gets

        # IO.gets

(from ruby core)
---
    gets(sep = $/, **getline_opts)   -> string or nil
    gets(limit, **getline_opts)      -> string or nil
    gets(sep, limit, **getline_opts) -> string or nil

---

Reads and returns data from the stream; assigns the return value to
`$_`.

With no arguments given, returns the next line as determined by line
separator `$/`, or `nil` if none:

    f = File.open('t.txt')
    f.gets # => "This is line one.\n"
    $_     # => "This is line one.\n"
    f.gets # => "This is the second line.\n"
    f.gets # => "This is the third line.\n"
    f.gets # => nil

With string argument `sep` given, but not argument `limit`, returns the
next line as determined by line separator `sep`, or `nil` if none:

    f = File.open('t.txt')
    f.gets(' is') # => "This is"
    f.gets(' is') # => " line one.\nThis is"
    f.gets(' is') # => " the second line.\nThis is"
    f.gets(' is') # => " the third line.\n"
    f.gets(' is') # => nil

Note two special values for `sep`:

*   `nil`: The entire stream is read and returned.
*   `''` (empty string): The next "paragraph" is read and returned, the
    paragraph separator being two successive line separators.


With integer argument `limit` given, returns up to `limit+1` bytes:

    # Text with 1-byte characters.
    File.open('t.txt') {|f| f.gets(1) } # => "T"
    File.open('t.txt') {|f| f.gets(2) } # => "Th"
    File.open('t.txt') {|f| f.gets(3) } # => "Thi"
    File.open('t.txt') {|f| f.gets(4) } # => "This"
    # No more than one line.
    File.open('t.txt') {|f| f.gets(17) } # => "This is line one."
    File.open('t.txt') {|f| f.gets(18) } # => "This is line one.\n"
    File.open('t.txt') {|f| f.gets(19) } # => "This is line one.\n"

    # Text with 2-byte characters, which will not be split.
    File.open('t.rus') {|f| f.gets(1).size } # => 1
    File.open('t.rus') {|f| f.gets(2).size } # => 1
    File.open('t.rus') {|f| f.gets(3).size } # => 2
    File.open('t.rus') {|f| f.gets(4).size } # => 2

With arguments `sep` and `limit`, combines the two behaviors above:

*   Returns the next line as determined by line separator `sep`, or
    `nil` if none.
*   But returns no more than `limit+1` bytes.


For all forms above, trailing optional keyword arguments may be given;
see [Getline Options](#class-IO-label-Getline+Options):

    f = File.open('t.txt')
    # Chomp the lines.
    f.gets(chomp: true) # => "This is line one."
    f.gets(chomp: true) # => "This is the second line."
    f.gets(chomp: true) # => "This is the third line."
    f.gets(chomp: true) # => nil