Calls the block with each successive line read from the stream.
When called from class IO (but not subclasses of IO), this method has potential security vulnerabilities if called with untrusted input; see Command Injection.
The first argument must be a string that is the path to a file.
With only argument path given, parses lines from the file at the given path, as determined by the default line separator, and calls the block with each successive line:
File.foreach('t.txt') {|line| p line }
Output: the same as above.
For both forms, command and path, the remaining arguments are the same.
With argument sep given, parses lines as determined by that line separator (see Line Separator):
File.foreach('t.txt', 'li') {|line| p line }
Output:
"First li" "ne\nSecond li" "ne\n\nThird li" "ne\nFourth li" "ne\n"
Each paragraph:
File.foreach('t.txt', '') {|paragraph| p paragraph }
Output:
"First line\nSecond line\n\n" "Third line\nFourth line\n"
With argument limit given, parses lines as determined by the default line separator and the given line-length limit (see Line Separator and Line Limit):
File.foreach('t.txt', 7) {|line| p line }
Output:
"First l" "ine\n" "Second " "line\n" "\n" "Third l" "ine\n" "Fourth l" "line\n"
With arguments sep and limit given, combines the two behaviors (see Line Separator and Line Limit).
Optional keyword arguments opts specify:
Encoding options.
Returns an Enumerator if no block is given.
Writes a character to the stream. See Character IO.
If object is numeric, converts to integer if necessary, then writes the character whose code is the least significant byte; if object is a string, writes the first character:
$stdout.putc "A" $stdout.putc 65
Output:
AA
Calls the block with each remaining line read from the stream; returns self. Does nothing if already at end-of-stream; See Line IO.
With no arguments given, reads lines as determined by line separator $/:
f = File.new('t.txt') f.each_line {|line| p line } f.each_line {|line| fail 'Cannot happen' } f.close
Output:
"First line\n" "Second line\n" "\n" "Fourth line\n" "Fifth line\n"
With only string argument sep given, reads lines as determined by line separator sep; see Line Separator:
f = File.new('t.txt') f.each_line('li') {|line| p line } f.close
Output:
"First li" "ne\nSecond li" "ne\n\nFourth li" "ne\nFifth li" "ne\n"
The two special values for sep are honored:
f = File.new('t.txt') # Get all into one string. f.each_line(nil) {|line| p line } f.close
Output:
"First line\nSecond line\n\nFourth line\nFifth line\n" f.rewind # Get paragraphs (up to two line separators). f.each_line('') {|line| p line }
Output:
"First line\nSecond line\n\n" "Fourth line\nFifth line\n"
With only integer argument limit given, limits the number of bytes in each line; see Line Limit:
f = File.new('t.txt') f.each_line(8) {|line| p line } f.close
Output:
"First li" "ne\n" "Second l" "ine\n" "\n" "Fourth l" "ine\n" "Fifth li" "ne\n"
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.each_line(chomp: true) {|line| p line } f.close
Output:
"First line" "Second line" "" "Fourth line" "Fifth line"
Returns an Enumerator if no block is given.
Immediately writes to disk all data buffered in the stream, via the operating system’s: fdatasync(2), if supported, otherwise via fsync(2), if supported; otherwise raises an exception.
Reads and returns the next 1-character string from the stream; returns nil if already at end-of-stream. See Character IO.
f = File.open('t.txt') f.getc # => "F" f.close f = File.open('t.rus') f.getc.ord # => 1090 f.close
Related: IO#readchar (may raise EOFError).
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
Pushes back (“unshifts”) the given data onto the stream’s buffer, placing the data so that it is next to be read; returns nil. See Character IO.
Note that:
Calling the method has no effect with unbuffered reads (such as IO#sysread).
Calling rewind on the stream discards the pushed-back data.
When argument integer is given, interprets the integer as a character:
File.write('t.tmp', '012') f = File.open('t.tmp') f.ungetc(0x41) # => nil f.read # => "A012" f.rewind f.ungetc(0x0442) # => nil f.getc.ord # => 1090 f.close
When argument string is given, uses all characters:
File.write('t.tmp', '012') f = File.open('t.tmp') f.ungetc('A') # => nil f.read # => "A012" f.rewind f.ungetc("\u0442\u0435\u0441\u0442") # => nil f.getc.ord # => 1090 f.getc.ord # => 1077 f.getc.ord # => 1089 f.getc.ord # => 1090 f.close
Returns true if the stream is associated with a terminal device (tty), false otherwise:
f = File.new('t.txt').isatty #=> false f.close f = File.new('/dev/tty').isatty #=> true f.close
Sets the stream’s data mode as binary (see Data Mode).
A stream’s data mode may not be changed from binary to text.
Returns true if the stream is on binary mode, false otherwise. See Data Mode.
Returns the path associated with the IO, or nil if there is no path associated with the IO. It is not guaranteed that the path exists on the filesystem.
$stdin.path # => "<STDIN>" File.open("testfile") {|f| f.path} # => "testfile"
With a block given, passes each element of self to the block:
a = [] (1..4).each {|element| a.push(element) } # => 1..4 a # => [1, 2, 3, 4]
Raises an exception unless self.first.respond_to?(:succ).
With no block given, returns an enumerator.
Returns the maximum value in self, using method <=> or a given block for comparison.
With no argument and no block given, returns the maximum-valued element of self.
(1..4).max # => 4 ('a'..'d').max # => "d" (-4..-1).max # => -1
With non-negative integer argument n given, and no block given, returns the n maximum-valued elements of self in an array:
(1..4).max(2) # => [4, 3] ('a'..'d').max(2) # => ["d", "c"] (-4..-1).max(2) # => [-1, -2] (1..4).max(50) # => [4, 3, 2, 1]
If a block is given, it is called:
First, with the first two element of self.
Then, sequentially, with the so-far maximum value and the next element of self.
To illustrate:
(1..4).max {|a, b| p [a, b]; a <=> b } # => 4
Output:
[2, 1] [3, 2] [4, 3]
With no argument and a block given, returns the return value of the last call to the block:
(1..4).max {|a, b| -(a <=> b) } # => 1
With non-negative integer argument n given, and a block given, returns the return values of the last n calls to the block in an array:
(1..4).max(2) {|a, b| -(a <=> b) } # => [1, 2] (1..4).max(50) {|a, b| -(a <=> b) } # => [1, 2, 3, 4]
Returns an empty array if n is zero:
(1..4).max(0) # => [] (1..4).max(0) {|a, b| -(a <=> b) } # => []
Returns nil or an empty array if:
The begin value of the range is larger than the end value:
(4..1).max # => nil (4..1).max(2) # => [] (4..1).max {|a, b| -(a <=> b) } # => nil (4..1).max(2) {|a, b| -(a <=> b) } # => []
The begin value of an exclusive range is equal to the end value:
(1...1).max # => nil (1...1).max(2) # => [] (1...1).max {|a, b| -(a <=> b) } # => nil (1...1).max(2) {|a, b| -(a <=> b) } # => []
Raises an exception if either:
self is a endless range: (1..).
A block is given and self is a beginless range.
Related: Range#min, Range#minmax.
Returns the numerator.
Rational(7).numerator #=> 7 Rational(7, 1).numerator #=> 7 Rational(9, -4).numerator #=> -9 Rational(-2, -10).numerator #=> 1
Returns the denominator (always positive).
Rational(7).denominator #=> 1 Rational(7, 1).denominator #=> 1 Rational(9, -4).denominator #=> 4 Rational(-2, -10).denominator #=> 5
Returns true if rat is less than 0.
Returns rat truncated (toward zero) to 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).truncate #=> 3 Rational(2, 3).truncate #=> 0 Rational(-3, 2).truncate #=> -1 # decimal - 1 2 3 . 4 5 6 # ^ ^ ^ ^ ^ ^ # precision -3 -2 -1 0 +1 +2 Rational('-123.456').truncate(+1).to_f #=> -123.4 Rational('-123.456').truncate(-1) #=> -120
Returns a simpler approximation of the value if the optional argument eps is given (rat-|eps| <= result <= rat+|eps|), self otherwise.
r = Rational(5033165, 16777216) r.rationalize #=> (5033165/16777216) r.rationalize(Rational('0.01')) #=> (3/10) r.rationalize(Rational('0.1')) #=> (1/3)
Returns a new set that is a copy of the set, flattening each containing set recursively.
Equivalent to Set#flatten, but replaces the receiver with the result in place. Returns nil if no modifications were made.
Calls the given block once for each element in the set, passing the element as parameter. Returns an enumerator if no block is given.
Calls the given block with the value of each member; returns self:
Customer = Struct.new(:name, :address, :zip) joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345) joe.each {|value| p value }
Output:
"Joe Smith" "123 Maple, Anytown NC" 12345
Returns an Enumerator if no block is given.
Related: each_pair.