lineno # => 0 f.gets # => "First line\n" f.tell # => 12 f.lineno # => 1 f.rewind # => 0 f.tell # => 0 f.lineno # => 0 f.close
Note that this method cannot be used with streams such as pipes, ttys, and sockets.
Returns true if the underlying file descriptor of ios will be closed at its finalization or at calling close, otherwise false.
Sets auto-close flag.
f = File.open(File::NULL) IO.for_fd(f.fileno).close f.gets # raises Errno::EBADF f = File.open(File::NULL) g = IO.for_fd(f.fileno) g.autoclose = false g.close f.gets # won't cause Errno::EBADF
Returns the integer file descriptor for the stream:
$stdin.fileno # => 0 $stdout.fileno # => 1 $stderr.fileno # => 2 File.open('t.txt').fileno # => 10 f.close
Reads a line as with IO#gets, but raises EOFError if already at end-of-stream.
Optional keyword argument chomp specifies whether line separators are to be omitted.
Iterates over the elements of range in steps of s. The iteration is performed by + operator:
(0..6).step(2) { puts _1 } #=> 1..5 # Prints: 0, 2, 4, 6 # Iterate between two dates in step of 1 day (24 hours) (Time.utc(2022, 2, 24)..Time.utc(2022, 3, 1)).step(24*60*60) { puts _1 } # Prints: # 2022-02-24 00:00:00 UTC # 2022-02-25 00:00:00 UTC # 2022-02-26 00:00:00 UTC # 2022-02-27 00:00:00 UTC # 2022-02-28 00:00:00 UTC # 2022-03-01 00:00:00 UTC
If + step decreases the value, iteration is still performed when step begin is higher than the end:
(0..6).step(-2) { puts _1 } # Prints nothing (6..0).step(-2) { puts _1 } # Prints: 6, 4, 2, 0 (Time.utc(2022, 3, 1)..Time.utc(2022, 2, 24)).step(-24*60*60) { puts _1 } # Prints: # 2022-03-01 00:00:00 UTC # 2022-02-28 00:00:00 UTC # 2022-02-27 00:00:00 UTC # 2022-02-26 00:00:00 UTC # 2022-02-25 00:00:00 UTC # 2022-02-24 00:00:00 UTC
When the block is not provided, and range boundaries and step are Numeric, the method returns Enumerator::ArithmeticSequence.
(1..5).step(2) # => ((1..5).step(2)) (1.0..).step(1.5) #=> ((1.0..).step(1.5)) (..3r).step(1/3r) #=> ((..3/1).step((1/3)))
Enumerator::ArithmeticSequence can be further used as a value object for iteration or slicing of collections (see Array#[]). There is a convenience method % with behavior similar to step to produce arithmetic sequences more expressively:
# Same as (1..5).step(2) (1..5) % 2 # => ((1..5).%(2))
In a generic case, when the block is not provided, Enumerator is returned:
('a'..).step('b') #=> #<Enumerator: "a"..:step("b")> ('a'..).step('b').take(3) #=> ["a", "ab", "abb"]
If s is not provided, it is considered 1 for ranges with numeric begin:
(1..5).step { p _1 } # Prints: 1, 2, 3, 4, 5
For non-Numeric ranges, step absence is an error:
(Time.utc(2022, 3, 1)..Time.utc(2022, 2, 24)).step { p _1 } # raises: step is required for non-numeric ranges (ArgumentError)
For backward compatibility reasons, String ranges support the iteration both with string step and with integer step. In the latter case, the iteration is performed by calculating the next values with String#succ:
('a'..'e').step(2) { p _1 } # Prints: a, c, e ('a'..'e').step { p _1 } # Default step 1; prints: a, b, c, d, e
With no argument, returns the first element of self, if it exists:
(1..4).first # => 1 ('a'..'d').first # => "a"
With non-negative integer argument n given, returns the first n elements in an array:
(1..10).first(3) # => [1, 2, 3] (1..10).first(0) # => [] (1..4).first(50) # => [1, 2, 3, 4]
Raises an exception if there is no first element:
(..4).first # Raises RangeError
With no argument, returns the last element of self, if it exists:
(1..4).last # => 4 ('a'..'d').last # => "d"
Note that last with no argument returns the end element of self even if exclude_end? is true:
(1...4).last # => 4 ('a'...'d').last # => "d"
With non-negative integer argument n given, returns the last n elements in an array:
(1..10).last(3) # => [8, 9, 10] (1..10).last(0) # => [] (1..4).last(50) # => [1, 2, 3, 4]
Note that last with argument does not return the end element of self if exclude_end? it true:
(1...4).last(3) # => [1, 2, 3] ('a'...'d').last(3) # => ["a", "b", "c"]
Raises an exception if there is no last element:
(1..).last # Raises RangeError
Returns an array containing the elements in self, if a finite collection; raises an exception otherwise.
(1..4).to_a # => [1, 2, 3, 4] (1...4).to_a # => [1, 2, 3] ('a'..'d').to_a # => ["a", "b", "c", "d"]
Returns a string representation of self, including begin.to_s and end.to_s:
(1..4).to_s # => "1..4" (1...4).to_s # => "1...4" (1..).to_s # => "1.." (..4).to_s # => "..4"
Note that returns from to_s and inspect may differ:
('a'..'d').to_s # => "a..d" ('a'..'d').inspect # => "\"a\"..\"d\""
Related: Range#inspect.
Returns the largest number less than or equal to rat with a precision of ndigits decimal digits (default: 0).
When the precision is negative, the returned value is an integer with at least ndigits.abs trailing zeros.
Returns a rational when ndigits is positive, otherwise returns an integer.
Rational(3).floor #=> 3 Rational(2, 3).floor #=> 0 Rational(-3, 2).floor #=> -2 # decimal - 1 2 3 . 4 5 6 # ^ ^ ^ ^ ^ ^ # precision -3 -2 -1 0 +1 +2 Rational('-123.456').floor(+1).to_f #=> -123.5 Rational('-123.456').floor(-1) #=> -130
Returns the truncated value as an integer.
Equivalent to Rational#truncate.
Rational(2, 3).to_i #=> 0 Rational(3).to_i #=> 3 Rational(300.6).to_i #=> 300 Rational(98, 71).to_i #=> 1 Rational(-31, 2).to_i #=> -15
Returns the value as a Float.
Rational(2).to_f #=> 2.0 Rational(9, 4).to_f #=> 2.25 Rational(-3, 4).to_f #=> -0.75 Rational(20, 3).to_f #=> 6.666666666666667
Returns the value as a string.
Rational(2).to_s #=> "2/1" Rational(-8, 6).to_s #=> "-4/3" Rational('1/2').to_s #=> "1/2"
Returns a string showing the options and string of self:
r0 = /ab+c/ix s0 = r0.to_s # => "(?ix-m:ab+c)"
The returned string may be used as an argument to Regexp.new, or as interpolated text for a Regexp interpolation:
r1 = Regexp.new(s0) # => /(?ix-m:ab+c)/ r2 = /#{s0}/ # => /(?ix-m:ab+c)/
Note that r1 and r2 are not equal to r0 because their original strings are different:
r0 == r1 # => false r0.source # => "ab+c" r1.source # => "(?ix-m:ab+c)"
Related: Regexp#inspect.
Replaces the contents of the set with the contents of the given enumerable object and returns self.
set = Set[1, 'c', :s] #=> #<Set: {1, "c", :s}> set.replace([1, 2]) #=> #<Set: {1, 2}> set #=> #<Set: {1, 2}>